Acrylic fabrication questions? I can help!

Two things.

First is the calcium reactor I built and had problems with the cracking is up and running......and holding water just fine!! Was leaking water quite a bit at first and I thought I would have to redo the top flange, but I realized that I did not tighten the recirc hose clamp.....oops. Water tight now! Thanks to all who helped me out on this!

Second is that I got two sheets of 1/4" acrylic (30x96") for FREE and I am planning several projects with them. They are covered in paper with no labels or anything else. The guy I got them from has had them forever and can't remember specifics on them. My question is this, How can you tell if it is extruded or cast??? Any way to tell the quality of the acrylic by appearance?

The outside edges are rounded and smooth and taper down a bit if that helps at all.

Thansks!
 
no masking typically means import(cheaper stuff) as you might expect from something without a label on it. Just because its not as quality as others, doesnt mean its not build worthy, its just not commercially worthy.

Have to wait for james to chime in on how to look at it and tell diff between extruded and cell. I can tell by cutting them which is which, but appear the same at the start to me.
 
If the paper is all brown, no marking, no labels, and has the texture of crepe paper - it's prolly cheap import cell cast. The better mfrs will *almost* always print their name and brand on the one side of the sheet, if not both.
You can also check thickness, if it varies by more than .005" - it's cell cast.

If you could explain "The outside edges are rounded and smooth and taper down a bit if that helps at all" - I might be able to help more :)

James
 
Acrylic Blow Mold?

Acrylic Blow Mold?

I am looking to make a dome.....No used for it yet but I eventually would make a skimmer and use it for the neck connection.

So I was thinking of making a circular jig like one that you would use for flanges(one side with a center opening the other without) both with screw holes in the jig. I would then insert an o-ring about 3/8" larger diameter than the opening and a 1/4" peice of acrylic. Then drill the holes and screw down the jig and acrylic. The closed side of the flange jig would be threaded and hooked up to a compressor with a valve in line.

I would heat the acrylic exposed in the opening and add a little air pressure. My question is do you think the dome will come out even? Or will it look goofy.

Thanks,
Tres
 
Tres,
Your close but would end up with a nipple where the air blows into the acrylic. If that will work for you, go for it :)

If you want a bettter dome....
Make 3 pcs of 3/4" material total:
On the bottom goes the solid sheet with the 1/4NPT tapped into the middle. over that hole place a 1/4" thick disc on a coupla 1/4" risers, the disc is there to diffuse airflow to the outside.
On top of the bottom piece, make another with the hole diameter equal to the desired dome diameter. Screw this piece to the bottom.
Make another just like previous piece, keep this piece free.
Put your acrylic in the oven, heat until very pliable. Place the heated acrylic on the 2-piece assembly, place the free piece on top and clamp it down using quick clamps. Blow air to the desired height is reached.
Trim flashing.
Done.
I don't like putting wood in the oven so that's why we do it this way. Your previous way will work but wood easily can warp in the oven causing a deformed dome. This way also negates the need for the large o-ring which will get destroyed by the hot acrylic.

HTH,
James
 
Rich, if you're still looking...
I found a coupla pics, I'll post either tomorrow or the next day. Tomorrow will be busy so not sure I'll be able to get to it at work.

James
 
That would be great James! I'm not having much luck getting a good bond on the end of the tubes. Had to break out the 16. Haven't had to do that in quite some time.
 
Rich,
The way we do it is to tape a sheet of 220 grit wet/dry to a flat table and grind the ends on the paper in one direction only until flat - should take about 2-3 minutes per end. Follow this with 320 paper (about 5 strokes each side) and you're good to go. The router fixture doesn't really work on anything smaler than 8" diameter, just to difficult wt rotate small diameter tube without tilting and the sandpaper works well :)

HTH,
James
 
<a href=showthread.php?s=&postid=9684708#post9684708 target=_blank>Originally posted</a> by Acrylics
If the paper is all brown, no marking, no labels, and has the texture of crepe paper - it's prolly cheap import cell cast. The better mfrs will *almost* always print their name and brand on the one side of the sheet, if not both.
You can also check thickness, if it varies by more than .005" - it's cell cast.

If you could explain "The outside edges are rounded and smooth and taper down a bit if that helps at all" - I might be able to help more :)

James
Click to expand...

Thanks James!

Yep the paper is all brown with no labels or printing. Pretty sticky to the acrylic though. The guy I got it from said he has had it for "years". Don't know if that makes any difference.

The edges (except the saw cut ones.....the sheet was cut in 1/2 length wise) are rounded, clear and not the same thickness (taper down the last 1/2 inch with a visible line running the length of the acrylic where the taper starts), and on one edge it has little everted "dimples" about every 6". They look like paint drips made from acrylic. Tried taking a pic of it but you could not see what I am talking about clearly.

Basically I am thinking of making a sump(s) out of it. In addition, I want to play around and make a small (~10 gal) species tank for a mantis shrimp with a built in overflow and closed loop in a back chamber. Going to use NO lighting as no corals, just some LR is going in there.

Think this stuff will do for what I have planned?

Thanks again.
 
Sounds to me like a cheaper imported material, not something *I* would use for aquaria as many of these material simply do not want to glue well. But then again, the price was right and it's not like you'd be losing anything by trying it. Even if it doesn't work well, you will have gained some more experience which will pay dividends down the road :)

HTH,
James
 
extruded acrylic??

extruded acrylic??

Acrylics,

I have built a small sump 17X14X10 out of extruded acrylic, held together with WeldOn #3 and a bit of #16. I will be installing a 1.5" top brace(4 pieces, not enough left for a one piece).

I recently read that extruded can absorb a lot of water and therefore weaken the joints possibly resulting in a flood. Is this true? With the anove dimensions do you think I have to worry?

I will probably do the tank out of Cell Cast. It will be cube'ish in dimensions 24x24x16 3/8" thick with a 1 piece Euro Brace. Is there a big advantage to cell cast or will I be throwing my money away? What is the most scratch resistant?
 
Re: extruded acrylic??

Re: extruded acrylic??

<a href=showthread.php?s=&postid=9695626#post9695626 target=_blank>Originally posted</a> by newreef8584
Acrylics,

I have built a small sump 17X14X10 out of extruded acrylic, held together with WeldOn #3 and a bit of #16. I will be installing a 1.5" top brace(4 pieces, not enough left for a one piece).

I recently read that extruded can absorb a lot of water and therefore weaken the joints possibly resulting in a flood. Is this true?
Click to expand...
Not really, IMO. If the joint pops, it is *not* due to moisture absorption. Extruded acrylic absorbs 1.6% moisture (by weight), cell cast absorbs 1% moisture (by weight). If this idea was true in extruded, one would think it would happen in cell cast as well, since people don't worry about it in cell cast - it is my opinion that they shouldn't worry about it extruded either.

With the anove dimensions do you think I have to worry?
Click to expand...
As long as you get those top braces on, I woudn't worry :)

I will probably do the tank out of Cell Cast. It will be cube'ish in dimensions 24x24x16 3/8" thick with a 1 piece Euro Brace. Is there a big advantage to cell cast or will I be throwing my money away?
Click to expand...
There is a significant advantage to good quality cell cast (Polycast, Acrylite GP, Plexi-Glas G) but it primarily involves stress resistance. Extruded acrylic is far more apt to craze than cell cast given any similar conditions. Crazing is the definition given to stress fracturing in acrylic, these fractures can lead to material degradation and (possibly) material failure. Since cell cast is far more resistant to stress - far less likely to craze under similar conditions.

What is the most scratch resistant?
Click to expand...
Neither, both are the same in this regard. If there is any difference - it is negligible.

HTH,
James
 
Thanks for the quick reply. You have put my mind at ease on the water absorbsion. I was lead to believe it was a much higher percentage in extruded.

I think I will still pick up the cell cast for the tank just for the added securitydue to the water volume and this tank will be on the main floor.

Thanks again....
 
"It's just a fixture in which the router is mounted horizontally. You can slide the height up and down and set it with screws. Basically, you just set the height and turn the tube under it to get a good, routed edge."

James,
After seeing your "right angle router jig" years back (That was quick) I made one awhile back- scrap MDF, and some caulking gun type quick clamps to set the height.
Wow, that thing is super handy! I actually use it alot for perfect tops and bottoms. And if you think your router table throws acrylic chips, try lifting your router 2 feet in the air!
I cut tubing on the tablesaw fairly accurately, then over to the router to true up and baby-butt smooth the ends.
Smaller tubing is a bit trickier (and slightly more dangerous), but I just cut a little and slide the tubing straight out from under the bit, reposition my fingers, and continue.
I have also made a jig to hold a cone up off of the router table to cut a perfectly flat top for gluing tube, etc.
Until I am CNC fluent, I'll just have to keep doing things the old fashioned way:)

PS; I recently had some grainy looking joints in some 3/8" cast (WO4). Tell me again, is this from soaking too long, or not enough? Thanks!

Chris
 
Rich,
I'll have to take some of the 90 deg jig. The cone jig is simply a piece of MDF with a hole cut into it to hold the cone upside down. some strips double side taped to the bottom provide the general height adjustment, then the router height adjustment is used for fine tuning.
 
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