TAP Plastics/Acme Plastics experience?

[Michael R]

The gears are a confusing rathole. McMaster was where I first looked. They have nylon and acetal. If you look up chemical compatibility charts for acetal/Delrin, photographic solutions are explicitly indicated to be bad (although exposure tests are typically 24-48 hour immersion). There are many types of nylon. A common type for gears seems to be MC901 (Nylon 6). Chemical compatibility is indicated as good for photographic solutions, however these types of nylon do absorb water, which could be problematic over time. Not sure. They seem to generally be recommended for dry applications.

Stainless seems to predominantly be 303 because it’s much easier to machine gears out of it than 316. Perhaps 303 is resistant enough for this application. I don’t know.

PTFE (Teflon) would be best but I can’t seem to find suppliers.

Sourcing this stuff isn’t easy. Gears for hobbies are simple to find in general (brass, etc.) but not chemical-resistant plastic gears.

I suspect I’ll have to just try either nylon or 303 stainless and see what happens.

Any skilled small cabinet maker could be hired to do this very precisely, especially if you offered to buy the appropriate circular plastics blade for him, which don't come cheap. But exact dimension isn't as important as sheer consistency of dimension, which Tap should be able to provide once they lock down their settings. Just communicate well in advance and don't be in a rush, so that they can give the project due attention.

Gearing : there are specialty suppliers for this very kind of thing. Do a web search, or try McMaster first. No, you don't want ABS; nobody is likely to make gears out of that anyway unless its some toyish application. You want machinable solvent-resistant Delrin or durable HMW (high molecular weight) nylon, Acetal, or perhaps 316 stainless steel (noisier). At the heading of each catalog section, including their online catalog, McMaster gives good specification comparisons on the various materials. Then you can home in on more thorough solvent resistant specifications of potential candidates looking elsewhere.

[Dugan]

Maybe a Colex/Colenta rep or service tech can let you know what type of plastic they use(d) for their gears?

[Drew Wiley]

Searching for an Ivory Billed Woodpecker, eh?

[Dugan]

And that comment was helpful how, Drew?

[Michael R]

And that comment was helpful how, Drew?

As an aside, a quick google of Colex-Colenta turned up this place I was not aware of

http://www.footprintsequipment.com/I...a&P=Processors

Not directly related to my current project but might be an interesting potential resource for people.

I’ve reached out to a few people to see what they’d recommend.

It may be that I’m over-complicating/over-engineering. “Photographic chemicals” covers a lot of different things, but for my purposes the range is considerably narrowed. Photographic solutions are also typically fairly dilute, which helps. Still, what I might start out with are some MC901 (Nylon 6) gears, which are fairly standard, and just soak them for a while in water, and some photographic solutions, to see how they do. If I can find a source for gears made of more resistant plastic (ideally PTFE/Teflon, or perhaps HDPE) that would be better.

[Michael R]

Thought I'd post a quick update re Tap Plastics. I was pleased overall. I initially tried to place this order with Acme but was then advised by them they don't ship outside the U.S. Unfortunate. Anyway...

I placed an order for a bunch of 1/8" HIPS (styrene) rectangles in various sizes to assemble into tanks. Some sizes were too small to select routed edges but I selected the option where possible. Pricing for the material and cutting was very cheap in my opinion, especially considering the relatively low volume of my order (20 pcs total). In fact the shipping cost more than the order itself.

The order was done and shipped out the next day.

Accuracy/quality was good for the price in my opinion. Not precision work, but good enough for this application. Some of the pieces were pretty much bang on, and none were out by more than approx. +1/32" to +1/16" in any dimension. I had to fine tune a few of the pieces, but that was ok with me considering it would have taken me days to cut and sand all of this by hand (I don't have power tools). Perhaps most importantly, all the edges were perfectly square even where not routed, which is important for good solvent welding, and is brutal to do by hand.

Obviously this is not for things requiring high precision, and it won't be as good as one equipped with proper tools could do at home, but it was a good solution for me in this case.

[Drew Wiley]

Well, I guess I won't have to sober up my plastic-eating pet termite so it can walk a straight line.

[Michael R]

Seems like a strange choice for a pet, but ok.

[Drew Wiley]

All plastic termites only eat plastic, so no worries about the house timbers, unless its synthetic PVC decking or siding. But no worse than the plastic gophers and that eat Astroturf lawns and artificial flowers.

[Michael R]

All plastic termites only eat plastic, so no worries about the house timbers, unless its synthetic PVC decking or siding. But no worse than the plastic gophers and that eat Astroturf lawns and artificial flowers.

I’m not sure what any of this has to do with my Tap Plastics order, but ok.