Laser Cutting Pre-Stained Plywood?

[Brady Whitney]

Hi everyone!

So I recently launched a Kickstarter to purchase a laser cutter so I can build these wooden mechanical puzzle books. The problem is I have to build over 500 of these books now and I'm trying to find any way I can speed up the production process.

One way I found was to Sand, Stain, and polyurethane the sheet BEFORE cutting which saves hours of after cut work. But obviously oil based poly is extremely smelly when drying so I'm thinking of switching to water based poly which dries faster and should have far less stench. However I also know that water based poly doesn't respond to heat well and obviously a laser is pure heat, am I stuck with oil based polyurethane or is there a better/safer alternative?

Appreciate any help you folks can offer!

Boss Laser HP 5598 150 watt tube

-Brady

[Keith Downing]

Hi everyone!

So I recently launched a Kickstarter to purchase a laser cutter so I can build these wooden mechanical puzzle books. The problem is I have to build over 500 of these books now and I'm trying to find any way I can speed up the production process.....

Appreciate any help you folks can offer!

Boss Laser HP 5598 150 watt tube

-Brady

Personally, I prefer to sand and paint/stain the big projects before lasering; but still put the finish on after. Just feel it gives me better control over any imperfections that arise during the process, plus your sides of the pieces aren't going to be sealed after you cut them if you seal first.

Not sure if that would slow down your manufacturing line process significantly though. And no, I don't have any suggestions for other things to try other than maybe some of the oils.

Edit: Really the only reason I would put something on to seal the wood before lasering is when I plan to mask and stain or paint the engraved section afterwards and want to avoid those sections "bleeding" into the wood. Used both polyurethane and polycrylic without noticing any major adverse affects. But even then I still usually apply a final coat of finish at the end.

[Lee DeRaud]

A few random observations:

1. I haven't noticed any particular differences in how finishes react to the laser. The length of time oil-based poly takes to fully dry would be a deal-breaker in any case: I always triple whatever it says on the can, and I live in a low-humidity climate. If all you're depending on the prefinish step to do is make it easier to clean off soot etc, just use shellac and the top-coat of your choice after assembly.

2. YMMV, but I've never been able to prefinish, cut, and assemble anything without having to do enough post-processing to require at least one last coat of finish before completion. At that point any laser-induced differences are trivial annoyances.

3. For the quantities you're dealing with, it probably makes sense to invest in some quality spray gear and up your game to something like pre-cat lacquer. For more specifics on that, you might want to repost this question over in the Project Finishing forum.

[Kev Williams]

A few random observations:

1. I haven't noticed any particular differences in how finishes react to the laser.
boy, I wish I could say that, at least with lacquers, enamels or whatever they coat metals with-

I laser etch polished stainless switchplates for a company, 2 weeks ago they dropped off a brass plate. I ask if I could engrave their logo on the back just to see if their brass would 'take' Cermark. Worked great!
But the face was clearcoated. No biggie I thinks.... Right.. Twenty 80 watt passes at 50mm/second later, all the Triumph could muster was to graze the coating, and the Cermark simply wiped off... I ended up tool engraving and painting it.

And just yesterday I was engraving a bunch of medallions for a high school gymnastics team. They were gold and bronze, very nice actually but the base metal was cast aluminum. In addition to whatever bronze/gold coating, they were clearcoated. Some the coating was flaking off. I put these on the fiber. Some of these took a bit to get thru the initial coatings, then the trick was to lighten up the pot metal. But there were 2 medallions that had a smooth flat round pocket, and a good dose of clearcoat was obvious. The fiber simply would not penetrate the clearcoat, all it could muster was to ETCH the clear. Total Kryptonite to the fiber!

I don't do much wood, but I have run into some that was brought to me that took one or two good passes just to get thru the coating before decent engraving would happen. This was with my 40w LS900, I'm sure a 150w glass tube wouldn't have much trouble ;)

All that said, there's just some things about this business that won't go faster. Usually if you (I) find a fix, something else 'breaks'... Always a compromise... :)
.

[Lee DeRaud]

boy, I wish I could say that, at least with lacquers, enamels or whatever they coat metals with- Well, I was mostly talking about vector-cutting wood. What you describe is a whole 'nother animal.

[Robert Bonenfant]

Hey Brandy,

Great job on getting your project started. We only deal with wholesale and bulk orders and when i started out i was in the same boat. Cutting stained and finished plywood is not the way to go - Toxic fumes from poly (Most get removed) it also leaves residue in your machine - a few parts might be ok but once you get a few 100 parts finished, your gonna see everything is gonna get a sticky film on it (This is the same for MDF, its just not laser friendly). Also its an extra step to your process. Not sure if you have a warehouse or your making these at home ? Setup a spray area with exhaust - were you can lay out a ton of parts and then spray one side (let dry) Then hit the other side. You can learn to use a spray gun very fast (youtube helps) This is by far the fastest way to do it - If your sealing the parts then you want to make sure you seal the black edges as well, gets on customers fingers and clothes.

Few Extra Tips
Invest in a Drum sander (Bigger the better) You can sand parts super fast and this is how the big boys do it - Use a high grit like 120 - 180 (Takes a very thin layer off)
Im not sure how much space or resouses you have or if you have employees but setting up a production line really helps and saves alot of money.
We found laser cutting to be a huge time sink in our production and switched to cnc routers for cutting simple parts (10x faster) so you might want to try to incorporate both in future projects.
Lastly Bulk order your plywood, We saved 37% if we buy by the skid and 58% if we buy a full truckload, this can raise your profits very quickly. Also dont buy crap wood from big box stores find a wood distributor (You might already be doing this step).
Hope I was helpful
Robert

[Mike Null]

I always prefer tp pre-coat thin woods with a clear coat of some sort. If I have time I prefer polyurethane or lacquer. If I'm in a hurry I use acrylic. I like to use dna as my cleaner and that is a solvent for acrylic.

In terms of lasering, I don't detect any difference in these finishes. I've been doing this for 20 years so I've tried about everything.

[Rich Harman]

I've used a waterbased polyurethane (designed for floors) in the past with good results. It dries fast and makes cleanup much easier.

[David Somers]

Brady,

One item I make are boxes to contain Christmas Ornaments. They have living hinges on them so they are a bit delicate when it comes to sanding the parts once cut.

I take full sheets of the ply I use and put them up against my garage door (which is covered with a paint cloth to protect it) and I use a decent but inexpensive HVLP (High Volume Low Pressure) sprayer to apply lacquer or clear shellac on the wood. My preference is clear lacquer since clear shellac is not quite clear. Either is fine though. So long as the garage temp is above 50 degrees F this dries in about 5 minutes, maybe 10 if I have annoyed the gods. I apply two coats and then flip the sheets and do the same on the other side. I can do a bunch of sheets in a day. And I generally cut the sheets down to a working size for the laser at that time too.

Then I will cut the box parts and engrave them at the same time. I have no problems getting through the finish.
I then take the pieces and the board they were cut from over to a table and put all the parts back into the board and sand them lightly with a fine grit on a pad sander. With the pieces held inside the slots they came out of they stay put while I sand and I am not worried about damaging the living hinge. I can quickly sand the whole sheet, flip the pieces and sand that side, then go on and cut the next sheet. The sanding also removes any soot, though I have not been having much problems with it between my blower and the air assist combined with a power and speed rate that I spent some time fine tuning for this task.

My goal is to avoid having to apply a finish after the hinge pattern is cut since that just gums it up. This approach eliminates that and gives me a nice looking box that also feels good to the hand. I should add that beside the living hinges all joints are blind box joints.

And....I should add that I am a one man shop and I don't rely on this type of thing for a living (am retired and on an annuity) so I am not as sensitive to process as a production shop might be. And of course, this is just one persons approach to this type of work. There are many good ways to approach this.

Dave

[Brady Whitney]

Wow! Thank you so much for all the advice everyone! I've decided to go with the Water based Polyurethane since I'm cutting entire sheets of plywood on my large format laser. It dries very quickly and the soot wipes off with a damp cloth. This also means that I can pre-sand the entire sheet before cutting since the soot wipes of so easy.

I am operating out my own basement/garage with one employee working the machine for 8 hours a day with another 4-6 hours of operating by me when I get home from my full-time job. In regards to space, I'm already squeezed tight for room and since I live in a house with 5 roommates, I don't exactly have the safety capabilities/room for a full-on spray room so for now, hand rags and sanders will only be used. If I could restart it all, I'd certainly change how I might have done things, but so far I'm maintaining a good balance :)

Thanks again for all of your insight and support!