Lens question and cutting table question

[Mary Geitz]

Yesterday I took my lenses out to clean/check them. I found that the top lens has what looks like a burn mark right smack dab in the middle of it. I haven't really noticed a decrease in quality, although I've done a lot of cutting lately and not a lot of rastering. Should I bite the bullet and buy a new one anyway?

Secondly, I am experiencing EXTREME frustration with cutting tables. I have the original Epilog honeycomb but the holes are kind of smashed down and it is really warped. I ordered a LaZer Cutting grid and I'm having all sorts of trouble. I cut a lot of acrylic and I keep having these mini fires. It looks like it's on fire underneath, but luckily as it moves on the fire goes out. The paper on the back of paper-backed acrylic is actually burned. Yesterday I cut some of the blue plastic-backed acrylic and there were flames and the backing and the acrylic itself melted. I played with the settings but it's still a problem. I do use air assist when cutting.

So, I'm in the market for a cutting table that will hold paper down, not warp and not cause my acrylic to start on fire. I cut and raster a lot of paper, but I haven't been able to as of late.

Does anybody have suggestions or know of a cutting table that will fit my needs?

Thanks and I hope everyone has a happy, peaceful and profitable new year.

[George M. Perzel]

Mary;
Try cutting at a very high PPI (1500) and a faster speed. What thickness plastic are you cutting? Not sure what kind of table you have but raise the grid at least 2 inches above the table. Actualy, knife edge slat work better for plastics as contact area is minimal.
Best Regards,G
eorge
Laserarts

[Mary Geitz]

Thanks for the reply George. I cut both 1/8th and 1/16th. The cutting grid I'm using lifts the acrylic about 2" off the table. I use the recommended Epilog settings which is cutting at the highest PPI available. Usually this gives a wonderfully smooth edge. Do you happen to know where I can get a knife edge table?

Just as a side note, I have been searching for a solution for this problem for over a month. I'm just stumped!

[Glen Monaghan]

All of the acrylic I've come across with plastic-backing has been extruded, and it seems to me that extruded is more likely to flare up than cast for similar jobs. Also, cutting with the plastic backing in place usually makes for a worse edge in my experience. If I must cut extruded, I peel off the plastic and replace with transfer paper tape. For detailed cutting, I found the paper tape on the underside would sometimes flare up so I mist it lightly with water right before cutting.

The other thing I recently changed is that I had been using a pin table (pins spaced every 1/2" and sticking up 1" above the table" on top of the honeycomb. Between warpage of the pin table and having having several cuts ruined recently by flare-ups which I suspect was partly due to poor air movement between the acrylic and pin table, I have been trying something different with good success. I positioned several 1/8"x1/8"x4" wood strips around the edge and across the middle of the honeycomb table (away from any cutting location) to support the acrylic for cutting. I think the better exhaust through the honeycomb is key... no flare ups since I switched from the pin table to this makeshift approach. However, it takes longer to remove cut parts and insert new substrate since I can't just swap pin tables.

Still pondering a better solution, thinking about drilling a bunch of holes in the pin table, one hole in the center between every four pins to see if that improves exhaust, but figure it might make long term warpage even worse.

[Walt Langhans]

A metal honey comb table came with my laser, but I got some 1/2 magnets to attach it to the metal bed which also lifted it up for better air flow, and I have very few issues with flair up.

[dave cox]

I am cutting a lot of 3 mm acrylic and laminate for small objects, earrings etc, and as a matter of course now I remove all paper from the manufacture and replace with wet brown paper. Does away with flash back and easy to remove and clean. For wood that can't have water one side I got a vector bed made out of corian which works very well.

[David Somers]

Dave,

What does the Corian Vector Bed look like?

Just curious

Dave

[Mike Null]

Mary

I've been using that cutting grid for years without problems. I used them on my old Universal as well as my current Trotec. It is not the grid that causes the paper to catch fire. Most likely it is in your settings. I have my best results when I use just enough power to make the cut. I am more interested in a clean cut than speed. (I always leave the paper on the backside of the acrylic.)

As far as the lens is concerned, try to clean it with an approved cleaner. You may have to do a little scrubbing with a lens tissue or cotton swab. I clean my lens and mirrors frequently. It is not a bad idea to have a spare lens though I don't have one.

[Mary Geitz]

Thanks for all of the input. I did decide to bite the bullet and buy a new honeycomb table, (under protest with Epilog.) I told them that it seems to me they could have a studier cutting table available. The guy from Epilog told me about their pin table and I think that's about the dumbest thing I've ever heard of. On a positive note, the customer service from Epilog was outstanding as usual.

Mike, I have to ask you: Are you able to cut paper with the laser grid? I find that it moves around. I can tape the paper itself down but as soon as the piece is about halfway cut out, it starts to move. I've tried covering the whole thing with paper to increase the vacuum effect, but nothing has worked. I also gave that lens a good scrubbing (it's actually the mirror), but it's definitely a burn mark.

Oh well, great way to start the new year - in the hole. Last year around this time my laser tube went out. That was just in time for the Christmas rush.

I hope everyone has a very happy, healthy and prosperous new year! May your laser tubes sparkle with a beautiful light.

[George M. Perzel]

Mary;
Do a search for a steel honeycomb grid- the US importers of Chinese lasers should have them. They are great for thin material as you can use dime sized thin neo magnets to hold the paper down.
Best Regards,
George
Laserarts

[Mike Null]

Mary

I cut very little paper so I don't claim any expertise but I haven't had the paper move while cutting. The actual work that I've done was on card stock.

[Mike Lassiter]

Paper on a honeycomb cutting grid wouldn't move around while cutting if exhaust fan is adequate. I lay paper sheets on mine to cover unused area so exhaust will suck material down to grid. I have bigger laser and exhaust system than most but principal the same for you. Poor exhaust maybe causing lens issues due to smoke buildup on lens. Poor air flow under cutting grid will promote flaming under acrylic as good air flow would help suck flames away.

[Kev Williams]

Depends on where your exhaust is on the machine-- My old ULS and LS900 have solid tables, with the exhaust at the back of the machine, and as soon as you shut the door the air flow sucks the paper to the exhaust inlet, so anything like paper must be taped or weighed down. (tables are aluminum) My big Triumph sucks air from below thru the honeycomb table, which is new to me...

[Mike Lassiter]

solid table is not a honeycomb cutting table as discussed here. I have a solid aluminum table too. The honeycomb cutting table sits on top of it. I also have to remove panels in rear wall inside cabinet for air flow to be pulled thru cutting table correctly. And I agree paper can be blown by exhaust air when top is closed. I have that happen when sheets are overlapped. That happens the instant my top door is closed with the fan on. This has nothing to do with laser cutting process. I place something on them to hold the edge down so the air entering the cabinet from the front doesn't lift the paper up overlapped another sheet and them get blown across table. Can't see this being problem if you are cutting or engraving paper - wouldn't have sheets overlapped where air flow cannot keep full sheet pulled down on cutting grid.