Surface finish, another simple test

[1ctoolfool]

Ok, this is a test anyone can do easily.
Using the same 3/16" endmill feed at 5000rpm 50ipm at .005" depth in aluminum.
one cut is a straight line in X with one dead stop in the middle.
one cut is a straight line in Y with one dead stop in the middle.

The x direction cut mark(s) where the tool stops is easily removed with a scotch brite pad to be invisible to the naked eye.

The Y direction cut cannot be easily "scotch brited" away and resembles the "coining" that Mr. Flat is complaining about. Approximately .0001" depth marks.

Why don't these cuts produce identical results?

[Geof]

Originally Posted by 1ctoolfool ...The x direction cut mark(s) where the tool stops is easily removed with a scotch brite pad to be invisible to the naked eye. The Y direction cut cannot be easily "scotch brited" away and resembles the "coining" that Mr. Flat is complaining about. Approximately .0001" depth marks. Why don't these cuts produce identical results?

Because the Y change in direction puts and impulse into the machine in the same direction that the head 'nods'; the X change in direction is at ninety degrees and does not excite the resonant 'nodding' as efficiently.

[ktm666]

haas machines are less than perfect at harsh stops with flat or bullnose cutters. just a fact of rigidity.

[1ctoolfool]

also occurred to me the y axis is carrying much more mass and this may contribute

[Geof]

Originally Posted by 1ctoolfool also occurred to me the y axis is carrying much more mass and this may contribute

That is a good point; when X change direction only the table mass is involved but Y includes all the X axis stuff. So the 'Y' impulse is probably double and in the correct direction to excite the nodding most efficiently.

I guess it would be possible to experiment with different masses bolted to the table. Do a cut with something clamped directly to the table, then load the table to its maximum capacity and do a cut; I would expect to see some difference.

[Andre' B]

This be why when finish and accuracy really matter you get a bridge mill instead of a C-frame.

[mactec54]

Hi 1ctoolfool

I'm surprised the coining/marks left by the cutter are not greater as if you check the X-Y & Z axes you will have .001 to .0015 slop in the linear rails this is one of the problems on these Haas machines which give you not such a good finish on your work everything is moving a round while cutting

[gerard1959]

In 13.14 series software Haas added Setting 191 Default Smoothness to the settings page of the control which allows you to control the machines acceleration rates, which allows you to control the smoothness of the part, so by selecting FINISH on this setting you will eliminate the coining marks. I have attached a more detailed description for you to read.

If your machine software is below 13.14 series, then you should contact me directly and I can change some parameters on your machine to eliminate the coining.


Thank You,
Gerard Bailey
Applications Engineer
Haas Automation Inc
Tel. 800 331 6746 x7128
Fax. 805 278 1803
gbailey@haascnc.com

[ktm666]

we run every finish program with the smoothness on finish. still, we get coining. more of a problem on the vm6 than a vf3

[gerard1959]

then I would like to suggest you call your local Haas dealer to check the levelling and machine geometry etc.

Thank You,
Gerard Bailey
Applications Engineer
Haas Automation Inc
Tel. 800 331 6746 x7128

[Andre' B]

Does the smoothness setting just change the acceleration or does it take the motion control down to the next level, known as jerk?

http://math.ucr.edu/home/baez/physics/General/jerk.html

[MikeOD]

Originally Posted by gerard1959 In 13.14 series software Haas added Setting 191 Default Smoothness to the settings page of the control which allows you to control the machines acceleration rates, which allows you to control the smoothness of the part, so by selecting FINISH on this setting you will eliminate the coining marks. I have attached a more detailed description for you to read. If your machine software is below 13.14 series, then you should contact me directly and I can change some parameters on your machine to eliminate the coining. Thank You, Gerard Bailey Applications Engineer Haas Automation Inc Tel. 800 331 6746 x7128 Fax. 805 278 1803 gbailey@haascnc.com

Gerard,

I'm not sure if you're aware, but inside of Renishaw probing software, about a year ago we found that if setting 191 was set to smooth, it could occassionally break a probe stylus on a Z surface measurement. As a result, G187 P1 was added to the Renishaw code (it was added in RENIPS.V25 or V26...I can't remember which), followed by G187 without a P after the probe has finished running. When making parameter changes to make a machine without setting 191 behave like a machine with newer software set to smooth, you might want to verify if the machine in question has probes or not as it could introduce a risk for damage to the probe stylus.