# Homemade Rotary Axis too fast

Good evening. I have a Sainsmart 3018 Prover with a homemade rotary axis.

NEMA 17 stepper motor - 4mm per rotation
1:1 for my “mandrel” (I engrave pens)

I finally got around to getting my laser settings dialed in and figured out the optimal burn Power/Speed settings w/out the rotary axis being a factor. Then I brought the rotary axis to the mix.

Rotary settings:

Rotary Type: Chuck
Rotary Axis: Y
4.00 mm per rotation
11.250mm Object Diameter
35.343mm Circumference

GRBL Settings:

\$0=10
\$1=25
\$2=0
\$3=2
\$4=0
\$5=0
\$6=0
\$10=3
\$11=0.010
\$12=0.002
\$13=0
\$20=0
\$21=1
\$22=1
\$23=3
\$24=25.000
\$25=500.000
\$26=250
\$27=1.000
\$30=1000
\$31=0
\$32=1
\$100=800.000
\$101=800.000
\$102=800.000
\$110=2000.000
\$111=2000.000
\$112=600.000
\$120=500.000
\$121=500.000
\$122=10.000
\$130=500.000
\$131=400.000
\$132=100.000

Engraving Settings:

Speed: 500 mm/min
Max Power: 33.75
Fill+Line
Bi-directional Fill
Line Intreval (mm) 0.085
Lines per Inch: 298.82
Scan Angle: 90
Ramp Length: 0
Number of Passes: 1
Fill Shapes Individually
Line Settings:
Speed: 500 mm/min
Max Power: 35
Number of Passes: 1
Overcut: 0
Kerf offset: 0

So I believe what is happening is the distance of travel is shorter being that my the Y-axis is really going 35.343mm in the matter of 4mm. So when the X-axis is traveling 1mm, the Y-axis is really only traveling 0.11317658376482mm. The results are “ok” but I’m not getting consistent results on the X and the Y-axis due to this variation.

I have tried changing my Y-axis Max Rate \$111=56.588 but now the laser is compensating by going under power.

Any ideas?

Hi if youre saying the pen rotates too fast for detail and you have home made rotary like i have done, try increasing size of rotary gear leaving stepper motor same.changing it to a higher ratio will give you better control or ability for finer scanlines if that makes sense.

Funny you should say that. I ordered a new 60 tooth pulled last night and it got here this evening. The issue is that the x-axis and y-axis are not moving in the same speed. If I have the speed and power dialed in for x-axis and try to do a line around a square. The x-axis lines will be visible but y-axis will be invisible.

I cut my gears from perspex with the laser. From what you’re saying your rotary axis is too fast but it shouldn’t go that fast it won’t engrave ,as the rotator usually rotates 0.1mm at a time max. Have you changed increments to 0.075 mm?

Where do I change increments?

Hmm isn’t that in direct correlation with resolution? Anyways, I rebuilt my 4th axis over the weekend with the 60 tooth pulley. It’s not perfect, but it’s a lot better. One thing I have found is that the rotary engraving settings need to be set at a slower speed than doing engravings in a 2D plane. I assume that is because the rotary is still dependent on circumference as far as speed goes, and it doesn’t seem that lightburn takes that into account.

Youre correct in resolution i wasnt thinking.of course the best way is the bigger gear which i did 3:1 my large wheel being 60t as well. it worked better than 2:1. if you could go bigger it would be even more controllable.

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