Acrylic fabrication questions? I can help!

[A Reef Scene]

What is the best weld on to use?

 

[TAB]

Thats a depends kind of question. its like asking which hammer is best, it depends on what you need to do.

Generally speaking, #4 for the average DIYer, #3 is also fine, but drys faster.

 

[jdargonaut]

[/IMG]

Does anyone have advice for a beginner for using Weld On 40? I got my acrylic cut, it is now mocked up with tape. Unfortunately, the plastics shop could not route the edges for me, so they suggested to do some light sanding being careful not to round the edges, then use Weld On 40 instead of Weld On 4. My router table is not available right now. They said a sanding block with 600 grit would be fine, but I do have micromesh if that is better.

What should I use to apply the 40? Should I use the "pins" method? A little step by step direction or tips would really help. As mentioned by many others, this is a hugely valuable resource for us rookies, so thanks again!

spent several hours going through the thread, didn't see much on the 40. Did I miss it or is Weld-On 40 a no-no for a beginner? Even if I had my router available I'm not sure it's powerful enough to route 1-1/4" thick material (besides the cost of the bit), so is the Weld-On 40 a viable option?

 

[bigfalcon36]

40 is easy to use. Mix it and apply it with a plastic syringe without the needle tip on it. I use a 20ml syringe with a 65 gauge opening

 

[jdargonaut]

cool, thanks. I assume I shouldn't use the pins method then, just apply the 40 to each side, wait a few seconds and put them together? Is squeeze out a problem? Are there any other things to consider to make sure the joint looks nice?

 

[A Reef Scene]

I want to build a large skimmer, and am looking for the strongent bond I can get

 

[Acrylics]

I want to build a large skimmer, and am looking for the strongent bond I can get

In reality, WO 3, 4, and 40 are all stronger than we'll ever need on the hobby side. The trick is material, prparation, and technique, (generally) not the solvent/cement you use. So practice with whichever you are most comfortale with, and use that.

Skimmers/fractionators are easy to glue and glue well using any of the above, but you have to hold up your end of the bargain by choosing the correct materials and using proper technique.

James

 

[Lumpy Gravy]

I've been practicing solvent welding and I can get great joints, but I've come across one issue. In the "ooze" which occurs after pulling the pins (the fillet of melted acrylic pushed out by the weight of the part), I notice what appears as crazing. My first thought was the solvent, so I've tried a number of combinations. I typically use Weld-On 3 with about 5% acetic acid (99.5% purity) added for better flow. I never had good luck with Weld-On 4 (bubbles in the fillet and joint). I've also used straight methylene chloride, with different amounts of acetic acid added (3% to 10%).

Another thought was that perhaps the acid is causing the crazing, yet I have noticed it with even small concentrations. I prefer to leave it in there, as it helps avoid any hazing due to evaporation of the solvents. I do notice more crazing with higher amounts of acid, but it still occurs down to 3% (although, to a lesser extent). It could be that the additional acid allows the "ooze" to flow further when the pins are pulled.

I'm using Plexiglas G (the only cast acrylic available around here), 1/2" and 3/4" thick. My pins are 0.015" and I typically pull them after 30 seconds (never more than 45 seconds, or the pins leave voids).

Is this simply an issue of too much solvent action, combined with too large of pins? I'm assuming a smaller pin would result in much less "ooze", but is strength affected with the use of smaller pins?

Thanks in advance for any advice. I'll be sure to post some cool images after I get this issue nailed down.

~Lumpy

 

[Acrylics]

It could be that the additional acid allows the "ooze" to flow further when the pins are pulled.

yep, you got it

I'm using Plexiglas G (the only cast acrylic available around here), 1/2" and 3/4" thick. My pins are 0.015" and I typically pull them after 30 seconds (never more than 45 seconds, or the pins leave voids).

Is this simply an issue of too much solvent action, combined with too large of pins? I'm assuming a smaller pin would result in much less "ooze", but is strength affected with the use of smaller pins?

Strength itself is not affected provided you get adequate coverage of the joint and sufficient "soak time." One of the issues is that for long runs - you need the solvent to stay in solution until the joint is complete and that often requires the larger wires.

As with most things, it's a compromise

James

 

[rEd86]

Bending acrylic, tightest radius

Bending acrylic, tightest radius

Greetings.

I am interested in bending some 1/2" acrylic and was wondering what the tightest radius I should account for in the bend. (my assumption is if the bend doesn't have a rounded corner, the acrylic will stretch and/or form a weaker corner) My geometry skills are very rusty, otherwise I am sure I could figure out a formular that would give me the right curve...

I plan on routing the edge of a piece board to form the jig that would give me a nice, controlled line for the bend.

TIA!

--Ed

 

[RokleM]

One thing they'll need to know is... for what? Are you bending a corner for a rounded corner tank, or are you building something like a frag rack? Two different setups that will require completely different strengths.

 

[rEd86]

I am considering doing this for a tank. (a frag rack built out of 1/2" acrylic would be a pretty impressive frag rack! )

--Ed

 

[RokleM]

I am considering doing this for a tank. (a frag rack built out of 1/2" acrylic would be a pretty impressive frag rack! )

--Ed

All depends on what you have handy and/or find as scrap. We have a local place here you can get scrap by the lbs, even up to 1". Perfect for things that don't matter as much.

That being said, I've never researched the stress on heated/curved acrylic, so will default to the experts like acrylics

 

[troylee]

Rounded corners are weaker than a glued joint... The heat from the bending it puts a ton of stress on the material.... Do you want to do it for looks or do you not trust your welds???

 

[Acrylics]

Greetings.

I am interested in bending some 1/2" acrylic and was wondering what the tightest radius I should account for in the bend. (my assumption is if the bend doesn't have a rounded corner, the acrylic will stretch and/or form a weaker corner) My geometry skills are very rusty, otherwise I am sure I could figure out a formular that would give me the right curve...

I plan on routing the edge of a piece board to form the jig that would give me a nice, controlled line for the bend.

It doesn't really work that way. The radius is controlled by the temperature at which you heat, and the area you heat - usually a heat channel made by a strip heater. Narrow heat channels and cooler bending temps provide a tighter radius that a wide heat channel and higher temps.

In other words, if you heat a 3" wide area, you'll have a larger radius than if you heat a 2" wide area. IMO you should never heat an area less than 3x the material thickness, and that's pushing it.

Additionally, when material is slightly cold-bent - it will yield a tighter radius than material that is brought to full temperature.

IMO forget making a "form" to bend the piece around, the mark-off that you'll likely get from this will not look nearly as good as a bend without the jig.

And yeah, as a generality; line bent materials have far more stress on them than glued joints.

James

 

[H20ENG]

I keep seeing skimmer specs that say "precision machine glued acrylic".

I know there are automated dispensers for production. They use CNC dispenser needles for gasket goop, glues, etc. I would love to see the CNC dispensers and an automated acrylic gluing machine. Seems you'd have to stay within really tight tolerances, and environmental parameters to make repeatable, nice joints.

Whos seen this? Got a link?

 

[Dejavu]

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[sterling18]

Sorry I'm sure the answer is the two threads somewhere but is there a special blade I need for my jigsaw to cut acrylic. I need to trim down my overflow box. I mis-measured my box before cutting the hole my tank by 1/4".

Thanks

 

[COreef8]

I've got a question for you if this thread is still active. I know that 1/4" acrylic is supposed to be used for tanks up to about 12" but I'm curious if it would be ok for me to do 16" with 1/4" acrylic if I brace the top?

 

[Acrylics]

I've got a question for you if this thread is still active. I know that 1/4" acrylic is supposed to be used for tanks up to about 12" but I'm curious if it would be ok for me to do 16" with 1/4" acrylic if I brace the top?

Yeah, it can be used. Most acrylic 55 gallon tanks are 1/4" and they're 48 x 20"high.
That said, it's more prone to deflection and therefore scratching so I'd advise against it. Structurally fine, but will you be happy in the long run?

James