View Full Version : Cutting Paper with a Vacuum Table

Paul Castellana
05-05-2014, 9:02 PM
Hello! I'm trying to cut paper on my 80w Trotec Speedy 300 with a 1.5" lens using the built-in vacuum table, and can't get it to come out clean on the backside. The frustrating thing is that it is clean everywhere except where the cut lines cross over the holes for the vacuum table. The burn marks also occur over the heads of the bolts securing the table to the gantry, as they sit slightly beneath the table surface. I've tried a wide range of settings, so I'm pretty sure that that is not issue. I'm wondering if anyone else has had this experience and has advice on how to fix it. Considering that the vacuum table is designed for paper cutting, I can't imagine it should be doing this.

Scott Shepherd
05-05-2014, 9:34 PM
Hi Paul, welcome to the forum. My take on your issue is you have too much power being used. The excessive power (even if it's just barely over enough needed) will flashback on the grid. You want barely enough power to break the back of the paper. You might even want to back away just a little so it's hanging in there when your remove it from the laser.

Overpowering will cause flashback on all materials. @What speed and power are you using?

Paul Castellana
05-05-2014, 10:20 PM
Thanks for the response Scott. Lowering the power seems to help, but it's still not perfect. I've gone as low as 6p 0.7v 1000hz, at which the parts are just barely hanging on. I'm cutting 140lb paper. Again, the problem areas are bizarrely only over the holes, where it doesn't have anything behind it.

Matt Turner (physics)
05-06-2014, 1:45 AM
Could the airflow through the holes be causing the paper to burn more in those spots?

Allen Rawley
05-06-2014, 2:18 AM
Is there a change in the focus during cutting? In other words, does the vacuum table create a slight depression caused by the force of the vacuum blower, and is this depression magnified during the cutting process? The 1.5 inch lens, in comparison with other lenses, has an extremely small in-focus range. You could video and play back to examine.

You could test by turning off the vacuum table and holding the paper down by weights and running the job. If it solves the problem, then consider reducing your vacuum drag or (fabricating and) placing a second table above the first. The second table could be fabricated with tiny diameter holes in order to decrease the depression, and on the sides taped to keep the vacuum operational.

Regarding the paper, the best paper for laser cutting has two features--lignin free and chlorine free.

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Jiten Patel
05-06-2014, 6:39 AM
Try going a little quicker - say 0.9 to 1.4 with about 10-15 correction. Should sort that out. Also what bed are you cutting on? Use a clean honeycomb and you should eliminate flashback or smoke damage. Just a note on paper-stock....some stocks due to their makeup absorb smoke and brown regardless how perfect your settings are...so that may also be the issue. We cut paper and card all day long and it's not really an exact science and paper can vary within the same colour and family.