[34chev]

I am new to this forum. Need some help, I am running a plasma table, running sheet cam 3.0.16 and mach 3. Things run pretty good, using Mach 3 plasma post processor. I recently added a floating head and when I switched to the THC 300 post processor I am getting a stop and go or jerky motion on smaller curves. I put in a file with some small text (approx 1/2 inch high) and with the MACH 3 processor it seems to run pretty good but as soon as I switch to the THC 300 processor the problem starts.

Do you have any suggestions as to what the problem is?

[lukewarm]

Sounds like the other post processor is putting Mach3 into exact path mode. Can you copy and paste the preamble from the top of the jerky G-Code here?

If you see a G61 (exact stop mode) replace it with G64 P0.005 The P variable sets the tollerance, the higher the number the closer to the commanded velocity your machine will stay at the sacrifice of accuracy.

[lukewarm]

Can you post the top section of both outputted GCodes please. I just tested both on my computer and both pieces of GCode look essentially identical. The arcs are both handled the same and neither of them seems to specify exact path or constant velocity mode.

[lukewarm]

Try putting G64 P0.005 at the top of your gcode, run it, get back if the problem persists.

Also since you built your machine what are your max acceleration values? Are they consistent over each axis?

[34chev]

Sounds like the other post processor is putting Mach3 into exact path mode. Can you copy and paste the preamble from the top of the jerky G-Code here?

If you see a G61 (exact stop mode) replace it with G64 P0.005 The P variable sets the tollerance, the higher the number the closer to the commanded velocity your machine will stay at the sacrifice of accuracy.

Thanks for the help. I don't see a G61 and am not sure how or where to place the G64 P0.005, do I need (post in front of it). not familiar with coding.
Not sure which section G code starts. I played with acceleration and velocity with the Mach 3 plasma post seems to work pretty good. Velocity 231 acceleration 31 have turned velocity down to 130 and acceleration to 18 with not much change. Will try to post the G code you asked for soon.
Thanks again.

[lukewarm]

Just add it to the top of your gcode file!

[34chev]

Just add it to the top of your gcode file!

I have attached the screen shot for the jerky G-code. I tried putting in the G64 P0.005 with no success, providing I put it in the right place.

[34chev]

I have attached the screen shot for the jerky G-code. I tried putting in the G64 P0.005 with no success, providing I put it in the right place.

Here is the screen shot. Sorry never showed in last reply.

[lukewarm]

Alright I attached the file with the G64 command where it should be. Can you re-run it with the G64 in that position and tell me how it goes?

Also you never attached your non-jerky Gcode. Can you at least give me a line count for each file? If one file is substantially longer this means one post processor is not joining similar arcs together. I doubt this is the issue, however.


I notice you are in Canada, I'm also in Canada (BC) if you feel like PMing me contact info I can call you and walk you through some troubleshooting over the phone if you like.

[34chev]

I have attached the screen shot for the jerky G-code. I tried putting in the G64 P0.005 with no success, providing I put it in the right place.

Alright I attached the file with the G64 command where it should be. Can you re-run it with the G64 in that position and tell me how it goes?

Also you never attached your non-jerky Gcode. Can you at least give me a line count for each file? If one file is substantially longer this means one post processor is not joining similar arcs together. I doubt this is the issue, however.


I notice you are in Canada, I'm also in Canada (BC) if you feel like PMing me contact info I can call you and walk you through some troubleshooting over the phone if you like.

There is no attachment.
But the line count is MACH3 Plasma 31930
THC300 32530

[lukewarm]

You're right I must have forgot to attach it. Anyway put it after g53 at the top of the file. But after gauging by your for length I don't think you are combining short line segments. Can you upload the model file?

[34chev]

You're right I must have forgot to attach it. Anyway put it after g53 at the top of the file. But after gauging by your for length I don't think you are combining short line segments. Can you upload the model file?

Here is the whole file. Inserted the G64 made no difference.

[Mike 1948]

I am new to this forum. Need some help, I am running a plasma table, running sheet cam 3.0.16 and mach 3. Things run pretty good, using Mach 3 plasma post processor. I recently added a floating head and when I switched to the THC 300 post processor I am getting a stop and go or jerky motion on smaller curves. I put in a file with some small text (approx 1/2 inch high) and with the MACH 3 processor it seems to run pretty good but as soon as I switch to the THC 300 processor the problem starts.

Do you have any suggestions as to what the problem is?

Here is the post I use on my Orphan DynaCnc with floating head plasma based on the Caudle post. Set the switch offset to match your machine and give it a try. They look very similar.
After you load the Gcode in Mach go to the config page and make sure "exact stop" is not specified, it should be "constant Velocity".

Good Luck
Mike

[34chev]

Here is the post I use on my Orphan DynaCnc with floating head plasma based on the Caudle post. Set the switch offset to match your machine and give it a try. They look very similar.
After you load the Gcode in Mach go to the config page and make sure "exact stop" is not specified, it should be "constant Velocity".

Good Luck
Mike

Installed it, tried it and no change , Thanks for the help.

[lukewarm]

Chevy can you post the original dxf file you made the gcode from. I'm pretty sure I can fix your problem

[34chev]

Chevy can you post the original dxf file you made the gcode from. I'm pretty sure I can fix your problem

Here it is.

[lukewarm]

Chevy have you tuned your CV yet?

Check out this link, I still think it's a CV issue.

http://www.machsupport.com/docs/Mach3_CVSettings_v2.pdf

[34chev]

Chevy have you tuned your CV yet?

Check out this link, I still think it's a CV issue.

http://www.machsupport.com/docs/Mach3_CVSettings_v2.pdf

I have tried setting the motor acceleration and velocity, there was no change. I have checked the other CV settings will check again tomorrow. Will increase look ahead mine is set pretty low.
Thanks again

[lukewarm]

Try using G64 P0.05 instead of P0.005 and see if it improves any.

[lukewarm]

If still no change change it to P0.5 and check for a difference. Note that your cuts will be horrendous but it will let us know that your accelerations are too low to maintain a constant feed rate and give us a few options. One of which being increasing your acceleration rate (if possible) or using a lower amperage consumable to decrease your feed rate.