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Cast vs Extruded

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rfoote View Drop Down
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    Posted: April 23 2003 at 9:57pm
What are the pros vs cons of using either type of these acrylics?  I know from Jon cast is what is generally used, but unsure why.  Is it worth paying the extra price for cast?  Also, for a refugium would you go 1/4" acrylic?  Thanks!
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Flaz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Flaz Quote  Post ReplyReply Direct Link To This Post Posted: April 23 2003 at 10:33pm

Use at least 1/4" acrylic.  I used 3/8" on mine and it bows.  Acrylic also seems to bend under its own weight over time if it's not supported structurally.  Also, the more surface area you have the easier it will be to make good joints.  Just remember you bond it by holding the two pieces of acrylic together and applying the solvent to the joint, if the pieces are not flush they won't bond...

As for cast or extruded, the cast typically has a better finish and has a more precise thickness but that shouldn't matter for a sump.  There may be other benefits to cast but I couldn't tell you what they are...

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sarnack Quote  Post ReplyReply Direct Link To This Post Posted: April 24 2003 at 1:03am

Continuous Casting - ICI Acrylics has a unique process in the manufacture of Lucite L acrylic sheet. They employ a pair of highly polished steel belts that allow the sheet to form on a continuous basis, hence the name, and allow for a higher molecular weight. This material carries a small price premium and will work well in skylights and fish tanks. Available in .125 - .250 thickness only. Use solvent cements such as Weld On #3, #4 and #16. For special application a polymerizable 2 component cement, Weld On #40 can be used.

 

From: http://www.ecomplastics.com/formulations.html

A few acrylic links here:

http://reefcentral.com/diy/?s=&menu=12

Get questions on acrylic fabrication answered by a pro here:

http://reefcentral.com/forums/showthread.php?s=&threadid=96763

it is the guy that made my tank...

 

Don't know if any of this junk helps but there it is...

Dave

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jfinch Quote  Post ReplyReply Direct Link To This Post Posted: April 24 2003 at 8:14am

Flaz, does your sump have a splash guard around the top perimeter?  I was hoping 1/4 acrylic with a splash guard would keep the sides from bowing.

My understanding is that the cast material has better strength (higher molecular weight) and stronger solvent welded joints (less crazing, better aborbtion of the solvent).  There are fewer internal stresses in the cast material, which results in a more stable piece (easier to drill, ect). 

The lucite I've seen was very flexible.  Didn't seem good for a sump/tank.  Is the Lucite L stiff?  I've also heard that lucite can be hard to bond?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Flaz Quote  Post ReplyReply Direct Link To This Post Posted: April 24 2003 at 12:52pm

jfinch-

My sump doesn't have a splash guard, just a lid that sits on some acrylic blocks.  If I were to build one again I would consider a splash guard.  I think you're right about a guard providing extra rigidity.  If the cast acrylic is really that much stronger than the extruded it might be worth the extra cost.  What is the cost difference between the two types?  Here is a picture:

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jfinch Quote  Post ReplyReply Direct Link To This Post Posted: April 24 2003 at 2:30pm

Ok here's the prices:

Delvies Plastics:  1/4" $101 per sheet (cast)

                           3/8" $149 per sheet (cast)

 

Regional Supply:  1/4"  $76 per sheet (extruded), $112 (cast)

                            3/8"  $119  per sheet (extruded), $161 (cast)

The salesman also said the extruded was a no-no when it comes to water.  The extruded absorbes water and swells to the point that bonds can fail.  Cast, in his opinion, is the only way to go.  Any other places I should check with better prices?

Flaz, I like your skimmer, when I get around to making mine, I'd like to have a look at yours and have a little talk.

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