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Laser Not Cutting Perfect Circles: How to Fix



Hey I'm Unni. I am a laser and CNC expert at Mellowpine. You can also find me on Mellowpine Lasers YouTube channel. If you have any questions related to CNCs or Lasers, I'd be happy to answer them. Reach me at mail@mellowpine.com


Laser not Cutting perfect circles

Is your laser not cutting perfect circles?

I’ve been there too. It is a frustrating experience when your laser suddenly forgets what a perfect circle is.

I’m Unni, and I’m a laser engraving expert. In this guide, I will explain the three possible reasons why your laser is not cutting perfect circles and how you can resolve it.

1. Hardware Issue Such as Improper Belt Tension or Misaligned gantry

Adjusting belt tension
Adjusting belt tension

If the circles turn out wobbly or the ends of the circle do not meet, then it is most likely a hardware issue.

Generally, it is caused due to improper belt tension or a misaligned gantry.

A laser machine with improper belt tension is unable to maintain a uniform motion, which leads to wobbly circles.

On the other hand, a misaligned laser gantry is one where the X-axis gantry is not perfectly square with the Y-axis, or vice-versa.

As a result, the laser traces an improper circle whose ends do not meet.

Sometimes the issue can be a combination of both, so it is always recommended to check both aspects when resolving such issues.

Resolving Hardware Issues to Get Perfect Circles

To resolve hardware issues, first set the right belt tension.

An improper belt tension can also cause the laser to skip lines during engraving.

So, when setting the belt tension, perform test engravings and look for skip lines along the X and Y axes.

After setting the belt tension, it is time to square the laser gantry.

To do this, move the X-axis gantry a few inches away from the front end of the frame and measure its distance from the frame at both corners.

If the gantry is at exactly equal distance at both corners, the gantry is perfectly straight.

If not, then you need to lose the belts, manually move the gantry to make it square with the Y-axis, and then tighten the belts again.

Once you square the gantry and adjust the belt tension, perform test runs to see if the issue is resolved.

However, if the issue still persists, then it is recommended to look for issues in the belt or the wheel and replace the damaged component.

2. Software Configuration Issue

Rotary mode enabled in Lightburn
Rotary mode enabled in Lightburn

Improper software configuration can also prevent the laser from tracing perfect circles.

First, make sure that the rotary mode is turned off, as turning the rotary mode on traces a different path to create a circle.

Another possible reason that your laser is tracing improper circles is the high acceleration setting.

Make sure the acceleration setting of the laser is set as per the recommended value by the manufacturer.

However, if the circles appear to be stretched into an ellipse, the issue is likely related to the steps per millimeter settings for the individual axes.

This issue is generally common if you have upgraded your drive system or replaced an existing belt or stepper motor with a different one.

Configuring Lightburn with the Upgraded Hardware

The steps/mm setting for your setup is like a pre-set measurement in the machine’s controller, and it doesn’t automatically know when you change the hardware.

So, you’ll have to manually adjust the steps of the machine to make sure it works correctly.

To do this, you’ll need to find out the Belt pitch, Pulley tooth count, Motor step angle, and Driver microstepping for your setup.

Once you have these details, you can use a Stepper Motors Calculator to figure out the Steps/mm value for your setup.

Then, connect your laser to Lightburn and go to Edit > Machine Settings.

There, you’ll see the settings for X steps per mm ($100) and Y steps per mm ($101).

Depending on the axis you upgraded, enter the new value from the calculator, and click Write.

Once you click Write, Lightburn sends the command to the controller to save the new settings.

Note: The values under the Machine Settings are crucial, so it’s recommended to back up your current settings before making any changes. Click “Save to File” to create a backup of your settings.
Better safe than sorry!

3. Your Lightburn License is Not Genuine

Irregular Circles traced by the laser
Irregular Circles traced by the laser

Another possibility that your laser is tracing improper circles can be the authenticity of your Lightburn software.

Lightburn has the ability to detect the authenticity of the software, and if the software you are using is not authentic, the software deliberately produces wobbly circles, thereby ruining your workpiece material.

Apart from that, it is important to purchase your license from a reliable source, such as Lightburn’s official website, as several users have reported sellers providing a pirated copy of Lightburn software at a cheaper price.

Therefore, it is recommended always to use an authentic copy of Lightburn Software purchased from an authentic source.

Hey I'm Unni. I am a laser and CNC expert at Mellowpine. You can also find me on Mellowpine Lasers YouTube channel. If you have any questions related to CNCs or Lasers, I'd be happy to answer them. Reach me at mail@mellowpine.com