Acrylic solvent glue

I have a project making some acrylic display cases. I am using extruded acrylic as I am not engraving on them. I have 7 to make 12" x 12" x 15" with 1/4" extruded acrylic. I made the first as the customer wanted to view my quality which they were happy with. I made the first by cutting on table saw, jointer, 3 different grits sanding, then buffing. This was alot of work. I used the laser for some of the non glued areas as I know when you use solvent glues with lasercut edges you get "crazing". To save some time I thought I could laser cut all componants and just run the glued edges thru the jointer to remove the lasered edge and maybe do a little sanding. This would save me a ton of time and elbow grease but I am afraid I may still get crazing on the adjacent laser cut edges. I did a test and it seemed to work well but I know crazing does not always show up immediately. Anybody have any experience with this? I know flame polishing would probably be the way to go but I have no experience with this and I doubt it is easy enough to learn in the short time I have. I would appreciate any thoughts or personal experiences.

Bill

In general a sanded edge (to 220 grit) works best, although a scraped edge
will do if you are careful, and have no chips. Cast is easier to work with and glue. Practice on some scraps to learn to avoid bubbles.

Art

Thanks for the reply Art. So are you saying you have had success just sanding or scraping lasercut edges and avoided the typical crazing. I am not going thru the whole cutting, jointing, 3x sanding and polishing on the areas that are glued, I am just doing this on the edges that are visible after construction. The areas that are glued I am running thru the jointer and sanding quickly with 180 grit and I am getting good results. I am just wondering if I can expect crazing on the laser cut edge that is the visible edge in a typical 90 deg joint. I am sorry maybe I am not explaining myself well,


Bill

Bill:

I think running them through the joiner will help remove some of the heat effected area but I don't know if that will prevent the crazing. My solvent bonding experience is not with laser cut parts. It seems Rodney has talked about this. See if you can find any of his old posts that address it.
Sorry, not much help.

Art

Thanks for throwing out what you know Art. i have been reading everything I can get my eyes on but have not found what I am looking for yet. I know that cast has much less crazing than the extruded but it still does. I probably should have ordered the cast but I feel the extruded actually polishes up to a better edge. I guess I have a lot of sanding on my plate for tomorrow. Oh well I priced it expecting this. I would still like to figure out the best way to use laser cut parts to construct acrylic items as it would save so much time and energy.

Bill

Bill:
What kind of adhesive are you using. I use Weldon #3 a lot on my laser cut lettering and the like and see very little crazing with the acrylics I use. I use both cast and extruded. Crazing is related to the stress that is inherent with laser processing. It can also be caused by chemicals such as tolulene etc.
For recommendations on acrylic adhesives, go to http://www.ipscorp.com/industrial/indproducts.html
They are also very helpful on the phone and are really experts on glueing the stuff. You may want to consider another type of their adhesives also, like Weldon 40 or 16.
Good luck with your project.

Larry, I am using Weld-on #3 but I also have Weld-on #4 and #16. I agree that gluing the uncut edge of a piece of acrylic greatly reduces the crazing. But in my experience if I get any #3 on the actual laser cut edge of extruded it will Craze like Crazy:D. It seems like running the edges that are to be glued thru the jointer will work but i am nervous as this is for a big customer with a lot of potential for me so I think I will stick to the tried and true method this time. I will be doing some tests to see if the crazing shows up after some time.

Does anybody here have experience with flame polishing? Can you glue up a display case with weldon #3 and then flame polish the exposed edges? That would be worth the learning curve if it would work.

Thanks again Larry,

Bill

Bill:
Frank Corker has a lot of experience with flame polishing. Maybe send him a PM if he doesn't reply here. I tried it using a torch with that gas that is supposed be hotter than propane..the name escapes me..but it works to a point. I think the recommended method is with a special tip and proper gasses. Their are setups you can purchase online to do it correctly, but best I recall are pretty pricey.
Sounds like your using the right adhesives. What brand of acrylic are you using? I get good results from Cyro products.

Larry, is it MAPP gas your speaking of?