Acrylic fabrication questions? I can help!

[TropTrea]

What are you using for bonding? I now understand your use of the term catalyst, but (and forgive my analness here) it is not technically correct. A catalyst is something that speeds up a chemical reaction. Solvent bonding is not a catalytic reaction. Solvent just chemically "melts" each side so that 2 pieces can be joined and then "harden" together (not the technical terms but I'm short on time). So just substitute "solvent" for "catalyst"...

Yes I do stand corrected. It is a "solvent" that I get from the local Plastic store. It is actualy available in different thicknesses with it being a mixture of solvents and acrylic dust in different ratios. The straight solvent I tried once and it was extremly watery for my use but the second solution worked great as it has suposedly 5% acrylic dust in its composition. Just enough to give me some working time without it running. The 3rd solution is almost to thick for my application but would work good for decroative sculpturing of acrylic. It has I believe 10 % acrylic dust in the mixture.

Consistancy wise this #2 is very simular to Weldon 4, with there #1 being almost thinner than water. There numbering goes up to a number #4 which is almost like a paste. Suposedly the higher the number the longer the working time as well as the thicker the solution.

 

[Floyd R Turbo]

I can see where you would have an issue with the water-thin solvents when using your particular bonding technique - the solvent just runs out of the joint, especially if you are joining the piece flush at the edge, and then even more so when the outer edge of the joint has something in contact with it, which would give water-thin solvent a path to wick out rather easily.

When using the pins method, one sheet is horizontal (preferably on top of a piece of MDF with strips of "camper shell foam" on it) and the other sheet is vertical. A 90 degree bracket holds them in place. Once the joint is in full contact across the entire length of the joint using shims/etc, the pins are inserted and joint is adjusted again. The brackets are attached to the vertical piece such that when the pins are added, they are lifted up slightly off the horizontal piece. Then the pins are pulled, they won't hold the joint apart.

The vertical sheet is offset slightly from the edge of the horizontal piece (1/16" or 1/8") which is trimmed off later with a flush trim router bit. This allows the solvent to form a fillet on both sides of the joint, which prevents air from sucking into the joint as the solvent dries. The solvent is ran along the joint and after 15 seconds or so, you pull the pins and the solvent & melted acrylic from both sides 'squishes' out and forms the fillet. So the bottom panel with lip provides the ability to form a fillet on both sides, and also prevents the solvent from running out of the joint. Both of these prevent air intrusion during the curing process. Any other bubbles that appear "inside" the joint are usually due to edge prep errors, solvent application errors, dust/grease/fingerprints on the surfaces of the joint (which cause air pockets), etc.

After pulling the pins, I usually let this sit untouched for about 30-45 seconds, then I momentarily (and gently) release the clamps holding the vertical piece to the 90 degree brackets while adding a slight amount of pressure on top of the vertical piece. This ensures that any additional "gap" that is created as the solvent "bites" into each side of the joint during the soak time does not increase the space between the 2 sides of the joint beyond what it was when pre-setting the joint (which was flush). If I can, I put some weight on the top of the joint, but for a first end-to-front joint, it's not really feasible, unless you have a sandbag and trust your ability to balance the load. It's easier to do on the next side of the end joint, when you have a panel to place a weight on, or for the bottom or top joint (12 packs are my fav)

Then once I have place the clamps back in place, I don't touch the joint for several hours. If is it for a display tank, I try not to even bump the table that it is on for a minimum of 4 hours, usually 8 (overnight) and I do not flush trim with a router until a joint has sat for 20 hours. So if I add the ends to the front (2 joints) and wait 8 hours, then flip over and bond the back to the ends (2 more joints) and wait 8 hours, I can flush trim the lip off the front/end joints but I still have to wait 12 more hours to flush trim the back/ends. So I usually just let it sit for a full day then do all 4, then put the top on, wait 8, bottom on, wait 24, flush trim top/bottom, done.

 

[Floyd R Turbo]

Tank cleaned up



Welded the bottom joint and crack in the bottom panel. Solvent wicked in pretty well



Weight on it



I did skip the drilling of the crack. I will do this later...

 

[vitodog]

I saw this thread and thought, what the h---. My new rimless tank will be delivered next week and will begin the process of transferring everything from my 90g into my new rimless. I currently have a few potential jumpers in my current set-up and have the typical BRS screen on the tank. I don't want to ruin the look of the rimless with this type of screen. So, my question is this; Is it possible to build the same type of screen frame used in your typical frame using acrylic? I'm looking for that invisible look.

 

[Floyd R Turbo]

The problem is that unbraced acrylic will warp like crazy. So you will set it on your tank and then moisture on one side will cause it to expand and dry on the other side (plus heat from lights) and it'll get all wonky in just a few days.

PETG does not warp but it a lot more expensive, I'm not sure how well it bonds or routes either. I have a full sheet of the stuff myself, having some CNC cutting done with it for sump lids, and it would probably work for a inset euro like you are wanting. In fact I may do that myself for a similar purpose for what you are wanting - a lid/frame for a rimless glass tank.

 

[TropTrea]

Floyd I completly understand your system now. The real big difference is that your using a solvent that wicks much better than the solvent that I use. My suspecion is that your solvent has much less acrylic in it than the one that I use which makes your methiod impossible with my thicker solvent. Yes I do get that little beed along the inside and outside of the edge like you do as well. As far a air bubble goes these only show up when I did not use enough of my thickened solvent. On 99% of my joints the end result makes it nearly impossible to tell if there was two pieces there or if it was one piece to start with.

 

[Floyd R Turbo]

Straight Methylene Chloride with about 5-7% Glacial Acetic Acid is what I use. The AA just makes it flow a little better -> less chance of bubbles.

Your stuff sounds similar to weld-on #16 without all the extra fillers

 

[vitodog]

The problem is that unbraced acrylic will warp like crazy. So you will set it on your tank and then moisture on one side will cause it to expand and dry on the other side (plus heat from lights) and it'll get all wonky in just a few days.

PETG does not warp but it a lot more expensive, I'm not sure how well it bonds or routes either. I have a full sheet of the stuff myself, having some CNC cutting done with it for sump lids, and it would probably work for a inset euro like you are wanting. In fact I may do that myself for a similar purpose for what you are wanting - a lid/frame for a rimless glass tank.

I see. Thanks Floyd, I appreciate your help/response.

 

[TropTrea]

Straight Methylene Chloride with about 5-7% Glacial Acetic Acid is what I use. The AA just makes it flow a little better -> less chance of bubbles.

Your stuff sounds similar to weld-on #16 without all the extra fillers

Just read there brochure

Acetate Solvent Thin Bodied
Methylene Chloride 90%
Methyl Acetate 8%

Acetate Solvent Medium Bodied (The one I use)
Methylene Chloride 85%
Methyl Ethyl Keytone 7%
Methyl Acetate 5%

Acetate Solvent Heavy Bodied
Methylene Chloride 82%
Methyl Ethyl Keytone 14%

There is also a list of about 4 other compounds all listed as under 1%

My guess is what your using is very simular to the thin Bodied Solvent which I used once but did not like because to me it seemed too watery and did give me much working time at all. By the time I got it brushed on the first surface it seemed to already be dry on the first surface. I was able to snap the joing when I tried moving the pieces the next day.

 

[Floyd R Turbo]

By the time I got it brushed on

There is the problem, the water-thin stuff is not meant to be brushed on, at least not IMO. I think I recall product instructions saying you can do this, but they're not building aquariums...

 

[TropTrea]

There is the problem, the water-thin stuff is not meant to be brushed on, at least not IMO. I think I recall product instructions saying you can do this, but they're not building aquariums...

Yes instructions say to brush them on to both surfaces and for the thin solvent then position them them together with pressure. They actualy give you a small applicator wand built into the cap simular to the stuff you use for plumbing. Normal working time 15 seconds, 50% bonding strenght in under 1 minute, 80% bonding strenght in 2 hours, 95% bonding strenght in 24 hours.

For the medium thickness it gives your 30 seconds working time. But it does not say brush only apply a thin even coat to both surfaces. With the same for the other bonding strenght times. And for the heavy it gives you a full minute working time.

I will back up on my statement that it is as thin as water I think it is thinner more like thinner or acetone for the thin solution and the medium is just a little bit noticably thicker than water. I had tried wicking the medium a few times and it did not flow into the gap but simplu stayed where I put it in the corner. Actualy that is where I built the 46 degree fram thinking that gravity would help the wicking process. But for me speed in getting the job done was probably a big factor, and possibly not having a big enough gap initialy.

 

[Floyd R Turbo]

If they include a brush in the cap for the water-thin solvent, you are using the wrong stuff for the aquarium application in the first place, IMO. Maybe good for general acrylics bonding for crafts and such.

Weld-on #3 and #4 are generally referred to as water-thin. They just have less surface tension so they spread out faster. The applicator to use is the squeeze bottle like the ones from Craftics.

 

[TropTrea]

If they include a brush in the cap for the water-thin solvent, you are using the wrong stuff for the aquarium application in the first place, IMO. Maybe good for general acrylics bonding for crafts and such.

Weld-on #3 and #4 are generally referred to as water-thin. They just have less surface tension so they spread out faster. The applicator to use is the squeeze bottle like the ones from Craftics.

This solutions they sell are noted on the bottom

Made by IPS corperation exclusively for Midwest Plastics.

I checked the IPS web site. And see the solutions you are talking about.

Weldon 3 Low VOC Acrylic Plastic Cement
Weldon 4 Acrylic Plastic Cement (Longer work time than 3 but same strenght)
Weldon 16 Low VOC Acrylic Plastic Cement

They list others as well but they are two or three part mixes which give higher joint strenght values. The Suposed joint strenght is the same for all of these I listed above.

Comparing the Midwest brand I would guess
The thin solution is basicly a slightly thined version of Weldon 3 since it has the same chemicals listed on slightly more Methyl Acetate.
The medium bodies is probably a mix of Weldon 2 and Weldon 16
And the Heavy bodied is probably a thickened form of Weldon 16

As far as the applicator goes they sell all three in 1 1/2 ounce tubes and pint bottles. The medium does have an applicator in the pint bottle which is the only one I bought in the bottle form. The rest I bought as tubes. I do like the tubes as better to work with but you do not a lot in the tube for the price. I think I figured your spending almost 10 times as much buying in tubes for the same quantity. But with the pint youy get a lot more than I would use in a few years and it does not last forever. $12.00 per pint, or $4.00 for 1.5 ounces.

And yes Midwest Plastics also sells clear Acrylic Piping up to 4" Diameter in various schedules and they claim the thick solution is the ideal for it. I thought of doing my returns in the clear Acrylic but the price was out of this world.

 

[TalloneJosh]

I just picked up an acrylic tank locally cheap and it needs some work, the corners of the tank are not really rounded and are sharp. The tank is about 240 gallons 8'x2'x2' the sides are all 1/2" acrylic. Can i put a 1/2" radius on the edge using a router without damaging the integrity of the tank, then polish the seam to make it rounded?

 

[Floyd R Turbo]

I would not put that much of a radius on it. 1/8" roundover max, then wet sand with 800, 1200, 1500, 2000, then use 3000 grit sponge from an automotive store, then a random orbital polisher (black & decker) with Meguiars swirl-free polish.

 

[TalloneJosh]

Awesome, Thanks. The tank is pretty scratched up so I am going to wet sand and polish the whole thing, all the scratches are on the surface and can't be felt. The bottom of the tank is cracked and was repaired improperly, and I was planning on replacing it. I'm planning on routing off the bottom, by going around the inside of the tank and removing the center then going around the edges to remove the rest of the remaining bottom, then prepare the edges, sand and polish the compete interior of the tank, then glue a new sheet on the bottom. Would this be the proper way to do it? Does anyone have any experience replacing the bottom of a tank?

 

[TropTrea]

Awesome, Thanks. The tank is pretty scratched up so I am going to wet sand and polish the whole thing, all the scratches are on the surface and can't be felt. The bottom of the tank is cracked and was repaired improperly, and I was planning on replacing it. I'm planning on routing off the bottom, by going around the inside of the tank and removing the center then going around the edges to remove the rest of the remaining bottom, then prepare the edges, sand and polish the compete interior of the tank, then glue a new sheet on the bottom. Would this be the proper way to do it? Does anyone have any experience replacing the bottom of a tank?

Yes I repaired two bottoms in the past but did not remove the old bottom. Instead what I did was simply add a second layer of acrylic over the damaged area, from the inside of the tank. However the cracks I had were moving outward from where holes were drilled in the tank for drains, rather than from the edge. So if this will work for you is probably determined by how close you can get the repair pierce to the side piece where the crack originated.

 

[Floyd R Turbo]

To ad to this, if the crack on the bottom panel has expanded to the joint, you have to make sure the crack hasn't started to move into the vertical panel.

If I understand you right, you are going to remove the existing bottom using a flush trim bit (bearing on tip) and then remove the remaining part of the bottom panel by routing it off, so that you have a finished edge to bond a new bottom to, right?

I would consider what Trop mentioned. drill a hole at the end of the crack on each end of it (if you can) this stops the progression of the crack. Laminate a new bottom panel on (1/4" should be fine) and then laminate over the crack with another 1/4" panel that extends 4-6" in either direction of the crack.

The only problem becomes the crack that is close to the joint. You have to stop the crack (by drilling the hole) and if it is too far into the edge or has gone through the joint, it gets tricky.

A picture might help

 

[woodnaquanut]

Removing bottom - another approach...

Do the first cut to remove most of the bottom.

Build a holder for the router. Let's see if I can describe it!

Create a large 'L' shaped holder with the router mounted sideways (horizontal) on the vertical section of the 'L'. The bottom of the router bit should be off the base at the height of the cut. This is a form of a 'vertical router'. Googling it I find plans for tables that are stationary. In this application the router moves and the routed object is stationary.

With the tank upside down on a flat table, the cut can be made by sliding the 'L' around the tank.

 

[TalloneJosh]

covering the bottom with an acrylic sheet is not possible for 2 reasons:

1. The top is eurobraced and it is not possible to get the sheet inside the tank.
2. The previous owner tried to fix the crack and am told that the tank holds water, but it is fixed incorrectly. He glued a panel on the bottom of the tank but it does not cover the length of the crack, and it looks like he just put the acrylic adhesive over the rest of the crack to "seal it". I cannot remove his panel to replace it with another panel.

The crack does reach the corner of the tank but has not started to climb up the side, i cannot drill the end without drilling into the side. I will try and get pictures up in a few minutes.