Acrylic Fabrication Q & A

Turbo's Aquatics · Oct 30, 2017

The primary brace is on the longest dimension. The purpose of the brace is to prevent bowing. The brace absorbs some of the pressure that is placed on the vertical panel and transfers it throughout the brace. The stress point is going to be where the brace meets the side vertical panel, because there is A) no structural component to take it anywhere else and B) no brace on the top edge of the side panel, so these are additive forces

It's not a major stress as the tank is not very tall, but it's a stress nonetheless.

Adding the side panel top brace (like in the sketch) will help, as will the center brace. If you want peace of mind, do the 4 piece brace and then add 3 front-to-back braces and you should be very well set.

Also I just noticed that you are using 3/8" so I would definitely do a little over-building if you're not going with a 1-piece euro for that thickness of wall.

Turbo's Aquatics · Oct 30, 2017

The other thing you could do is reconfigure your tank dims so that you could use a full euro. Is there a reason you want it 70" long?

Matthias7 · Oct 30, 2017

The dimensions fit the room wanted to maximize space as best I could. The acrylic is cut already so no way to reconfigure the only way to go one peice now would be to buy another sheet, which I could do but would prefer not too

rbarr110 · Nov 3, 2017

Hoping to get a little input. I am intending on building my own acrylic sump (30"x16"x16" +/-). I have my own CNC machine so cutting will be a breeze. However, after pricing acrylic, I am thinking of using 1/4” extruded rather than 1/4” or 3/8” cast. For 3/8” the plastic shop only has cast.

A 4’x8’ sheet of ¼” extruded is about $180, and for ¼” cast I was quoted $370, didn’t even bother to ask about 3/8” cast as it will easily be over $400.

I am designing the sump similar to the Trigger Ruby 30, here are some screen shots of the model. I am leaning towards the ¼” extruded acrylic for obvious cost differences. I am considering routing channels for the acrylic to be placed in and then use capillary solvent welding. I also intend on using silicone at all the joints. Any thoughts or opinions on the plans so far? Model isn't complete yet.

Turbo's Aquatics · Nov 3, 2017

rbarr110 said:
A 4’x8’ sheet of ¼” extruded is about $180, and for ¼” cast I was quoted $370, didn’t even bother to ask about 3/8” cast as it will easily be over $400.

Holy @#$@ on that pricing. Maybe I just haven't purchased acrylic in a while, but I think you're getting hosed here.

Last I checked, 1/4" clear Plexiglas-G 48x96 was $130, 3/8" clear PMACS (which is the generic version of Plex-G) was $180, and 1/2" PMACS was $275 - and those are all cast prices.

Unless they're quoting you Polycast, yeah I'd go somewhere else.

Sabic Polymershapes (might just be Polymershapes now because "Sabic" is the parent company which is a Saudi company)
Laird Plastics
Port Plastics
Regal Plastics

Start there.

rbarr110 said:
I am considering routing channels for the acrylic to be placed in and then use capillary solvent welding

I would not do this. I get the idea, but it's just not going to turn out how you think. Just plan for the ends and baffles to be exact (cut the parts to their finished/final dims) and then add 1/4" or so to the length of the front/back panels (this is overage for flush trimming afterwards) and 1/4" to both length and width of the bottom and euro (again, overage for flush trimming) and use the pins method. It's not overly difficult, and results in a much better bond.

You can use extruded for the whole thing, but if it were me I would use 3/8" for the walls and baffle and 1/4" for the top/bottom. But for that layout, you can get it all out of one sheet so it's likely more cost efficient to get one sheet of 3/8" and make it all from that.

rbarr110 · Nov 3, 2017

Floyd R Turbo said:
Holy @#$@ on that pricing. Maybe I just haven't purchased acrylic in a while, but I think you're getting hosed here.

Last I checked, 1/4" clear Plexiglas-G 48x96 was $130, 3/8" clear PMACS (which is the generic version of Plex-G) was $180, and 1/2" PMACS was $275 - and those are all cast prices.

Unless they're quoting you Polycast, yeah I'd go somewhere else.

Sabic Polymershapes (might just be Polymershapes now because "Sabic" is the parent company which is a Saudi company)
Laird Plastics
Port Plastics
Regal Plastics

Start there.

So the quotes are from Tap Plastics, there is one less than a mile from where I work. Here is what I was told, the manufacturer is "Chemcast".
1/4" Extruded
50"x98" $175
60"x96" $195
72"x96" $243

1/4" Cast
72"x96" $355
51"x125" $329

3/8" Cast
50"x96" $360
60"x96" $408

Going to check with Onlinemetals.com as they sell acrylic as well and they also have a warehouse a few miles from where I work.

Turbo's Aquatics · Nov 3, 2017

Chemcast historically has been blacklisted by many tank manufacturers. They had a really bad history of tanks falling apart (literally) 6-12 months after being filled. I would only use Plexiglas (arkema) brand, or their generic version PMACS (pronounced "p-max")

Acrylite used to be #2 but they have fallen out as well, review comments by @mixer911 (Synergy Reef) and others on that (they had a batch that wouldn't solvent weld).

That's honestly highway robbery to charge those prices for Chemcast.

Laird: 650 S Industrial Way, Seattle, WA 98108
Port: 1228 Andover Park E, Tukwila, WA 98188
Polymershapes: 18292 Andover Park W, Seattle, WA 98188

Turbo's Aquatics · Nov 3, 2017

https://www.polymershapes.com/company/branch-locator/

cromag27 · Nov 4, 2017

i find that extruded cuts like garbage on my cnc machines.

but yeah, i don't like the slot idea. and silicone won't bond well to acrylic, therefore might not help at all.

S-t-r-e-t-c-h · Nov 6, 2017

Anyone have any advice on trimming and finishing the edges on cast acrylic tubes? I'm thinking 6" - 8" cylinders for skimmer & ca reactor bodies that will be seeing some pressure.

imustbenuts · Nov 6, 2017

S-t-r-e-t-c-h said:
Anyone have any advice on trimming and finishing the edges on cast acrylic tubes? I'm thinking 6" - 8" cylinders for skimmer & ca reactor bodies that will be seeing some pressure.

I’ve only cut and prepped 4” but I used a table saw with a stop on a cross cut sled. Then layed 400 grit paper on a flat surface and leveled the cut. It seemed to weld up strong.

rbarr110 · Nov 8, 2017

Thanks for the help there. I contacted polymer shapes and they quoted me
1/4" 4'x8' $136
3/8" 4'x8' $248

I have inquired about 3/4" but have not heard back yet. However, I ended up buying some upgrades for my CNC, and the tank/sump work will have to wait for a little more cash to build back up.

Turbo's Aquatics · Nov 9, 2017

rbarr110 said:
1/4" 4'x8' $136
3/8" 4'x8' $248

Better. Was this for Plexiglas-G or was that for Arkema PMACS? Sometimes you have to train your rep to get you the correct pricing. I write down the actual item numbers so I don't have to re-train every time but I'd have to dig those out (and they changed them not too long ago).

The PMACS is usually 30% cheaper, so that $248 for 3/8, you might be able to go down to $200

rbarr110 · Nov 9, 2017

Floyd R Turbo said:
Better. Was this for Plexiglas-G or was that for Arkema PMACS? Sometimes you have to train your rep to get you the correct pricing. I write down the actual item numbers so I don't have to re-train every time but I'd have to dig those out (and they changed them not too long ago).

The PMACS is usually 30% cheaper, so that $248 for 3/8, you might be able to go down to $200

So I inquired about 3/4" (0.708") and is $446 a sheet. They also confirmed pricing was for PMACS. I was considering making a 90-120 gallon tank with 3/4" and move to 3/8" for sump, but may just continue to watch for used 90-120 gallon tanks as prices for used have been a around the $400 or less mark.

Just put $1300 into CNC upgrades, so the waiting game for used tanks will be fine, but still probably going to build a sump from 3/8" after CNC upgrade installation is complete.