New LR4 help with troubleshooting asymmetry/warping

LowRider CNC Troubleshooting
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Hello, I’ve almost finished my lowrider v4 build. It’s sized for 1200 x 600 cutting area. The tubes are 31.8mm 304SS polished to #320.

I’ve calibrated the belts, squared, and levelled it, and have just tried engraving a test image (crown.dxf) and then cutting my strut plates.

After cutting the strut plates I noticed that some of the holes were doubled/offset, and that the edges of the indents aren’t symmetrical. Then I looked at the crown engraving and noticed it is.. not right. In particular the cross on the crown is weirdly asymmetrical.

Photos of the machine, engraved crown, and strut plates, below.

Due to the warnings in the build instructions, I didn’t want to over-tension my belts and break things. Do you think these inaccuracies are due to too low belt tension? Maybe in the X belt? My X belt does feel a bit loose, now I look at it.

Could you please help me with some guidance on what to check to troubleshoot this?

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PXL_20260222_055200928
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Congratulations on your build! It looks great Tom.

It’s hard to describe how tight to make the belts. For me, I press against the belt and see how far it deflects. I try to get my Y belts to deflect about a half of an inch when I press them. The X belt I tightened until it just barely touches one of the braces or the strut. It’s not a lot of force that I’m using. I think Ryan said around 7 lbs is about right.

You have some scrap material to experiment with, so I’d make some squares and circles to try out as you gradually tighten your belts.

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Thanks Britt!

Based on your advice, I had a go at drawing some concentric circles and overlapping rectangles. After adjusting the tension a couple of times I got them drawing the correct dimensions.

I’ve now been able to cut my strut plates properly.

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