proper procedure for welding acrylic or plexiglass tank? - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: May 19, 2019, 07:08:06 pm
content: So after giving it some thought I want to re-try the whole acrylic plexiglass etchant tank deal ( I found a big sheet of material).I thought that after cutting I would try to 'lap' the panels using a large glass plane with some sand paper on the side to ensure its flat.What should the surface finish of the edges to be welded be?Once I cut the panels, during the welding process, should some kind of shim be used to ensure a spacing between the sheets for the introduction of welding solvent to allow the solvent welding to take place? Say something like one thousandth shim (no ideas here) on both sides to separate the panels out? Is this necessary? I thought I saw some place that does plexiglass sell panels that have 'dimples' on them to ensure there is good penetration of solvent/mixing of dissolved products to form a interlayer, but I can't find it.I don't want a ferric chloride leak.

author: coppercone2
author_rank: Super Contributor
timestamp: May 19, 2019, 07:47:44 pm
content: thats a good primer but it does not elaborate on the specific details I wantI.e. is wetness of the joint enough, or do you want some kind of specific thickness of solvent between the two bits to allow for the bonding mechanism to occur properly.

author: ataradov
author_rank: Super Contributor
timestamp: May 19, 2019, 08:33:55 pm
content: They sell only one type of acrylic cement as far as I'm aware, it is a clear water-like liquid. It wicks between the surfaces very well, and if acrylic is transparent, you will see how far it penetrated. For thin (<1/2") acrylic, I would not worry about penetration at all, it will wet throughout.Note that in CA I had to tell them that I will be using it for "work", otherwise they refused to sell it to me. But that may be just another CA stupidity.

author: Mechatrommer
author_rank: Super Contributor
timestamp: May 19, 2019, 09:06:38 pm
content: that acrylic cement is probably just a chloroform, beware petrol gas will also dissolves plexiglass (acrylic) that is maybe an another clueymmv. if edge is not flat try AB glue. dont want FeCl leak? test with water beforehand, silicone glue may also helps afterward but that depends on the merged condition. want perfection? just buy off the shelf or be ready to fill your lab with some nice and heavy equipments. ymmv.https://www.allaboutcircuits.com/projects/diy-polychlorinated-biphenyl-chemical-tank/i dont say super glue is a good idea, but a hot glue maybe just as good, ymmv.

author: coppercone2
author_rank: Super Contributor
timestamp: May 19, 2019, 09:56:53 pm
content: well, I just recall some place sold transparant plastic sheets with some kind of 'dimples' on them to optimize glue spread or something. I can't find it. They were not particularly thick. I thought they said something about there being a optimize spacing distance

author: KL27x
author_rank: Super Contributor
timestamp: May 19, 2019, 10:04:00 pm
content: IME, you want a rough finish for the solvent to wick into.The main thing you want to be aware of is the solvent makes the acrylic brittle. It absorbs into and weakens the plastic in and around the joint.So when you are making something like a leakproof tank, you need to ensure high enough rigidity once it is filled. I.e., you need to use sheet of plexiglass that is thick enough to not flex under the pressure; this is in addition to maximizes the surface area of the weld. If it's not rigid enough, the stress will cause micro cracks in the joint over time.If you are trying to make a thin, vertical tank, you have some additional issues. You can't easily apply solvent into the inside seam on the last piece. For ferric, I suggest you either make it 4+ inches wide or if you want a thinner tank (and more frequent etchant replacement) make the front panel oversize, so when you attach it you can run the solvent into an outside corner. Then after it's welded, trim it back down.Even in a very thin vertical tank, there is significant pressure and stress when it's filled as the length and height go up. So in the end, you will get better results and at least some chance of success if you overbuild it with like 3/8" or 1/2" plexiglass. If you cheap out and try to save on materials, it is hard to get a good result. The "permanence" of solvent welding a thin vertical tank starts to get troublesome when the bill of materials gets to be expensive, and the resulting tank is so difficult to service or repair/rebuild in case of a problem due to how narrow it is.

author: coppercone2
author_rank: Super Contributor
timestamp: May 19, 2019, 10:08:59 pm
content: I am not making a narrow one because when the bubbler turns on it will do some weird shit when its thin and etch unevenly. It looks cool and is space efficient and it seems like a good idea but the little one I have now (I found it in the trash, I think it was someones plant root growth experiment or a fancy planter) etches like shit for some reason compared to garbage bags. They seem sensitive to turbulence. I think using bag walls some how disrupted the turbulence because they are not a stiff surface.I figure if I make it all enough and give it a vapor extraction fan I can make a steel cage to reinforce it. I am even thinking to make a glass heat exchanger so I can heat the solution (need to see what area requirement is). I also wonder if an air preheat (like using a soldering station heater on the compressor line) could increase uniformity and how much disruption the air has. Need to do some basic calculations.

author: KL27x
author_rank: Super Contributor
timestamp: May 19, 2019, 10:14:53 pm
content: QuoteI think with ferric, you don't really want to use a super thin tank, anyway. That just means more etchant changes. Vertical is still desireable, IMO, so you can etch both sides at the same time without sediment building up. I would think 4" thick tank would be great, if you want to go whole hog. This goes double, if you want to use an aquarium heater or the like. If the tank is too thin, and the heater is too close to the tank walls, this will create more stress in the plastic.My cupric tank is maybe a hair smaller than 3/4" thickness of interior volume. No problem with uneven etching. The bubbler I use is very fine and even and nothing like poking holes in a piece of tubing.

author: coppercone2
author_rank: Super Contributor
timestamp: May 19, 2019, 10:16:58 pm
content: Yes this one will have a glass bubbler and I want to make a syphon on the bottom with a little giant magnetic drive pump to extract etchant when its done into a storage container so I don't have a tall tower of corrosive bullshit to spill again. The strong acid rated one.Then I can flush out the tank with 2-3 fills after wards to clean the pump and tank.This stuff managed to eat through a milk jug and destroy a nice wooden shelf. Gonna get a nice tank that uses a bung wrench to open.I need to make this good because dealing with the stains and stuff makes me not want to make PCB. If it is done reliably then it will be easy.

author: KL27x
author_rank: Super Contributor
timestamp: May 19, 2019, 10:29:50 pm
content: QuoteIf you can manage to make a good leakproof tank, you can just leave it filled. It will hurt the wallet buying 1/2" plexiglass, though.I started with solvent welding and I cheaped out on the thickness of the plexglass. I increase the surface area of the joints, but it was still not leakproof in the long run. Talking just a drop collecting at a spot over a day or 3. But it was still annoying. I ended up changing gears and going with silicone and mechanical compression of the gaskets. Completely leakproof for 5 years now, exposed to sun and weather.

author: coppercone2
author_rank: Super Contributor
timestamp: May 20, 2019, 01:09:10 am
content: if I wanted to create a coiled heat exchanger inside of the tank, assuming the thermal calculations were done, what grade of titanium would be required to withstand etch cycles?i.e. grade 2 seamless titanium tubing is sold by onlinemetals.com.But I think it goes to grade 7I just don't like the idea of a werid vertical cylinder chamber holding a buncha ferric chloride out in the open anyway. I want to store that in a cabinet outdoors now.

author: jeremy
author_rank: Super Contributor
timestamp: May 20, 2019, 12:04:37 pm
content: As far as I know, Weld On #16 is the most common adhesive. It’s basically methylene chloride and MEK with acrylic dissolved in it. Surfaces do not need to be prepared other than being cleaned. Glue area should be clamped under moderate pressure while wet.I have made waterproof containers with acrylic by using Weld On to join the pieces, and then running a bead of silicone (the kind you would use in your bathroom) along the internal edges. Worked great. You can put the uncured silicone in a long needle to reach difficult areas if need be.

author: jeremy
author_rank: Super Contributor
timestamp: May 20, 2019, 12:08:49 pm
content: Quote from: ataradov on May 19, 2019, 08:33:55 pmYes, the stuff I use is always labelled that it causes cancer (but only if you live in California). The solvents are pretty nasty anyways.

author: coppercone2
author_rank: Super Contributor
timestamp: May 21, 2019, 06:26:22 am
content: Yes I am wondering how useful it is to see the PCB through the glass vs just lift the thing up periodically lol. Usually during the etching process your waiting on it like a hen. With the bubbles you don't really see the PCB too good anyway, I suppose if you install a vapor control system over the tank, then turning off the air supply to see the progress makes more sense then lifting a fuming thing.If it was gas weldable I would go for a titanium tank I think, and if I could establish how imporant clear walls are in a well controlled etch process (not using bootleg techniques).The rate of etching of titanium in HCl is very low, and ferric chloride actually acts as a inhibitor on titanium (so you are talking like 0.05mm/year of corrosion.. how that figure ends up looking practically I don't know (not familiar with corrosion engineering)).I am scared to try to learn TIG welding on a cheap machine just to make a titanium tank, and I am afraid of the beating/forming operation.

author: Mechatrommer
author_rank: Super Contributor
timestamp: May 21, 2019, 11:00:17 am
content: the purpose of the bubbles is so the etching process is continuous instead of dormant not etching. with bubbles you can time to say 5 minutes and when you lift your pcb its sure confirmed everything etched out. with dormant echant, you can wait 30 minutes and your board is still not etched properly. you wont see anything inside ferric chloride anything further than 0.1mm. if your purpose is to see through with FeCl you are going in the wrong direction, you should go with those china CCL blue clear etchant if you want that purpose. but that etchant is not meant for long storage.

author: CJay
author_rank: Super Contributor
timestamp: May 21, 2019, 01:04:07 pm
content: Old LCD monitors have a nice sheet of acrylic as part of the backlight asembly, find youself a bunch of 17" ones and you'll probably find 10-13mm thick acrylic sheets in them.

author: coppercone2
author_rank: Super Contributor
timestamp: May 22, 2019, 03:22:55 am
content: Quote from: Mechatrommer on May 21, 2019, 11:00:17 amHmm For some reason I thought if I got higher grade etchant it would be clearer. The stuff I mixed up is very murky but it was also very cheap reagents. And I used it for alot of etching in a non transparent container, so I figured it was just dirty with some kind of 'mud'.Is this the particulate or the actual solution? If you were to do continuous filtering with some kind of ceramic? fiberglass? filter would it stay clearer and possibly offer higher etching quality? Those little giant pumps could handle it.The idea would be to stop air flow every 30? seconds for a few seconds to monitor the progress through the tank walls, enough for the bubbles to subside.

author: KL27x
author_rank: Super Contributor
timestamp: May 22, 2019, 06:43:24 pm
content: Ferric chloride? You won't see much of the board. Even in a 3/4" thick vertical tank of cupric, I can't see the board, once the etchant reaches a steady state level of cuprous. Ferric is that dark, all the time. I suppose with a bright enough backlight, you might be able to see.But a clear tank is still useful to see the level and the color of the etchant and presence/amount of any sediment. Or for seeing and fishing out any debris that might unintentionally get in there. And for examining the board, you can see the board when you lift it over the level of the etchant. The tank should ideally be at least 6" taller than the level of the etchant, IMO, due to the fizz from popping bubbles. Extra height also reduces the evaporation rate, in case you decide to leave it filled. The lid I use is not air tight, and evaporation is very minimal. Takes on the order of year(s) before evaporation is significant.Constant monitoring the board is not important if you use proper etchant and a good tank and bubbler design. The margin for error in the etching is relatively gigantic. I have what feels like at least an hour long window to retrieve a board out of my etch tank on a fine pitch board. I have never even bothered to use a timer.

author: coppercone2
author_rank: Super Contributor
timestamp: May 22, 2019, 10:22:17 pm
content: how dirty is freshly prepared ferric chloride?Is there any benefit to continuously filtering the bath during the etch cycle? (at the cost of a expensive pump)>And yes I wanted to make a fitting on top of the tank that has some kind of filter so it can be used in doors (normally I set it up outside but its also annoying because I don't have epoxy coating outside, so if it spills you are left with nasty stains in masonry or it sits infront of the house ominousy

author: KL27x
author_rank: Super Contributor
timestamp: May 23, 2019, 05:15:55 am
content: It's not dirty. It's just not particularly transparent.QuoteCopper compounds will precipitate out, but filtering them out won't change anything. Adding some HCl and water will put them back into circulation and with aeration and/or peroxide you will gain a bit of life out of the ferric at the cost of etch quality. IME, when you have significant amount of sediment you might as well change out the ferric.QuoteI can't imagine this is practical. It is probably easier and more practical to ensure adequate ventilation if you are using it indoors. The fumes aren't much to bother with, other than keeping steel out of the immediate area of the exhaust from the bubbling.QuoteIf it's outdoors, it is easy to clean ferric stains from concrete. Pour a little HCl over the stain, use a bristle brush mop, then rinse with the garden hose.Give the tank a proper base with proper span and mass and you shouldn't have too much to worry about. Use a proper high volume high speed funnel when you change the etchant, like you can buy at the autoparts store.If you have an air compressor, and you are going to build a custom tank, anyway, I suggest you go with cupric. You never have to change out the etchant, so you don't have to deal with big volumes of waste. The ticket is to use fish tank bubble wall wands for aeration at around 20 psi. They last indefinitely and provide adequate aeration for a cupric tank.

author: coppercone2
author_rank: Super Contributor
timestamp: May 23, 2019, 10:41:39 pm
content: The stains I poured muratic acid on and scrubbed with a nylon brush attachment for a sawzall (stiff). A complete BITCH to take out. Only good use I found for that tool, if you don't mind acid splattering everywhere.https://www.amazon.com/PRODUCTS-LLC-400004-Attachment-Reciprocating/dp/B00FAMS0Q4I thought it would be easy too.I thought I could clean stuff with it, but its only good if you wanted to wash something clamped in a vise, or a very heavy object. I did not think it would fight you so much. And it worked on realllllly dank grout to give it some extra lifemuch more usable toolhttps://www.homedepot.com/p/Dremel-Versa-4-Volt-Cordless-Lithium-Ion-Power-Cleaner-Tool-PC10-01/304600901

author: coppercone2
author_rank: Super Contributor
timestamp: May 23, 2019, 10:47:17 pm
content: For the filter I just imagined a trapazoid shaped piece which tapers down to something like a generator engine filter to catch some of the mist that forms? Or sponge etc.

author: coppercone2
author_rank: Super Contributor
timestamp: May 23, 2019, 10:56:31 pm
content: I am actually wondering if having some crystals dancing around in the agitated bath can possibly help stir/break up surface things and kinda 'polish' the pcb as its being created?I wonder if there would be any changes in quality if you poured a buncha non reactive abrasive powder in there. Like a mud bath almost.

author: KL27x
author_rank: Super Contributor
timestamp: May 23, 2019, 11:14:28 pm
content: QuoteMy experience is the opposite. There might be difference between type of concrete. But it worked pretty good even without brushing, just pouring 30% HCl over the stain and then rinsing.QuoteWell, spray is one thing. For that, any cover will fix the problem. Wet rag, even. (If you plan to use this much, I suggest you just make it tall enough to contain any fizz). But you will have some gases/vapors. A mechanical filter doesn't stop that. If I leave the regulator attached to my tank, the regulator corrodes over time. This is through a 1 way aquarium valve with the fiber filter in it, and 5 more feet of tiny aquarium tubing. You don't necessarily need a fume hood to fun a small tank indoors, but I would plan for a certain amount of space around the tank to allow this chlorine gas to diffuse to an insignificant concentration (no electronics or good tools lying here), in addition to providing for adequate ventilation.QuoteWhat are you expecting to polish? The FR-4? You aren't going to shine up any traces unless the abrasive removes the etching mask. And then they'll corrode because... etchant.

author: coppercone2
author_rank: Super Contributor
timestamp: May 24, 2019, 01:04:44 am
content: I meant like, if some kind of film/gummy/viscous thin film is forming on the PCB during the reaction or something like that.

author: coppercone2
author_rank: Super Contributor
timestamp: May 24, 2019, 01:21:44 am
content: something like the thought that particles in the solution will have some kind of 'drag' or 'wake' behind them to agitate things more. I don't know how a bubble compares. I thought it might skid over a dissimilar surface rather then bumping into it and causing a disturbance. It would be much smaller then a bubble I think?Or even a bubbleless etch, so there is just a pump recirculating particles (though the pump would take a beating).

author: KL27x
author_rank: Super Contributor
timestamp: May 24, 2019, 09:07:22 am
content: Fixing stuff ain't broke.Conjuring up improvements with no rhyme or reason when your only baseline is a garbage bag.Combo sand blaster with bonus corrosive acid.Sound like you have your next winner.QuoteIf you try what i suggested, the bubbles are very, very small. When my etchant is overdue for a titration, there is a lot of precipitate swirling around in the tank. It'll settle to the bottom several minutes after disconnecting the air. If you want to add some kind of solid abrasive particles with some sort of acid and abrasive-proof pump (which might exist, but you will be trying to build this out of free junk out of your garage with a budget of half a shopping cart of recycled cans, no doubt), you might experiment with fine high pressure bubblers and an abrasive of the right density to easily remain in suspension and also be immune to the echant. Diatomaceous earth?But I suggest you try walking, first, before designing your space ship that goes around the moon and back just to get you across the street.

author: coppercone2
author_rank: Super Contributor
timestamp: May 24, 2019, 08:19:44 pm
content: I did plenty of etches in garbage bags (works great like I said), I don't see the problem with thinking about an idea?This is a big project and its just brain storming.and why don't you read the posts, I clearly mentioned a little giant brand acid resistant magnetic shaft drive pump and titanium piping heat exchanger. that is not low budget.I do low budget stuff so I can afford high budgets on things I find interestingLittle Giant HC series since you are probably too lazy to look for ithttps://littlegiant.com/media/124593/995403_LG_Industrial_Catalog.pdf