Getting Started - Cutting Ply???

[Tony Calver]

Hi, I have recently got a Gravograph LS100 30W machine. Im using coral draw and LS100 drivers. I have been experimenting with cutting 4mm ply today, but with frustrating results. I have set machine to auto focus, its doing 9 passes on full power at 10% speed, but barely cutting through. I have played around with the re-fofus setting too but after my 10th piece of ply, I still am none the wiser to were I'm going wrong. Any help would be appreciated.

[Mike Null]

Tony

I would suggest reducing your speed to 2% and set your power at 100. You'll still have to make more than one pass but this should improve your result. If you have a manual focus tool give that a try as well. Auto focus is not always accurate.

[Tony Calver]

Thanks Mike I will give it a go. there is a manual focus but I'm not sure what setting to put in!

[Michael Hunter]

Before giving in to despondency, make sure that the ply you have is suitable for laser cutting.

If the ply is "marine", WBP or even just water resistant, then it is likely to be laser-proof too because of the glues used to bond the layers.

The type that normally cuts OK on the laser is "interior grade" - also sold as "laser ply" at twice the price for the same stuff.
Some "moisture resistant" types cut reasonably well, but the glue used varies between manufacturers so you can't be sure until you try it.

You need good air assist too.
(John Banks has reported here that fierce air assist has allowed him to cut much thicker wood that the power of his laser would suggest).

[Scott Shepherd]

Just for reference, and it might be different in the U.K., but we recently did a CNC router job and they specified Marine Grade Plywood. We started calling lumber reps in to discuss the order and get pricing and delivery and the education we got was that there is no different glue or adhesives used in marine grade. The only difference is the quality. Marine grade plys are all free of any voids. That's what makes it marine grade. There's no voids internally for water to get into and freeze or stay and rot.

We were told by multiple suppliers that the woods and glues are exactly the same as any other plywood.

I don't know if it's true or not, but it seemed to be the story they all told.

[Larry Bratton]

I cut 1/4" nominal with 40 watts at 10s/100p/500f all the time. This is regular old garden variety interior plywood. If your having to make that many passes, if the plywood is the same, then something else is amiss. You should be able to cut it at 8s/100p/500f in one pass (assuming it's flat). These are Epilog settings but should still be close. Check your optics and alignment.

[Kevin Berkshire]

I have a 60 watt laser and I cut though 1/8" plywood with one pass. Try not using the auto focus and make sure the laser is the correct height. Sounds like its out of focus.
I use 100% power and he speed is 5%.
Good luck

[Ross Moshinsky]

Roughly 7 year old LS100 here. 3mm plywood I can cut at I believe 3 speed and 100 power. One pass. I really don't recall the exact setting because we do it fairly infrequently. Based on my experience, I don't see this machine as something to do much else other than awards type engraving. 30 watts just isn't great for vector cutting period but doing much thicker than 3mm plastic, acrylic, or wood is typically a bit of a waste of time.

[Rich Harman]

Marine grade plys are all free of any voids. That's what makes it marine grade. There's no voids internally for water to get into and freeze or stay and rot.

We were told by multiple suppliers that the woods and glues are exactly the same as any other plywood.

Marine Grade may be made of harder woods, have more plys and have a core not as thick as with regular EXT grade plywood. I have not seen EXT grade ply that is anywhere near as good as Marine Grade ply.

[Henri Sallinen]

My guess is that the plywood isn't interior grade and the glue is what is stopping you from getting through with a single pass even though 30 watts is quite low for vector cutting, as has been mentioned earlier.

[Michael Hunter]

We were told by multiple suppliers that the woods and glues are exactly the same as any other plywood.

True of waterproof plywoods - nearly all have a phenolic/formaldehyde glue which can resist long-term dampness.
Phenolic glue bubbles up and makes a fine mess when hit with the laser beam.

Interior grade is usually made with urea/formaldehyde glue (cheaper than phenolic) which breaks down if left damp for long, though other protein or vegetable based glues may be used.
Urea glue lasers easily (unless it is too thick where it has filled a void in the wood).

"Moisture Resistant" ply is an unknown - could be a cheap phenolic applied skimpily or could have a laser-friendly glue.

[Scott Shepherd]

Marine Grade may be made of harder woods, have more plys and have a core not as thick as with regular EXT grade plywood. I have not seen EXT grade ply that is anywhere near as good as Marine Grade ply.

In our case, it was just Fir. Same as any other fir plywood.