Newbie- New laser arrived, questions about pmma cutting

[siemed]

Hello everyone,

We finally received our laser cutter (60 Watt CO2).
On the bottom of the machine there is a big metal plate. Should we put something on the metal plate or is this not necessary?
In some movies we see some type of plate with holes on the bottom.

We are now cutting PMMA plates. The cutting goes well, but we see some cracks on the cutted sides at the bottom. How can we prevent this?
Does this have something to do with the combination of power and speed or is this a reaction from the metal plate?

Thank you very much in advance for your reply.

[Signmaker]

You shouldn't be cutting directly on top of a solid metal plate... the bed of your laser should be either a hollow honeycomb design or it should be a series of metal strips with gaps in between.

The cracks are most likely caused by the metal plate getting hot... the laser energy is cutting through the acrylic and heating the metal underneath.

A solid bed is bad for your laser tube and optics and it's not going to allow you any sort of fume extraction.

Check in the packaging.... you might find the strips which should slot in above the metal plate.

[siemed]

Hi, thank you very much for your reply. Unfortunately there ar no metal strips or a honeycomb plaet send with the machine.
From wich material should a honeycomb plate be?

Does anyone know where to buy a honeycomb plate?

I have attached two pictures from the plate and the machine. On the plate there seems to be no holes or anything for fixing metal plates.

Thanks again.

[smoe]

Hi,

a honeycomb table is surely a good thing to have. we use it for for cutting plywood, mdf or cardboard.
But for cutting acrylics it´s best to rise the sheets a little off the table to have some "air" under the material. Just put some small magnets (the "neodyme" type) as spacers on your iron cutting table and put the acrylic sheet on top of these. To avoid reflections that could damage the acrylic be sure to not use too much power and use magnets/spacers that are tall enough (20 mm at least)

Stephan

[bob pfohler]

What I use is called called egg crate. You can buy it here already sized and powder coated , Lazer Cutting Grid new at St. Louis Laser for sharper engraving results.

You can also order it from Grainger.

[twehr]

Originally Posted by bob pfohler What I use is called called egg crate. You can buy it here already sized and powder coated , Lazer Cutting Grid new at St. Louis Laser for sharper engraving results.

This looks interesting, and certainly seems more affordable than anything else I have seen. I have been looking, and trying to decide what route to go for several months now and this looks like it may have potential.

In the mean time, I have been using a surprisingly simple and cheap alternative. I bought a 2'x4' piece of plastic grid that is intended for recessed ceiling light fixtures. Got it at Menards (or any other home-improvement store) for a few dollars. I cut out a piece to size using side-cutters. It works.

I can do an amazing number of cuts (hundreds?) before it has eaten up the plastic ribs. Getting about 10 grids (to fit my machine) out of a single 2x4 piece makes my cost about 50 cents each.

If you have a very large table area, and place very heavy objects on it, you would possibly get a slight deflection, but I have not had an issue with that.

Mine does not look as nice as the one you suggested, but certainly wins on cost, availability, and sizing.