When I cut acrylic sheets on the honeycomb cutting table I get “melt” marks wherever the metal honeycomb touches the bottom of the sheet that continues up the side of the cut about 1/8″. How can I eliminate this? Thanks.
You might check out the new table offered at Laser-Bits. it uses pins in several places so you work does not come in contact with the table. I believe the pins changed by the user.
You could probably stick something to the bottom of the material (small cork risers, bit of foam pad, another bit of acrylic etc.) in areas that won’t be lasered to raise it off the table. Cheaper than a new or different table.
I used to have the same problem, then made up some 3/4″ tall spacers/supports out of scraps of acrylic. I won’t use the honeycomb anymore when I need to cut acrylic that’s thicker than 3mm, but just raise the acrylic above the laser bed with the spacers. Depending on the size and shape I’m cutting determines where I position the spacers, especially if I don’t want a piece to drop out before I’ve cut out all the necessary holes.
We scatter some 14 x 20 nuts (trophy nuts) or stack up pennies 2 or 3 high to space substrates off the baed of the laser for profiling out with minimal smoke on the back.
We are considering a laser engraver, what kind of stuff are you cutting out? I am just not all sure of the capabilities of a laser.
I have a similar issue. The problem is that the exhaust fan isn’t pulling enough air from below the honeycomb table, so the acrylic vapor has enough time to settle back on the underside of the plastic. If the table or bed is dirty, the marks get darker.
The simplest thing is to leave the protective sheet on the acrylic until after you cut it. Unfortunately the sheet is made of a different type of plastic and tends to want to stick on the edges. Transfer paper or masking tape can also be used to protect the acrylic.
The only other thing you can do is try to increase the airflow. On my laserpro explorer I keep the right half of the exhaust pickup taped over to give a better air draw where I typically need it.
I ran into this on the first acrylic sheets I cut. Since I am a Technician, I just felt that one Fred is correct and the vapors oils from the plastics were part of the problem, the next item that I thought of was that I was using to much power and going to slow. I decreased my power for vector cutting and bumped up the speed and my problem vanished. I do not know if this will work for everyone, but if the laser is getting the metal that ho, then it should be going fast at a lower poer setting. My opinion.
I’ve been told it’s not getting the metal that hot - but it’s actually a reflection of the beam in all directions when it hits the honeycomb?
I wonder if perhaps putting down a “backing” of say thin (1/64th”) plywood or cardboard below the plastic would resolve it. That way, no parts would drop out, but there would be a buffer between the grid and the material.
Btw — I don’t have a laser yet but am going for a demo tomorrow am. Any hints, suggestions or caveats?
You have one of 2 problems: Either you are having “fires” (would be accompanied but burn marks - I doubt this is the case) in the honeycomb (often happens if its dirty)or the pex is flaming on the bottom side/ Or its the flashback as the laser passes over the individual strips of honeycomb aluminum. This sort of presents itself as nicks in the edge you cut. There are ways to minimize this. 1) Put a sheet of black anodised ally under the cutting table it acts as a sort of backstop for the beam 2) Don’t use a cutting table and elevate with blocks of pex or the like 3) Buy or make a pin table (pins support the pex) 4) Make sure you use air assist and not only use it , direct it properly and use it at the right pressure - directed so it ejects the melt out the cut and just enough pressure to avoid flaming and not too much so it cools the melt and prevents a polished edge and a clean cut. 5) Strip off the masking if its not laser friendly If you are getting distinct honeycomb marks on the underside of places near where the pex is cutting , then you have a big problem in that you are likely to see the machine go up in smoke as that is a very strong indication of fire!!!!!!!