I am using a homemade Lowrider2 CNC machine with a NEJE 30W (input power) laser.
Attached are some test burns which you can see go way outside the edges of the squares. Any advice or settings to fix this?
The lowrider2 is not the most stable platform especially doing small precise movements.
I hadn’t heard of the Lowrider2 CNC so looked up some information on it. It’s an interesting platform but I think some of the design elements of it are going to make it inherently a challenge to get clean accurate burns with a laser. Having said that, let’s see how it can get tuned.
Can you share some high quality photos of the actual CNC setup? Might provide some additional insight of where to focus or where some of the artifacts may be originating from.
Let’s start with some basics.
- The filled portions clearly have some issues with burns overshooting the end point. I’m not sure if that’s the only thing going on. Can you take physical measurements of the lines and take note of the following:
1a. How does total width of each line in the square compare to nominal design width
1b. Does it appear that the lines are starting earlier than expected or ending later than expected or both?
1c. You may want to try using the fill+line option to create outlines of the squares. This might make it more apparent where the fill is going off.
- I suspect you have some backlash somewhere in your system. Focus initially on the X-axis. Check your belt tension and make certain there’s no slack in the belt but also not being overly stretched. The design I saw in a video was a little unusual so it may be difficult to get this quite right. Check that the pinions on the stepper motors are not slipping on the stepper shafts. I don’t necessarily think this is happening here because you don’t seem to have a persistent shift but hard to say. It almost looks like it’s getting off in one direction, correcting back at times, and going off in the other direction.
- There might be an offset scan issue going on but hard to tell at this point. Normally this would show as a very consistent offset of start and end that alternates between every line. But this is not consistent in this case. If you do have this issue it’s being masked by another mechanical issue.
Let’s talk a bit about some of the architectural challenges with the design.
- There seems to be a ton of mass that’s being carried on the gantry. This will make any fast movements very difficult. Make sure to keep acceleration very low as well as keep overall speeds down. It’s a lot of weight to try to get moving and then slow down. It could easily result in overshooting.
- Depending on the size of the system and materials used you may have some issues with rigidity. It’s possible you’re getting some chassis flex as the laser head is accelerating and decelerating. Again, keeps speeds and acceleration low.
- Depending on the materials used for linear motion on the X and Y you may have uneven travel along those axes. I saw one system using inline skate wheels riding on a groove cut in plywood. The natural inconsistencies in the material will directly transfer into the burn.
Can you share the .lbrn file that you used to burn the samples in the photos? I’d like to review cut settings and laser path used for the job.
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