keeping 1/4 ply flat during cutting

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Tony Bellville
Posts: 10
Joined: Fri Nov 11, 2016 12:42 pm
Location: San Diego

keeping 1/4 ply flat during cutting

Postby Tony Bellville » Tue Jan 03, 2017 6:05 pm

Hello,

I get my lumber from either Home depot or Loews, i buy in 4x 8 sheets (the project i want to do is rather large). The 1/4 ply (birch or oak) seems to always have a curve to it. This causes inconsistencies in the cut, where it cuts through parts and then not in others. I am running my laser 6mm from the piece, speed is 3 and power is 45. half gets cut clean, others are not getting through.

Do you have a "trick" to hold the piece flat? In the CNC is rather easy, but this seems to be an entirely different issue.

Thanks
Tony
Tony
Sunny San Diego
60W Tek-Tonik Laser (I think) :D

Doug Fisher
Posts: 288
Joined: Sat Aug 20, 2016 10:42 am
Location: Atlanta, Georgia, USA

Re: keeping 1/4 ply flat during cutting

Postby Doug Fisher » Tue Jan 03, 2017 6:24 pm

What type of cutting bed do you have? Blade? Honeycomb? None?

I read on other forums where people were having this issue. They resorted to weights and bar magnets but the were cutting thinner stock. In the end, some people found the best thing was to pay more and buy quality flat stock from a smaller local lumber yard or specialty wood place. If you have a Rockler or Woodcraft store near you, you might go in and ask their advice.
80 Watt 700mm x 500mm Ke Hui KH-7050 Laser (Similar to the Red Sail),T.R.
LaSea/EFR F2 Series laser tube, RuiDa RDC6442G EC controller, 2" lens, RDWorks v8.01.18, CW 5000 chiller, Chuck type of rotary attachment
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Willy Ivy
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Location: Pattison, Texas
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Re: keeping 1/4 ply flat during cutting

Postby Willy Ivy » Tue Jan 03, 2017 8:39 pm

I use the same plywood. I cut it to 24x48 and stack it in my laser room where I also keep a dehumidifier. I stack the plywood flat on 3/4" level shelves with my mdf, acrylic, etc. stacked on top of it.
When I am ready to use it, I then cut it the size needed.
Also, as mentioned by Doug, the better the plywood the less the warpage.
This stuff from home depot has all kinds of junk mixed in with it. Sometimes the cut is not so much the warpage as the junk between the layers. I have pulled out some kind of string between the layers that the laser WILL NOT cut. I think some of that junk is a lot of glue.
If it still has too much warpage I leave the piece larger than needed and use flagstone to weight it down.
50w Chinese laser KH-7050, 500x300, TL, 2" lens, hot dog rotary
Modifications: 60w tube & power supply, honeycomb bed, amp meter, easy access mirrors
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Tony Bellville
Posts: 10
Joined: Fri Nov 11, 2016 12:42 pm
Location: San Diego

Re: keeping 1/4 ply flat during cutting

Postby Tony Bellville » Tue Jan 03, 2017 8:57 pm

Thanks!!
Tony
Sunny San Diego
60W Tek-Tonik Laser (I think) :D

Chris Berry
Posts: 13
Joined: Mon Jan 02, 2017 11:58 am
Location: Crete, Greece

Re: keeping 1/4 ply flat during cutting

Postby Chris Berry » Tue Jan 03, 2017 10:09 pm

Depending on what you're cutting, cut shape with a border will reduce by how much the piece is raised off the bed and would make this less of an issue. on my 1.3m machine we run into this all the time with ply.
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Chris
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Weike 130 x 90 100W RECI Laser TR
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Pete Cyr
Posts: 18
Joined: Sun Nov 27, 2016 3:16 pm
Location: Virginia

Re: keeping 1/4 ply flat during cutting

Postby Pete Cyr » Wed Jan 04, 2017 3:35 am

I quit buying plywood from Lowes. Their material is almost always warped because it got wet in transit, or was stored outside or any other number of reasons and they won't refuse a shipment.
I recommend checking out a few of the local lumber yards and compare pricing - there are a number of lumber yards in San Diego I found doing a Google search. I am not sure how convenient they may be to your location. In my experience the worst piece of sheet ply I have purchased from a lumber yard far exceeded the best piece of sheet ply I could find at Lowes.
Location - VA
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Michael Dunning
Posts: 42
Joined: Sat Nov 26, 2016 11:02 pm
Location: Alabama USA

Re: keeping 1/4 ply flat during cutting

Postby Michael Dunning » Sat Jan 07, 2017 3:12 am

Here is my $5 Walmart solution to warped plywood. We have been cutting a lot of 1/8 inch material lately and the warping was especially bad.

I bought some 1/8" by 2" drywall anchors and matching 3/4" diameter washers. The hope was that the drywall anchor portion would push through the holes in the honeycomb. Unfortunately, they didn't fit. And just like a CNC, sticking the screws up was a bad idea, since I ran into them twice.

My remaining cuts were done with the washers on top and up to six anchors in place. Certainly time consuming, but it did work.
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