Laser randomly not cutting all the way through 1/4 ply

[Mike Maloney]

My high school recently opened a FabLab that includes an Epilog Mini 45W. I have been using it and incorporating it into my Engineering and Physics class since it opened. I designed and started making some puzzle maps of the city I teach in. When I went to cut 5 on one 2' x 1' sheet of 1/4 baltic birch ply, I noticed that there were many random spots where the laser did not go all the way through. I had to end up cutting them out with a scroll saw. I even went to a slower setting and it still did not go through. I do not think it is a level problem as they are randomly scattered throughout. The only thing I can think of is the nonuniformity of the plywood, and the fact that it was already close to the limit that my Epilog machine could cut through. Wondering if anyone else has any suggestions. I attached a picture of one of the non cut pieces.

thanks.

[Bert Kemp]

1/4 BB with a 45 watt is a tough cut. BB has glue and it has footballs making it harder to cut then some of the straight hardwoods. I have a 60watt co2 and sometimes I need a second pass to get all the pieces to fall out.

[Matt McCoy]

My high school recently opened a FabLab that includes an Epilog Mini 45W. I have been using it and incorporating it into my Engineering and Physics class since it opened. I designed and started making some puzzle maps of the city I teach in. When I went to cut 5 on one 2' x 1' sheet of 1/4 baltic birch ply, I noticed that there were many random spots where the laser did not go all the way through. I had to end up cutting them out with a scroll saw. I even went to a slower setting and it still did not go through. I do not think it is a level problem as they are randomly scattered throughout. The only thing I can think of is the nonuniformity of the plywood, and the fact that it was already close to the limit that my Epilog machine could cut through. Wondering if anyone else has any suggestions. I attached a picture of one of the non cut pieces.

thanks.

You're likely hitting knots in the interior layers, which are very dense and hard to cut through. You might experiment with frequency and passes to see if that helps.

[Glen Monaghan]

You didn't mention cutting parameters but, as a guess, with a 45W Epilog you should be 100P and something less than 10S at about 500Hz to cut 1/4 BB ply in a single pass. Check the lens to ensure it's clean before you start cutting and, if smoke swirls around the head while cutting rather than sweeping straight back, you may need to clean the lens again between each puzzle. Also, it couldn't hurt to check the machine's alignment and focus (are you using manual or autofocus?) to make sure you have the most power and best beam possible. Another consideration is the substrate itself. I cut a fair bit of 3 mm (1/8") BB (no 1/4") and some sheets are like cutting butter while others won't cut through in spots using two passes at 100P and 16S, sometimes just making a charred mess (when this happens, I usually can see a significant change in the light on the surface of the wood where the beam is cutting; the light spot changes from a smaller shape to a larger circle which makes me think the beam is being diffused by the glue layer in those areas...but I really don't know why it happens). Likewise, some BB sheets cut virtually smokeless while others kick out massive smoke clouds that deposit resins on the lens, rulers, etc. and require cleaning every sheet or two. Keep the wood flat and dry before cutting, and try different sheets and/or sources if you have consistent problems cutting through. You probably won't get the best edges, but you could also try using two passes rather than powering through on just one pass.

[Mike Maloney]

Thanks for the reply. I am at 100P, 6%, and 500Hz, Autofocus. I have ramped it down to 2% speed without really any change. I think it may be due to nonuniformity, and the fact that it is on the limit of its capability for cutting. I am not the one responsible for cleaning, but I am guessing it has not been as it is used for classes during the day and open shop at night. I talked with the people who are responsible, and hopefully they will either teach me or clean it themselves regularly.

[Pat Pollin]

When I am making fixtures out of 1/4" i usually use speed 2% in order to minimize those types of mis-cuts
Cleaning is so easy and worth the 2 minutes if you are setting up a new job
Use lens cleaner and a few Q-tips to clean both sides of the lens, the mirror above the lens, and the mirror at the far left side of the X-axis slide
You be able to tell the condition of your lenses by how dirty the Q tips are when you start cleaning

Official instructions: http://support.epiloglaser.com/article/8205/11940/cleaning-epilog-optics

[Robert Bonenfant]

Try cleaning the lens First - We cut a ton of 1/4" BB (3-4 Pallets a month) when one of our machines starts skipping, its normally a dirty lens or mirror. If the cleaning doesn't work also check your air assist pressure, try increase it to 10 - 20 PSI if possible and see what happens. We run ours at 25 PSI and the cut is 10x cleaner than the manufacturer recommend 5 - 10 psi.