Machine Shop Math – Common Formulas and Strategies

Machine shop math blog detailing feeds, speeds and formulas associated with CNC machining and milling machines.

One of the more common problems I have seen in my years in the machine shop is a general lack of readily available and handy information on machine shop math – specifically on feeds, speeds and related formulae.

Machine shop math for feeds, speeds and other important aspects of CNC machining and milling applications.
Machine shop math is an important consideration for CNC programmers and machinists.

Whether you are programming a 5-axis CNC machine or turning handles on a 60 year old knee mill the numbers don’t lie.  However, one very important lesson I have learned is to respect the variables.  Any common formula you are going to use in the machine shop will provide you with the information you need to approach the cut appropriately but remember to always treat that number as a starting point.  There are an immeasurable number of variables with any cut, all the way down to the atmospheric conditions in the shop.  Tooling manufacturers will provide you with suggested numbers whether it be surface feet per minute, chip load per tooth, revolutions per minute, inches per minute or any combination of those and more.  It can all get very confusing and overwhelming but don’t quit on me now.  I am hoping this post can serve as go-to information for you and your shop, and hopefully I can make some sense of it for you.

Machine shop math formula for RPM, SFPM, Feed Rate and Chip Load per Tooth to help machinists and operators of CNC milling machines.
Machine shop math formula for SFPM, RPM, Feed Rate and Chip Load per Tooth.

As you can see in the above formulae in order to calculate any of these you need to already know some of the other data to input.  This is where the tooling manufacturers come in.  They can provide information to you for their specific tools and applications.  However there is some basic information based on the material you are cutting that I will provide to you right now.  Keep in mind that these are starting points, the best judge will be your eyes and ears.  The following is a list of suggested SFPM for common materials:

Machine Shop Math – SFPM for Common Materials:

Surface feet per minute parameters associated with particular millable materials.
Surface Feet Per Minute (SFM) parameters based on material.

So let’s say we are using a .500” solid carbide end mill cutting aluminum.  Looking at our chart the suggested SFPM is 800.  In order to determine our suggested RPM we use the above formula SFPM x 3.82 / Tool Diameter:

Machine shop math formula for calculating revolutions per minute (RPM) can be used by CNC machine programmers and machining center operators.
Machine shop math to calculate RPM (revolutions per minute).

I will give you another example, this time with a significantly smaller tool.  We are going to use the same material but this time with a .125” solid carbide end mill.

In machine shop math SFPM or surface feet per minute can be calculated using this formula.
In machine shop math SFPM is surface feet per minute and can be calculated with this formula .

You can clearly see where the tool diameter drastically changes the suggested parameters, and where a high RPM spindle is a valuable factor.  This table can be used for these common materials however the manufacturer of the tools you choose will most likely have specific information on the tools you purchased which should always be used when available.

Are you still with me?  I know, you feel like you are in high school algebra again.  All of these numbers will make more sense when you start applying them to jobs in YOUR shop on YOUR machine, until then stick with me!  I promise it will be worth your time.  We are going to move on to Inches per Minute.  If you reference the formula above Feed Rate (inches per minute) = RPM x Chip Load per Tooth x Number of Flutes you see that in order to calculate this you need tool information.  Chip Load per Tooth is the amount of material a tooth, or flute, of the tool is removing in one revolution.  Most tooling manufacturers have suggested chip load information available, but you can also use your own knowledge and expertise to make a suggestion.

In this example we are going to be using a .500” solid carbide end mill with three flutes to cut aluminum.  Since we already know from the first example that the suggested RPM is 6,112 all we need is the chip load per tooth.  The manufacturer suggests .005” per tooth chip load on this tool, so we have all of the information we need to calculate our feed rate.

Machine shop math inches per minute formula used by CNC machine programmers and operators.
Machine shop math inches per minute formula.

See?  That is not as confusing as it looked.  However, here is where some of variables come into play.  Serious consideration needs to be made for the type of cut you are performing.  If you are milling a slot with full tool engagement then you need to be more conservative.  However, if you are utilizing a dynamic strategy (as discussed in another blog post) then you could potentially be more aggressive.  As I stated in the beginning, these numbers are starting points.

Finally, we will discuss how to calculate Chip Load per Tooth.  This is a useful formula for both preparing for a cut or programming and analyzing an existing cut.  You can easily look at your program while trying to optimize either surface finish, cycle time, or tool life and this will be a good indicator of proper tool utilization.  Let’s say we were running that last example at 4,000 RPM instead of the suggested 6,112.  We also ran it at 120 IPM rather than 91.68 IPM.  Our results weren’t great and Quality Control wants answers… NOW!  I know!  Let’s check the numbers!

Machine_Shop_Math_Chip_Load

This is double the manufacturers suggestion, therefore a very good place to start looking for problems.  Using the formula that you have now mastered, you know that you either need to bring your feed rate down or your RPM up to meet the requirements.

Now that you are armed with a basic understanding of these formulae and the knowledge that NONE of this is set in stone, you are ready to start applying it to your everyday work.  You will be amazed how quickly you won’t need to reference any charts or websites to be confident in your numbers and the job of programming a very expensive CNC machine will become a little less stressful.

If you want to put these formulas to work using the best cutting tools of the market, just download the DATRON Cutting Tools Catalog by filling out the following form.

Download Cutting Tool Catalog:

Halftone Engraving on a CNC Machine

Halftone engraving of a DATRON M8Cube high speed milling machine that is actually made on the M8Cube milling machine.

When you get to work with a DATRON every day, you get to see some pretty cool things. There are so many cool things to observe, or be involved in, that you can become a little numb to just how cool these things are. So, every once in a while, it’s good to stop and look back at what you’ve been doing and take a second to appreciate it. In this case, it’s halftone engraving.

I thought this might be a unique topic to share with you, the reader, so you too can enjoy the cool things you can do with your CNC machine (hopefully a DATRON!).

What is a Halftone?

First, a little background on our subject. A halftone image, according to Wikipedia, is “the reprographic technique that simulates continuous tone imagery through the use of dots, varying either in size or in spacing, thus generating a gradient like effect.”

Halftone engraving is the simulation of a continuous tone image using dots that vary in size or distance.
Halftone engraving is a reprographic technique simulating a continuous tone image.

Essentially, the trick behind a halftone image is to use varying size dots to create a grey scale image. It’s comparable to some comic book printing or pointillism, but is a bit unique.

Halftone engraving using different size dots milled into the surface of blue sheet material (with a silver surface finish) to create a grayscale.
Halftone engraving on blue sheet material with a silver surface finish requires milling varying size dots to create a grayscale image.

Halftone Engraving Software (Free)

Now, let me introduce you to Halftoner, a free application created by Jason Dorie. It allows you to easily import any image and not only convert to a halftone image, but also apply a tool path to it at the same time. The elegance of this software comes from its simplicity; first, import an image and choose your values for minimum and maximum dot size, dot spacing, dot offset, etc… Then determine your milling values; retract height, minimum depth, feed rate, RPM, and so on. One of the most important values for Halftoner is the tool angle, since it will take the included angle of your tool to determine the necessary depth to make a certain size of dot. It’s really quite intuitive.

Once that’s all done, click “Write GCode” and voila, you’ve got a program ready to go.

Engraving halftone images with a DATRON high speed machining center and a free application called Halftoner.
Engraving halftone images with a high speed CNC milling machine can be done easily with a free application called Halftoner.

I was fortunate enough to get to play with this for a while on a recent project, and the outcome you get for a minimal amount of effort can be very impressive.

Engraving halftone graphics on an engraving machine requires the engraving of different sized dots that reproduce a graphic by simulating a continuous tone image.
Engraving halftone images is quick and fun using a high speed milling and engraving machine like the DATRON M8Cube.

Want more info on engraving? – Download Engraving Brochure

Hard Milling on CNC Machine

Hard milling of 63 Rockwell steel on a DATROn high speed CNC milling machine

The mention of hard milling is usually enough to give the average machinist/programmer anxiety.  Well save your Xanax friends, because hard milling is not as scary as you think.

There are many factors involved with successful hard milling and I am going to touch on them today.  My hope is that you will take the information I give you today and go learn even more.  The best thing you can do in approaching any hardened steel is educate yourself before you cut a single chip.

Hard milling steel like this 63 Rockwell 6,000 RPM, 100 inches per minute at .012 per pass (ramping)
Hard milling steel – 63 Rockwell, 6,000 RPM, 100 inches per minute at .012 per pass (ramping).

The first and probably most important consideration in hard milling is the construction of your machine.  In order to achieve ideal results with hard milling you need an extremely rigid machine that has a high degree of dampening ability.

Hard milling CNC milling machines require rigidity that can be provided by a machining table made of granite or concrete polymer.
Hard milling CNC machines require rigidity provided by polymer concrete or granite machining beds and cast steel construction.

Generally, machines constructed with polymer concrete have many times the dampening ability as machines made with cast iron. It is also important to have a CNC control that will handle the dynamic requirements of the constant and rapid acceleration and deceleration.

Hard milling machine with a solid granite machining table provides the rigidity needed for milling hardened steel.
The thick solid granite machining table on the DATRON M10 Pro makes it a rigid hard milling machine.

Next on the list is the spindle and tool holding.  Two very different things, but if one is off the other won’t matter much. You need a rigid spindle capable of high RPM with very little runout.  If your spindle has runout then the most concentric and true tool holder in the world will only help you so much.  That being said, combining a great high speed spindle with the best tool holders will yield results you never thought possible.  HSK series tool holders are probably one of the most popular in terms of hard milling because the interface with the spindle promotes great rigidity and concentricity.

Hard milling spindle and HSK tool holders exhibit both rigidity and low runout for superior results in machining hardened steel.
Hard milling spindle and tool holders should be selected based on rigidity and low runout. We’ve found the HSK tool holding system to be extremely effective.

Of course we cannot forget tooling itself.  If you do a little research you will find there are many tooling manufacturers who make application specific tooling for hard milling.  I tell my kids all the time that I know everything, unfortunately I don’t think you are quite so gullible. The majority of these tooling manufacturers have experts who can assist you in selecting the tool for the material and specific cut you are making, and I suggest utilizing those services.  The cutting tools you choose for your hard milling applications will need to be coated to stand up to the high heat and extremely high abrasive forces involved with these materials, so take your time and learn something.

Also, the tools will most likely not be cheap, so don’t be caught off guard.  DO YOUR RESEARCH!  If you bring a purchase request to your boss and he chokes on his coffee because the end mills you are buying cost so much, you will be able to throw so many big words at him to justify the purchase that he will have no choice but to sign it.  Also, if you need two make sure you request four.  That way when he authorizes the purchase of only two he feels he saved the company money and he can puff out his chest while you get what you wanted in the first place.  Tried and true techniques, this isn’t my first rodeo.

Hard milling tools including the 8mm 4 flute end mill, 0.5mm edge radius with x.ceed coating from DATRON perform extremely well and last longer
Hard Milling Tools like this DATRON 8mm 4 flute end mill, 0.5mm edge radius with x.ceed coating exhibit superior performance and extended durability.

OK, back to business.  The final piece of the puzzle (not really, the puzzle never ends…) is the CAD/CAM software.  One of the most important considerations in hard milling is a programming software that can control the load placed on the tool.  You want a constant load on your cutting tool without spiking, which means trochoidal milling is in order, or as I usually call it, dynamic strategies.  The principle behind dynamic milling in relation to hard milling is the light, constant engagement of your tool into the material.  No sharp plunges, smooth constant force.  Most of the major CAD/CAM packages out there now have some form of dynamic milling.  For more specifics on dynamic strategies see my recent blog post on the subject.

Hard milling program developed with the appropriate CAD/CAM software for the effective machining of hardened steel
Blog author, Kevin Mulhern, the qualities in CAD/CAM software required for an effective a hard milling program.

 

As with anything you do in the machine shop, or garage, or anywhere else you are using these tools and strategies, KNOWLEDGE IS POWER.  Research, study, ask the old guys, google it – whatever you have to do, the name of the game is learning. The more you know heading into a challenge the easier it will be to overcome it.  Good luck in your first steps into the world of hard milling- it will open your eyes.

Need Tools for Hard Milling? – Download Tool Catalog

6 Easy Ways to Optimize CNC Program

Optimize CNC Program with tips and directions provided by DATRON Applications Engineer Dann Demazure in this blog.

“Optimize CNC Program” – it’s the instruction you hear in your head when you’ve finished a machining program. And it can be an arduous process that, if you’re like me, you slave over. Typically a bit too much, wasting a lot of time on changes that don’t add up to a substantial improvement. As we all know, time is money, so, I’ll try to relieve you of some of the labor of revamping your program. Here’s a list of quick, easy, and effective tweaks for your DATRON programs.

Optimize CNC program tips and detailed instructions in this blog by Dann Demazure from DATRON Dynamics.
Blog Author and DATRON Applications Engineer, Dann Demazure, optimizing a CNC milling program.

 

Optimize CNC Program Tip 1 –  Leave the coolant on

It may not sound like much, but this gain can really add up. If you’re using coolant in your program, consider switching it from the Positioning/Cutting feed setting from Cutting <0>, to Travers<1>. You may not easily perceive it, but there is a very brief dwell programmed into the software so that the coolant has time to begin spraying. This change in the command will leave your coolant spraying between positioning movements, thus avoiding the initial dwell. Now, each dwell may only last 1/10th of a second, but if you have 200 retracts in your program, you just shaved 20 seconds of your program, and that’s not nothing.

Optimize CNC program by leaving the coolant running during positioning movements to avoid the initial dwell.
Optimize CNC program by leaving the coolant spraying during positioning movements.

 

Optimize CNC Program Tip 2 – Ramp

If you’re cutting along a contour, consider changing your method. If you are currently doing depth cuts, try a ramp instead. A ramp keeps the tool engaged in your desired amount of material throughout (except for the very beginning and the very end), and has no retracts. Let’s say again that your part has 200 retracts cutting contours on 20 different features (10 retracts per feature). By ramping, you’d bring that number down from 200 to 20 (final retract), and if each retract takes half a second, you just saved 90 seconds.

Optimize CNC Program Tip 3 – Be smooth

If the devil is in the details, then small contours are your devil. If you’re doing intricate engraving or 3D contouring, then you’ve probably noticed that the machine will slow down to follow all contours tightly. It’s just following orders, but if you have a little leniency in your adhesion to contours, Smoothing can make a huge difference.

Optimize CNC program with smoothing functions to clean up jagged geometry for a tighter milling path.
Optimize CNC programs using Smoothing functions like PerfectCut to smooth jagged geometry. See the results in red above.

 

Smoothing will take jagged geometry, like what is pictured above (purple), and apply arcs to the contour to create a smooth, more continuous motion (red). Not only does this have benefits for surface finish, but since the machine doesn’t need to slow down nearly as much in an arc as compared to a vector, time savings can be abundant. And utilizing it is as easy as writing the code in your macro, editing the preset values (which work well for most things), and pressing the “Go” button.

Optimize CNC Program Tip 4 – Be dynamic

I’ve talked about dynamics at length before and all the benefits from using them to fine tune a process for speed optimization and ideal surface finish, so why am I mentioning them again? Easy, besides the fact the dynamics settings are one of the easiest ways to reel in cycle time, adjusting them in conjunction with smoothing yields even better results. A high dynamics setting combined with a smoothing filter means that a very minimal amount of deceleration is needed to turn a corner quickly, thus cutting your cycle time even further.

Optimize CNC Program Tip 5 – Get low

This is usually a gimme, but it takes about 10 seconds of your time to change your retract heights from 0.5”, to 0.050” (or lower). Minimizing your retract height won’t save you much time per retract, but think of the big picture. Even if you only saved 5 seconds per part, if you’re making 20,000 parts per year, you just saved over a day of machine time. Every second counts.

Optimize CNC Program Tip 6 – Keep your tools in order

It seems obvious, but try to keep your operations organized so that when a particular tool is done, it never gets used again in the program. Sometimes this is unavoidable, but each tool change will cost you somewhere around 15 seconds of time. Consider using combination tools to cut down on tool changes. Most importantly, if you have parts nested, use tools sequentially rather than by part. If you have to cut 24 parts, and each part uses 4 tools, you’ll either spend 24 minutes changing tools again and again, or 1 minute changing all the tools once.

If you’d like more information on the PerfectCut Smoothing mentioned in Tip 3, Download the Data Sheet by filling out the form below:

Download Optimizing CNC Program Smoothing Tip #3 Data Sheet

Machine Shop Career: Where Do You Start?

A machine shop career can offer a breadth of experience with diverse projects and processes.

There are very few things that you can look at today that has not passed through a machine shop on some level.  Therefore, a machine shop career can be both interesting and rewarding. 

A machine shop career can bring on projects as diverse as F18 ejector seats and swizzle stick molds.
Just a few of the parts that may present themselves in the span of a machine shop career. Can you spot the F18 ejector seat part, the knife handles or the swizzle stick mold?

Answers:  F18 Ejector Seat  |  Knife Handles  |  Swizzle Stick Mold

I am sitting in a hotel room right now so let’s look at some examples.  This laptop, my cell phone, the remote for the TV, the TV itself that’s allowing me to watch Monday Night Football right now, the microwave, the trash barrel – all of these things have parts that are molded.  All of these molds require machining. The desk chair that I am sitting in right now has machined parts.  The rental car out in the lot has too many machined parts to name.  The knobs on the bureau, the lamps, the alarm clock.  OK, you get the point.  In my machine shop career I have worked for two tool and die shops that made molds for plastic injection molding; I worked in a maintenance machine shop for a power company that machined 8’ diameter pump housings and 27’ long pump shafts along with map brackets and any other parts the field techs needed; I worked for a company making parts for benchtop educational milling machines;  I worked for a machine shop that machined nothing but man-made sapphire (interesting stuff by the way);  I worked for a company that produced bridge and communications systems for the U.S. Navy, and I worked in a machine shop that made parts for commercial printers.  I also did a short stint in a standard job shop.  I know, I know you get the point.  I just love talking about myself.  My point is that no matter what your interests are you can find a shop that takes part in the finished product.  There are so many different machine shop career paths available to anybody willing to get their hands dirty and deal with a sliver or two.

A machine shop career lead Kevin Mulhern to DATRON Dynamics where he now works as an application Engineer
Kevin Mulhern’s machine shop career lead him to a position as an Application Engineer for DATRON Dynamics where he helps some of the world’s greatest manufacturers optimize their machining processes.

Machine Shop Career – How to Choose Your Path

My first piece of advice is HOLD YOUR HORSES!  No matter what path you want to take and no matter what vision you have of your machine shop career do yourself (and your future coworkers) a favor and start with the basics.  I will be writing another blog in the near future that will explain some of the basic things you will see and experience in the machine shop.  So at the very least when you walk out there with your clean hands, nicely ironed khakis and goofy looking safety glasses you can hold an intelligent conversation with the old barnacle behind the engine lathe.  Your first stop on the path to your machine shop career should be one of two places – a machine shop program at a technical college or an entry-level job in a machine shop that is willing to teach you the trade.  As soon as I graduated high school I entered an apprenticeship program which paid my tuition at the local tech college.  You can’t all be as cool as I am, and that’s OK … I set the bar high.  The fact of the matter is this is one situation where you want to start from the ground floor.  There are so many things that you need a firm understanding of before you can be a competent machinist that you won’t get by skipping past the basics.

One thing you will discover quickly is that there is no substitute for industry experience.  That is not unique to the world of machining, but since this is a machining blog I don’t care.  School will teach you many of the skills you need to succeed, but it’s that grumpy old bastard who hates his job that will polish you to a high sheen.  The industry right now is in desperate need of KNOWLEDGABLE machinists.  Go through school and sharpen your skills on the engine lathe, Bridgeport and bench grinders (as well as hobbs, drill presses and broaches) for a while … and THEN it’s time to really choose a path for your machine shop career.

Manual vs. Automated in a Machine Shop Career

There are many different directions to go.  For the longest time I preferred manual machining.  My abilities and knowledge on the manual machines afforded me respect from the old timers that a lot of my young counterparts never enjoyed.  It allowed me to truly decide what I WANTED to do and where I wanted that to bring me.  I know what you are asking yourself … and no, I didn’t put all those years in so I could write these fantastic blogs.  This is just the icing on the cake.  You’re welcome.  Really though, once you build a solid base the sky is the limit.  You can stay in manual machining, it is a dying breed and pretty soon will probably earn as much or more than a CNC programmer.  None of the young kids want to turn handles anymore, and it really is a shame because the best programmers are the guys who never wanted to program.  You can specialize in CNC lathe, swiss screw, CNC milling, four or five axis milling with live tooling.  There is so much new technology out there that you will never run out of new things to learn.  You can go towards engineering in CAD/CAM design, you can program as we have discussed, and you can start as an operator and earn your way up the ladder.  The machining world is your metallic oyster.

As usual I ramble.  I love this stuff, I can’t help it.  I hope that you can follow my advice and find yourself in the same position.  In short, put your time in.  Learn your trade.  Build a good base and there will be nothing standing in your way.  Don’t sell yourself short, just trust in the numbers.  I promise they don’t lie.

If you want to study up on the greatest of all CNC machines (again I’m biased) download this brochure:

Download DATRON CNC Milling Machines Catalog:

 

Machine Shop Jobs – Why Work in a Machine Shop?

Machine shop jobs can be very rewarding and in this blog, Kevin Mulhern explains how to get started and where it brought him in his career

Perhaps you are trying to decide what you want to do when you grow up.  Or maybe you are looking to change your career path.  It really doesn’t matter why you are here, I just hope that maybe I can convince you to consider a move into one of the most progressive and exciting industries out there – machine shop jobs.  When I was in high school and trying to decide between auto mechanics and machine shop, my father suggested the machine shop because it was something he had done and there were lots of machine shop jobs available.  Well, I didn’t have any idea what machining was say nothing of CNC machines and I had no interest.  I signed up for auto shop instead.  Fortunately for me, the class was full and I was forced into the machine shop class.  After the class started it did not take me long to fall in love.  However, after I finished high school,  trade school and an apprenticeship program, it seemed as though all the machine shop jobs had dried up.  So here’s my first bit of advice … don’t base your future on now.  It’s not an easy thing to comprehend when you are young, but just because there are jobs available now doesn’t mean there will be in five years.  So, find something that you love to do, can do well, and can make a career out of.  Sometimes easier said than done, but if you love what you do you will find a way to make it happen.

What’s so great about machine shop jobs?

Clearly, I am biased.  I think I am in the greatest industry in the world.  With machine shop jobs there is endless variety, always something new to learn, and while production might go overseas there will never be a day that a good machinist is not in demand.

Machine shop jobs led blog author, Kevin Mulhern, to a successful career as an Application Technician helping some of the worlds biggest manufacturers to optimize their manufacturing processes.
It all started with a couple of machine shop jobs and now I’m an Application Technician helping some of the biggest manufacturers in the world to optimize their production processes.

There are very few things that you will be able to find in your immediate surroundings that have not been through a machine shop somewhere in the production process.  Even the plastic toys that your kids play with, or the water bottles your favorite player drinks from have been through a machine shop to produce the mold, which in turn produces the final product.  No matter what industry interests you the most, somewhere along the line there is a machine shop job that directly supports that industry.  Here’s an example video below … ever wonder how radio-controlled drones (quadrocopters) are made?

What’s it take to qualify for machine shop jobs?

No matter what interests you – whether it’s getting your hands dirty, math, or computers – there is a solid career waiting for you in the machine shop.  Manual machining requires not only mechanical aptitude, but a steady hand, and a good eye.  A good manual machinist is becoming difficult to find, which is why finding a decent paycheck as a manual machinist is not too difficult.  CNC programmers and QC inspectors tend to be math heavy.  Don’t get me wrong, math is a vital part of working in any capacity in the machine shop, but as far as crunching numbers and putting those numbers to action programmers take the cake.  Any time you delve into the world of CNC machines, a comfort with computers is important.  Since CAD/CAM packages are PC based and many CNC controls have also moved that direction there is no getting away from it.  If you enjoy computers, have an affinity for math and don’t mind getting your hands dirty, you will never be out of work for long.

There seems to be a growing trend lately, though it’s more like a return to old practices where companies are starting to hire with less experience and complete on the job training.  This makes it a little easier to get a job in a shop since they aren’t going to require ten years of experience and an associate’s degree just to get your foot in the door.  It might take a little longer to climb the ladder to the higher paying jobs, but it certainly opens doors that weren’t open when I was breaking into the industry.  Keep an open mind, always stay hungry for more knowledge and work your ass off … you will have a long and prosperous career in the machine shop.

If you want to study up on the greatest of all CNC machines (again I’m biased) download this brochure:

Download DATRON CNC Milling Machines Catalog:

Bulk Material Removal CNC Milling Strategy

CNC bulk material removal with high speed machining center at 35,000 RPM using a single flute end mill and a helical milling strategy

When it comes to CNC milling strategies for bulk material removal you may be asking the wrong question.

As the account manager for industrial CNC sales in the Northeast USA, I routinely get asked, “What is the biggest tool you can put in a DATRON machine?” And while I always take time to answer this question, it gives me a bit of a chuckle because DATRON high speed CNC milling machines are all about efficiency with small tools! Now, of course I understand that in spite of the fact that this equipment has huge headroom in the RPM department, it must at the same time be capable and efficient when it comes to milling out larger features and bigger parts – most of our equipment does after all have a work envelope of 30” by 40” – but in the world of high RPM and high speed cutting strategies large features or bulk material removal does not necessarily warrant a large diameter tool.

An easy example is the simple process of pocketing: taking a workpiece and milling out an area to create an open space. In this example we’ll assume the pocket is to be 0.75” deep by 2.75” wide by 7” long. Traditional machining methods would involve the use of something on the order of a 1” diameter end mill making a traverse path along the length of this part with standard step down and step over values at typical RPMs of less than 15,000.

Bulk material removal with a CNC milling machine can be effectively performed with smaller tooling using a high speed spindle and a spiral (helical) tool path.
Bulk material removal can be done effectively with small tools using a spiral (helical) tool path and high RPM rates.

In the world of high speed cutting and new school cnc milling strategies, a more efficient toolpath can be realized by use of a comparatively small tool, such as a 6mm end mill, and beginning with a helical toolpath that circles all the way down to the final depth. From there, a large percentage of the cutting flute can remain engaged in the material as the tool circles around removing material continuously as it widens it’s circular X/Y path until the full pocket has been created. This type of strategy, when combined with the right RPM and cutting tool geometry, can outperform a physically larger tool that is using lower RPM and traditional strategies.

Milling bulk material removal or dynamic roughing in high speed CNC milling can be performed with a single flute end mill using a helical strategy and high RPM around 35,000
Bulk material removal area (or dynamic roughing) represented in orange done with single flute end mill using spiral pocketing strategy and full Z infeed.

To summarize, in the world of high speed machining it’s all about making a lot of small chips very quickly. The necessity of a dimensionally large tool to create a dimensionally large feature have been eclipsed by the advent and proliferation of high speed milling machines with the CAM strategies and cutting tool geometry to go along with them.

For more information on the CNC Milling Strategy used on the aluminum housing shown above:

Download CNC Milling Strategy Application Notes with Bulk Material Removal (Aluminum Housing):

CNC Workholding for Milling Machines

CNC Workholding for milling machines and machining centers that reduce set up and job change over times.

DATRON_Workholding_Solutions from DATRON Dynamics on Vimeo.

In the world of manufacturing, specifically machining of material, there is an art to proper CNC workholding.

You may have the concept and design of a valuable product or part, the program skillfully complete with the optimum machine and material.  But if you do not have a means to hold the material during your process, rigid throughout all surfaces and vibration free, the race is lost.  “A horse, a horse! My kingdom for a horse!”  This quote is fully understood by every machinist, tool and die maker, Production Cell Supervisor, Project and Plant Manager.  Nothing will stop a successful process in it’s tracks like material poorly held causing tool breakage, material slip, high scrap rates, possible machine damage and worse, potential operator injury.  A fixture, a fixture my process needs a fixture!

At DATRON we have heard this cry many years ago and sought solutions to be used with our machines for the many varied process requirements that the DATRON machine is used for.  These had to be versatile, minimal labor requirement for use, repeated usage, allow accuracies to match the DATRON machine and like the DATRON machine provide thousands of hours of reliable use.

Another great benefit of using tested CNC workholding with your DATRON machine is the savings of time and material loss.  Once you have optimized your product, program, material and machine process the last element to review and add profit margin points to your product is time.  Operator time lost while loading and unloading the machine.   Increased scraping of product due to slippage. The loss tool rate or shortened tool life requiring operators to change tools prematurely.  These are all examples of time cost/time loss occurrences that translate to dollars lost. The end loss could be in cents or dollars per part but multiplied by the number of parts could very well be a significant amount of money making or breaking the production project.  The reduction or elimination of these occurrences will reduce the loss or add profit margin points to your end result.

I would like to introduce the CNC workholding royalty to augment the DATRON machines:

T-Slot Tables

T-slot CNC workholding segments can be secured on the bed of a DATRON high speed machining center and can be equipped with a multitude of clamping devices.
T-Slot table CNC workholding mounts to the machine bed and can be equipped with wedge clamping or short stoke pneumatic clamps among other solutions.

Work Pallets

Work pallet CNC workholding systems can be custom configured and use a boss in cavity method to make sure you hit the right spot every time.
Our work pallets or QuickPallets are one of our CNC workholding solutions that are are keyed using a beveled boss-in-cavity system to insure location repeatability.

Wedge Clamping Elements

Wedge clamping CNC workholding units add functionality to T-slot tables and allow for adaptable setup.
The wedge clamping CNC workholding units can be configured for single as well as for multiple clampings. Due to their clamping screw and the T-nut, they can be flexibly used on the DATRON T-slot plate.

Compact Centric Clamps

Compact centric clamp CNC workholding is protected from chips and debris through a special slide geometry that helps prevent particle build up and malfunction.
The compact centric clamp is completely protected from dirt, chips and debris. Due to special slide geometry with a guide length of 150 mm, the KZS is the first fully encapsulated centric clamp.

Pneumatic Clamps: Short stroke, positional

Pneumatic short stroke and positional clamps used in conjunction with T-slot tables as CNC workholding on milling machines.
Pneumatic Clamps (short stroke and positional) are smart time-saving elements used when flexibility and short cycle times are required.

Pneumatic Vertical Clamps

Pneumatic clamp system is CNC workholding that integrates onto the bed of a milling machine or machining center to shorten set up time.
Pneumatic clamping systems are an example of CNC workholding solutions offered by DATRON to help reduce setup times.

Vacuum Chuck, Vacuum Table

Vacuum table CNC workholding solutions are integrated on DATRON high speed milling machines and allow for quick setup of sheet material from 0.001" to 0.250" thick.
Vacuum table CNC workholding is designed to swiftly and efficiently secure flat workpieces to the bed of a machining system. Thin stock, which could be secured only with great difficulties before, is now secured literally within seconds. Quickly secure plastic foils as thin as 0.001”, to 0.250” large aluminum sheets.

Precision Rotary Axis

Precision rotary axis CNC workholding adds 4th axis functionality to DATRON high speed CNC milling machines.
Precision rotary axis CNC workholding for 4-axis functionality on a standard DATRON milling machine.

Precision Rotary Axis with Tailstock

This precision rotary axis with a tailstock can be integrated on the CNC milling machine to add 4th axis workholding and machining capability.
Precision rotary axis with tailstock used to add 4th axis capability to DATRON milling machines.

Rotary Swivel Table (Trunnion 5 Axis)

Rotary swivel table CNC workholding or trunnion 5-axis rotary axis used in conjunction with DATRON high speed machining centers.
Rotary swivel table CNC workholding a.k.a. Trunnion 5-axis system mounts in the cut away portion of the machining bed on a DATRON machine.

 

Pick n Place System (Automation)

Pick and place CNC workholding solution is highly customized and automated based on the user's specific part and application.
Pick and Place CNC workholding solutions are custom configured based on both part type and application. Pallets hold blanks and automated arm moves parts to a fixture for milling and returns them to the pallet after milling is completed.

In the coming weeks I will discuss each of these products, description and use.  Each of the above products have the DATRON “Test of Time” for versatility and longevity of use.  When used properly they can achieve perfect holding with production labor time/material loss savings adding profit margin points to your process.

For more information on these Workholding Options, download our Accessories Catalog.

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Climb Milling vs. Conventional Milling

Climb milling vs. conventional milling is a common question among machinists. Both have their own advantages for example climb milling offers a superior surface finish while conventional milling can be more suitable when machining cast iron or hot rolled steel.

As a machinist you hear lots of technical terms getting thrown around. The old guys call it one thing and the young guys call it another. If you are not a machinist or are just entering the world of machining this can be confusing. Today I am going to discuss two of these confusing terms – climb milling and conventional milling.  Knowing the difference between the two and the proper application can set you apart from your peers and bring your overall part quality to the next level.

First things first, let’s set some ground rules. We will be running our spindle forward (clockwise) and using a standard end mill – we’ll get into down-cutting end mills and many other tooling options in a later blog post. For now, we are going with standard tools and we will go through the benefits and drawbacks on both manual and CNC machines.

With the tool rotating clockwise climb milling goes WITH the rotation. Think of the flutes, or teeth of the cutter as pulling the material, or CLIMBING through the material. When climb milling the flute hits the material at the top of the cut, and the thickness of the chip decreases as the flute cuts. This results in the chips being deposited BEHIND the cut, which is important. The chips clear the cutter, which means you are not re-cutting chips. Since you are not re-cutting chips, the result is a better surface finish and longer tool life. Less power is required from the spindle to climb mill, and the result of the cut is down-force on the material, which can simplify workholding considerations. Also when finishing the floor of a feature or face milling thin material the down force can assist in stabilizing the part.

Climb milling vs. conventional milling is determined based on the machining application and the advantages and disadvantages of both milling strategies.
Climb Milling – chips are evacuated behind the cut, so that you are not re-cutting them which results in a better surface finish.

There are however downsides to climb milling, the most severe of which will be found on manual machines. When performing a climb mill on a 60 year old Bridgeport you can run into some serious issues with backlash. Due to the pulling action of the tool on the material if you are using a machine that has a good amount of backlash the tool will grab the material and the table will move whatever distance that backlash is – on some machines this could be not only disastrous to the part, but incredibly dangerous to the machinist. Tool deflection (which we will cover in another post) with a climb mill will be perpendicular to the tool – so away from and into your part which will affect the thickness of your chip and potentially compromise your accuracy.

With the tool rotating clockwise conventional milling goes AGAINST the rotation. The flutes of your cutter are hitting the material and pushing against the rotation, depositing chips IN FRONT of the cut.  As expected, that will result in re-cutting of the chips which will both increase tool wear and decrease surface quality. Since the tool hits at the bottom of the part and the flute cuts upward with the chip getting heavier as it cuts, you are creating upward force on the part which can cause workholding issues.

Conventional milling vs. climb milling is the topic of this blog and advantages and disadvantages of both are discussed.
Conventional Milling – offers a significant benefit when machining hard materials like cast iron or hot rolled steel.

Just as there are downsides to climb milling there are upsides to conventional milling. When machining things like rough cast iron, or hot rolled steel, conventional milling is the preferred method. Especially with hot rolled steel due to the hard black layer on the outer surface. Performing a climb mill on hot rolled steel can result in chipped cutting edges because of the hardness of that outer layer and the more aggressive way the tool engages the rough surface, causing more deflection and potentially heavier chips. Since the tool deflection with a conventional mill tends to be parallel to the tool, it engages the rough surface at a more forgiving rate. Another strong suit of conventional milling is on finish passes. If you rough your profile with a climb mill, which will give you a good surface finish to begin with and then switch it up on the finish with a light conventional mill you will be surprised by the results. Due to the tool deflection seen with climb milling the conventional mill finish pass will give you a good finish on a light pass. Another option is a “ghost pass” or “spring pass” which is a cut in the opposite direction, in this case conventional, without actually taking a heavier cut. You will see the amount of material being removed, which was left by the tool deflection and it will leave a great finish as long as you lubricate.

Hopefully I clarified the issue of climb milling vs. conventional milling for you at least a little bit.  Both are useful strategies when applied in the proper situation. Always remember, when it comes to machining it’s the small details that make all the difference – no matter how small they may seem.

Learn More: Download the DATRON Cutting Tool Catalog:

How to Machine the End of a Long Part with Vertical Clamping

Vertical clamping for CNC machining on the end of long parts such as aluminum extrusions, enclosures and housings using a pneumatic clamping system integrated on a DATRON high speed milling machine.

It is always a challenge when faced with a long part that requires machining on the end or ends. Equally challenging is when you have to machine the side of a large part. Unless your facility is equipped with a machine tool that is large enough to mount such a part within the working volume above the machine bed, you are pretty much out of luck. Even if you have a machine that is physically large enough to accommodate the over-sized part, often securing or mounting the part can be very challenging. Traditionally any gantry-style machine or router-style machine would immediately be disqualified due to the limited clearance under the bridge. Unless that machine is a DATRON M8Cube.

The German-engineered gantry style M8Cube has a machining area of 1,020mm (40”) x 830mm (32 ½”) x 245mm (9 ½”). This is a good solution when having to machine large, precision parts not larger than 9” tall or deep. What if you are faced with a large mold or electronic housing that is 12” tall? The M8Cube offers an open area in the front portion of the machine table that allows you to mount taller parts that would not normally fit under the gantry. This is sort of like a trap door opening with vertical mounting holes on the front face of the opening to securely mount your over-sized parts. Often parts can be mounted while still remaining within the machining area. You could even mount a long extrusion (for example 36” long) vertically within this open area with the end slightly above the table surface. This allows you to keep the end of the extrusion to a minimum above the clamp, reducing vibrations in the work piece. Now all you need to do is machine the end of the part while the rest of the linear piece extends far below the table surface. This is a unique feature that is built-in to their standard machine. This feature offers a lot of flexibility and diversity for the job shop that never knows what kind of project they will be facing next.

Pneumatic vertical clamping system for securing long or tall parts that need to be machined on the end.
Pneumatic vertical clamping system for use in the “cut-away” area available as an option on many DATRON milling machines.

DATRON also offers a unique line of pneumatic vertical clamping systems to make it easier to mount linear or over-sized parts within the open area. These vertical clamping systems were designed specifically for the M8Cube open area. The work holding solution quickly mounts to the M6 threaded holes located on the front face of the open area. This vertical clamping system is pneumatically driven for quick clamping and release of work pieces by the touch of a button. For parts that have a short cycle time, this vertical clamping system is ideal because a part can be removed with a new part inserted and clamped again within seconds. You can also devise your own vertical clamping system and mount it to the provided mounting holes.

Vertical clamping system on a DATRON ML-1500 high speed CNC machining center is used as workholding for long or tall parts such as aluminum housings and enclosures that need to be machined on the end.
Vertical clamping system integrated on the front of the machining bed on a DATRON large format milling machine.

If you are faced with an unusual work piece that cannot fit in your conventional CNC machine, we would be happy to consult with you to see if this unique, simple design accommodation could be the answer to your most challenging part.

Download the DATRON Pneumatic Vertical Clamping System Brochure: