"How to train your people for CNC"

Heinz R. Putz · Jul 2, 2015

I have been teaching large and small shops the skills for efficient CNC machining for a great number of years.
Here is how I usually do it:
!) Make it as simple as possible.
To figure RPM, its SFM times 4, divided by Diameter.
Lets say you cut 1018 steel with a .5" diam. HS endmill, so its
cut at 100 SFM.
100 times 4 divided by .5= 800 RPM.
Next the feedrate:
Each flute removes .005 per rev and there are 4 flutes, so its .02 removal per rev.
RPM times feed per rev+ feedrate of F16.0.
All of these can be done in your head, remember the are simplified, once actually making parts, there is room to cut cycle times.
More to come obviously.
Heinz at doccnc.com

Spinit · Jul 2, 2015

I like the way you do it. I know that SFM chart (a good one) is needed as a starting point. It gets involved the more different vendors we use for tooling with end mills and inserts of various types and so on. The newbies who will go and ask for help are the best to train because they do not end up making bad parts or tearing up a lot of expensive tooling and expensive insert holders like lathe tools and inserted face Mills, or profile type cutters. They often do not know when a insert is going bad because they do not hear the snap when it breaks nor do they understand the noise level is just not right. At times the wrong tooling for trial setup is on the setup folder and they do not know better yet the programmers or the ones who write down setup instructions for jobs that run regularly or not do not take the care to have attention to detail. I know it is a tough job. The idea anyone can do it simply is a myth and a very expensive one also.

NAST555 · Jul 3, 2015

Your solution seems pretty simple to understand.

I have trained a few guys and being metric it seems easy to me but not always easy for them. RPM = mm/min divided by (pi multiplied by dia). So 99.9% of the time the surface speed specs are given in M/min so it works out to (M/min X 1000) divided by (dia X pi). The Pi X Dia is obviously there to get the circumference so having a learner that knows basic math is a bonus to understand the concept. I normally give them an example of a car wheel that travels a certain distance per revolution dependent on Diameter as an example. Then I get them to write it out as much as possible and if possible put a laminated page or a white board up in the shop with the formula where they will see it OFTEN.

Feed is obviously the easy part. Once the rpm is calculated it is first multiplied by the load per flute (or removal rate per flute,I like that term Heinz I am going to have to remember that, thanks!) and then by the amount of flutes.

So a 10mm dia cutter with 4 flutes of a load of 0.1mm/flute running at 180M/min:

180 000 divided by (Pi X 10) = 5730 RPM
(5730 X 0.15) x 4 = 2292mm/min

Mtndew · Jul 3, 2015

Heinz R. Putz said:
I have been teaching large and small shops the skills for efficient CNC machining for a great number of years.

cut 1018 steel with a .5" diam. HS endmill

No offense, but cnc machining and cutting 1018 with a hss endmill should never be uttered in the same sentence.

doug8cat · Jul 3, 2015

I learned by the following method.

1)machine delivered
2)riggers placed it in postion.
3)bosses handed the boxes of books and parts.
4)asked that I learn to program, fix and run.

Took a few monthes to asemble the machine and get it working, but misssion acomplished

DMF_TomB · Jul 3, 2015

personally i would start training by training on how to use Excel and Powerpoint.
.
i would train on how to enter math formulas into Excel and using it as a programmable calculator. also using Powerpoint for editing setup information.
.
i also use Excel to create a setup, startup, and 1st inspection checklist. on checklist is anything important or has caused scrap parts in the past. bad enough to scrap a part. whats worse it doing it a second time.
.
for at least the past 10 years every CNC i have run has had a computer nearby for cnc file transfer, drawing access, and using it for setup info, startup checklist, 1st inspection checklist.
.
like a pilot checking the airplane before take off checklists to not forget anything and to record measurements is an extremely powerful tool.
.
they teach using Excel, PowerPoint, Word in grade school now. By the time they leave high school they should know how to use it fairly well.

wheelieking71 · Jul 3, 2015

The first thing I beat in to my best apprentices brain was "no chips in the vise jaws or fixtures".
Feeds and speeds didn't come for years.

wheelieking71 · Jul 3, 2015

DMF_TomB said:
personally i would start training by training on how to use Excel and Powerpoint.
.
i would train on how to enter math formulas into Excel and using it as a programmable calculator. also using Powerpoint for editing setup information.
.
i also use Excel to create a setup, startup, and 1st inspection checklist. on checklist is anything important or has caused scrap parts in the past. bad enough to scrap a part. whats worse it doing it a second time.
.
for at least the past 10 years every CNC i have run has had a computer nearby for cnc file transfer, drawing access, and using it for setup info, startup checklist, 1st inspection checklist.
.
like a pilot checking the airplane before take off checklists to not forget anything and to record measurements is an extremely powerful tool.
.
they teach using Excel, PowerPoint, Word in grade school now. By the time they leave high school they should know how to use it fairly well.

I wish I did! (know how to use excel)
I have an excel file I use for quoting (I stole it LOL). Been using it for many years, and still struggle.

A structure like you outline would sure help me!

Larry Dickman · Jul 3, 2015

The best way to train someone on a CNC?

Stick their ass in front of a Bridgeport, an engine lathe, and a surface grinder. When they've mastered all 3, show them hoe a CNC works.

vettedude · Jul 3, 2015

Larry Dickman said:
.

Not very effective if you are small or need someone in a hurry (Few months)
We used immerse2learn.com
Once that was mastered had them sit and watch for a week
then sat and watched them button push for about 5 months
finally let them loose on setups
This seems to be working okay right now.

Throughout all of this we communicated alot and when mistakes were made we always fixed them together.

Myrmidon · Jul 3, 2015

Training someone for CNC is the easy part.

Teaching them how to think/react and adjust on the fly. How to make less then optimal setups/tooling work, How to build repeatable setups/fixtures and how to think in a way that prevents as many mistakes as possible... Now thats the hard part.

BUT if you can teach someone the mechanics of how and why things work. Then teaching them CNC isn't going to be so hard.

(so basically a longer version of what larry said

)

Limy Sami · Jul 3, 2015

Larry Dickman said:
The best way to train someone on a CNC?

Stick their ass in front of a Bridgeport, an engine lathe, and a surface grinder. When they've mastered all 3, show them hoe a CNC works.

+ 1 on that, and have them read and understand South Bend's HTRAL - that will save a bundle of time on any machining course.

SND · Jul 3, 2015

Still slowly working at training myself, maybe someday I'll open that big yellow book and see what's in there, maybe... until then, cad/cam and keeping it extra simple.

wheelieking71 · Jul 3, 2015

What really sucks is when you are 7 years deep training a guy, and you realize:
Crap! I have either hit his limit, he has totally lost interest, or I screwed up and picked the wrong guy.

After 7 years, its hard to stop trying to spoon feed him knowledge.
But, you eventually realize: you are wasting your time, as the definition of insanity creeps up on you.

And, you need to start preparing for the next step, as you slowly begin to detach yourself.

Heinz R. Putz · Jul 3, 2015

Thanks for all the replies, guys.
Some comments:
Of course you would not cut 1018 with a HS endmill, but to use carbide, use the same calculation, but triple the SFM value, so its
300 times 4, divided by .5, for 2400 RPM. And of course, the feedrate goes up.
When it comes to cutting AL you usually run out of RPM especially on older machines.
About programming with all the different CAM packages.
Its obviously faster, but cutting is not as efficient: Remember that whoever wrote the Software, most likely had never actually run a machine.
In all my years of training shops, I have never seen a CAM made program that I could not improve by at least 10%
Everything having to do with speeds, feeds, finishes, workholding, chuck pressure, etc., is on my DVD called "Prep for CNC".
There is lots and lots more to come.
Heinz at doccnc.com

vettedude · Jul 3, 2015

wheelieking71 said:
And, you need to start preparing for the next step, as you slowly begin to detach yourself.

I think in this case you would just need to limith the person to what they can do.

Weather that's run setup
push button
light programming
sweeping the floor.

Not everyone will have the ability to do it all.

jrmach · Jul 3, 2015

2400 rpm for .500 Carbide EM cutting 1018 :nono:

Larry Dickman · Jul 3, 2015

jrmach said:
2400 rpm for .500 Carbide EM cutting 1018

Maybe if it were a footlong :willy_nilly:

wheelieking71 · Jul 3, 2015

Larry Dickman said:
Maybe if it were a footlong

Or, 25 years ago?

SND · Jul 3, 2015

wheelieking71 said:
What really sucks is when you are 7 years deep training a guy, and you realize:
Crap! I have either hit his limit, he has totally lost interest, or I screwed up and picked the wrong guy.

After 7 years, its hard to stop trying to spoon feed him knowledge.
But, you eventually realize: you are wasting your time, as the definition of insanity creeps up on you.

And, you need to start preparing for the next step, as you slowly begin to detach yourself.

Next time a girl brings up marriage I'm handing her a printed version of this!

"How to train your people for CNC"

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