Odd jog on curves

[Orangejbird]

Hello all,

As you can see from the photo these parts have an odd jog on the lower curve. I reversed the direction of cut on the second one to see if the jog moved. It did.
Soooo . . . software, hardware . . operator error?
DXF into Sheetcam into Mach3 on a DynaCNC.

Thanks for looking.

[Dennis]

Looks like a table problem, does it only do it on arcs or circles.

[urbnsr]

I would first check that each axis is not loose.
Paul

[jimcolt]

Backlash or flex in your machine.....mechanical issue for sure.

Jim Colt

[Orangejbird]

I'm not finding and looseness on any part of the table, racks, motor mounts, or gears.
Just cut a 13" circle and it did the same thing. Looks like the motors are making the jog.

[Gamelord]

Check your rollers and see if they have a piece of garbage embedded in them, or if there is a nick or gouge in any of your tracks or rails. The gantry could be "hitting a speed bump" and causing the issue. Does it do it ever time or is there another part of the table that seems to cut better? Like moving the gantry over to the other end of the table and cutting?

Just giving some other options to check.

[Orangejbird]

I can cut 20 of the same part nested on a large sheet. each piece will be the same, so seems it's not one part of a rail or track?
Good question Gamelord.

[Gamelord]

If it does it on every single piece, at the exact same place then I would have to suspect it is your software or the drawing itself. If it does it on multiple drawings then that narrows down to the software and/or the way it is sending the info to the drives.

[I Lean]

When I've seen similar shapes on my machine, it has ALWAYS been a set screw a little bit loose. (either a pinion gear or a pulley setscrew)

[muzza]

Sheetcam occasionally changes the cut lines especially with arcs, try saving your original drawing as an SVG instead of a DXF and bring the SVG file into Sheetcam to create your gcode.
Murray

[jimcolt]

If you share the file as a .dxf.....I will cut your part on my machine. We can look at it to see if the bump exists.

Jim Colt Hypertherm

[Orangejbird]

Here's the file. I cut test pieces on 1/8" @ 120 IPM
Actual parts will be made from 1/4"

[natewelding]

is that where your lead ins and lead outs are? thatll cause that problem too

[trucutcnc]

It's not in the drawing. If it's at the start/stop point, it's a mechanical issue for sure.

[plasmapros]

Is your gantry a single side drive style with a motor only on one end of the gantry? If so it could just be undriven end trailing behind the driven end of the gantry. Not much you can do about that aside turn down your amperage and cut speed and be sure all mechanical parts are working well to reduce drag on the trailing side.

[Orangejbird]

Gantry is dual motor (stepper) drive. When it makes the jog you can hear the motors change speed. Maybe posting the G-code will help? Might be a problem between Sheetcam/Mach3 and my control box? I didn't think it would be the DXF file.

[Orangejbird]

DynaCNC with their 6000 controller.

[trucutcnc]

DynaCNC with there 6000 controller.

We did a controller/motor retrofit on one of those last year. It did not have any mechanism to firmly engage the pinion into the rack. That being the case, if the rack is not perfectly parallel to the pinion travel, you could have varying degrees of backlash.

An easy way to tell is it's the machine/controller or something in Sheetcam is to look at the toolpath display. If the jog appears in the toolpath display, it is in the code. If not it's in the machine.

Is the jog where your leadin/out is? You should be using a tangent leadin/out at one of the sharp corners.

[Orangejbird]

Leadin/out is at the sharp corner.
Sure appreciating you all looking and helping troubleshoot.
I'll look at the tool path displays closer.
Many Thanks!