Incomplete cuts

[ruralfencer]

I'm using Qcad, Sheetcam and Mach 3 and my last couple of projects having been cutting complete shapes. The torch is moving in the x y before the torch fires. I've increased pierce delay, moved start points, moved earth clamp and changed consumables. I'm not using THC.

[adbuch]

When I see that with a Plasmacam system, then the it is usually caused because the box for "wait for signal before moving" is not checked. I would assume that Mach3 has a similar setting. I can't tell you what it is, because I only use Mach3 for my cnc router. Perhaps one of the Mach3 experts will chime in here.
David

[adbuch]

What plasma cutter are you using. For the Hypertherm with Duramax torch using FineCut consumables, this can happen with new consumables. The remedy is usually to increase the cut height from 0.060" to 0.080" for the first 100 or so cuts, and then drop back down to the 0.060" cut height.
David

[ruralfencer]

Thanks David I'll try that and have a look at the delay. I'm using hypertherm 45xp and fine cut consumables at the moment.

[acourtjester]

Have you changed the post processor you were using, it needs to be a Plasma type to look for the Arc Ok signal before moving.

[weldguy]

Good point from acourtjester, should let us know what post processor your using and post some of your gcode for review.

[adbuch]

Have you changed the post processor you were using, it needs to be a Plasma type to look for the Arc Ok signal before moving.

[ruralfencer]

So I've done everything above and rung my tech support, still no joy. When I'm back at the desk top I will up load the .tap.

[weldguy]

That's a bummer. Something you could do in the meantime until you find the problem is add long leadins so by the time the torch gets to the end of the lead in the material has been pierced and your parts will drop out like they should.

[tnbndr]

In Sheet Cam for the tool you are using, play with the pierce delay setting. It will vary with metal thickness.
The 6th line down is the one you should play with. Start out with .5 and see what happens.

[ruralfencer]

I have just run another job out with my normal settings for fine cut and 1.6mm and it ran with no problems. Could there be something with the drawing? It was one I downloaded here

[adbuch]

I have just run another job out with my normal settings for fine cut and 1.6mm and it ran with no problems. Could there be something with the drawing? It was one I downloaded here

Please share your downloaded file so we can take a look.
Thanks,
David

[ruralfencer]

Here is the file

[adbuch]

Mick - you file appears to be fine. Nice and clean. What specific problems are you having trying to cut it?
David

[ruralfencer]

On some of the cuts the torch is moving before firing. It's touching the material then lifting to pierce height then moving down to cutting height and moving along the cut before torch fires. It's frustrating me because everything else cuts fine just this job isn't

[adbuch]

Do you have all your settings for your controller set the same as for the other files which cut without problems? Tom had previously mentioned "Have you changed the post processor you were using, it needs to be a Plasma type to look for the Arc Ok signal before moving." - but I would assume that if all your other files cut fine, then this is not a post processor issue. Is there a place in your control panel for Mach3 to check a box for "wait for signal before moving"?
David

[ruralfencer]

Yes, I've been through all the settings, it just seems weird that it's just this drawing.
I haven't been able to find a wait for signal but I did play around with the pierce delay and nothing changed

[adbuch]

Your file has 218 intersections and 35,725 nodes.

Here it is with all intersections linked/joined. I also smoothed it to reduce the node count. Now 22,747 nodes. Maybe try this one.

skull with no intersections.dxf

(161.02 KiB) Downloaded 71 times

skull with no intersections.dxf

(161.02 KiB) Downloaded 71 times

[ruralfencer]

Thank you David, finally got a chance to cut it today and it worked.
Maybe I need to look for intersections closer.
I'm happy we found the solution because it was driving me crazy.

[adbuch]

Thank you David, finally got a chance to cut it today and it worked.
Maybe I need to look for intersections closer.
I'm happy we found the solution because it was driving me crazy.

Mick - it is also possible that the large file size was causing your problems. I did two different things.
1. Join/Link to remove intersections/crossovers
2. Smooth to reduce the node count and overall file size.

You original file was over 1 Mb in size. After smoothing the size is 161 Kb. That could have made the difference.
In any case, I'm happy to hear that it worked out for you with a successful cut. Be sure to post some photos when you finish it.

David

[ruralfencer]

Is it worth looking at design edge for these functions as qcad is limited?

[adbuch]

Is it worth looking at design edge for these functions as qcad is limited?

It certainly would be worth it for me personally. In my case I already own several of the Plasmacam tables which come with "Basic Design Edge". I paid an additional $998 to upgrade to Advanced Design - which is what I use to edit files like yours. If I didn't own the Plasmacam tables, I would gladly pay the approx. $2000 cost to purchase Design Edge as a stand-alone program. For cnc plasma files, this is (in my opinion) "hands down" the most powerful design/editing program available. I also use Fusion 360, Inkscape, AutoCAD, BricsCAD, LightBurn, VCarve Pro/Aspire, Solid Works, and several others. But by comparison, Design Edge is miles ahead of the others for cnc plasma work.

Your budget will most likely dictate your choice of design software. Here are some excerpts from a recent post on the Plasmacam Facebook Group discussing Design Edge and the stand-alone purchase.

David

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[alanmccabe]

I was having a similar problem, I have a proma 150 but the arc ok signal comes from the plasma cutter. I wanted to do some tests without thc and when I switch the thc option off in uccnc the machine starts running before the arc is established missing the first few mm. I had asked on the uccnc forum and it was suggested I add a makro to force uccnc to wait for the arc ok signal from the plasma cutter when the thc option is disabled. Going to try the makro and see if it helps, maybe someone has a better solution. Thanks Alan

[acourtjester]

Have you tried another post processor?? I use a UCCNC controller on one of my tables, I will think about that problem. I need to wonder around the back of my memory to see if I can remember about it. I have been tied up with my last LinuxCNC controller build and have not used the UCCNC table for a while.

[acourtjester]

Have you looked at the setting for the THC like the ones shown here. Your screen may look different.