[adamvs]

I've been watching a lot of CNC NYC and there NO way I can get the kind of step overs that John gets with his 1100. I just watched a vid where he was getting a clean .12 step over with a 1/4" end mill. The most I'll attempt is one tenth that! It seems that vibration upsets the Z brake, which will start Z axis on a slow plunge down off it's plane. I have a series 2 with the series 3 upgrade and motors about a year old, am using solid end mill holders. I've never really pushed the machine. Any ideas?

[popspipes]

I have a contour on a part that I run at 40 ipm .125 deep .250 stepover (slot), I clean up with a finish path though, about 5 to 7 thousanths @20 ipm. This is in 6061 though and cutter is a 3 flute hss .5 flute length. I dont lose any Z height though, I am using Pathpilot, and no pullout of the cutter.

[keen]

I've been watching a lot of CNC NYC and there NO way I can get the kind of step overs that John gets with his 1100. I just watched a vid where he was getting a clean .12 step over with a 1/4" end mill. The most I'll attempt is one tenth that! It seems that vibration upsets the Z brake, which will start Z axis on a slow plunge down off it's plane. I have a series 2 with the series 3 upgrade and motors about a year old, am using solid end mill holders. I've never really pushed the machine. Any ideas?

Hi - So your Z is coming down under heavy vibration cuts? Sounds to me like your stepper coupling is slipping. Take the cover off and put a white out etc mark on each side of the Z coupling and induce the problem - you will soon see if it is that.

Please let us know how you get on.

Keen

[cncmakers001]

Sometimes the driver parameters setting could also affect the vibration.

[CadRhino]

Johns tormach us not special but he is a shap guy and used the right tool for the job. He uses special roughers sometimes so that may be part of it.


I have the same issues as you but mostly when I use 1/2" em with .2" or more doc and .25" or more step over. This won't happen with a rougher, though.

It is always better when I use a rougher first.

I've been watching a lot of CNC NYC and there NO way I can get the kind of step overs that John gets with his 1100. I just watched a vid where he was getting a clean .12 step over with a 1/4" end mill. The most I'll attempt is one tenth that! It seems that vibration upsets the Z brake, which will start Z axis on a slow plunge down off it's plane. I have a series 2 with the series 3 upgrade and motors about a year old, am using solid end mill holders. I've never really pushed the machine. Any ideas?

[adamvs]

Johns tormach us not special but he is a shap guy and used the right tool for the job. He uses special roughers sometimes so that may be part of it.


I have the same issues as you but mostly when I use 1/2" em with .2" or more doc and .25" or more step over. This won't happen with a rougher, though.

It is always better when I use a rougher first.

On the video he was using a new 4fl TiAl coated em in 4140. .250 DOC with over .125 step over, .001 chip load per tooth, it cut clean as could be. So maybe a brand new cutter certainly helps.

@Keen: I'll try marking the coupler to see if there is any slipage. Could also be the gibs are little loose, or the ball screw is a little worn from lack of lubrication ( previous owner ), that allows the vibration some slack to work in.

[mountaindew]

Imho a NEW cutter as mentioned above will make a world of difference on any operation. While back I crashed an end mill that was in use far to long apparently.
When replaced my finish and overall machine performance went back up. Also I find having the material very secure will help a great deal. Not long ago I had a number of parts trying to lift out of vise. I think the material was not real square / parallel and vise was not getting full contact on surfaces and lifting out. Had to tighten more then usual to keep in place. And looking at the results it would appear the z axis was drifting down when in my case it was the material lifting up!
something to consider and watch for

[adamvs]

@mountaindew: I think you're absolutely right about a new cutter. Truth be, I was using a 3/8" coated carbide cutter that was 'just laying around'. The lakeshore cutters with TiAlN ( titanium - aluminum - nitride ) coatings are really good on steel.

@keen: I found one of the screws on the Z axis coupler to be not exactly super snug, so I tightened it. Hopefully that will make a difference.

I'm also looking to reduce vibration from the motor, by getting it super balanced and bearings replaced. Vibration sets in about 3K; at 5.1K is very noticable. The fan gets gunk on it over time and gets out of balance. I really like the tactical keychains solution of using an external fan.