Author Topic: Problem cutting plywood  (Read 127 times)

ameersh

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Problem cutting plywood
« on: August 11, 2017, 02:19:54 PM »
Hi,

I'm using BenCutLaser to cut 3mm plywood and it works fine when i test shapes in the application, but when i make large cuts on A4 size sheet it cuts parts and make it through the whole 3mm but other parts it couldn't.

I attached a photo for more explanation.

I have 5.5w GearBest machine.

In BenCutLaser i used speed of 300, Power 100% and 4 Passes.

1.1e Grbl



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Re: Problem cutting plywood
« Reply #1 on: August 11, 2017, 02:30:37 PM »
It's the differences in the grain and texture of the wood.

You're using 4 passes at the moment, you'll have to set 5 or 6 passes (go with 6) to 'make sure' you cut all the way through all the time. It's the nature of wood.
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ThothLoki

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Re: Problem cutting plywood
« Reply #2 on: August 11, 2017, 03:07:11 PM »
I have noticed that when I cut smaller parts, they cut easier than larger parts. I wonder if some of it is the heat dissipation in the wood.
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Re: Problem cutting plywood
« Reply #3 on: August 11, 2017, 03:21:29 PM »
I think so. When doing cutting tests using the shape tests, there are three sizes to choose from. Always choose the largest size to test cutting passes.
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treinbert

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Re: Problem cutting plywood
« Reply #4 on: August 12, 2017, 12:57:53 AM »
I have also noticed, that it is sometime more effective to do single passes, but repeat the process multiple times. It is not only the heat dissipation, but also the heat stays a while and when the laser returns to quickly the material is still hot, so by returning after a while the material at that place has cooled down.

I did get too large burns at small holes and no cut through at larger holes. By repeating the lot all was more evenly distributed. Also as Ralph says the grain has a lot of influance. Also the surface of the material has a lot of influance. When it is too shiny, or too polished, the laser will be refle ted more.
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Poeli

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Re: Problem cutting plywood
« Reply #5 on: August 12, 2017, 01:05:20 AM »
If you want to cut more effective, you have to assemble an air assist.
At cutting the left grain blocks the laser, so you canīt cut through.

The air pressure blows the fume -and more important- the grain out of the cut, so it is clean for the next cutting pass.

Search teh forum for air assist, there are several postings.

With air assist (good pressure) you will get cleaner cuts in less cutting passes.

laser_cutter

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Re: Problem cutting plywood
« Reply #6 on: August 12, 2017, 01:43:42 PM »
Hi,

I'm using BenCutLaser to cut 3mm plywood and it works fine when i test shapes in the application, but when i make large cuts on A4 size sheet it cuts parts and make it through the whole 3mm but other parts it couldn't.

I attached a photo for more explanation.

I have 5.5w GearBest machine.

In BenCutLaser i used speed of 300, Power 100% and 4 Passes.

1.1e Grbl

Follow Administrator's advice

AND

increase speed to 425 - 475, with 6 - 8 passes.

nottingham82

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Re: Problem cutting plywood
« Reply #7 on: August 12, 2017, 01:52:46 PM »
also remember you are vaporizing the wood.  That gas needs to go away.  You need an air gap under the wood and over the wood.  Do not lay it flat on a sheet of metal or you will have trouble getting the last little bits to cut.  Also air assist is a great help for consistency and removing soot from the cut path.  It also doesnt hurt to have an extra pass thrown in. 
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Re: Problem cutting plywood
« Reply #8 on: August 12, 2017, 04:51:47 PM »
>You need an air gap under the wood.

Excellent and important point...!!!
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