N00b needs help: Collet slipage on MaxNC/Taig style holder

[Tj256]

Hi Guys,

I'm pulling my hair out over what seems like a simple issue. Very excited to finally have MachIII working on my MaxNC mill (I had to gut the stock controller) I've milled wood and foam up until now, and I'm in new territory with aluminum.  I've got a MaxNC15 which has a Taig collet system for holding endmills. No matter what I set my feed speed and RPM to, the endmills eventually decide to slip up or down wrecking either the endmill or the part. I've attached a photo of my lame attempts to route around a 1" square to show you what I mean. The bit I am using, as well as the holder is pictured. I've tried 10k rpm, 1"/min feed rate as well as a lower 1k rpm which started to produce larger pieces of aluminum shavings (a good thing?) but still started to crap out after a few minutes. I've also lowered the feed rate to an excruciating .25"/min and the same thing happens. I've tried both no coolant and oil. The oil actually seems to make things worse and speeds up the time until the bit slips. What could I be doing wrong?

Thanks for any help. This is indeed frustrating!

[tjstamp]

i've had that problem once. 4 flute, depth of cut and the style of grind on the cutter is all a factor. changed to a cutter that is made (ground ) for al. and soft metals worked great. ER collets will have slippage if the cutter force is to great. try to use 2 flute and look in your tool supplier for cutters for al. good luck

[ASC]

What is your depth of cut?  Aluminum can be tough to machine, especially with 4 flutes or more on your mill.  The metal actually clogs the flutes and creates more resistance.

[Tj256]

I'm cutting .1", so visually it doesn't seem like it should load up the machine.  I'll have to try .025" per pass and see if that works any better.

[Tj256]

@tjstamp - Thanks! Yes now that you put it that way, perhaps an ER collett is a good thing. It prevents things from breaking when forces are running too high. I'll get a new endmill and do more passes and see where that gets me. Will let you know in a week when my parts get here

[ASC]

.1" seems like a fairly heavy cut to me!  I usually do .25 mm/10 thou passes and make up the time with higher feedrates and rpms.

[TramAlot]

I have a sherline which is close in power and .010 is a big cut for alum. Less flutes and either wet lube or Nikx Stikx will help too. the NS is sherline #7560

[Tj256]

Wow, .01"! If that's what you guys have to do then no wonder I'm having trouble. I have literally seen my machine cut .2" when the bit slipped in once, and it wasn't having trouble in the least. I have encoders, so I am certain it was actually OK in X and Y. Now as far as whether this is good for the machine I am not sure. But cut at that depth it did. Mind you it was at .2"/min.

I'll try the 100 cuts per inch tonight. I am just amazed that you can't "bite" more than this each pass. I did upgrade to a beefy 1/2hp spindle motor and I have the more powerful steppers (and a nice 48v Gecokdrive). So the only worry would be that I'd wreck the aluminum machine with too much force by trying more depth.

I suppose that it really is an issue of "too much force" and the weak link is the collet.

One thing I've noticed about these cheaper mills (and the maxnc in particular) is the weakness of the collet system. I am starting to wonder if this was done on purpose and/or is a good thing that was done to keep you from destroying the machine. I was pondering on upgrading to an endmill holder but of course if the bit gets pushed beyond the limit, I really wonder if the bit will break first, or if it will be my machine! On a real machine the bit breaks, but on MaxNC machines, who knows.

[Speedtwin69]

I take .04 a cut all day on my maxnc with the same collets you are using.
Hanita Varimills is all I use, the machine has enough power to break a .25 mill.
I'm using the gecko 540 also.

[Bjorn Toulouse]

Is that an ER collet in the pic??   

If so, it looks as though you might have a problem with your spindle taper. 

You really need to get a handle on appropriate feeds and speeds for the material you are cutting and the cutting tool you are using.
Randomly stabbing at the settings will get you nothing but wasted material and trashed milling cutters.
Many cutting tool manufacturers/suppliers have feed/speed recommendations for their tooling on their web sites, and there a number of good general references to be found.....Google "milling feeds and speeds".


Rex