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Sheetcam - Mach 3 Help

Mach 3 CNC from Artsoft questions or tips can be posted to this forum.
JodiB
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Sheetcam - Mach 3 Help

Postby JodiB » Tue Mar 28, 2017 1:38 pm

Good day,

I've been posting on various cnc and software forums for the past while and have gotten some great help and advice.  We've made progress, but for every step forward, we take 3 back.  I try to give a brief history of the issues...

Brand new to all of this.  New 4 x 4 plasma table purchased last year - my husband assembled it.  Hypertherm PM45 with machine torch.  Using Corel X8 and Sheetcam TNG on pc with windows 10 and Mach3 on separate pc with no internet connection using windows XP.  Could not cut a clean file from the beginning - jagged edges, wobbles/waves.  Started with the mechanical side of things - we basically took the table apart, put it back together, received some upgraded parts (motor, gears), squared it off a dozen or more times, hardwired it, bolted it to the floor to avoid any possible movement...and the list goes on.  To us, it then seemed accurate and ran smoothly.  Next Corel Draw...fixed some glitches in the software and now export all drawings in SVG format - appears much cleaner in sheetcam than DXF.  Next Sheetcam...all imported drawings look clean and toolpath looks accurate - no deviations from the drawing.  We've worked a great deal with the settings and now have them set to where we think works best for our setup.  Finally Mach3...again, we've received a great deal of feedback and we played with the settings a fair amount, but the end result is always the same.  The torch "judders" in random areas (yes, we've experimented relentlessly with the CV settings) and several arcs look flat - especially in fonts.  We've experimented and simple files come out much cleaner - more detailed files have several errors in them.  I'm posting some screenshots of a file that we've been working with, some of our current settings and some pics of the end result - a heads up, because of all of the issues, we've attached a pen to the torch and have been drawing all of our files - wasting too much metal.

Please let me know if there is any other info that would help to diagnose the issue and I'll be more than happy to provide it.

Thank you!!
Jodi

Attach 1 - Sheetcam imported file
Attach 2 - Toolpathed file in Sheetcam
Attach 3 - Gen Config settings Mach3
Attach 4 - X axis motor tuning settings
Attach 5 - Z axis motor tuning settings
Attach 6, 7, 8 - pics of end result...only a few errors shown but they are several areas throughout

Any thoughts?
Attachments
Screenshot (41).png
Screenshot (42).png
gen config.PNG
x axis.PNG
x axis.PNG (23.53 KiB) Viewed 535 times
Z Axis settings.PNG
Z Axis settings.PNG (23.47 KiB) Viewed 535 times
pic1.1.JPG
pic1.2.JPG
pic1.3.JPG

tcaudle
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Re: Sheetcam - Mach 3 Help

Postby tcaudle » Wed Mar 29, 2017 6:53 pm

so its either backlash in an axis (mechanical) or the really low acceleration you are running at. 15 on the X and 6 on the Z . If that is all your table will support you need to upgrade the motors or lighten the gantry. 15 is marginal MACH will compromise the toolpath (cut or round corners).

See if you can get the acceleration up to 25. If it gets WORSE then its almost for sure mechanical. If it tracks better its MACH .

Messing about with CV yields marginal results. I sure looks mechanical to me and the flats on corners/arcs could be mechanical but are typical if the mechanics cannot handle the toolpath at the speed and acceleration for the axis. Anything you do to X you need to do to Y as far as velocity and acceleration. If its a dual drive table make sure the slave axis is tuned the same as the master and nothing is slipping/

SInce you are drawing with a pen in SheetCAM slow the feedrate down to 50 or less and see if things follow the toolpath better. It can be deceptive because slowing down causes less wabble and forces if its slipping but it will also work better at the low acceleration number.

JodiB
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Re: Sheetcam - Mach 3 Help

Postby JodiB » Thu Mar 30, 2017 10:52 am

Good morning Tcaudle,

Thanks again for taking the time. We've been experimenting with our motor turning settings - our table is definitely rigid enough to handle higher accel/velocity, so I'm going to try increasing the accel to 25 this morning. Does increasing the velocity to 250 then make sense? Do you have any suggestions to try for the z axis? It is a dual drive table and slave axis is tuned the same as the master.

I'll also give slowing the feedrate a try - thanks for the advice and hopefully I'll have some good news to report :)

tcaudle
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Re: Sheetcam - Mach 3 Help

Postby tcaudle » Thu Mar 30, 2017 7:09 pm

velocity is the max velocity the axis can run at. Acceleration is how long it takes to get there. So the higher the velocity the more acceration you need to accelrate over the same distance.

in short the more acceleration you have the better you can turn a corner and the faster you can change directions. Its tied to the velocity because its about distance over a given time. so the higher you jack the velocity and feedrate of the cut the more acceleration you need to go from zero to the full speed in the same distance .

Leave you speeds down until you can confirm it's an acceleration issue, If moving to 26 UPS/sec at 150 fixes it you will need to move to 35 IPS/sec at 250.

Paint Chip
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Re: Sheetcam - Mach 3 Help

Postby Paint Chip » Wed Apr 26, 2017 1:08 am

Have you checked all the set screws on your motors and pulleys (creates extreme backlash) - they come loose pretty easy if they are only snugged tight. That bird got me a few weeks ago. Some of my parts looked similar to the photos above. I have since Loctited the pulleys on the shafts and the set screws on the pulleys. It was a PITA to get done but my parts are coming out perfect now.


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