What would cause "stuttering" in X and Y axis? Haas VF3

comp 670 · Feb 1, 2017

I'm running a program where I have a Iscar 2" face mill roughing out the center of a plate of 19X19X6" deep alum. Its doing it in a somewhat cloverleaf pattern and when X and Y move are the same time to do a corner the table "stutters" and does not move in a smooth motion.. The feed rate is 75, if I turn it down to 60 its not nearly as bad but still does it. Do I have a X or Y motor going out?

Going in a straight X or Y move the table moves smoothly. It only stutters when both X and Y are moving at the same time.

This is on a 2001 Haas VF3. Thanks.

Mr. PishPosh · Feb 1, 2017

Sounds like a programming issue. What was the part programmed with? I've had lots of instances where MasterCAM outputs a bunch of linear moves on something like a splined radius and it caused the mill to do that. Oddly enough, this is also on a VF3.

Josh

Sent from my XT1093 using Tapatalk

comp 670 · Feb 1, 2017

Programmed with Gibbs.

apoc_101 · Feb 1, 2017

Look at the code. is it a fuckton of tiny little linear moves and tiny G02/G03's?

comp 670 · Feb 1, 2017

Mr. PishPosh said:
Sounds like a programming issue. What was the part programmed with? I've had lots of instances where MasterCAM outputs a bunch of linear moves on something like a splined radius and it caused the mill to do that. Oddly enough, this is also on a VF3.

Josh

Sent from my XT1093 using Tapatalk

What was your solution when this happened?

comp 670 · Feb 1, 2017

apoc_101 said:
Look at the code. is it a fuckton of tiny little linear moves and tiny G02/G03's?

There is a LOT of G1 and G2.......

pmack · Feb 1, 2017

Does your machine have high speed machining? If not, pull back the accuracy settings in your CAM to make less code for the control to process(only to the extent necessary to smooth it out). Hopefully not a super tight tolerance part.

Mr. PishPosh · Feb 1, 2017

comp 670 said:
What was your solution when this happened?

I think last time I was able to change a parameter in MasterCAM, though I can't remember exactly where... Probably in the options for importing the dxf. I have no experience on Gibbs, so I can't be of much help there.

Josh

Sent from my XT1093 using Tapatalk

eaglemike · Feb 1, 2017

Set your output to use arc moves, and set your minimum arc size larger.

apoc_101 · Feb 2, 2017

eaglemike said:
Set your output to use arc moves, and set your minimum arc size larger.

bingo, and in addition to this, there may be an option in the CAM toolpath generation for "smoothing". Will make a huge difference alongside proper arc output settings in the post for both program file size, and observed smoothness of the machine movements.

npolanosky · Feb 2, 2017

apoc_101 said:
bingo, and in addition to this, there may be an option in the CAM toolpath generation for "smoothing". Will make a huge difference alongside proper arc output settings in the post for both program file size, and observed smoothness of the machine movements.

THIS! Makes a huge difference. Also, the short linear moves may be too much for the processor. On my '91 VF-1 I put an M76 at the beginning of programs and an M77 at the end. It turns off the display updating and frees up a lot of processor resources. That's how I got mine to stop shaking and allow such an old machine to pull off HSM toolpaths with ease. If you need to see anything on the display (distance to go, etc) you can just hit feed hold and it will update, then stop updating again when cycle start is pressed.

apoc_101 · Feb 2, 2017

npolanosky said:
On my '91 VF-1 I put an M76 at the beginning of programs and an M77 at the end. It turns off the display updating and frees up a lot of processor resources.

Learn something new every day... I had no idea what those codes were for. good to know for older machines outpacing their processing power!

DMF_TomB · Feb 2, 2017

you got cnc ability to handle gcode fast enough and also
.
most cnc at corners and go exact stop mode or allow corner errors due to less than perfect acel and deceleration . at high feed rate often corners are not true perfect corners. often there is gcode for more precise corners (and stuttering) or faster going around corners allow more error in tracking tool path

hanermo · Feb 2, 2017

There is a parameter that controls "accuracy" vs speed.
Or two.

It is a blended P of position/accuracy/acceleration/speed.
Don´t remember more, but one does exist.

And as said, CAM parameter changes usually make huge differences.

comp 670 · Feb 2, 2017

Thanks for all the help!!

comp 670 · Feb 2, 2017

eaglemike said:
Set your output to use arc moves, and set your minimum arc size larger.

Where do I find this? Is it in Gibbs or on the cnc control itself? Sorry but I am completely new to all this....

pmack · Feb 2, 2017

comp 670 said:
Where do I find this? Is it in Gibbs or on the cnc control itself? Sorry but I am completely new to all this....

Maybe in NC or post settings in Gibbs? I am not familiar with Gibbs, but you should be able to pick if you want arc output as g02 or straight lines and quarter turn or half turn increments.

guest · Feb 9, 2017

hanermo said:
There is a parameter that controls "accuracy" vs speed.
Or two.

It is a blended P of position/accuracy/acceleration/speed.
Don´t remember more, but one does exist.

Those are servo gain parameters, and shouldn't be messed with.

Tappedout59 · Feb 9, 2017

Maybe can help!

Maybe the control can't handle the feed rates.
In the control change X Y In Position Limit parameter #101 from 1000 to 2117.
This will allow smoother feeds at higher rate.

In GibbsCam line or arc output only pertains to toolpaths created from solid models, not wireframe.
Check that wireframe geometry is truly lines, circles and arcs, not B-splines.
Toggle Ctrl+L (labels) to see.

apoc_101 · Feb 9, 2017

have you looked at the code yet to confirm that's the issue? Cimco Edit is your friend... especially with backplotting enabled

What would cause "stuttering" in X and Y axis? Haas VF3

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