K40 Did not cut 2mm Plywood

TKaemmerer
Posts: 3
Joined: Tue Aug 02, 2016 6:24 am

K40 Did not cut 2mm Plywood

Postby TKaemmerer » Tue Aug 09, 2016 7:58 am

Hello,

I`m a newbie in Lasercutting. I use a Chinese K40 III machine, with new Gold Mirrors from Marco an a new Lens and Lens Holder. The Machine is setted up an I get on the Focus from 63,5 mm a fine dot. I have a water chiller an Air support, too.

I can cut Paper with a very fine line and I can cut Plexi Glass in 2 or 3 cuts. But if I try to cut Playwood from 2mm it burns and I get a cut from about one millimeter. If I do this with 5mm cutting speed it burns heavy on the Plywood, if I cut with 10mm cutting speed I get a better cut without heavy burning but not so deep. Cutting with 90 percent LaserPower an 10mm speed I can not cut the 2mm Plywood in two cut sessions.

Can anyone help me?????

Oh, and I use the original cutting software with Corel.

I have ordered from Lightobjects the upgrade kit last year, but I am still afraid to upgrade. I use only a student License and Im not able if Laser Cad works with them.
I know that it is not a professional Laser, but I expect only a machine that cuts 2 and 3 mm Plywood for building a plane.

Hope someone has an idea!

Thanks for that

Thomas

bobbanger1
Posts: 6
Joined: Tue Sep 06, 2016 10:57 am

Re: K40 Did not cut 2mm Plywood

Postby bobbanger1 » Wed Sep 21, 2016 3:06 pm

I'm not an expert but I have a K40 and I've learned a few things (may be helpful to you)

I have the standard focus lens (18mm) and standard 20mm mirrors that came with the system and I can cut 5mm Baltic birch plywood in a single pass. It's all about focus, speed and perfect beam alignment. My system originally would cut better on the right side than on the left. After fidgeting with mirror alignments I finally figured out the XY table was misaligned. It's bolted in four corners and was not parallel with the laser tube. After a realignment of the XY table, a readjustment of the mirrors a cleaning of the mirrors and lens it would cut like a fire-breathing-dragon. In fact, the focal temperature was so much hotter that the plywood kept flaming up and getting my lens dirty again. I solved that problem and improved the cutting power by adding a $70 Harbor Freight Air-Brush compressor, very quiet, controllable air volume. I got some spiral tubing from Mc-Master Carr (next day shipping) and very inexpensive. Now with air assist it cuts even better and much cleaner.

Some other things to check on your machine:
- Focus Lens is properly oriented (ie. concave curve is facing the laser tube, convex curve is facing your table).
- Focal length is perfectly set (for my 18mm lens is about 51mm to the work piece)
- Lens and 3 mirrors are perfectly clean.
- Confirm the laser cuts exactly same in all four corners of the table
- Laser beam reflects off of the mirrors is as near the center of the mirror as possible (use thermal paper like a losing lottery ticket or grocery receipt and very low laser power to check this (high power and paper just burns the paper and puts more junk on the mirrors), moving and test firing at all four corners of the table. Make sure the tube beam is hitting exactly in the center of the hole on the laser head at every table position.
- for thicker materials the focal point should be slightly below the material surface, or first cut at surface, second cut 2mm closer.
- Slow cut speed (3-4mm/s) It's painfully slow but does the cut faster.
- Laser tube should last longer if you do more passes using lower power (maybe 75% and two passes instead of 90 or 100% one pass)

Hope this helps, It certainly has for me.

-bobbanger1

Tech_Marco
Posts: 4405
Joined: Mon Jun 15, 2009 3:00 pm

Re: K40 Did not cut 2mm Plywood

Postby Tech_Marco » Sat Sep 24, 2016 9:49 am

@bobbanger1. Good post!


Marco ;)

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

Re: K40 Did not cut 2mm Plywood

Postby ChrisBorg » Sat Dec 31, 2016 4:00 pm

another suggestion for poor cutting performance - remove the lens and inspect it carefully. The laser machine at a local maker lab was cutting poorly and it turned out that the lens had been damaged - it looked discolored and cloudy. Not sure what happened to it, but it certainly affected the performance.


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