Cutting jerky

[jliggett]

I am using Corel X3, exporting as an .EPS, then using Cut 2D to generate G-Code out to Mach 3 running a Vortech router. in Corel, and Cut 2D, the files look clean, with minimal nodes.
However, when I run the machine, it cuts like crap, going around curves, (and sometimes straight lines), with a jerky motion, like it's starting and stopping hundreds of times. The number of lines in the G-Code is in the thousands for a relatively small part. I am sure that it is generating way too many lines. Does any body have an idea of how I can reduce the number of segments in the code to get a smooth cut?

[tamathumper]

I'm marginally more familiar with Mach3 than with Cut2D being a newbie with it. If you can't "join" vectors or use some kind of group/combine function on your EPS, then in Mach3 you can try the following:

Make sure Constant Velocity (CV) is turned on, and lookahead is set to 50+ lines. This may generate slight issues with corner rounding, but CV is a balance between jerkiness and "exact stop" machining.

Actually, here's a better thread on it - http://forum.artcam.com/viewtopic.php?p=25546

[RoutnAbout]

Hello jliggett,
Welcome to the forum.
This sounds like a setting in Mach that isn't set quite right.
But if you'd post your crv file.
I'll take a look to see that you don't have any duplicate or open vectors.

[tamathumper]

Although I shouldn't talk - now my setup won't route a simple circle/hole - tonight they're all coming out wobbly. I thought I had a clamping/taping issue, but my setup is now clamped solid and I still am getting wobbly holes

It's also routing the holes REALLY fast, in four discrete steps/arcs... not like it was originally where it was slowly stepping around the inside of the holes and I could hear the stepper motor harmonics rising and falling in lockstep as it turned its way around the inside of the holes, so apparently I need to do some tweaking as well...

[metalworkz]

Some software will use multiple line segments to draw a vector and when the toolpaths are created from this multitude of segments the program can be bigger and it will sometimes be visable in the finished cut as many starts and stops. I think it is a good idea to observe the composition of the lines and arcs generated at the CAD stage and many times you will be able to trace/redraw the vectors so as to reduce the segments and end up with a smoother final vector to use for the toolpath generation. It may be a little more work but you will probably notice the difference in the final cutting of the part.
The fact that you said it looks like many 'starts and stops' leads me to believe the vectors are in fact created that way before the toolpaths were generated, and a close look at the file from Corel X3 will probably reveal a lot. Did you 'join' all the vectors before creating the toolpaths? You may be able to clean a lot of it up by 'joining' the vectors in Cut2D and that way they will not have as many starts and stops.

[James E]

Welcome to the forum jliggett.
There is a lot about this effect on the forum, mostly resolved with Mach settings, as suggested above,but that doesn't mean it isn't your file as you suspect.
If someone could send you a test code that cuts smooth, from cut 2d, and it was jerky for you, that would say settings, and if it cut smooth that would say cad software problem.
I would post a vcp, but I'm not sure it would be a help. Oh - are there some test files on the Vectric website?
Jim

[mboydraska]

I would try your settings in Mach3, my settings are look ahead 50 lines - CV is set at 180 and 45 degree angle. If that doesn't help look at your cad file.

Happy Cutting!

[moto633]

I have a Vortech router as well and I am finnally getting pretty good results. It has a lot to do with setting up mach properly.

Nick

[ger21]

You might want to look into this.

http://www.candcnc.com/DXFTOOLDetails.htm

[jliggett]

Hey Guys,
Man I really appreciate all the responses, sorry I haven't been available. Anyways, I would like to post some screenshots of my settings, along with a Cut 2D file that's cutting unacceptable. Also, I cut the wingspar sample file that came with Cut 2D. Still cut eratic. I hope the files post properly, and hope someone can help me find the needle. Thanks again. j0n

Screenshots.zip

(554.25 KiB) Downloaded 226 times

Screenshots2.zip

(514.84 KiB) Downloaded 229 times

[James E]

Well Jon, they download fine.
Sorry I cannot spot anything, but i'm not the sharpest on Mach 3 by a long way, plus I'm not at my own machine to compare. Did you have a look on the Mach2/3/4/ forum (Artsoft)?
A search for 'jerky' brings up plenty of mentions, and they are really helpful guys like we are here.

Jim

[Greolt]

First thing to do is turn "CV Feedrate" off on the settings page. That is what is mucking it up right now.

Looking at your motor tuning settings, you have nice crisp acceleration.

That means you will most likely not have the corner rounding problems those with lesser spec'd machines have.

Have CV turned on in the General Config and every CV option turned off. Right hand side, lower down.

This is always the place to start. Only get into the other CV setting if you find you need to. I don't think you will need to.


As regards the the short segment DXFs that Corel Draw is producing, look at the link that Ger provided above for more info.

Greg

[jliggett]

Turned CV feedrate off, ran a couple "air" runs and got prematurely excited. Put some material on the table and cut the BIG file( I work with Building Image Group, hence BIG) and got terrible results. I am posting a couple (bad cellphone) photos so You guys can get an idea of how my machine is cutting. Yes I have been on the ArtSoft forum but haven't posted because i am new to forums and just decided to start here. Will probably see how far I can get here then move over. Oh I will post the cut file too. Thanks again. j0n

[metalworkz]

I looked at your .crv file and it does not look bad at all. The pictures of the parts look much more choppy than the .crv file. I still think it may have something to do with the line segments Corel used to create the arcs on the CAD side as when I exported the BIG.crv file vectors to a .dxf file the arcs looked like many small line segments when opened in Autocad. Have you ever heard of 'garbage in = garbage out' ? Maybe somewhat the same principal?
You could try to redraw(trace) the arcs and see if and how much of a difference it makes? I know for some controllers toolpaths created with too many lines causes problems and have had to redraw many files to reduce the size and optimize the toolpaths for running in specific machines. Many times it is the small line segments that cause a lot of the problems when used to create arcs. I hope this helps find the needle.

[moto633]

I don't cut acrylic just wood for now and I can sand most of that chatter out of my work.

Did you talk to any one at Vortech yet? I was trying to decide if I should up grade to the servo motors to see if that would help. Also there is a product on the mach site called Smooth Stepper that is a break out board that is suppose to smooth out the stepping. I can only get good resolution with SLOW fed rates.

It would be nice to get higher res and speeds.......

Nick