Posts

How to Select a Spindle

When trying to develop efficient processes, many machinists and programmers turn to tool selection first. It is true that tooling can often make a big difference in machining time, and speeds and feeds, but did you know that your machine’s spindle can have an equally impactful effect? The legs of any CNC machine, spindles are comprised of a motor, a taper for holding tools, and a shaft that will hold all of the components together. Often powered by electricity, spindles rotate on an axis which receives its input from the machine’s CNC controller.

Why is Choosing the Right Spindle Important?

Choosing the right spindle to machine your workpiece with is of very high importance to a successful production run. As tooling options continue to grow, it is important to know what tooling your spindle can utilize. Large diameter tools such as large end mills or face mills typically require slower spindle speeds and take deeper cuts to remove vast amounts of material. These applications require supreme machine rigidity and require a spindle with high torque.

Contrastingly, smaller diameter tools will need a higher-speed spindle. Faster speeds and feeds deliver better surface finishes and are used in a variety of applications. A good rule of thumb is that an end mill that is a half inch or smaller will run well with lower torque.

Types of CNC Spindles

After finding out what you should look for in a spindle, it is time to learn about your different options. Spindles typically vary by the type, style of the taper, or its size. The taper is the conical portion of the tool holder that fits inside of the opening of the spindle. Every spindle is designed to mate with a certain taper style and size.

CAT and BT Holders

This is the most widely utilized holder for milling in the United States. Referred to as “V-flange holders,” both of these styles need a retention knob or pull stud to be secured within the machine spindle. The BT (metric style) is popular overseas.

HSK Holders

This type of holder is a German standard known as “hollow shank taper.” The tapered portion of the holder is much shorter than its counterparts. It also engages the spindle in a different way and does not require a pull stud or retention knob. The HSK holder is utilized to create repeatability and longer tool life – particularly in High Efficiency Milling (HEM) applications.

All of these holders have benefits and limitations including price, accuracy, and availability. The proper selection will depend largely on your application requirements.

Torque vs. Horsepower

Torque is defined as force perpendicular to the axis of rotation across a distance. It is important to have high torque capabilities when using an end mill larger than ½ inch, or when machining a difficult material such as Inconel. Torque will help put power behind the cutting action of the tool.

Horsepower refers to the amount of work being done. Horsepower is important for smaller diameter end mills and easy-to-machine materials like aluminum.

You can think of torque as a tractor: It can’t go very fast, but there is a lot of power behind it. Think of horsepower as a racecar: It can go very fast but cannot pull or push.

Torque-Horsepower Chart

Every machine and spindle should come with a torque horsepower chart. These charts will help you understand how to maximize your spindle for torque or horsepower, depending on what you need:

Image Source: HAAS Machine Manual

Proper Spindle Size

The size of the spindle and shank taper corresponds to the weight and length of the tools being used, as well as the material you are planning to machine. CAT40 is the most commonly used spindle in the United States. These spindles are great for utilizing tools that have a ½ inch diameter end mill or smaller in any material. If you are considering using a 1 inch end mill in a material like Inconel or Titanium, a CAT50 would be a more appropriate choice. The higher the taper angle is, the more torque the spindle is capable of.

While choosing the correct tool for your application is important, choosing a tool your spindle can utilize is paramount to machining success. Knowing the amount of torque required will help machinists save a lot of headaches.

John Force Racing – Featured Customer

John Force Racing has been dominating the motorsports world for over 30 years, winning 20 championships and hundreds of races in the National Hot Rod Association (NHRA) drag racing series. John Force Racing features both Funny Car and Top Fuel teams, and just recently in 2017 they won both the Funny Car and Top Fuel championships in the same season.

John Force Racing invested in Force American Made to develop and create parts and components that would help drive all the teams to success and safety. The 84,000 square foot shop is located in Brownsburg, Indiana (just outside of Indianapolis) and is the heartbeat of John Force Racing. Thousands of parts are forged by Force American Made and its team of employees every season giving the team a competitive edge that has led to the team’s on-track success.

The Force American Made team has relied on Helical Solutions tooling to get the best performance and quality out of their CNC mills for years. The Harvey Performance Company team was invited out to Indiana to take a tour of Force American Made and spend some time with Tom Warga, Lead Machinist, to talk with him about his experiences with Helical Solutions tooling, his first time trying Machining Advisor Pro, the success they have had using the new Helical tool libraries for Mastercam, and the value their distributor, Dolen Tool, brings to the shop. Check out the video interview below to see the inner-workings of Force American Made and how Helical Solutions tooling has contributed to the success of this motorsports dynasty.

Effective Ways To Reduce Heat Generation

Any cutting tool application will generate heat, but knowing how to counteract it will improve the life of your tool. Heat can be good and doesn’t need to totally be avoided, but controlling heat will help prolong your tool life. Sometimes, an overheating tool or workpiece is easy to spot due to smoke or deformation. Other times, the signs are not as obvious. Taking every precaution possible to redirect heat will prolong your tool’s usable life, avoid scrapped parts, and will result in significant cost savings.

Reduce Heat Generation with HEM Tool Paths

High Efficiency Milling (HEM), is one way a machinist should explore to manage heat generation during machining. HEM is a roughing technique that uses the theory of chip thinning by applying a smaller radial depth of cut (RDOC) and a larger axial depth of cut (ADOC). HEM uses RDOC and ADOC similar to finishing operations but increases speeds and feeds, resulting in greater material removal rates (MRR). This technique is usually used for removing large amounts of material in roughing and pocketing applications. HEM utilizes the full length of cut and more effectively uses the full potential of the tool, optimizing tool life and productivity. You will need to take more radial passes on your workpiece, but using HEM will evenly spread heat across the whole cutting edge of your tool, instead of building heat along one small portion, reducing the possibility of tool failure and breakage.

heat generation

Chip Thinning Awareness

Chip thinning occurs when tool paths include varying radial depths of cut, and relates to chip thickness and feed per tooth. HEM is based off of the principal of chip thinning. However, if not properly executed, chip thinning can cause a lot of heat generation. When performing HEM, you effectively reduce your stepover and increase your speeds and feeds to run your machine at high rates. But if your machine isn’t capable of running high enough speeds and feeds, or you do not adjust accordingly to your reduced stepover, trouble will occur in the form of rubbing between the material and tool. Rubbing creates friction and mass amounts of heat which can cause your material to deform and your tool to overheat. Chip thinning can be good when used correctly in HEM, but if you fall below the line of reduced stepover without higher speeds and feeds, you will cause rubbing and tool failure. Because of this, it’s always important to be aware of your chips during machining.

heat generation

Consider Climb Milling

There are two ways to cut materials when milling: conventional milling and climb milling. The difference between the two is the relationship of the rotation of the cutter to the direction of feed. In climb milling, the cutter rotates with the feed, as opposed to conventional milling where the cutter rotates against the feed.

When conventional milling, chips start at theoretical zero and increase in size, causing rubbing and potentially work hardening. For this reason, it’s usually recommended for tools with higher toughness or for breaking through case hardened materials.

In climb milling, the chip starts at maximum width and decreases, causing the heat generated to transfer into the chip instead of the tool or workpiece. When going from max width to theoretical zero, heat will be transferred to the chip and pushed away from the workpiece, reducing the possibility of damage to the workpiece. Climb milling also produces a cleaner shear plane which will cause less tool rubbing, decreasing heat and improving tool life. When climb milling, chips are removed behind the cutter, reducing your chances of re-cutting. climb milling effectively reduces heat generated to the tool and workpiece by transferring heat into the chip, reducing rubbing and by reducing your chances of re-cutting chips.

 

heat generation

Utilize Proper Coolant Methods

If used properly, coolant can be an extremely effective way to keep your tool from overheating. There are many different types of coolant and different ways coolant can be delivered to your tool. Coolant can be compressed air, water-based, straight oil-based, soluble oil-based, synthetic or semi-synthetic. It can be delivered as mist, flood, high pressure or minimum quantity lubricant.

Different applications and tools require different types and delivery of coolant, as using the wrong delivery or type could lead to part or tool damage. For instance, using high pressure coolant with miniature tooling could lead to tool breakage. In materials where chip evacuation is a major pain point such as aluminum, coolant is often used to flush chips away from the workpiece, rather than for heat moderation. When cutting material that produces long, stringy chips without coolant, you run the risk of creating built-up edge from the chips evacuating improperly. Using coolant will allow those chips to slide out of your toolpath easily, avoiding the chance of re-cutting and causing tool failure. In materials like titanium that don’t transfer heat well, proper coolant usage can prevent the material from overheating. With certain materials, however, thermal shock becomes an issue. This is when coolant is delivered to a very hot material and decreases its temperature rapidly, impacting the material’s properties. Coolant can be expensive and wasteful if not necessary for the application, so it’s important to always make sure you know the proper ways to use coolant before starting a job.

Importance of Controlling Heat Generation

Heat can be a tool’s worst nightmare if you do not know how to control it. High efficiency milling will distribute heat throughout the whole tool instead of one small portion, making it less likely for your tool to overheat and fail. By keeping RDOC constant throughout your toolpath, you will decrease the chances of rubbing, a common cause of heat generation. Climb milling is the most effective way to transfer heat into the chip, as it will reduce rubbing and lessen the chance of re-chipping. This will effectively prolong tool life. Coolant is another method for keeping temperatures moderated, but should be used with caution as the type of coolant delivery and certain material properties can impact its effectiveness.

B&R Custom Machining- Featured Customer

B&R Custom Machining is a rapidly expanding aerospace machine shop located in Ontario, Canada, focused primarily on aerospace and military/defense manufacturing. Over the past 17 years, B&R has grown from a 5 person shop with a few manual mills and lathes, into one of Canada’s most highly respected manufacturing facilities, with nearly 40 employees and 21 precision CNC machines.

B&R focuses on quality assurance and constant improvement, mastering the intimacies of metal cutting and maintaining the highest levels of quality through their unique shop management philosophies. They seek to consistently execute on clear contracts through accurate delivery, competitive price, and high quality machined components.

We talked with Brad Jantzi, Co-Founder and Technical Manager of B&R Custom Machining, to learn about how he started in the industry, his experience with High Efficiency Milling, what he looks for most in a cutting tool, and more!

B&R Custom machining

Can you tell us a little bit about how B&R Custom Machining started, and a little background about yourself and the company?

My brother (Ryan Jantzi, CEO/Co-Founder) and I started working in manufacturing back in 2001, when we were just 20/21 years old. We had 5 employees (including ourselves), a few manual mills and lathes, and we were wrapping our parts in newspaper for shipping. We took over from a preexisting shop and assumed their sales and machines.

We bought our first CNC machine in 2003, and immediately recognized the power of CNC and the opportunities it could open up for us. Now, we have 21 CNC machines, 38 employees, and more requests for work than we can keep up with, which is a good thing for the business. We are constantly expanding our team to elevate the business and take on even more work, and are currently hiring for multiple positions if anyone in Ontario is looking for some challenging and rewarding work!

What kind of CNC machines are you guys working with?

Right now we have a lot of Okuma and Matsuura machines, many of which have 5 axis capabilities, and all of them with high RPM spindles. In fact, our “slowest” machine runs at 15k RPM, with our fastest running at 46k. One of our high production machines is our Matsuura LX160, which has the 46k RPM spindle. We use a ton of Harvey Tool and Helical product on that machine and really get to utilize the RPMs.

B&R Custom Machining

What sort of material are you cutting?

We work with Aluminum predominantly, but also with a lot of super alloys like Invar, Kovar, Inconel, Custom 455 Stainless, and lots of Titanium. Some of those super alloys are really tricky stuff to machine. Once we learn about them and study them, we keep a recorded database of information to help us dial in parameters. Our head programmer/part planner keeps track of all that information, and our staff will frequently reference old jobs for new parts.

Sounds like a great system you guys have in place. How did B&R Custom Machining get into aerospace manufacturing?

It is a bit of a funny story actually. Just about 12 years ago we were contacted by someone working at Comdev, which is close to our shop, who was looking to have some parts made. We started a business relationship with him, and made him his parts. He was happy with the work, and so we eventually got involved in his company’s switch division and started to make more and more aerospace parts.

aerospace machining

We immediately saw the potential of aerospace manufacturing, and it promoted where we wanted to go with CNC machining, so it was a natural fit. It really was a case of being in the right place at the right time and seizing the moment. If an opportunity comes up and you aren’t ready for it, you miss it. You have to be hungry enough to see an opportunity, and confident enough to grab it, while also being competent enough to handle the request. So, we took advantage of what we were given, and we grew and went from there.

Who are some of the major players who you work with?

We have great relationships with Honeywell, MDA Brampton, and MDA Quebec. We actually worked on parts for a Mars Rover with MDA that was commissioned by the Canadian Space Agency, which was really cool to be a part of.

Working with large companies like that means quality is key. Why is high quality tool performance important to you?

High quality and superior tool performance is huge. Aside from cutting conditions, there are two quick things that cause poor performance on a tool: tool life and consistency of the tool quality. One without the other means nothing. We all can measure tool life pretty readily, and there is a clear advantage that some tools have over others, but inconsistent quality can sneak up on you and cause trouble. If you have a tool manufacturer that is only producing a quality tool even 95% of the time, that might seem ok, but that means that 5% of the time you suffer something wrong on the machine. Many times, you won’t know where that trouble is coming from. This causes you to pause the machine, investigate, source the problem, and then ultimately switch the tool and create a new program. It becomes an ordeal. Sometimes it is not as simple as manually adjusting the feed knob, especially when you need to rely on it as a “proven program” the next time around.

So, say the probability of a shortcoming on a machine is “x” with one brand of tooling, but is half of that with a brand like Harvey Tool. Sure, the Harvey Tool product might be 10-20% higher in upfront cost, but that pales in comparison to buying cheaper tools and losing time and money due to machine downtime caused by tool failure. The shop rate for an average machine is right around $100/hour, so machine downtime is much more expensive than the added cost of a quality tool.

B&R Custom machining

Inconsistent tool quality can be extremely dangerous to play around with, even outside of machine downtime. We create based on a specific tool and a certain level of expected performance. If that tool cannot be consistent, we now jeopardize an expensive part. The machine never went down, but the part is no good because we programmed based on consistency in tool quality. Again, the cost of scrapped parts heavily outweighs the upfront cost of quality tooling. Tooling is a low cost of what we do here, but poor tooling can cost us thousands versus a few dollars more for quality tools. Too many people focus on the upfront cost, and don’t look downstream through the rest of the process to see how poor quality tooling can affect your business in a much bigger way. We get to see the whole picture because I am involved from cradle to grave, gaining feedback and knowledge along the way.

That’s great feedback Brad, and I think it is important for people to understand what you have laid out here. Speaking of tool performance, have you guys been using High Efficiency Milling techniques in the shop?

Absolutely. We feel that we are on the front edge of efficient milling. We are quite capable of all the latest techniques, as our programmers are well-versed and up to date. For our larger production work, we have programs dialed in that allow us to push the tools to their limits and significantly cut down our cycle times.

What advice would you have for others who are interested in High Efficiency Milling?

Make sure you are smart about using HEM. If we have one-off parts, particularly expensive ones, that do not have time restraints, we want to make sure we have a safe toolpath that will get us the result we want (in terms of quality and cutting security), rather than pushing the thresholds and taking extra time to program the HEM toolpaths. HEM makes total sense for large production runs, but make sure you know when to, and when not to use these techniques to get the most out of HEM.

B&R Custom machining

Have you been using Machining Advisor Pro in your shop when you run Helical end mills?

We have been, and it makes for a great point of reference for the Helical end mills. It has become a part of our new employee training, teaching them about speeds and feeds, how hard they can push the Helical tools, and where the safe zones are. Our more experienced guys also frequent it for new situations where they have no data. Machining Advisor Pro helps to verify what we thought we knew, or helps us get the confidence to start planning for a new job.

If you could give one piece of advice to a new machinist, or someone looking to take the #PlungeIntoMachining for the first time, what would it be?

Learn the intimacies of metal cutting. Get ultra-familiar with the results of what is actually happening with your tool, your setup, your part, and your machine. As well, don’t be limited to thinking “it sounds good,” or “it’s going good so far, so that must be acceptable.” In order to push the tools and confirm they are performing well and making money, you need to identify and understand where the threshold of failure is, and back off the right amount. This doesn’t end here though. Cutting conditions change as the tools, holders, machines, and parts change. Learning the nuances of this fluctuating environment and adapting accordingly is essential. Verify your dimensions, mitigate against risk, and control the variables.

Also, get intimate with what causes tools to succeed and fail, and keep a log of it for reference. Develop a passion for cutting; don’t just punch in and punch out each shift. Here at B&R, we are looking for continuous improvement, and employees who can add value. Don’t stand around all day with your arms folded, but keep constant logs of what’s going on and always be learning and thinking of how to understand what is happening, and improve on it. That is what makes a great machinist, and a successful shop.

B&R custom machining

How To Maximize High Balance End Mills

High speed machining is becoming increasingly widespread in machine shops all over the world due to the proven benefits of greater efficiency and productivity through increased spindle speeds and metal removal rates.  However, at such high spindle speeds, otherwise negligible errors and imperfections can cause negative effects such as reduced tool life, poor surface finish, and wear on the machine itself. Many of these negative effects stem from an increase in total centrifugal forces leading to vibration, commonly referred to in the industry as chatter. A key contributor to vibrations and one of the more controllable factors, is tool unbalance.

Why Balance is Critical to Machining

Unbalance is the extent to which the tool’s center of mass diverges from its axis of rotation.  Small levels of unbalance may be indistinguishable at lower RPMs, but as centrifugal force increases, small variations in the tool’s center of mass can cause substantial detrimental effects on its performance. High Balance End Mills are often used to help solve the problem of vibrations at the increased spindle speeds. Balancing is used to make compensation for the intrinsic unsymmetrical distribution of mass, which is typically completed by removing mass of a calculated amount and orientation.

Image Source: Haimer; Fundamentals of Balancing

Helical Solutions offers High Balance End Mills in both 2 and 3 flute options (see Figure 2), square and corner radius, along with coolant-through on the 3 fluted tools. These end mills are balanced at the industry standard of G2.5 at 33,000 RPM: G stands for the potential damage due to unbalance, which can be expressed as “Balancing Quality Grade” or G and 2.5 is the vibration velocity in MM per second. These tools are designed specifically to increase performance in highly balanced machining centers that are capable of elevated RPMs and feed rates. With high balance tooling, improved surface finishes are also achieved due to reduced vibrations during the machining process. Additionally, these end mills have been designed around current high-end tool holding, and come in a variety of neck lengths at specific overall lengths. These dimensional combinations result in maximum rigidity and reduced excess stick out, allowing for optimal performance and the ability to push the tools to the limit.

High Balanced Tooling Cost Benefits

Machinists who choose to use High Balance End Mills will see certain benefits at the spindle, but also in their wallets. Cost benefits of opting to run this type of tool include:

Utilizing Tap Testers

What Tap Testers Do

Vibrations are your applications worst enemy, especially at elevated RPMs and feed rates. Using resources such as a Tap Tester can help decrease vibrations and allow you to get the most out of your High Balance End Mills by generating cutting performance predictions and chatter limits.

How Tap Testing Works

High balance

Image Source: Manufacturing Automation Laboratories Inc.

Tap Testing generates cutting performance predictions and chatter limits. In a tap test, the machine-tool structure is “excited,” or tested, by being hit with an impulse hammer. In milling, the machine-tool structure is usually flexible in all three directions: X, Y, and Z, but in milling applications where High Balance Tooling is used, the flexibility is commonly only considered in two planes – the X and Y directions. By hitting the X and Y directions with the impulse hammer, the impact will excite the structure over a certain frequency range that is dependent on the hammer’s size, the type of tool being used, and the structure itself. The frequencies generated from the initial hit will produce enough information that both the impact force measurement and the displacement/accelerometer measurement are available. Combining these two measurements will result in the Frequency Response Function, which is a plot of the dynamic stiffness of the structure in frequencies.

After the information from the Tap Test is gathered, it will then process the information into useful cutting parameters for all spindles speeds such as cut depths, speed rates, and feed rates. In knowing the optimum running parameters, vibrations can be minimized and the tool can be utilized to its full potential.

High Balanced Tooling Summarized

Keeping vibrations at bay during the machining process is extremely important to machining success. Because one cause of vibration is tool unbalance, utilizing a balanced tool will result in a smoother job, a cleaner final product, and a longer life of both the tool and spindle. Machinists who choose to use High Balance Tooling can utilize a Tap Tester, or a method for generating the perfect running parameters for your tool and machine setup to ensure that machining vibration is as minimal as possible.

Best Practices of Tolerance Stacking

Tolerance stacking, also known as tolerance stack-up, refers to the combination of various part dimension tolerances. After a tolerance is identified on the dimension of a part, it is important to test whether that tolerance would work with the tool’s tolerances: either the upper end or lower end. A part or assembly can be subject to inaccuracies when its tolerances are stacked up incorrectly.

The Importance of Tolerances

Tolerances directly influence the cost and performance of a product. Tighter tolerances make a machined part more difficult to manufacture and therefore often more expensive. With this in mind, it is important to find a balance between manufacturability of the part, its functionality, and its cost.

Tips for Successful Tolerance Stacking

Avoid Using Tolerances that are Unnecessarily Small

As stated above, tighter tolerances lead to a higher manufacturing cost as the part is more difficult to make. This higher cost is often due to the increased amount of scrapped parts that can occur when dimensions are found to be out of tolerance. The cost of high quality tool holders and tooling with tighter tolerances can also be an added expense.

Additionally, unnecessarily small tolerances will lead to longer manufacturing times, as more work goes in to ensure that the part meets strict criteria during machining, and after machining in the inspection process.

Be Careful Not to Over Dimension a Part

When an upper and lower tolerance is labeled on every feature of a part, over-dimensioning can become a problem. For example, a corner radius end mill with a right and left corner radii might have a tolerance of +/- .001”, and the flat between them has a .002” tolerance. In this case, the tolerance window for the cutter diameter would be +/- .004”, but is oftentimes miscalculated during part dimensioning. Further, placing a tolerance on this callout would cause it to be over dimensioned, and thus the reference dimension “REF” must be left to take the tolerance’s place.

stacking tolerances

Figure 1: Shape of slot created by a corner radius end mill

Utilize Statistical Tolerance Analysis:

Statistical analysis looks at the likelihood that all three tolerances would be below or above the dimensioned slot width, based on a standard deviation. This probability is represented by a normal probability density function, which can be seen in figure 2 below. By combining all the probabilities of the different parts and dimensions in a design, we can determine the probability that a part will have a problem, or fail altogether, based on the dimensions and tolerance of the parts. Generally this method of analysis is only used for assemblies with four or more tolerances.

stacking tolerances

                                                               Figure 2: Tolerance Stacking: Normal distribution

Before starting a statistical tolerance analysis, you must calculate or choose a tolerance distribution factor. The standard distribution is 3 . This means that most of the data (or in this case tolerances) will be within 3 standard deviations of the mean. The standard deviations of all the tolerances must be divided by this tolerance distribution factor to normalize them from a distribution of 3  to a distribution of 1 . Once this has been done, the root sum squared can be taken to find the standard deviation of the assembly.

Think of it like a cup of coffee being made with 3 different sized beans. In order to make a delicious cup of joe, you must first grind down all of the beans to the same size so they can be added to the coffee filter. In this case, the beans are the standard deviations, the grinder is the tolerance distribution factor, and the coffee filter is the root sum squared equation. This is necessary because some tolerances may have different distribution factors based on the tightness of the tolerance range.

The statistical analysis method is used if there is a requirement that the slot must be .500” wide with a +/- .003” tolerance, but there is no need for the radii (.125”) and the flat (.250”) to be exact as long as they fit within the slot. In this example, we have 3 bilateral tolerances with their standard deviations already available. Since they are bilateral, the standard deviation from the mean would simply be whatever the + or – tolerance value is. For the outside radii, this would be .001” and for the middle flat region this would be .002”.

For this example, let’s find the standard deviation (σ) of each section using equation 1. In this equation represents the standard deviation.

standard deviation

The standard assumption is that a part tolerance represents a +/- 3  normal distribution. Therefore, the distribution factor will be 3. Using equation 1 on the left section of figure 1, we find that its corrected standard deviation equates to:

tolerance stacking

This is then repeated for the middle and right sections:

standard deviation

After arriving at these standard deviations, we input the results into equation 2 to find the standard deviation of the tolerance zone. Equation 2 is known as the root sum squared equation.

root sum

At this point, it means that 68% of the slots will be within a +/- .0008” tolerance. Multiplying this tolerance by 2 will result in a 95% confidence window, where multiplying it by 3 will result in a 99% confidence window.

68% of the slots will be within +/- .0008”

95% of the slots will be within +/- .0016”

99% of the slots will be within +/- .0024”

These confidence windows are standard for a normal distributed set of data points. A standard normal distribution can be seen in Figure 2 above.

Statistical tolerance analysis should only be used for assemblies with greater than 4 toleranced parts. A lot of factors were unaccounted for in this simple analysis. This example was for 3 bilateral dimensions whose tolerances were representative of their standard deviations from their means. In standard statistical tolerance analysis, other variables come into play such as angles, runout, and parallelism, which require correction factors.

Use Worst Case Analysis:

Worst case analysis is the practice of adding up all the tolerances of a part to find the total part tolerance. When performing this type of analysis, each tolerance is set to its largest or smallest limit in its respective range. This total tolerance can then be compared to the performance limits of the part to make sure the assembly is designed properly. This is typically used for only 1 dimension (Only 1 plane, therefore no angles involved) and for assemblies with a small number of parts.

Worst case analysis can also be used when choosing the appropriate cutting tool for your job, as the tool’s tolerance can be added to the parts tolerance for a worst case scenario. Once this scenario is identified, the machinist or engineer can make the appropriate adjustments to keep the part within the dimensions specified on the print. It should be noted that the worst case scenario rarely ever occurs in actual production. While these analyses can be expensive for manufacturing, it provides peace of mind to machinists by guaranteeing that all assemblies will function properly. Often this method requires tight tolerances because the total stack up at maximum conditions is the primary feature used in design. Tighter tolerances intensify manufacturing costs due to the increased amount of scraping, production time for inspection, and cost of tooling used on these parts.

Example of worst case scenario in context to Figure 1:

Find the lower specification limit.

For the left corner radius

.125” – .001” = .124”

For the flat section

.250” – .002” = .248”

For the right corner radius

.125” – .001” = .124”

Add all of these together to the lower specification limit:

.124” + .248” + .124” = .496”

Find the upper specification limit:

For the left corner radius

.125” + .001” = .126”

For the flat section

.250” + .002” = .252”

For the right corner radius

.125” + .001” = .126”

Add all of these together to the lower specification limit:

.126” + .252” + .126” = .504”

Subtract the two and divide this answer by two to get the worst case tolerance:

(Upper Limit – Lower Limit)/2 = .004”

Therefore the worst case scenario of this slot is .500” +/- .004”.

Slaying Stainless Steel: Machining Guide

Stainless steel can be as common as Aluminum in many shops, especially when manufacturing parts for the aerospace and automotive industries. It is a fairly versatile material with many different alloys and grades which can accommodate a wide variety of applications. However, it is also one of the most difficult to machine. Stainless steels are notorious end mill assassins, so dialing in your speeds and feeds and selecting the proper tool is essential for machining success.

Material Properties

Stainless steels are high-alloy steels with superior corrosion resistance to carbon and low-alloy steels. This is largely due to their high chromium content, with most grades of stainless steel alloys containing at least 10% of the element.

Stainless steel can be broken out into one of five categories: Austenitic, Ferritic, Martensitic, Precipitation Hardened (PH), and Duplex. In each category, there is one basic, general purpose alloy. From there, small changes in composition are made to the base in order to create specific properties for various applications.

For reference, here are the properties of each of these groupings, as well as a few examples of the popular grades and their common uses.

Category Properties Popular Grades Common Uses
Austenitic Non-magnetic, outstanding corrosion and heat resistance. 304, 316 Food processing equipment, gutters, bolts, nuts, and other fasteners.
Ferritic Magnetic, lower corrosion and heat resistance than Austenitic. 430, 446 Automotive parts and kitchen appliances.
Martensitic Magnetic, moderate corrosion resistance – not for severe corrosion. 416, 420, 440 Knives, firearms, surgical instruments, and hand tools.
Precipitation Hardened (PH) Strongest grade, heat treatable, severe corrosion resistance. 17-4 PH, 15-5 PH Aerospace components.
Duplex Stronger mixture of both Austenitic and Ferritic. 244, 2304, 2507 Water treatment plants, pressure vessels.

Tool Selection

Choosing the correct tooling for your application is crucial when machining stainless steel. Roughing, finishing, slotting, and high efficiency milling toolpaths can all be optimized for stainless steel by choosing the correct style of end mill.

Traditional Roughing

For traditional roughing, a 4 or 5 flute end mill is recommended. 5 flute end mills will allow for higher feed rates than their 4 flute counterparts, but either style would work well for roughing applications. Below is an excellent example of traditional roughing in 17-4 Stainless Steel.

 

 

Slotting

For slotting in stainless steel, chip evacuation is going to be key. For this reason, 4 flute tools are the best choice because the lower flute count allows for more efficient chip evacuation. Tools with chipbreaker geometry also make for effective slotting in stainless steel, as the smaller chips are easier to evacuate from the cut.

stainless steel machining

Finishing

When finishing stainless steel parts, a high flute count and/or high helix is required for the best results. Finishing end mills for stainless steel will have a helix angle over 40 degrees, and a flute count of 5 or more. For more aggressive finishing toolpaths, flute count can range from 7 flutes to as high as 14. Below is a great example of a finishing run in 17-4 Stainless Steel.

 

High Efficiency Milling

High Efficiency Milling can be a very effective machining technique in stainless steels if the correct tools are selected. Chipbreaker roughers would make an excellent choice, in either 5 or 7 flute styles, while standard 5-7 flute, variable pitch end mills can also perform well in HEM toolpaths.

stainless steel

HEV-5

Helical Solutions offers the HEV-5 end mill, which is an extremely versatile tool for a variety of applications. The HEV-5 excels in finishing and HEM toolpaths, and also performs well above average in slotting and traditional roughing. Available in square, corner radius, and long reach styles, this well-rounded tool is an excellent choice to kickstart your tool crib and optimize it for stainless steel machining.

stainless steel machining

Running Parameters

While tool selection is a critical step to more effective machining, dialing in the proper running parameters is equally important. There are many factors that go into determining the running parameters for stainless steel machining, but there are some general guidelines to follow as a starting point.

Generally speaking, when machining stainless steels a SFM of between 100-350 is recommended, with a chip load ranging between .0005” for a 1/8” end mill up to .006” for a 1” end mill. A full breakdown of these general guidelines is available here.

Machining Advisor Pro

Machining Advisor Pro is a cutting edge resource designed to precisely calculate running parameters for high performance Helical Solutions end mills in materials like stainless steel, aluminum, and much more. Simply input your tool, your exact material grade, and machine setup and Machining Advisor Pro will generate fully customizable running parameters. This free resource allows you to push your tools harder, faster, and smarter to truly dominate the competition.

In Conclusion

Stainless steel machining doesn’t have to be hard. By identifying the proper material grade for each part, selecting the perfect cutting tool, and optimizing running parameters, stainless steel machining headaches can be a thing of the past.

Attacking Aluminum: A Machining Guide

Aluminum is one of the most commonly machined materials, as most forms of the material feature excellent machinability, and is thus a commonly used material in manufacturing. Because of this, the competition for aluminum machining can be intense. Understanding the basics behind tool selection, running parameters, and advanced milling techniques for aluminum can help machinists earn a competitive advantage.

Material Properties

Aluminum is a highly formable, workable, lightweight material. Parts made from this material can be found in nearly every industry. Additionally, Aluminum has become a popular choice for prototypes due to its low-cost and flexibility.

Aluminum is available in two basic forms: Cast and Wrought. Wrought Aluminum is typically stronger, more expensive, and contains a lower percentage of outside elements in its alloys. Wrought Aluminum is also more heat-resistant than Cast and has a higher level of machinability.

Cast Aluminum has less tensile strength but with a higher flexibility. It costs less, and has higher percentages of outside elements (silicon, magnesium, etc.) in its alloys, making it more abrasive than Wrought.

Tool Geometry

There are a few coating options available for Aluminum tooling, including the popular gold-colored ZrN (Zirconium Nitride) and the lesser known but highly effective TiB2 (Titanium Diboride). Uncoated tooling can also provide solid machining performance. However, the real key to high performance machining in Aluminum is knowing the proper flute count and helix angle required for your operation.

Flute Count

End mills for aluminum are often available in either 2 flute or 3 flute styles. With higher flute counts, it would become difficult to evacuate chips effectively at the high speeds at which you can run in aluminum. This is because aluminum alloys leave a large chip, and chip valleys become smaller with each additional flute on an end mill.

flute count for aluminum

Traditionally, 2 flute end mills have been the preferred choice for Aluminum. However, 3 flute end mills have proven to be more successful in many finishing operations, and with the right parameters they can also work successfully as roughers. While much of the debate between 2 and 3 flute end mills for Aluminum boils down to personal preference, the operation, rigidity, and desired material removal rates can also have an effect on tool selection.

Helix Angles

The helix angle of a tool is measured by the angle formed between the centerline of the tool and a straight line tangent along the cutting edge. Cutting tools for aluminum typically feature higher helix angles than standard end mills. Specialized helix angles for Aluminum are typically either 35°, 40°, or 45°. Variable helix tools are also available and make a great choice for reducing chatter and harmonics while also increasing material removal rates.

Aluminum Machining

A helix angle of 35° or 40° is a good choice for traditional roughing and slotting applications. A 45° helix angle is the preferred choice for finishing, but also for High Efficiency Milling toolpaths as the high helix angle wraps around the tool faster and makes for a more aggressive cut.

Tooling Options

When machining aluminum, standard 2 or 3 flute tools will often get the job done. However, for certain applications and machine setups there are some more tooling options to consider for even better performance.

Chipbreaker Tooling

One of the most important things to consider when machining aluminum (and many other materials) is effective chip evacuation. Standard 2-3 flute end mills running at recommended speeds and feeds and proper chip loads can evacuate chips fairly well. However, 3 flute chipbreaker tooling can run at increased speed and feed rates for even better performance. The unique offset chip breaker geometry creates smaller chips for optimal evacuation while still leaving a semi-finished surface.

Chipbreaker Aluminum

These tools are excellent for more advanced toolpaths like High Efficiency Milling, which is another important tool for a successful aluminum machining experience.

High Balance End Mills

High balance end mills are designed to significantly increase performance in highly balanced machining centers capable of elevated RPMs and feed rates. These tools are precision balanced specifically for high velocity machining in aluminum (up to 33,000 RPM).

High Balance Tools for Aluminum

Helical Solutions offers high balance tooling in standard 2 flute styles, as well as coolant-through 3 flute styles for reduced heat, enhanced chip evacuation, and increased material removal rates. These tools, like the chipbreakers, are also an excellent choice for High Efficiency Milling toolpaths.

Running Parameters

Setting the right parameters for aluminum applications is vital to optimizing productivity and achieving better machining results. Since aluminum is an easier material to machine, pushing your machine to its limits and getting the most out of your tool is vital to stay ahead of the competition and keep winning business.

While there are many factors that go into the parameters for every job, there are some general guidelines to follow when machining aluminum. For cast aluminum alloys (i.e. 308, 356, 380), a surface footage of 500-1000 SFM is recommended, with RPMs varying based on cutter diameter. The basic calculation to find a starting point for RPMs would be (3.82 x SFM) / Diameter.

In wrought aluminum alloys (i.e. 2024, 6061, 7075), a surface footage of 800-1500 SFM is recommended, with the same calculation being used to find a starting point for RPMs.

High Efficiency Milling

High Efficiency Milling, commonly known as HEM, is a strategy that is rapidly gaining popularity in the manufacturing industry. Many CAM programs are now including HEM toolpaths, and while virtually any machine can perform HEM, the CNC controller must feature a fast processor to keep up with the additional lines of code. A great example of High Efficiency Milling toolpaths in Aluminum can be seen below.

At its core, HEM is a roughing technique that utilizes a low Radial Depth of Cut (RDOC) and a high Axial Depth of Cut (ADOC) to take full advantage of the cutting edge of the tool. To learn more about how High Efficiency Milling can increase your efficiency, extend your tool life to keep costs down, and get greater performance for aluminum (and other materials), click here to download the HEM Guidebook.

In Summary

Aluminum is a versatile material with a high level of machinability, but it should not be overlooked. Understanding the best ways to tackle it is important for achieving the desired results. Optimizing your tool crib, machine setups, and toolpaths for aluminum is essential to stay ahead of the competition and make your shop more efficient.

TL Technologies – Featured Customer

TL Technologies helps manufacturers reduce time to market and drive down per-piece cost with their unique “Intelligent Design and Planning” processes. Located in Lancaster, Pennsylvania, TL Technologies serves manufacturers throughout the mid-Atlantic from their centrally located, 10,000 sq. ft. facility. Their unique manufacturing processes and services quickly made them stand out in the industry since their inception in 2012.

Jonathon Thompson is the Vice President of Engineering at TL Technologies. Jonathon talked with us about their rigorous manufacturing and inspection processes, the advantage of using high-quality tooling, their unique on-site assembly services, and much more in this Featured Customer interview.

Tell us a bit about your shop, how you got started, and what sort of products you manufacture.

TL Technologies got started in January 2012. Our first customers were firearms and defense based. Since then we have diversified our business through growth within customers and word of mouth. We started with the intent to be precise and accurate in a lights-out or nearly automated fashion.

What sort of machines do you use in your shop?

We use an array of modern equipment. 4 axis Kitamura HX400G Horizontal Mills. Nakamura Tome 9 axis Turn Mill, Star 6 axis, and two 5 axis vertical Hurco Machines. All our machines are optioned out with Renishaw probing and all the bells and whistles required to handle high accuracy runs for 24 hours a day with no process issues. Most of the machines have glass scales and thermal packages.

kitamura cnc machine

Which materials do you most often work with at your shop?

Mostly steels; the usual 4000 and 8000 series steels. Comparatively less 6061 and 7075 aluminum and other common stainless grades. We’ve been fortunate to have many of our materials within a reasonable range of Rockwell so that we may tool accordingly for most of the business.

How has your experience been with multi-axis machining?

Fantastic. Multi axis Machining has been excellent for us. It requires high-level understanding to fully maximize but the benefits are huge.

On your website, you mention that TL Technologies has never delivered a rejected part. What sets your quality apart from the competition?

From day one and job one, we worked with the customer to understand exactly how they were measuring the parts, exactly with what tools, processes, and methods to identically duplicate the process in our shop. After replicating key processes we performed many correlation studies to ensure that our measurements were within single-digit microns of what our customers were seeing on their end during inspection. This methodology was scaled up into our overall quality program and allows us to greater understand and manufacture our goods. Our ISO process coupled with this method truly does prevent bad work from getting out. We have never had a case where a part did not function or perform due to our oversight or bad specs. There have been failures on the customer side of things due to engineering, bad prints, and tolerance stackups, but we have not supplied parts that were flat out incorrect.

TL Technologies

What sort of tolerances do you work in on a daily basis?

Typically single or double-digit microns. .0002” to .003” total is common for a large percentage of specs. It is not unusual for +/-.0002” to run long-term over many fixture stations with no manual adjustment. Our machined products are from 1” to 8” cubed.

What are some of the coolest projects you have had come through the shop?

That’s a good question. TL Technologies sat on the United States Senate committee in 2013 for Small Business and Entrepreneurship. We were featured on the cover of New York Times business section in 2013 as well. Throughout our years we’ve been fortunate to meet many amazing people from high branches in the government, the US Military, top name manufacturers, lenders, and local municipalities. Some of the coolest contacts were folks that formerly operated with US Special Forces. Unfortunately, we cannot comment.

As for projects not covered by an NDA, one of my personal favorites was producing low impact physical therapy products for rehabilitating shoulders after surgery. Though simple in manufacturing, this project provided an array of fun challenges that required high performance tooling, 3D printing, and using our machines with custom cycles. This allowed us to use the equipment very unconventionally. In this way, we were able to provide a cost-effective product utilizing the maximum ability of our equipment with a very short lead-time and low up-front cost.

harvey tool catalog

You also offer assembly services on-site, which is fairly unique in the industry. Can you talk a little bit more about this?

Sure. Both my business partner and I have tremendous experience with assemblies in both hands-on and directorial roles. Whether it was a high precision multi-axis mechanism that ended up being a custom machine, on and off-road vehicles, or even things like child safety seats, we have had our hands in a lot of things over the years. At TL Technologies we’ve provided assistance to machine tool builders, special tooling designers, consumer goods of various types, and most frequently to firearms builders. Mostly we drive out cost, but as we age we’ve been called upon to troubleshoot high-end assemblies where the issues were not immediately apparent. This led to us creating sub-assemblies and even semi-finished OEM products. This includes hand fitting and assembling collectible pistols and precision bolt action rifles. This is usually offered as a temporary solution or process engineering service to larger companies developing new goods or revamping existing ones, and is offered as part of our comprehensive knowledge to attract clients. It has been very successful.

You service a variety of industries, including defense, automotive, agricultural equipment, and consumer products. Do you have a personal favorite?

I’d have to say the products we make that almost every soldier carries and relies on are my favorite. We take great pride in knowing that these parts have not failed due to machining error since we took over the production years ago on the core components.

TL Technologies

Why is American manufacturing important to you?

It’s everything. It’s the heart and soul of all products and by extension facilitates the means with which goods and services exist in our society. By bolstering the skills, knowledge, and experience, we can not only succeed economically but also further the craft and pride of making quality goods. We will always need to be able to make our own goods. The skill and craft to create is more than just economic. We absolutely must embrace and respect the skill and hard work it takes to create. We must pass that knowledge on for posterity so the next generation might find the satisfaction and pride of skilled work.

Why is high-quality tool performance important to you?

It’s everything. The old adage, “Garbage in, garbage out,” is accurate for us. We feel that if we invested so much in these high-end machining centers, it would be criminal to put insufficient tooling and holders into them. We found that by selecting the proper tool with the appropriate sciences behind it we have been able to create products with a cost per cut that is not only competitive, but required to stay current. By keeping the quality as high as possible on the part making side of things, we’ve insured as much ease and reliability into our downstream process as we could. Quality tooling also provides predictability and added safety into the workflow. High-quality carbide tooling is the lifeblood of the business.

Have Harvey Tools had an impact on your performance?

Oh man…frequently. Harvey Tools are a mainstay in our company. If I had to think of some key examples it would have to be your variety of Keyseat Cutters, 3 Flute Counterbores, Extended Reach Ball End Mills, and Miniature End Mills under .040”. The 270 degree Lollipop Cutters are excellent for deburring, and we also rely on the 140° spot drills, corner radius forming tools, and more. In short, not only are the tools good, but they provide exactly what we need and the specifications to handle major OEM jobs. We absolutely love metric and you’ve got that too. Your catalogs help us eliminate the need for customs. That is key to cost and lead time.

harvey tool

 

If you could give one piece of advice to a new machinist ready to take the #PlungeIntoMachining, what would it be?

Embrace the old knowledge and techniques. The manual skills learned with files and hand ground tools translate critically into the concepts you will need to master if CNC becomes your career. Understand how and why materials cut or refuse to cut, what rake angle to use and when, and how to leverage machine physics to help you work smarter instead of harder. Don’t be afraid to jump down the rabbit hole of engineering concepts, materials, physics, elementary chemistry; these all help give you an edge. Machining is done best with comprehensive knowledge of the machines and machining environment. You never stop learning. All that said, keep a fresh perspective. Old knowledge can be great, but operationally each business will likely have its own methods and flow. Try to understand there is more to the overall business picture than you can often see.

Is there anything else you would like to share with the In The Loupe community?

Oh definitely! Buy our stuff!! Ha. We are a supplier of choice for OEM, and small batch bolt actions for rifles, pistol components, and pistol slides. We machine to spec and provide cost-competitive options as well as super-premium options.  We are working now to release our own line of aftermarket products in 2018, so keep an eye out for those!

TL Technologies


Would you like to be considered for a future “Featured Customer” blog? Click here to submit your information.

5 Ways Your Shop is Inefficient

5 Ways Your Shop is Inefficient

In today’s ultracompetitive industry, every machine shop seeks even the slightest edge to gain an advantage on their competition and boost their bottom line. However, what many machinists don’t know is that improving their shop’s efficiency might be easier than they thought. The following five ways your shop is inefficient will provide a clear starting point of where to look for machinists desperate to earn a competitive edge.

1. Premature Tool Decay / Tool Failure

If you’re finding that your tools are failing or breaking at an unacceptable rate, don’t mistake it for commonplace. It doesn’t have to be. Prolonging the life of your tooling starts with finding not just the right tool, but the best one; as well as running it in a way to get its optimal performance. Many machinists mistake premature tool failure with running parameters that were too aggressive. In fact, not pushing the tool to its full potential can actually cause it to decay at an accelerated rate in certain situations.

Tool failure can occur in many different ways: Abrasive Wear, Chipping, Thermal Cracking or Tool Fracture, just to name a few. Understanding each type and its causes can help you to quickly boost your shop’s efficiency by minimizing downtime and saving on replacement tool costs.

tool wear

An example of a tool with excessive wear

For more information on tool wear, view Avoiding 4 Major Types of Tool Wear.

2. Subpar Part Finish

Your shop spends money to employ machinists, run machines, and buy cutting tools. Get your money’s worth, lead the industry, and ensure that you’re providing your customers with the highest quality product. Not only will this help to keep your buyer-seller relationship strong, but it will allow you the flexibility to increase your prices in the future, and will attract prospective customers.

Many factors influence part finish, including the material and its hardness, the speeds and feeds you’re running your tool at, tool deflection, and the tool-to-workpiece orientation.

For more information on ways to improve your part finish, view our Part Finish Reference Guide.

3. Inefficient Coolant Usage

One often forgotten expense of a machine shop is coolant – and it can be pricey. A 55-gallon drum of coolant can run more than $1,500. What’s worse is that coolant is often applied in excess of what’s required for the job. In fact, some machines even feature a Minimum Quantity Lubricant (MQL) functionality, which applies coolant as an extremely fine mist or aerosol, providing just enough coolant to perform a given operation effectively. While drowning a workpiece in coolant, known as a “Flood Coolant,” is sometimes needed, it is oftentimes utilized on jobs that would suffice with much less.

For more information about coolants and which method of application might be best for your job, view What You Need to Know About Coolant for CNC Machining.

4. Not Taking Advantage of Tool Versatility

Did you know that several CNC cutting tools can perform multiple operations? For example, a Chamfer Mill can chamfer, bevel, deburr, and countersink. Some Chamfer Mills can even be used as a Spotting Drill. Of course, the complexity of the job will dictate your ability to reap the benefits of a tool’s versatility. For instance, a Spotting Drill is obviously the best option for spotting a hole. If performing a simple operation, though, don’t go out of your way to buy additional tooling when what’s already in your carousel can handle it.

chamfer mills

To learn more about versatile tools that can perform multiple applications, check out Multi-Functional Tools Every Shop Should Have.

5. High Machine Downtime

What use is a machine that’s not running? Minimizing machine downtime is a key way to ensure that your shop is reaching its efficiency pinnacle. This can be accomplished a variety of ways, including keeping like-parts together. This allows for a simple swap-in, swap-out of material to be machined by the same cutting tool. This saves valuable time swapping out tooling, and lets your machine to do its job for more time per workday. Production planning is a key factor to running an efficient machine shop.