DIY- "Pins" method of gluing acrylic.

[adrinal]

The acupuncture needles work great IMO. It is nice to not have to always be able to pull the "pins with your bare hands. The cheap Sharp brand ones are nice. They have a solid metal grip/vs a bendy spring like one. Any of them will do though.
I like the .20mm versions.
I might not have got the longest of each version though. Much longer than the width of your acrylic seems unneccesary and just adds an element of gangly-ness. Having a few of the .16mm is nice as well.

 

[melev]

I tried out some today, and wasn't as impressed as you were. I ended up with quite a few bubbles in my seams, more than usual. I think the thinness of the needles allows less solvent in the joints, which made getting good seams a real struggle for me.

I'll keep trying though. I used .18 and .20 needles on this sump.

 

[1234]

I just use those twist-t-ties from the market for those produce bags. Just strip some of the paper off of it and presto instant "pins" free

 

[adrinal]

I guess I should have got some of the thicker ones. They go up to .30mm.

I had far less bubbles than when I used the guitar wire... but we are not compairing apples to apples since I machined the edges better on this batch.

Did you get the "pins" in past the sharpened tips?

 

[melev]

Yes, they are pretty much fully under the 1/4" material, without coming out the other side. I use Weld-On #4, and with a jointer I cleaned up my edges first.

Using shims helped, but what seems to occur is as it cures, it sucks inward (shrinks) and creates air pockets down one side of the seam or the other. It was annoying, but I wanted to try it out. I'll keep at it in case it was just an issue this first time.

 

[adrinal]

I just checked. I did the sides on 5 "3/8"acrylic 8"x48"x24" tanks. I found one edge with some bubbles on the side. All the other edges were fine.
At first if a bubble would form while I was applying the weldon, I would poke it with a smaller needle. But, I found that to be sloppy and ineffective for the most part. So, I just let the sides go with bubbles after that. The bubbles would always squirt out when I pulled the "pins".

I know you have built tons of tanks, so let me know if my questions get annoying. I am trying to figure out if this method SEEmed to work for me this time, just happens to be a method that does work for me and not you, or you had some other problem this time. I would hate to make weak tanks thinking I had ones done well! Would you assume if the Weldon is wicking through to the other side I probably have strong welding?

You talked about needing to shim. I probably only had to use only 4 shimps for all 20 welds do you rest your pieces on foam to level out?

BTW: thanks for posting your results Marc.

 

[melev]

Zephrants examples on the first page illustrate how a shim is used with each pin to make the pressure even along the full length of the joint that is to be seamed.

I work on a sheet of MDF, not foam because the solvent will melt the foam pretty easily.

I build sumps, not display tanks, but I'd really like to get perfect seams one day. Seeing a few bubbles really aggravates me, even though I'm not a professional acrylic worker. Merely a hobbyist that tries to get things just right.

On the next sump, I'll see if I have better success.

 

[Zephrant]

A few random thoughts- I still use basic sewing pins- The thicker pin allows more solvent, which makes for a clear joint. This overkill for 1/4", good for 3/8" and perfect for 1/2" material.

I put the pin all the way though to extend out a little on the other side.

I do get some marking from the extra glue around the joint, but I accept that as a trade off for perfectly clear joints.

Let it soak 30 seconds to a minute- The extra solvent action makes for a clean joint, but more ooze when you pull the pins. Again, I accept the tiny ooze mark in exchange for the clear joint.

I find that in the rare instance that I do get a bubble or two, it is because I did not get a clean pass through the router- I bumped the table, or something that made a divot in the side. Or I did not shim well enough.

The shims counter for the table that is not perfectly flat, as well as the acrylic that is not flat. I had a piece the other day that varied 0.100" over 12". It went from 0.290 to 0.390", and was supposed to be 3/8".

Zeph

 

[adrinal]

Theoretically, if I am getting perfectly clear welds with this size needle, then it should be strong right? I do have weldon come out both sides when the piece is lowered. Or do I need to be melting more of it to get a good weld?

Curently I am waiting 30-45 seconds to pull the pins. I am using mostly 3/8" acrylic.

 

[melev]

Since I'm using extruded 1/4" material, I pull the pins at 15 seconds as Zephrant and Acrylics both suggested to me in the past. Waiting longer has not proven to be at all beneficial.

I'm getting decent seams, but not perfect ones like Zephrant is describing. I'm sure part of it is the material is extruded and thinner than what many use instead.

 

[FINFISH]

I tried the pin method for the first time with good success. That said, I *did* have some pooling of excess solvent at one end- any recommendations for removing the white haze which has formed where the pool was? I suspect the cool temps in my shop contributed.

 

[melev]

finfish,

[welcome]

As soon as I see a puddle forming, I quickly wipe it off with a finger. The faster you do that, the less smear you'll end up with.

 

[Zephrant]

High moisture tends to do that too- I either wipe it off with a paper towel fast, or buff it out later.

Zeph

 

[aqua5]

i read those but i am still confused what the pins are for?are they top hold the 2 pieces in place?it says 1 pin every 6 inches but if you are doing a small sump could you do more?also once the top of the sump is glued on (so it looks like a box) how do you route it so it looks like it has "trim" work on the inside of the sump or a "lip" on it?



do you just put a pin half way inbetween the acrylic?like if it was 1/4" you would put the pin approx 1/8" up?where do you apply the glue?

 

[adrinal]

i read those but i am still confused what the pins are for?

The pins hold the two pieces you are joining apart just a tiny bit. That tiny bit is enough for the solvent (Weldon 4 most popular on the boards here) to wick in. This is the same physical property of wicking you would see in wicking sodder into copper pipes.

it says 1 pin every 6 inches but if you are doing a small sump could you do more?

You can use as many as you like. I have mine 3-4 inches apart. Of course on a bigger piece you may want to lean toward the 6 inch gap, because it it tough to pull out all the pins in time if you are working alone I have been with one in each corner and work from there.

also once the top of the sump is glued on (so it looks like a box) how do you route it so it looks like it has "trim" work on the inside of the sump or a "lip" on it?

after you route it out with the jig you can come back with a roundover bit.



do you just put a pin half way inbetween the acrylic?like if it was 1/4" you would put the pin approx 1/8" up?where do you apply the glue?

 

[melev]

i read those but i am still confused what the pins are for?are they top hold the 2 pieces in place?it says 1 pin every 6 inches but if you are doing a small sump could you do more?also once the top of the sump is glued on (so it looks like a box) how do you route it so it looks like it has "trim" work on the inside of the sump or a "lip" on it?



do you just put a pin half way inbetween the acrylic?like if it was 1/4" you would put the pin approx 1/8" up?where do you apply the glue?

I do not want to appear rude, but did you look at the pictures on Page 1 of this thread? That is exactly why I gave you this link. Those pictures Zephrant put up are worth thousands of words.

And I told you in a PM to look at this page to see how the lip was routed out. I have 3 or 4 images that help you visualize how it was accomplished.

http://www.melevsreef.com/tools.html

It isn't that I don't want to help, but I get a lot of email and PMs on this topic, so I referred you to the information that is available rather than typing it all out yet again.

 

[aquadok]

I have fround that endmills leave a better finish on any type of plastic, that I have cut,(delron,Acrlic,phenolic,PVC slate,plexiglass,oh yah crylon as well.

I f you can take a peice of human hair and split that peice of hair into 30 peices(long wise), that is how fine our cnc machines are. So any imperfection on any surface of the peice you are working on can litteraly be shaved smooth, so smooth it looks better than when you got it.
Then when you are done you would put a solvent that creates a realy realy high shine on the surface of the plastic. In the end, the project would look that much nicer too.(by the way the solvent removes alot of surface scratches as well)

 

[kimoyo]

James or Zeph,
I was wondering. Since you do this professionally, when you guys make sumps or tanks are there bubbles at all. Not big bubbles but very tiny ones. The ones I'm specifically talking about are on the edges of the joint, not inside. If there are, is that a mistake of person doing the sump or tank? Thanks.
Paul

 

[Zephrant]

If everything is perfect- edge, surface, temperature, humidity, air flow, etc... then they come out without any bubbles at all.

The stars don't always align however, so small bubbles can happen.

I don't usually get the ones along the edges- It might be that your edges are not perfect (dull router bit, or sanding the edges?) Maybe the solvent is evaporating too fast, or not enough solvent was used to prevent their occurrence. I am thinking that the extreme edge of the joint is getting dry too fast.

Nothing to worry about though. I tend to use more than enough solvent on the grounds that I'd rather have some ooze out and get a perfect joint, then have not enough solvent action and get a weaker joint.

These are sumps, not the viewing pane of a fighter jet. Go for strength first, always.

Zeph

 

[kimoyo]

Zeph,
Actually I was wondering for show tanks. I've seen a lot of pics of tanks but not the edges of them. There was this one picture of one of Jame's tank and it looked like there where not bubbles but I couldn't be sure. Just wondering if your spending a lot for a custom acrylic tank, should you still expect those little bubbles? Thanks.
Paul