Acrylic fabrication questions? I can help!

Thanks for your input Floyd.

I had originally had the sides machine routed smooth. Since this was flush cut I had to trim one edge of the side pieces by 1/8" to allow for the lip between the back and bottom piece. I didn't have a router table so I used a table saw (actually got my uncle to do it for me). Now this edge is not as smooth as the routed edges. This edge has the teeth marks from the saw (60 tooth blade).

So how do I prepare this edge to be glued?

My thought from what I remember reading somewhere is to:
  1. use a utility knife with a brand new sharp blade and scrape this edge and then
  2. use a 400 grit sand paper and block to sand it down smooth (can I use 200 grit or 300 grit?)
 
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Sanding usually puts an round on the edge, no matter how well you try to avoid it. You can double-stick tape a piece of sandpaper down to a table and then slide the acrylic across it, that might avoid the rounding a little better.

Personally I would sand first then scrape with the blade, or skip the sanding all together.

After I bond the sides to the front and back, I have to use a razor blade in the corners of the top/bottom joint because the solvent squishes out of the joint and when I adjust the piece to it leaves little spots of dried solvent. So I just use the blade in hand and scrape this stuff off. It takes a *really* long time to remove 1/32" off an edge, so this might take you a while. Use long, smooth strokes and switch blades if it starts to get a burr on it (a light pre-sanding might help prevent this). Try to keep the blade square w/r to the sides of the piece. You'll get plenty of practice using this technique, by the time you're done with the first piece you'll be an expert LOL
 
I decided not to do the edge prep myself as i read in this thread by acrylics that machine routed smooth is the way to go and if we're to do it then do it right. So i took the two pieces back to the shop and asked them to route it smooth for me but the guy chipped a corner. Now i will have to wait until monday before he can cut me a new piece. To think i was so close to actually welding. I guess patience is the key in this hobby. Lol.
 
Hi Floyd, i want ask you one, how i can fill the old overflow holes without visible weld? I want to change the tank orientation in the room... i know it's difficult but i want try. :)
I'm thinking to late a cilinder with tollerance, insert, weld with liquid glue (like weld on
capillar) and after sanding and polishing the excess material.
The holes are on vertical wall but i can turn the tank because now is empty.
Many thanks for any help in advice. :)
 
If you're thinking of plugging the holes with a round piece of acrylic, I don't think that's going to be very easy. You would have to get the piece perfectly in contact all the way around, and then when you wick in the solvent without something to hold the pieces apart and allow for the solvent to soak for a bit and bite into both pieces, it will instantly bond and would leave a weak bond IMO. Plus using a solid acrylic rod for that would be quite expensive, because it generally comes in 2' or 4' lengths, etc, and you're looking at $100 or more for just that I believe. You're better off sealing over the hole with a square piece, I know it doesn't look the best, but there you have it.

You could also just get a threaded bulkhead and screw in a plug or a slip one and solvent weld in a cap.
 
Bumb

What would you guys suggest for welding one inch acrylic-I plan on using the WO product but which one? Also is the pin method a good choice for this.
 
Yes, pins and #4 if you're going to use Weld-on products. Otherwise just get straight MC and some Glacial AA and mix in about 5% of that before you start welding (but you have to store in a glass container). Also you will want high-flow needles and for the longer joints you will want someone else running solvent as it will start to set up before you can pull the pins. We had 2 of us on a 12' joint of 3/4" and it started to set up on us even then.
 
So WO4 for a one inch weld the tank is 8x3x3 do you think WO4 is strong enough or better than WO42-I have the option to use either one if it were you building this size thank which one would you use?
 
If you read back enough in this thread (I've read all 3 splits from the beginning and took notes) you'll find this (mostly from James IIRC)

As for joint strength with 40/42; it would be a rare occurance than 2800psi is ever reached in a hobbyist aquarium - ever. 2800psi is the rating for solvent bonded joints (using WO4 IIRC) and roughly 4200psi for WO 40/42 joints (non-annealed 7 day joint), the problem with this is simple - it does not take the material being glued into account. Differences in various brands and various batches of acrylic (cell cast or not) can & will have vastly different physical properties, more specifically - molecular chain length which, for our purposes, is the material's ability to handle stress. There exists an inverse relationship between this stress handling property and solubility which is required for acrylic solvents and resins (such as 40/42) to "bite" into the acrylic. WO 40/42 do need to bite into the acrylic, they don't just stick to it as a glue.
One of the nicest things about solvents is you know immediately whether the joint is strong. With 40/42 - you can't tell until you actually stress the joint. I've seen more than a few tanks that had beautiful "cast" joints that literally fell apart upon first fill that used #40. While the "bond" intself *may* have been very strong - this has little to do with how well the agent sticks to the acrylic. WO 40/42 can yield perfect looking joints in stainless steel - will this yield a strong joint? nope. While this may border on hyperbole, it's just to demontrate that bond strength and actual joint strength are two totally different things.
Click to expand...

Personally, I use solvents for everything up to about 2.5" as I have the capability of machining material accurately up to this point. After that, cutters flex too much to get the accuracy and consistency needed. It is at this point where #40/42 becomes fantastic products. Casting sheets together in series such as bullnose tanks and extra long panels are other great situations for these resins but are usually done in shops very familiar with working with thicker materials.
Click to expand...

and a good 'thread'

Hi James,
A quick question for you.

A good friend of mine used to make acrylic tanks for a living. He always told me to use Weld-On 40 for anything 3/8" or thicker. One thing that I have been reading from your discussions is confusing me a bit. My friend told me it is best to put a 3/32" angle on all edges to be glued....to create a channel I guess you would say and to create a stronger bond when using Weld-On 40, but in all of these pages I havent seen any reference to creating the same/similar angle for the edges to be glued (or maybe I missed it). I have also seen this same reference for creating the 3/32" angle in a few acrylic guides (Craftics for example). I will be making a sump (72"x18"16") using 3/8" cell cast (plexi-G) in the coming week using Weld-on 40 and want to make sure I am doing this right.

-Ryan

Ryan,

For the most part, using WO40 because it is "stronger" is waaaay past the point of diminishing returns. Even WO4 is good to something like 2500psi which is far greater than we will ever see in these tanks.
I don't go into placing the slight chamfer here (or 40 for that matter) because A) *very* few are going to do it and B) for most practical purposes it's not the normal method that most would use to build tanks, sumps, etc. it requires more tooling than most hobbyists are going to use so teach the simplest method that most would be comfortable with.

FWIW, a WO40 "joint" is strong, no doubt, but that does not translate into "bite" into acrylic. Put it this way, you can make a beautiful WO 40 "joint" between 2 pieces of steel, you can pull the pieces apart very easily since the 40 doesn't actually bite into the steel yet the joint itself may be very strong, get my meaning?

There are other reasons and esp why mfrs recommend 40 which is another story but hopefully this is a start

James

Thanks James. So for me to use the WO 40 would it be even necessary to put the angle/chamfer on the glued edges?

-Ryan

Hi Ryan,

While not *absolutely necessary*, the angle does help a good bit so yes, I'd recommend it. The 40 will follow surface tension (similar to capillary in this regard), since the gap will be smaller toward the inside - the 40 will "want" to go there first. To not have the angle leaves much more probability of voids and that sort of thing which we don't want

HTH,
James
Click to expand...

Those were pretty much the extent of the WO40/42 conversations I found useful in over 4000 posts.
 
when your ready, chime in and let us know what your process is, and what your doing.

that way we an Tell you NO or YES haha (which is what it feels like sometimes...)
no, but seriously...
i would rather see someone succeed then to not.....
Plus, its a great thing to say you did it, and your confident in it!
 
Yeah I think I will use WO4 with pins. Now when using pins do you only insert the pins half way in order for the solvent to run the lenght of the weld or do you insert the pins all the way between the twp sheets.
 
Is this your first project? If so, I would 1) attempt something smaller first, like a sump or something using 3/8" ('cause it's relatively cheap) and 2) read this entire thread. I mean from the beginning, which goes back to 9 years ago - this current thread is the 3rd section (split twice). It's by far one of the best threads I have ever read.

The reason I say this to you is to save you some possible costly errors. Don't take offense, but the question you just posed is one of the basics and it tells me you need to study more before trying to do this build, if you want it done right. Make an error on a 1/4 or 3/8" build, no biggie. Make an error on a 1" build, big $ and lots of work to 'recover' and start over, if you even can.

The answer is that you insert the pins only far enough to cause the two pieces bonding to separate enough to wick the solvent in, and that ends up being only a few millimeters.

I just did a build with 3/4" material and I found that we had to insert the pins a little further due to the weight of the material, putting the pins in 2mm cause enough pressure to put a little 'dent' into the upper sheet, though that didn't matter much because the solvent bit in well and that edge was flush trimmed, but the point is that you do not want to make a dam that would cause you to need to start a new bead section, you want the solvent to wick right past the pin.
 
I was wondering if it would be ok to use Weld-on 3 for acrylic to acrylic center brace replacement. FYI The tank is a 40 gallon tall, the brace is 5 inches wide and 3/16 inch thick, and I sanded both sides and I used a clamp on the outside of the tank to hold the center brace in place and everything seemed to go well. How long should I leave the clamp in place? Is Weld-on 3 strong enough for this? Thanks.
 
Wo3 and wo4 is the same strength, but 4 has AA which slows the drying process which makes it better for thicker material.

wo3 is fine. And I would give it a few days,but 24-48 should be good. But if you can. Stand 72, then that's what I would do
 
weld-on #5 is what had AA. Weld-on 4 has no acetic acid or it would eat through the can. #4 just has additional fillers (Methyl Acetate I believe) that slow down the bonding time a little bit and allow more working time.

+1 on time frame.
 
Floyd R Turbo said:
I know exactly what you're talking about. From looking at the pics, it looks like he made the staggered look by taking 1/4" and rounding off the edge, then bonding that to another piece that had the same done to it, then again. Sound right?

If that's the case, then you have a routered roundoff and that is the part that you are talking about. The first thing I would do it try to take off the router marks with a fine grit wet/dry sandpaper and this is where taping off the finished area around it will probably help. Start with 1200 or 1500 and a soft block to hold, keep the area you are sanding wet by spritzing with a spray bottle and also spray the sandpaper also. It helps to have a couple small buckets of water to dip the sandpaper into, one to get the dust/particles off mostly, and other to get the rest off (these can be small containers). This keeps the sanded particles from making more scratches.

You can probably go for 30 seconds to a minute between 'dips' depending on how fast you're working. you shouldn't need to work an area very hard to get the router marks mostly removed.

At this point, you can probably flame-polish it with MAPP gas and a flare nozzle, making passes as moderate, even speed (this takes some getting used to), but if you haven't done it before, practice on some scrap. If you mess up, you can sand again, etc, but eventually there might be no going back. Not to scare you, just sayin.

The other option is to buff it. Rinse the acrylic and use a buffing wheel with an arbor bit on a drill. You can get these at most hardware stores. Look for a 3-stitch wheel (it is a bunch of cotton circles stitched together with only 3 lines, others have many more stitch lines, you don't want those. Get some plastic polish, something like this

http://www.meguiarsdirect.com/product_detail.do?q=4729

http://www.meguiarsdirect.com/product_detail.do?q=4814

The first will take out the 1200 sanding marks, the second will polish to a mirror shine. You will want to use separate wheels for each compound.

This is what one company in CA uses (featured on LA fishguys recently) to polish tanks. You can get cheaper stuff, most 'final' car polish will work since this isn't in the tank.

Anyways, Spread a very thin layer of it on the acrylic (leave the tape on, or likely replace the tape) and let it dry a little, then run over it with the wheel at relatively high speed (2000-3000 RPM for a 4 or 6 inch wheel even). You won't need to press down on it, just get the wheel close enough to touch the acrylic. Oh yeah you will want to secure the piece to something sturdy before buffing. You will probably want to re-apply the polish several times as the wheel will soak it up. Anymore I drizzle it right on the wheel edge and even it out with a paper towel or cloth, but when you spin it up it will spray that stuff everywhere so be careful (eye protection).

After you get the hang of that, you'll probably be done with the ultra-cut step. It won't be finished yet, but it'll look a lot better, and you might be happy stopping there. It may still have a dull look to it yet. Go with the 205 (ultra finish) and you will likely get very close to a mirror finish. Then, if it's still not to your liking, a couple quick passes with the MAPP gas should make it shine up really nice.

HTH

Bud
Click to expand...


Bud, I used this method and it worked great! I ended up not using the MAPP Gas, the edges were good without it. Thanks!

Chad
 
Is it OK to build a tank that is

60'' long X 24'' tall X 30'' wide 187gal.
With 1/2'' Plexiglas MC ?
I would use a 4'' euro brace with 3/8'' Plexiglas MC and a 3'' center brace. and a 3-4'' bottom euro brace.

I know James recommends 3 different brands of Acrylic for tank build.
Why not Plexiglas MC??
 
Can you? Yes. Would I? No.

I wouldn't build a tank that size out of any 1/2" material.

MC is extruded. All the other three are cell cast. Big difference.

Also, it's only Polycast and Plex-G now. Acrylite GP is out.
 
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