Squealing like a stuck pig.

[Smitty911]

ok here's the set up. X-2, MACH 3, Gecko 203V, KDN Tools CNC conversion (no backlash, ok I can't measure that low), 2 Flute .500" cutter, 6061 aluminum >.500" plate, Feed 20ipm, depth of cut .020", Aluminum cutting fluid liberaly applied in front of cutting path = SQUEALING

I've sped up and slowed down the cutter speed, increased and decreased the feed rate, it still persist.

Any Ideas???

Also does anyone know of a good speed feed calculator?

How do you figure "Chip Load" per tooth?

Thanks

Smitty

[Geof]

What type of toolholder; generally setscrew type are more rigid than collet. How much tool is sticking out; keep it back to have the minimum length possible.

Chip load per toothis the distance the feed advances during the rotation of one tooth. So if you want a chipload of .005" per tooth on a two flute cutter running at 3000 rpm you multiply .0005" per tooth b y two teeth which equals 0.01" per revolution so at 3000 rpm the feed has to be 30 ipm.

Generally to reduce squealing, actually called chatter, you want to increase the chipload; slower rpm or faster feed. But first make sure your tool is held securely and not sticking out too far.

Incidentally 0.02" depth of cut is a bit skimpy; ten times this should be possible provided you do not run out of hp.

[toastydeath]

Originally Posted by Geof What type of toolholder; generally setscrew type are more rigid than collet. How much tool is sticking out; keep it back to have the minimum length possible.

I have to disagree - for the purposes of roughing and holding the tool still, an endmill holder is more rigid. But for the purpose of chatter, and endmill holder is a wind chime compared to a collet. There's lots of data out there on this.

[Geof]

Originally Posted by toastydeath ...But for the purpose of chatter, and endmill holder is a wind chime compared to a collet. There's lots of data out there on this.

Okay give me some links.

There was a recent thread about setscrew type holders that discussed this and I think the concensus was that these are more rigid than the ER, taper collet, type holders. My experience is that collet holders are simply not up to taking the kind of speeds, feeds and chiploads that a setscrew holder can handle.

[Smitty911]

The correct Collet (LMS) to hold a 3/8 end mill. It is shoved all the way up so that only the cutting edges are sticking out.

So I should be taking deeper cuts? I watch the videos of Hoss doing depth and feed rate test and based my set up on that. He was taking 0.075 at 5ipm and it stalled.

Oh I forgot to mention that the 0.500" plate is held to a second sacrifical plate with some wax paper that I bought for holding parts like this.

I will edit the code to speed the feed rate up some and see if that helps.

Thanks

Smitty

[Geof]

Originally Posted by Smitty911 ....So I should be taking deeper cuts? I watch the videos of Hoss doing depth and feed rate test and based my set up on that. He was taking 0.075 at 5ipm and it stalled....Smitty

If you have limited power sometimes it is difficult to get enough load to prevent chatter before you stall the machine. And, despite what toastydeath suggests, I think you should try a setscrew holder. If it doesnt't help I will crawl back under my bridge and keep quiet.

[Smitty911]

I thought only trolls went under bridges, I don't think you qualify as a troll.

I'll have to run down to the corner Tool Shop and get one to try. It's only money at this point, and that's what hobbies are for.

Smitty

[Geof]

When I get a reply that treats me like a troll I will respond as one.

I am not always sweetness and light.

[maxboostbusa]

The noise could also come from a dulled cutting edge on the end of the mill or possibly chip welding. I have got a few import endmills that were not all that sharp out of the pack. On 6061 they possibly could have made a squealing sound but they would have been hot also and the surface finish would have been terrible. They were used on large equipment so they were taking heavy cuts and were only used for roughing so it didnt really matter. As far as the Collet vs. Endmill holder debate there is alot of debating back and forth with everyones opinion, to my knowledge there has not been any actual proof in the pudding tests that show one way or the other. This I do know. I have had endmills slightly slide out in a collet during heavy cuts which ruined a few parts in the batch until it was caught. The collet was name brand used very little with the correct size mill and it was tight. The movement was only .0025" but that was enough on that job. For roughing I will always use a setscrew type holder other than that either has proven adequate to me. Alum., Stainless, Toolsteel, Titanium I have used both in each and it is about the same story. With your depth of cut and feed in 6061 I would use either, but if I had a problem I would definately try another holder to rule it out if nothing else comes to light. Just my 2 pennys though.

[toastydeath]

Originally Posted by Geof Okay give me some links. There was a recent thread about setscrew type holders that discussed this and I think the concensus was that these are more rigid than the ER, taper collet, type holders. My experience is that collet holders are simply not up to taking the kind of speeds, feeds and chiploads that a setscrew holder can handle.

Physics doesn't obey a consensus vote, and just saying an unqualified "rigid" doesn't mean anything in the context of machine tools.

Endmill holders have a higher static rigidity, collet holders have a higher dynamic rigidity. Higher static rigidity means less deflection and overall holding force in the endmill. It won't slip, and it will stay straight at low RPMs. Higher dynamic rigidity means less deflection at high speed, and higher vibration damping at all speeds.

The ASPE has a video series, one of which is Dr. George Tlusty. He determined the equations that describe chatter in machine tools, and it's a very robust presentation on how chatter occurs and why. If you're interested in the subject, I recommend finding the two-part presentation and watching it.

I don't have any webpages on this, nor would I trust any, as the quality of information regarding machine tool dynamics is generally piss poor. The places I've seen quality vibration and chatter analysis of toolholders is in journal articles, personal conversations with people who have a doctorate in the subject, and from people who do high speed machining and have done vibration analysis as part of the toolpath. I believe there was a semi-recent issue of Modern Machine Shop that briefly detailed the advantages of collet holders, but I don't subscribe to it and don't know which issue it was.

[tauntdesigns]

Originally Posted by Geof Chip load per toothis the distance the feed advances during the rotation of one tooth. So if you want a chipload of .005" per tooth on a two flute cutter running at 3000 rpm you multiply .0005" per tooth b y two teeth which equals 0.01" per revolution so at 3000 rpm the feed has to be 30 ipm.

Howdy Geof,
Typo above, .0005 should be .005 (oops)

feedrate = rpm x number of teeth x clipload per tooth

rpm = (cutting speed x 3.8) / diameter of tool for mill or workpiece for lathe

Cheers, Jack

[Geof]

Originally Posted by toastydeath Physics doesn't obey a consensus vote, and just saying an unqualified "rigid" doesn't mean anything in the context of machine tools.........etc, etc,

Well I guess I have been put in my place. Okay I will retire to my bridge.