Acrylic Fabrication Q & A

[Turbo's Aquatics]

Would it be except able to laser cut all the 3/8" panels instead of cutting them with a router?

No, laser cutting melts the acrylic and is probably the most stressful method of cutting, and the edge is only marginally weldable if at all. A laser cut edge will craze when you weld it. You "can" laser cut and then route, but the laser cut edge will need to be trimmed back enough to get rid of the affected material that it just isn't worth it. Easier to rough cut with a saw then route.

 

[cromag27]

Also, laser cuts are not always straight and they can produce small ridges on the cut surface.

 

[Adkins]

No, laser cutting melts the acrylic and is probably the most stressful method of cutting, and the edge is only marginally weldable if at all. A laser cut edge will craze when you weld it. You "can" laser cut and then route, but the laser cut edge will need to be trimmed back enough to get rid of the affected material that it just isn't worth it. Easier to rough cut with a saw then route.

Thanks for the information. I kind of wondered that myself. Would laser cut parts be suitable for drop ins? Sock holder, probe holder, etc?

Also, laser cuts are not always straight and they can produce small ridges on the cut surface.

Thanks cromag. I could see both those points as well.

 

[cromag27]

I use one for parts that don't have to be welded. having said that, a sock holder and probe holder should be fine.

 

[Adkins]

Thanks again. Sounds good then.

Follow up question. Would a water jet produce the same effect?

 

[cromag27]

i've never used one, so i don't know.

 

[Adkins]

Fair enough then.

Well I did some digging and I found a guy in town that has a CNC router. He will cut whatever as long as you provide DXFS for $60/hr. Seems like the way to go. Says he will flame edges for free even.

 

[cromag27]

Just make sure the flame polishing is done after it's built.

 

[Turbo's Aquatics]

Or don't flame the edges. That's the worst thing you can do. I can't tell you how many tanks I've seen with crazing after a few years of use due to flame polished edges. Tell him no thank you and then wet sand and buff/polish the edges yourself.

 

[Lowell Lemon]

Floyd is right to an extent about flame polishing. Without the proper set up you are going to experiance problems. It takes a special Hydrogen/Oxygen torch that is about 4300 F and quick movement over the parts being polished. Most people do not have access to the proper torch so they over heat the edge and then clean up with something like alcohol and you get an immediate craze.

Only clean acrylic with water and a little dish washing liquid in a spray bottle and a soft cotton cloth.

If you sand and polish make sure to use a water system to keep the parts cool. Heat generated by dry abrasives or machine buffers will in effect render the same result as a flame polisher that remains on the part to long. Heat induces stress and creates the tendency to craze. Even hand polishing can induce stress just like the cutting process with saws and routers. Either way when you machine or polish you induce stress. So no matter the process you can create induced stress that leads to crazing.

The only cure is to polish and heat anneal the final assembled parts but no one in the hobby or industry has access to or is willing to spend money to reprogram the plastic memory through the annealing process. To bad since the parts are much stronger and resist crazing much better. I have only used the annealing process for high tech computer systems that used clear acrylic as the "box" to contain the CPU and components for testing a fluid cooling system for the chip sets. Highly effective and in use by various users around the world. Some where in the world is a 13 million dollar computer that I helped polish and assemble before the final annealing process. That thing was awesome! Had led lights and all sorts of magic almost 15-20 years ago.

 

[cromag27]

Now that's a lot of slots.

 

[Drauka99]

I was gifted a acrylic ato resivoir over the weekend. It had a pin hole lead on one of the vertical seams. The rest of the container is built very well.

To repair it, weldon 4?

 

[Turbo's Aquatics]

I pic of the affected area would help. Likely, WO4 will not get into the area very well. Ideally you would want to use WO40 but that's $$ for the repair area. A better solution would be to take a small piece of acrylic (really just 1/4" x 1/4" and round one corner so that it fits in nice and tight to the corner (there is usually a bead on the inside that will cause the gusset to stand off of the panels - you need to account for that) and then weld it in with WO #16 (the gel stuff). WO16 is not a gap filler, it will dry to a thin profile, but after you let it dry you can add a few more layers of WO16 and build up the thickness around the patch.

You might be able to get away with just using WO16 over the leaking area but a small patch is better.

 

[Drauka99]

I'll try to get a picture tonight. I filled it last night and it was only a small trickle from about midway up the seam. He had said he had tried to repair it a few times and couldn't get it right, I don't know what he was using to try to fix it though

 

[Drauka99]

Double post

 

[Colin Chaplin]

Thanks again. Sounds good then.

Follow up question. Would a water jet produce the same effect?

From my experience of water jet you get ridges not a smooth cut.

 

[zemuss]

Do you go over what solvent is needed? I will be putting together a ATS soon.

Also is there a difference in Acrylic? I have always been told to use cell cast acrylic.

 

[cromag27]

I'll try to get a picture tonight. I filled it last night and it was only a small trickle from about midway up the seam. He had said he had tried to repair it a few times and couldn't get it right, I don't know what he was using to try to fix it though

What turbo said. if you can pile on the wo16, you could patch it up. this is still an 'iffy' fix, however. a photo would be great. just remember - a small trickle will eventually become a large flood.

 

[Turbo's Aquatics]

Do you go over what solvent is needed? I will be putting together a ATS soon.

Also is there a difference in Acrylic? I have always been told to use cell cast acrylic.

Weld-on #3 or #4 is fine for most small projects.

Extruded is fine for small projects and even sumps, it just machines a bit differently and bows a bit more under pressure. For a scrubber, just fine.

 

[Drauka99]

Pics, I can actually fit my thumbnail in where the leak is happening