Horrible surface finish from endmill

Last week I ordered a couple of Hertel 2 flute, high helix, HSS, coated end mills to try out. Today I needed to run a batch of these parts and I was really baffled by what I saw.

At first I thought my machine was out of tram or some other problem had cropped up but then I tried Maritool 3/8" endmill and it was much better. The machine is a RF 45 type bench top so while it is not a perfect machine it works well.

My question is what would cause that type of surface finish? I have used plenty of 2 flute endmills and have never seen anything like that?

From left to right in the picture: Hertel 2 flute 1/4", Hertel 2 flute 3/8", Maritool 3 flute 3/8" carbide. The speeds and feeds were set using Gwizard and previous experience. Material is 6061-T6, I hit the parts with a bead blaster so you could see the marks.

Were all tools coated? I never used coated tools on aluminum. Looks like deflection of tool, material, or machine. What was the tool stick out on each? What speeds, feeds and depths of cut on each tool? What did the chips and chip evacuation look like on each? Coolant or air blast?

1/4" 2 flute: .06 DOC, 32 IPM, stickout 1", coated
3/8" 2 flute: .1 DOC, 42 ipm, stickout 1", coated
3/8" 3 flute: .1 DOC, 48 ipm, stickout 1", not coated

All cuts on mist/fog buster type system using Koolmist.

All the speeds and feeds are from G Wizard and defections are well within specs. .0002 if I recall.

Picture of the 3/8 end mills.

looks like the problem is the way your holding your stock

try double edge tape or supper glue to a sacrificial plate

Quote:

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Originally Posted by kregan

1/4" 2 flute: .06 DOC, 32 IPM, stickout 1", coated
3/8" 2 flute: .1 DOC, 42 ipm, stickout 1", coated
3/8" 3 flute: .1 DOC, 48 ipm, stickout 1", not coated

All cuts on mist/fog buster type system using Koolmist.

All the speeds and feeds are from G Wizard and defections are well within specs. .0002 if I recall.

Picture of the 3/8 end mills.

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Calculated tool deflections and actual deflections may be different. Hopefully the GWizard guy will explain this.

As you indicate above, the cutting scenario that resulted in the best finish was the one with the uncoated tool. The coatings on tools tend to be "sticky" when cutting aluminum and cause a slight built up of aluminum on cutting edges making the tool artificially dull within seconds.

I thought the coatings like Ti were supposed to help reduce "gumming" with alu? That's not the case?

cheers,
Ian

Is the workpiece vibrating/flexing? I've had that happen more than once.LOL

Dick Z

Wrong coating for aluminum is the problem, you need ZrN or uncoated. I've tried a few coatings and this is what I've found, NEVER any Ti coatings on aluminum.

Put the table at the + and - x end of travel, and pull backwards and forwards.
is there ANY free play. I thinks so.

Z axis height variation.
Put a DTI on the head and bring it DOWN (and only down) to a some position.
Zero the indicator. Move up a small amount very slowly. The indicator show down before up.
That is head nod. Friction on Z way makes causes drag as the screw pulls the head down. Excess counterbalance force greater than the weight of the head makes it even worse, as it dances around, balanced on a stick.

As the cutter wears (microscopically) the Z load can range from 200 grams to 6KG with a 3/8" cutter skimming stainless steel. Varies with material.
Use the right type of cutter for the material. Carbide rocks. 3 flutes less chatter.

Gibs again, and the only way to get perfect Z on this machine is to go below the required Z level, my the head nod amount, then up by the head nod amount.
You need that for every Z down move, on the final cut.

http://www.cnczone.com/forums/syil_p...trut_x3_-.html
Look at post #13 for head nod.

I've tried the Hertel HSS bits before from Enco, and had similar horrible finish quality. I only use carbides now, and am happy.

Hi guys,

Here is the Hertel end mill I purchased.
They are listed as specifically for aluminum but do have the TiN coating not the ZrN.

http://www.use-enco.com/CGI/INSRIT?PMAKA=337-6798
Material: High Speed Steel;
Length of Cut (Inch): 5/8;
Finish/Coating: TiN;

I am pretty sure the material was not moving. All 3 parts where cut consecutively with the same clamping system on a fixture plate. Two 1/2" table clamps hold the bar of material in place.

I really think it was the end mill because I have cut that part before with a uncoated HSS 2 flute end mill and never had a finish like that. Honestly I have never had a finish like that on any part and that is why I posted it. It felt like concave grooves in the material and that equates well with the idea that material was sticking to the TiN coating on the bottom of the end mill.

I was only using a 30% step over BTW.

I ran about 30 of the parts today with the Maritool 3/8" and the feed rate was turned up to 50 ipm and the parts are fine.

what i see of those endmills, you posted, they have a very flat end..
when i have this type, i grinding back them...
so the edges will contacting on one point only ...

on the attached picture you can see better... i believe this really has effect..
for aluminum, and plastics this type works better..
what you posted, that works for steel, because the corners are stronger..

also for aluminum a little wd40 helps a lot... as its lube the tool preventing buildups..