I recently came across some scrap 1/4-inch plexiglass. I am assuming there is no reason why this material would not be appropriate for building a printwasher for 8 x 20 fiber prints.
I would very much appreciate some info from those of you who have worked with this material and have attempted such a project.
1. What sort of glue/solvent is appropriate for assembly?
2. The 1/4-inch thickness would allow screws at some points for added strength. Is this necessary?
One product that is used for bonding plexiglass/acrylic is Weld-On #40. If you do a search for that product you may find the price and specs for it. It is used for making and repairing aquariums.
Plexiglass is quite brittle so be careful if you do try to add screws. It chips easily.
There are two recommended by my plastics supply shop, the first Weld-On #4 to be used with a needle bottle and then afterwards Weld-On #16 a thickened cement. The #4 dissolves the acrylic and joins them and the #16 is used at the juncture to reinforce the seem. You could probably use the #16 alone as you not needing to consider appearances. A bandsaw or tablesaw is the nuts to have as the edges must fit flat without gaps.
You might want to consider your supply and drain outlet. Flow turbulence seems to be the most important factor. If your doing a fill and dump you should have no problem.
I tried some aquarium stuff a few months ago for making 8x10 processing tanks that hold about 5 liters. The guy at the hardware store that sold me the plexi said "this is the stuff they use", it didn't work. It was a silicone type stuff not a solvent and the tanks leaked and split apart easily. I ended up stripping it off and using my hot glue gun which seems to be holding up well so far. I cut the stuff with a 7 1/4 inch plywood blade on my table saw. I'll try the solvent stuff next time. that's my two cents
Acetone or Weld-On is the way to go. Silicone on Plexi is... well... silicone works on GLASS. Not plexi really. I was actually thinking of doing the same thing. Must be something in the air! But I was thinking of using a GLASS aquarium of correct proportion. Think about it. It's PERFECT. EVERYTHING you could possibly need is already out there -and available on the cheap;
i.e. - undergravel filter with powerheads - sucks water from the bottom and recirculates water evenly throughout. You could build a really great 'green' setup this way and use MINIMAL water to get an archival wash - the only trick is to keep adding fresh water to the system as you siphon off the old. Not QUITE sure how to do that yet.
The Weld-on #4 and #16 are the most common cements. #40 is a two-part material that actually forms new acrylic in the joint. It's the strongest, but it's also more expensive and a pain to use. It is what commercial aquarium manufacturers use but they have special mixing guns that mix the two parts on the fly.
I'm not sure how you are planning to use screws, but if you are putting them into the edge of 1/4" they won't add enough strength to be worth the trouble. I've used #4 to bond small tanks, then after the joints were dry added a bead of silicone to the inside of the joints. Seems to work pretty well. Most of the strength comes from the #4, but if there is a small bubble or void that crosses the joint (when you try this you'll see what I mean) you can get a leak in a joint that is otherwise adequately strong. The sealant will take care of the leak though it may not add a huge amount of strength. As was suggested above, #16 could probably be used in place of the silicone but I can just about guarantee you'll find it to be much messier.
If you use #4, be aware that last year IPS had to reformulate it to reduce the VOC and it is no longer the same product as the old stuff. Old #4 in a polyethylene dispenser bottle would literally evaporate through the bottle in a matter of days. The new stuff doesn't, and it also doesn't work as well. If you have access to chemicals, ethylene dichloride works as an acrylic cement. Needless to say these are all fairly nasty to breathe so use good ventilation.
Incidentally if you've never used the stuff, #4 just wicks into the joint by capillary action. Get a little applicator bottle with a needle on the end and practice on some scrap until you get a feel for it.
Cutting plexiglass is best done on a tablesaw, ideally with a blade intended for plastics. Such a blade has a negative rake to the teeth and it is less likely to chip the edges. You can also use a good carbide-tipped 40-tooth (on a 10") crosscut blade if it's sharp and you don't feed too quickly. Sometimes you can find a blade for melamine with negative rake in a woodworking or hardware store and that should be good too. As was mentioned above, joints should fit with no gaps.
No one mentioned the issue of drilling holes in acrylic. If you can get them, use a plastic drill. They are more pointed and have a cutting edge that scrapes instead of lifting a chip like a standard drill. I would not advise using a large conventional drill (> 1/4") to drill the hole in one shot. Start with a smaller drill, then work up to the final size. It's best to clamp the work for drilling, but if you hand-hold it on the drill press hold it very firmly. The drill will often try to grab and lift the part off the table which will trash the hole (or worse). Feed slowly, and I'd practice on a scrap or two.
If you need large holes they can generally be drilled successfully with spade bits (the flat kind), believe it or not. Slow the spindle down to one of the lowest speeds and definitely clamp the part.
To the last poster who wants to replace water, use a fairly large (maybe 1/2" - 3/4") tube that is open at the top, positioned so the top is at the desired water level. Run it through the bottom or with an elbow through the side of the tank to the drain. The idea is like an overflow drain in your bathtub. Then just put a tube in to add water near the bottom of the tank. As the water level rises it just runs out the overflow.
You can get anything plastic as well as glues, including the ones mentioned here at www.usplastic.com. They even have a plastic welder. Do not drill or try to screw into plexiglass it will only fracture and wouldn't supply enough strength to be of any help.
Be very careful when cutting the plexi on a tablesaw. Its the right tool for the job but when something goes wrong it can be quite an explosion of plastic shards. Wear safety glasses and a face shield. Maybe more than a t-shirt might be a good idea too. And think about your saw set up carefully before you start cutting.
I also suggest against screws, they're not helpful. Tight joints and then a second application of Weld-On to build a small filet inside the joints will do the job fine. The second coat can make it ugly but the added material helps strength wise.
I'd make the tank so the open end is about 10x10, 10x12 or so and maybe 24 inches tall. If you make a horizontal tank you probably will need to support the 24" long sides or they will bow considerably when its filled with water. But thats not that big a deal to overcome by building a flange around the top.
When I cut plexi I put a line of masking tape along the cut line (top and bottom) like you do with plywood. Not sure if this is really needed but works for me.
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