Acrylic fabrication questions? I can help!

[thejuggernaut]

6" is a little small, and will limit your blade choices. a 7.25" is a more popular choice.

The blade I would recommend is:

http://www.diablotools.com//search?search=D0756N&submit=

They are $42 at HD. Not very expensive, but will give a good quality cut. Probably not good enough to joint, but will get you close.

http://www.homedepot.com/p/Diablo-7...lade-D0756N/202035231?N=5yc1vZc2jqZgeZ1z0sjn9

Everyone is right though. You will have a hard time getting a perfectly straight and accurate cut that way. I have a large 4X8 table, and clamp the material hanging over the edge. Clamp a straight edge and run the saw down it. I used some of those little adhesive felt feet that you put on furniture. I stuck them to the bottom of the saw so it won't scratch up the acrylic. I can then cut the smaller pieces up on a table saw, then finish them up on a router table. It is a process if you aren't set up for it, but isn't difficult. It just requires decent tools to get consistent results every time.

 

[rickztahone]

I really don't want to dump another $50 on the blade. It may just be cheaper to get them cut at HD. Would they cut realiably do you think? I am talking quite a few cuts here though.

 

[CatsnClownfish]

I really don't want to dump another $50 on the blade. It may just be cheaper to get them cut at HD. Would they cut realiably do you think? I am talking quite a few cuts here though.

Most Home Depots I've been to will not cut actual plastic sheets, etc., unless they have a diamond etch-and-break, which many don't have. I don't know how the edges turn out on such a machine on thicker material.

Lumber will probably have a panel saw, I doubt the edges will be pretty if they use their panel saw. If you're going to get it cut using a panel saw, I'd plan to use a router on the edges afterwards.

Did you try checking to see if you have local plastics fabrication options? If you do, they might cut it for you. It won't be as cheap as HD, but they'll have the right equipment for the job.

 

[Floyd R Turbo]

There actually is a way to get a good cut on a circular saw, but it takes a lot of setup time. First, you have to have a fence that is perfectly straight, then clamp it down to the top of your piece so that the plate of the saw rides up against it. Then you have to position it such that is ti perpendicular to the front and back edges so you get a square cut. Very difficult.

But all of this is assuming that you are going to use rough-cut edges to bond, which I don't recommend, not at all, especially when you aren't using a very sturdy and high quality table saw, or a panel saw.

 

[rickztahone]

There actually is a way to get a good cut on a circular saw, but it takes a lot of setup time. First, you have to have a fence that is perfectly straight, then clamp it down to the top of your piece so that the plate of the saw rides up against it. Then you have to position it such that is ti perpendicular to the front and back edges so you get a square cut. Very difficult.

But all of this is assuming that you are going to use rough-cut edges to bond, which I don't recommend, not at all, especially when you aren't using a very sturdy and high quality table saw, or a panel saw.

Under these circumstances, how do I avoid rough cuts?

 

[Floyd R Turbo]

Use a router to clean up the edges after rough cutting.

 

[Bamm Bamm]

I've got a question.. I bought a 60g cube that previously had 6 holes in the back wall drilled for a closed loop.. I'm not going to run the closed loop so I picked up some acrylic discs from tap plastics and some weldon #16 do I have to glue do these from the inside of the tank or can I do them on the outside of the back wall?? Thsnks in advance..

 

[rickztahone]

I've got a question.. I bought a 60g cube that previously had 6 holes in the back wall drilled for a closed loop.. I'm not going to run the closed loop so I picked up some acrylic discs from tap plastics and some weldon #16 do I have to glue do these from the inside of the tank or can I do them on the outside of the back wall?? Thsnks in advance..

I can only imagine that having them on the inside would be the better option of the two. Think about it, if it is on the inside, the pressure of the water against it will make it stay in place better than if it was on the outside and that same pressure is pushing against it

 

[MarlinHooker]

Hi Floyd ....I'm in the initial research phase for my 260g in-wall upgrade from my current system (atch pic). the tank will be 24 x 30 x 84 and I pretty much decided to go with the internal/external overflow design of yours from post#4005. my question is there a recommended size for the internal box relative to tank length and a corresponding size for the external box? Also, same question for the box depths?

I've only built a few small things out of acrylic but own a custom woodworking business and built my current setup so I expect I should be able to do acrylic with a little practice ...

 

[rickztahone]

Use a router to clean up the edges after rough cutting.

I dont own a router. Can I use something else instead? I was thinking of purchasing one of those scraper tools (not sure of the name) to clean up the edges. Thoughts?

 

[pandimus]

I dont own a router. Can I use something else instead? I was thinking of purchasing one of those scraper tools (not sure of the name) to clean up the edges. Thoughts?

Check pawn shops, i found a cheap craftsman router for 15 bucks. Had some flush bits with it.

Otherwise your gonna have some sanding to do

 

[rickztahone]

Check pawn shops, i found a cheap craftsman router for 15 bucks. Had some flush bits with it.

Otherwise your gonna have some sanding to do

Never thought about that. I will check the local pawn shops. What kind of bits do I need in order to get a good surface to weld?

If I were to sand, I have a dremel 200 that I bought for another project. It has some sanding bits that I may be able to use? I'd be scared of diggin in to the ends too much though.

 

[Floyd R Turbo]

I dont own a router. Can I use something else instead? I was thinking of purchasing one of those scraper tools (not sure of the name) to clean up the edges. Thoughts?

If your rough-cut edges are straight and true enough, you can clean up the edges with a razor blade clamped between 2 pieces of wood, so that you can hang on to it and keep it at a 90 degree angle to the piece. takes practice though and it's easy to round the edges if you don't pay attention

Otherwise your gonna have some sanding to do

I wouldn't sand any edge that you are prepping to bond. That rounds the edges and leads to bubbles creeping in the joints as the solvent dries up.

 

[Floyd R Turbo]

Hi Floyd ....I'm in the initial research phase for my 260g in-wall upgrade from my current system (atch pic). the tank will be 24 x 30 x 84 and I pretty much decided to go with the internal/external overflow design of yours from post#4005. my question is there a recommended size for the internal box relative to tank length and a corresponding size for the external box? Also, same question for the box depths?

I've only built a few small things out of acrylic but own a custom woodworking business and built my current setup so I expect I should be able to do acrylic with a little practice ...

Post #4139 would be better. match the external box to the tank top

for internal box, ideally, full length of tank. Arguments abound for teeth vs weir. I would say weir if you can, gutter-guard is a good option vs teeth and you do get better surface skimming without teeth, but some people want teeth and hey, there's nothing wrong with that.

int box depth is just driven by the bulkhead locations. external box depth is driven by the operational needs of the box. If you know your target actual flow through the box, then you can calculate what is needed in order to make it operate safely. This also depends on your pipe sizes and overall design

 

[rickztahone]

If your rough-cut edges are straight and true enough, you can clean up the edges with a razor blade clamped between 2 pieces of wood, so that you can hang on to it and keep it at a 90 degree angle to the piece. takes practice though and it's easy to round the edges if you don't pay attention



I wouldn't sand any edge that you are prepping to bond. That rounds the edges and leads to bubbles creeping in the joints as the solvent dries up.

Cool. Thanks Floyd. I actually saw this being done by another member a few weeks back. I will emulate that setup to clean up the edges.

 

[marcus2529]

Hello all,

Fantastic thread so far, a lot of information here. So I am looking at making myself an acrylic tank and sump. I have a huge advantage because I work at a plastics workshop. I've been practising because my aim is to get perfect, bubble free joins. I used a CNC router to cut my self and the edges are extremely smooth. I'm using Weld On 4 (well the equivalent that can be found in Australia). Everything is set up square and clean. I'm using 0.5" acrylic and a bottle and needle applicator. I'm not using the pin method but using the capillary action method.

Sometimes I get a near perfect join, others aren't so good. I don't believe I've changed method but my results vary. I really want to nail this so I can get a show quality tank. Is there something I'm missing here? Any help or guidance would be amazing. I've watched all the videos on YouTube and I'm so keen to get a tank up and running

Thanks in advance.

 

[Floyd R Turbo]

You need to use the pins method. It's not just about making the joint look clear and bubble free - I agree, you can achieve this with the capillary method, but that doesn't mean it's a strong joint.

The point of the pins method, where it relates to joint strength, is that you allow for a soak time - typically, 15-30 seconds - before you join the 2 piece together. The soak time allows the solvent to dissolve enough of each side of the joint so that when you join them, these areas will merge together. You just don't get that at the same level of strength without the pins method, because the joint bonds almost instantly.

Try this. Set a joint with the capillary method and see how long of a time you have between when you add the solvent and when you can no longer adjust the joint. Now try that with the pins method. The pins method will result in a much longer time. This is because more material has been dissolved and it takes longer to set once the pieces are joined.

Also remember to leave a lip for a fillet to form on the outside of the joint. This prevents are from intruding into the joint. Flush trim off afterwards.

As far as YouTube goes, I would ignore any one of them that says you can build a tank using the capillary method. Anyone who says this has a vast lack of understanding of the requirements of acrylic bonding for pressure vessels. Sure, their tank may hold and you'll see vids of it full of water and looking fine. Show me how many of those tanks are still holding water with perfect seams in 3 years...probably not many. Bump one of those joints really hard by accident and it's "pop".

I've repaired sumps built with capillary welds because the joints snapped clean at the joint, like they were held together with elmers glue. Just don't do it.

 

[marcus2529]

Thanks very much for the information Floyd. Like everything, each person will tell you something different! I will try the pin method and see what results I get.

I am looking to make a jig to help hold each piece at 90° to help make the job easier. Something where the base piece sits on a very slight angle and then I can slide the side wall onto the base. Could possibly do away with pins after I run an amount of adhesive and then slide/place the side panel on.

Do you think this could work? Have you had any experience with jigs at all?

 

[Floyd R Turbo]

I'm not following you at all. You want the base piece sitting perfectly level and on boards with foam strips so you can shim it up, use a 90 degree jig to clamp it into final position, sung up the joint, then add the pins, run solvent, pull pins, adjust...search my posts in this thread for one from earlier this year that explains this in great detail.

 

[thejuggernaut]

You need to use the pins method. It's not just about making the joint look clear and bubble free - I agree, you can achieve this with the capillary method, but that doesn't mean it's a strong joint.

The point of the pins method, where it relates to joint strength, is that you allow for a soak time - typically, 15-30 seconds - before you join the 2 piece together. The soak time allows the solvent to dissolve enough of each side of the joint so that when you join them, these areas will merge together. You just don't get that at the same level of strength without the pins method, because the joint bonds almost instantly.

Try this. Set a joint with the capillary method and see how long of a time you have between when you add the solvent and when you can no longer adjust the joint. Now try that with the pins method. The pins method will result in a much longer time. This is because more material has been dissolved and it takes longer to set once the pieces are joined.

Also remember to leave a lip for a fillet to form on the outside of the joint. This prevents are from intruding into the joint. Flush trim off afterwards.

As far as YouTube goes, I would ignore any one of them that says you can build a tank using the capillary method. Anyone who says this has a vast lack of understanding of the requirements of acrylic bonding for pressure vessels. Sure, their tank may hold and you'll see vids of it full of water and looking fine. Show me how many of those tanks are still holding water with perfect seams in 3 years...probably not many. Bump one of those joints really hard by accident and it's "pop".

I've repaired sumps built with capillary welds because the joints snapped clean at the joint, like they were held together with elmers glue. Just don't do it.

+1

I've tried just using capillary on small pieces cause they are too small the clamp, and you can just snap the off by hand. When you use pins, it melts the acrylic, and when you remove the pins and let it settle down, it creates a perfect little fillet which dries up quickly. Doing it that way you can't break it, trust me I've tried pulling them apart as hard as I can.