Trying to cut shape in lightburn

[Wouldman55 (Stephen Paul Whitman)]

I have this trinket tray which I made and

engraved and I am trying to cut out a acrylic insert to fit inside the tray which is 179mm x90mm and the insert is 169mm x 80mm but when I attempt to cut the shape it comes out like this.

.

[JTR (Tyler Raps)]

What does the shape look like in LightBurn? Are you seeing a similar issue with other projects, or just this project? Can you share the .lbrn2 project file you’re working with here?

Sometimes stretching like this is caused by Rotary Mode being unintentionally enabled — a good check is to go to Laser Tools > Rotary Settings and make sure it is disabled. Since your laser has a Ruida controller, you’ll need to be connected to it when you do that.

[ednisley]

@Wouldman55

it comes out like this

If I understand the problem correctly, the plywood is an ellipse laid out with LightBurn’s Ellipse Tool, but the trinket tray isn’t an ellipse.

The tray ends look like a pair of semicircles, so:

• Draw a circle with diameter 80 mm
• Duplicate it
• Use the Numeric Edit toolbar to move the duplicate +169-80 mm along the X axis
• Select both circles
• Edit → Create Rubber-Band outline from selection
• Profit!

If that’s what you’ve already done and still ended up with an ellipse, then other forces are at work: tell us more.

[bernd.dk (Bernd)]

By finding the 2 diameter of the circles (the one in the middle and the end of a symmetrical elipse) you can get reasonably close to the desired result.

[Marcus_Wakefield]

I might have misunderstood the original post but I don’t think it’s the elliptical shape he’s attempting to cut. I think it’s the rounded rectangle he’s after but as @ednisley said; I think he’s used the Ellipse tool and that’s the problem.

[Marcus_Wakefield]

Another way would be to draw a rectangle then set its corner radius to 40mm.

Hope this helps.

[ednisley]

@Marcus_Wakefield

draw a rectangle then set its corner radius

An even faster path to profit!

[debraanderton]

I have been trying to get little circle about a 1/4 in round. but they also turn out like an oval, I am not sure how to set the corner radius,

[ednisley]

@debraanderton

little circle about a 1/4 in round. but they also turn out like an oval

If the LightBurn layout shows a circle, but it engraves as an oval, then the machine most likely needs careful attention to eliminate backlash. Although this was written with Sculpfun lasers in mind, it will give you an idea of what to inspect:

Guide to mechanical adjustments and maintenance

You may also want to burn a backlash test pattern on cardboard while you’re adjusting things:

Dot Test with Angle.lbrn (46.3 KB)

If the result doesn’t look exactly like the layout, it’s almost certainly a mechanical problem.