Waviness (vertical) on cut acrylic?

g00se
Posts: 2
Joined: Mon Jan 22, 2018 10:49 am

Waviness (vertical) on cut acrylic?

Postby g00se » Tue Mar 13, 2018 1:58 pm

disclaimer: I am a complete newbie to using a laser cutter!

I am engraving/cutting some 3mm red transparent acrylic sheet with paper backing on both sides.

I am using 40% power and 100% speed (default) initially to engrave down about 2mm. This takes about 7 passes at these settings.
The surface of the acrylic after several passes starts to have regular waviness instead of a smooth surface.

I assume this must have something to do with PWM of the laser power?

What is the best way to eliminate the waviness?

Here is an example photo to show the waviness:
Image

ChrisBorg
Posts: 14
Joined: Fri Nov 25, 2016 6:57 pm

Re: Waviness (vertical) on cut acrylic?

Postby ChrisBorg » Mon Mar 26, 2018 6:06 pm

I'm not sure from your photo what the orientation is... is vertical the Z depth or Y axis? I've had issues with wavy lines on the Y axis and found them to be due to mechanical issues with the XY gantry system. Loose belts, debris on the rollers, or a bad motor. PWM is very high frequency and unlikely to cause visible lines like that.

g00se
Posts: 2
Joined: Mon Jan 22, 2018 10:49 am

Re: Waviness (vertical) on cut acrylic?

Postby g00se » Sat Mar 31, 2018 11:32 am

Vertical is the Z-axis (up/down). The work piece is stationary (no z-axis movement). Cuts on the x-y are nice and straight.
I suppose it could be small speed variations in the x-y due to gantry belts? This could cause periodic fluctuation and waviness on the z-axis as the laser dwells.

I experimented with different speeds and powers and engraving directions. Each generated different amounts of waviness.
The machine is new (this is about the 4th cut I've done on the machine).

Here is a video of the engraving, you can see the waves becoming apparent on the second pass:
https://youtu.be/4mq9k-32Hx0

Tech_Marco
Posts: 4369
Joined: Mon Jun 15, 2009 3:00 pm

Re: Waviness (vertical) on cut acrylic?

Postby Tech_Marco » Sat Mar 31, 2018 12:08 pm

What happened if you cut a straight line?
Let’s say what a happen for cutting a a ft longer plywood with different power setting

Let’s do a simple experience:
Get a piece of wood (any) with possible 3/4” thick
Make up power to cut 2/3 deep but not cut through
After cut, break the wood manually see if you see “waiving “
Post what you found here fore review.


Marco


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