Capilary bond acrylic from the outside edge?

[SNiiPE_DoGG]

I have pieces of acrylic coming in from the laser cutter's today and I am wondering something about the construction:

The last piece I will be putting on is the front piece and I will have no access to the inside of the reservoir at this point - do I just use the same "injection" style method for the acrylic cement that you would use on the inside of the joint except on the outside seam?

I will post pics of the parts and the situation I am talking about later tonight when I get the parts...


-Ian

[kimoyo]

Yes, you can do it from the outside but your probably going to have some serious crazing issues because it was laser cut. The good thing about laser is they polish the edges, but the bad thing about lasers is they polish the edges.

[SNiiPE_DoGG]

I have to sand the edges to be bonded anyway so then I shouldn't have an issue right?

[kimoyo]

yeah, if you sand the edges you should be okay but you want to sand them down a little bit. Make sure it doesn't have that polished/melted look anymore.

[SNiiPE_DoGG]

yeah, I think I am going to go at the edges with 800 grit taped to glass so they stay square

[coolmiester]

I had to do exactly that on a couple of reservoirs i made a while ago for the Skulltrail Cosmos which is still holding together fine a year later

I had my pieces cut with a bench saw so the edges were perfectly true and didn't need any sanding but a friend did it with laser cut plexi and tried sanding the edge but unfortunately it was just enough to knock the straight edge off and he had problems.....well basically it leaked so watch what you're doing when sanding.

[Bei Fei]

Depending on the bonding agent laser cut acrylic will get micro fissures or "crazing" because of the heating involved in the laser cutting process. If you sand the edges you may not have the problem.

[SNiiPE_DoGG]

hmmm, maybe I will use my bench saw to trim the edges very slightly - the laser tapers at 1-2degrees on the edges it cuts so I could use a saw to get rid of that

[ecat]

Would annealing the perspex in an oven prior to bonding help ?

http://www.gcip.co.uk/pdf/perspexmanual.pdf

Edit:
See page 6 in the linked document

[bakeshow]

hmmm, maybe I will use my bench saw to trim the edges very slightly - the laser tapers at 1-2degrees on the edges it cuts so I could use a saw to get rid of that

Just don't keep the acrylic in the cut too long, it will start to melt again, and put you back to square one. Lets see some pics when you're finished!

[kimoyo]

Probably not. The laser burns thru the material and while annealing helps relieve stress by easing the acrylic the damage done by laser is not going to get fixed by heating it up, at least to my understanding.

But if you had the ability to anneal the acrylic, then your probably not going to laser cut it in the first place when there are cheaper and more convenient options out there for this specific application. So, I don't think most people will have a definite answer anyway.

Would annealing the perspex in an oven prior to bonding help ?

http://www.gcip.co.uk/pdf/perspexmanual.pdf

Edit:
See page 6 in the linked document

[iandh]

hmmm, maybe I will use my bench saw to trim the edges very slightly - the laser tapers at 1-2degrees on the edges it cuts so I could use a saw to get rid of that

This ^

Probably not. The laser burns thru the material and while annealing helps relieve stress by easing the acrylic the damage done by laser is not going to get fixed by heating it up, at least to my understanding.

Annealing would reduce spreading of cracks into undamaged material, but as you said wouldn't help at the damage zone. Basically you'd have a a bunch of teeny tiny cracks along the edges where it was cut.

[SNiiPE_DoGG]

so guys here my plan - I am going to buy two 90 degree aluminum extrusions and make them into a clamp - then I am going to clamp the acrylic pieces upright in between the vertical portions and "lap" the edges on 800 grit taped to a glass table. Sound good?

[iandh]

so guys here my plan - I am going to buy two 90 degree aluminum extrusions and make them into a clamp - then I am going to clamp the acrylic pieces upright in between the vertical portions and "lap" the edges on 800 grit taped to a glass table. Sound good?

That's a pretty legit homebrew way to do it.

[SNiiPE_DoGG]

So after going to home depot today and not finding what I needed there I drove over to lowes (a bit farther away) and realized that I will never be going to home depot again. Lowes has so much more selection, better prices and better employees.

here's what I made, real quick with a hacksaw, file and drill I call it a acrylap

[voigts]

That's a neat idea. I have found it very difficult to sand edges like that and get them straight. I however always capillary solvent weld joints from both sides. I think it could be tricky to get solvent completely through the seam from only one side. What I use to get solvent into inside seams is a small piece of brass tubing that you can pick up from a hardware store like ACE. I make sure to drill and tap any holes before solvent welding to make sure one that I don't get shavings stuck inside the res, but two, as points to use to put solvent in the joints.

[SNiiPE_DoGG]

I am still trying to find some of that brass pipe small enough but in the mean while - I have been using the acrylaper on the laser cut pieces using 400grit paper and it is working perfectly! super square super flat edges that are much better than the laser edges when checking with a razor blade

[JoeChuo]

So after going to home depot today and not finding what I needed there I drove over to lowes (a bit farther away) and realized that I will never be going to home depot again. Lowes has so much more selection, better prices and better employees.

here's what I made, real quick with a hacksaw, file and drill I call it a acrylap

Nice! Flash some heat to that edge with blow torch ... get it shiny.
Ian ... get a router table. Best for working with acrylic.

[SNiiPE_DoGG]

oh you have no idea how shiney that actually is - all the laser edges are very glossy and polished you will see when I take the paper off and get the photosetup to shoot clear parts sometime next week

[Waterlogged]

SNiiPE, try hobby stores that cater to scale train and R/C folks. I have one near me that claims to be "the biggest in the U.S.A.".

[SNiiPE_DoGG]

SNiiPE, try hobby stores that cater to scale train and R/C folks. I have one near me that claims to be "the biggest in the U.S.A.".

thanks for the tip, ill check out a few of the ones local to me

[SNiiPE_DoGG]

here is my finished product guys - i used some 1/8" glue lined heatshrink to get the welding cement inside the res when it was done, worked out well leak testing info hopefully soon.

[Spawn-Inc]

not only is that a nice res, but wicked photography!

[voigts]

That's a big reservoir. What are the dimensions? It looks great.

Make sure to leave it alone for a few days to cure fully before you do any pressure testing. I personally pressure test with air pressure using a cheap vacuum gauge (about $13) that I got at Harbor Freight and my air compressor. This way I can pump the res up to 20psi or so and make sure that it doesn't leak. I figure that if it holds 20psi for an hour, it won't leak. So far any res that has passed this test has never failed.

[Eddie3dfx]

Snipe, that looks great! you can barely see the welds.