Laser Engravers: Does your Laser Rotary Stretch your Image?

You've created the perfect design in your graphics software, set up your cup on the laser rotary attachment (hopefully a PiBurn!), and sent the job to your laser.

But when you check the cup you realize the image is distorted. Frustrating.

It doesn't look like the original design because it is either stretched, warped, or appears oval when it was meant to be circular.

You're thinking: I don't understand why my laser rotary stretches images. What could I be doing wrong?!

Below are the most common fixes for stretched, squished, or distorted artwork on cups—ordered from most to least likely (for roller rotaries).

What to do when a laser rotary stretches images: 3 things to check

1) Setup on the rotary: Is the bottle’s neck on the drive wheels?

This is the most common cause of distortion—especially “stretched” designs. If your flask or bottle has a narrow neck and that neck is on the motorized wheels, the larger body surface travels farther per rotation than the neck. Your settings are based on wheel diameter, not the object’s body diameter, so the laser “thinks” the surface travel equals the wheels—when in fact the body moves more.

Fixes:

• Flip the bottle so the narrow neck rides the smaller (rear) wheels; remove the clamp if needed. For extra traction, consider the PiBurn Mega Clamp.
• Compensate in artwork (scale down along the rotation axis). Test with masking tape at low power to avoid wasting cups.
• Change steps per rotation (reduce), but we rarely recommend this—people forget to change it back.

2) “Oval circle” optical illusion: Measure your engraving

That “circle” looks oval on a cylinder—often it’s an illusion. Edge areas are slightly farther from the viewer, so they appear smaller. On smaller diameters, this becomes obvious.

Check it: Engrave the circle on a flat scrap—then measure the height and width on your tumbler. They’re likely equal.

Fix: Slightly adjust artwork to compensate. There’s a handy calculator in the files of our support group: PiBurn Labs — direct file: link.

3) Steps per rotation are off: Run the 100 mm test

Pulses/steps per rotation that aren’t dialed in will distort art around the circumference. Calibrate once and you’re set (with PiBurn).

See Chapter IV (p. 18) of the PiBurn manual or watch the video guide.

4) Slipping on the rollers (heavy handles, unbalanced items)

Rollers rely on friction; heavy handles/unbalanced items can slip (one drawback vs. chucks—see our long-form comparison here). Check out our chuck option, the PiBurn Grip—the Grip don’t slip!

The latest PiBurn metal clamp has adjustable tension—tighten the thumbscrew to boost traction on stubborn cups.

Still slipping? Add a small counterweight (e.g., magnet) opposite the handle.

5) Belt or pulley tension

Artifacts at the start/end of wraps often trace back to loose belts or pulleys. Quick check/walkthrough:

6) Still stuck?

Post details (laser model, settings, photos) in our support group PiBurn Labs. Our community of PiBurners is fantastic at troubleshooting.

Hope this helps you nail perfect geometry on tumblers. We’re here to help!

Happy PiBurning!
Len and Stan