Acrylic bonds keep breaking

[Dan Ashlin]

I've had some interest in acrylic cases lately, I made one for myself and a few people have asked me if I can make them for them. I'm using 1/8 inch cast acrylic, cut on the laser and IPS weld on 3 to bond them. The problem I'm having is they seem to come apart at the seems on the open side of the case. Is there any way I can make the bonds stronger? I'm trying to make them as bubble free as possible, but that's pretty tough. I've even made squared locking corners, but that doesn't seem to help either. They are ok if you handle them lightly, but some pressure will break the seam open. Any advice? It seems like I'm sitting on a pile of business here, but it does me no good if the product is lacking lol.

[Rob Hermann]

What glue are you using? Weld-on 3 or 4 should work well. When you assemble it you should put a small peice of wire or needle in the joint, apply the glue and let it sit for about 30 seconds to a few minutes then pull the pins and it should weld tightly. Also, make sure your joints are clean. I usually wipe the glue surface with some rubbing alcohol right before I glue it.

[Larry Bratton]

Rubbing alcohol is definitely NOT the thing to use. It will/can cause previously lasered acrylic to craze. Worst part is, that it won't necessarily do it immediately and can appear at a later date. Best thing to clean acrylic with is pure clean water.
When using Weldon #3, the two pieces of acrylic have to be absolutely flush with each other. Gluing with #3 takes some practice. I use a small artist brush and let the cement wick from the brush into the joint. These joints need to be kept tight as possible during the bonding process. Some people use a small syringe to inject the cement but the brush works ok for me.

[Mike Null]

I do mine without the pins but be sure you don't starve the joint. Keep in mind that high humidity makes this task more difficult.

Your material should be square at the joint even if you have to use a mechanical means of sanding or scraping to get it smooth and square. I also use dna to clean before gluing. ( I use only cast acrylic so the dna will not harm it; if you are using extruded then do not use dna.)

[Rodne Gold]

Use Tensol 12 First , if that doesnt work , tensol 70
Alternatively , you can use chloroform with a small bit of acrylic dissolved in it

[Dan Ashlin]

I'm making the joints pretty square and tight. Using a right angle clamp and painters tape to hold the sides together tightly. I run the IPS 3 down the seem with a syringe. I don't knwo whats up. Would something like weldon 16 be better since its viscous? might reduce bubbles. I also think my laser cuts the acrylic at a slight angle as well. is that normal?

[John Noell]

I also think my laser cuts the acrylic at a slight angle as well. is that normal?

Yep. The shape of the beam and they way it affects the acrylic results in a tapered cut wider at the top.

[Dan Ashlin]

Yep. The shape of the beam and they way it affects the acrylic results in a tapered cut wider at the top.

Well, poop. The way I have them designed, I can't rout them to make them straight. I guess Weldon 16 is a good bet. I tried some superglue today and it seemed to do a better job lol.

[Mike Null]

Dan

The proper way to apply the solvent is shown in this film. If you're using acrylic staright out of the laser and trying to glue it you've probably found your problem.

It's a ways down on the page.

http://www.tapplastics.com/info/video.php

[Dan Ashlin]

What's the problem with using it straight out of the laser? Just since it's not perfectly straight I guess? I've glued acrylic before and do it just like in the video, I just use a syringe. I'm not sure why my cases aren't staying together though.

[Larry Bratton]

Dan, I don't think Weldon 16 is the answer. That stuff is really really hard to work with. You think your frustrated now, just try that stuff. Why don't you contact IPS. They have a good technical support dept. I have talked to them before and they are very helpful and knowledgeable.

[Rodne Gold]

Capilliary type glueing wont cut it for applications that need heavy duty bond strength. If you use the right glue then the pex near the bond will break before the bond does - problem with 2 part/filler acrylic glues is that you need to put the part in a jig for an hour or more for it to set .
You MUST use a glue that fills the joint , not one that disolves the 2 surfaces being joined hoping for a bond - those disolving type joins are very weak. I do tons of pex fabrication ansd we use acrifix (from degussa) for extruded and tensol (Bostick make it) for cast.

[Dan Ashlin]

Where o I get tensol 12 in the US? seems like it's only available in the UK

[Dan Ashlin]

OK, looks like tensol 12 is the UK equivalent of IPS 3/4 and Tensol 70 is IPS 40. Im going to order a small container of ips 16 and ips 40 and run some experiments.

[Richard Rumancik]

. . . You MUST use a glue that fills the joint , not one that disolves the 2 surfaces being joined hoping for a bond . . . .

This is especially true for laser cut parts where you are attempting to make a box-type structure. Due to the angles on all the laser-cut edges you cannot get perpendicular sides without leaving a gap at the interfaces. The solvent adhesive can work okay for bonding flat surfaces together and for laminating layers.