Source
r/CNC•
Kathemy

In need of advice on high feed end mills

Gentlemen,

I've been gifted a Kennametal 3 flute 32mm end mill by my boss. I am running it at Vc225 and F0.8 per tooth. (S2240 F5400.) Plain steel (2172). Max Ap is 1.5mm (I never go over or under 1.0.)

I need some advice on how to use this thing. Right now I just use it to do straight lines. I'm wary of turning inside the material, and I don't know if I'm right or not.

So I have some questions:

1, are there any issues with changing direction while in contact with the material? I'm talking abruptly (x100, y50, x-100, y-50 etc.) Does this create more stress on the tool? How much to decrease feed in that case? Near to 100% contact is assumed at all times; I've heard the tool likes that.

2, the tool should be used to either engage fully or no more than half the insert diameter. If I choose the latter, how would I adjust speed/feed, or should I?

3, would it be a good idea to decrease feed for entry to and exit from the material?

4, if I simply have to use only 50% of the diameter, how to adjust feed in such cases?

Please note I am running a rather old machine with limited memory (Mynx 750/50 Fanuc 21i). CAM-generated code 50+ pages long simply won't fit. We're talking straight Gcode here. I'm a very good coder.

Any advice, even nonrelated to the questions, would be very welcome. Any questions you have that I could answer, likewise.

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Posted Nov 2, 2018, 2:31 PM UTC

67
dimoko•

high feed mills are better than most at abrupt changes, but arcs are always better than right angles.

in my experience you can go about 75% of diameter. feed/speed and technical info usually is available from the manufacturer, not sure what technical info kennametal offers.

3
albatroopa•

Use CAM generated code and use line/arc fitting to decrease your file size. You can also run it off of the memory card, but you may run into data starving.

As good as you are, you can't beat generated toolpaths for consistent engagement and gentle lead-ins.

I've run high feed mills at 300 Ipm with no issues, but it was a small step down. Coolant availability is also a big factor.

2
KathemyOP•

I'll check the possibility of using memory cards, thanks for that input.

Coolant availability is also a big factor.

Seller/technician recommended only air coolant. I do that. What are your thoughts on that?

As good as you are, you can't beat generated toolpaths for consistent engagement and gentle lead-ins.

I'm aware, I'm certainly no superhuman.

In this case I'm talking the very simple operation of flat-facing an area X*Y. I could program a macro to do that for any such area if I knew the best approach. Right now I just do intro-exit the material in straight lines.

1
albatroopa•

Okay, that's fair. To use the memory card, you'll need a PCMCIA to CompacFlash adapter, they used to be prevalent in laptops about 10 years ago.

The buttons you need to push to run the program from it are:

  1. remote mode (as opposed to memory)

  2. prog

  3. left arrow soft key, then right twice. It's a glitch that you need to go left first.

  4. DNC-CD

  5. select your file, usually 1

  6. DNC ST

  7. cycle start

I'm doing this from memory, so it may be slightly different, but it should be pretty close.

Edit: saw your question on air blast. That's good for some coated inserts and solid endmills. TIALN likes a bit of heat, for example. As long as your chip evacuation is good and you aren't shocking the tool you should be fine in steel. If the sales rep says air and you use air and have issues, he should comp you a box of inserts.

1
travellering•

I'll agree you should start with what the rep recommends, but IME, if the inserts fail on a high feed mill, or on an insert drill, the cutter body is damaged before you can stop it.
On steel, if your chips are copper/coffee colored, you are in the cutter's happy zone. I could get away with blue edges on the chips, but if they showed full blue, i knew i had only a minute or two to exit the cut and rotate inserts. How rigid is your machine? If any panels are rattling on heavy rough cuts, you will probably want to stay in the 80 to 100 percent cutter engagement range. The workpiece will dampen vibrations much better than a sloppy machine.

1
KathemyOP•

On steel, if your chips are copper/coffee colored, you are in the cutter's happy zone. I could get away with blue edges on the chips, but if they showed full blue, i knew i had only a minute or two to exit the cut and rotate inserts.

Hm. I completed a job yesterday using said mill and ALL the chips were dark blue. And the inserts look great! (No kidding. I didn't have to turn them even once.)

How rigid is your machine?

Don't know how to check for it. It's a big old beast, though.

1
CNC_Codnig_Guide•

comment:

Do not use kennametal!

sry, work at sandvik that made the cormant stuff.....

and for shure, never tied something else, what if the coro-guys cheated me?

keep ut the good work!

1