Automated Casting Adventure in the UK!
Hello Practical Machinists! I apologise if this particular project is not within the purview of the forum, but despite the name, it does say manufacturing technology on the banner, so I've assumed it is!
I have been attempting to design a machine (for the first time) to automate a casting process, about which I have been deliberating with members in the following threads at other forums on similar subjects:
Small Scale Automation Adventure in the British Isles! - Forums.MrPLC.com
http://www.*******.com/forums/genera...enture_uk.html - For some reason I cannot link cnc zone, but simply switch out the asterisks and I'm sure you'll find your way!
I had hoped that I could garner some advice from seasoned manufacturers on some problems I have been facing with creating a design for my machine, which are as follows for the moment:
1. Finding a good way to transport or dispense a liquid that cures, i.e. resin, to a cavity.
2. Making it so that I can use a system such as pneumatics with AOO to bring parts of a silicone mould together at a reasonably constant (not to mention slow) speed and can compress them only up to a point without deforming the mould (see the cnc zone discussion for more details on this point).
3. Sourcing parts that can be acquired at a reasonable price in the United Kingdom.
If anyone has some pointers, advice or links to good explanations of suggestions or good places to acquire parts, I would be much obliged.
An overview of the project and it's necessities can be found in the Mr. PLC forum.
Thanks in advance answerers!
P.S. Out of interest, why can't I write the name of that other forum, is there some sort of internet rivalry going on?
Not really a rivalry.. We prefer not to attract hobbyists, many of whom conflate cnc with video games. Any mention herein of that other forum (of which we do not speak) provides a search path to our door. Your questions are germane to this forum. Theirs generally are not.
Originally Posted by Zookes
Firstly there's a lot of places out there that do mouldings exactly like you want that have already cured all the issues. That said if you want to go it alone here's some possible things to look into, unless you provide specific questions here its kinda hard to be more accurate.
Firstly you try to never pump mixed components, pump individual resin components that ideally don't pass through a mixer till just before they enter the mould cavity. Minimizes clean up and set-up issues. Static mixes are common items and are cheep - disposable. So long as you keep pumping resin through them they work just fine. There's all sorts of diffrent pumping options, a lot of that depends on qty, viscosity and needed precision. Idelay there's multiple moulds, but only one fill station, like this parts can cure and be released before the resins set in the mixer. Ie one moulds being filled, one or 2 curing and one being emptied. Also look at preheating the components prior to mixing, can dramatically improve setup - de-mould times with some resins.
Don't over automate it (it can be as bad to profit levels as under automating it). If you need only a couple of hundred a week self opening and ejecting moulds can be a expensive luxury and take a lot of maintenance. A simple rotary carousal and a couple of operators can on certain things at certain qtys be a far cheaper option. Have a look at some of the T shirt screen printing videos on you tube. Multiple stations, but simple and flexible to meet the products needs.
Above all finding parts at reasonable prices is a interesting issue. Above all my advise to you is don't skimp too much especially if your going to be employing a operator or 2, down times not free. Try and stick to a common PLC from a well known manufacturer, avoid propitiatory sensors and parts were ever possible. Stick to off the shelf pneumatic components, don't use specials unless you have too. Above all try and make things a bit modular, most machines like this have to be adapted as things change - problems appear. If you can't weld don't try and make it fully welded etc Make it easy for your capabilities to make and modify.
Above all good luck, manufacturing is a hard thing to do over here in the uk competitively these days.
To Doug: Ah, good to know, no hobbies to speak of here (to wit: they are unspeakable).
To adama: Crikey, of all the people I've spoken to so far, you seem to be highly intimate with this particular application; there's a lot of wisdom here.
Though I do have my heart set on automating the process myself, would you happen to know whether any of these casting services have a website? (always good to have a plan B, eh?)
As for my PLC, does a Siemens LOGO fit the bill? I chose it because of the easy-mode programming suite it has.
Also, I was thinking of moving the mixed resin with gravity, but I still need a valve solution if that's the case. And with my current design, it'll need to resist a bit of a vacuum.
Do you know of any valve solution that would be able to counteract the obvious build-up problem? Dispensing chambers that evacuate the whole chamber have been recommended before, FYI.
Furthermore, you mention maintenance; do you refer to the cleaning of moulds, applying release agent and casting related stuff, or mechanical maintenance?
Lastly, I don't want to barrage you with questions, but in your experience, what is it about the UK that makes it such a difficult place for manufacture?
Thanks to both of you for your interest!
Look at some of the products from Henkel/Loctite, particularly their two part resin syringe packs. Of course you want something in bulk, not a syringe. But notice the needle they use. It's a poly tube with a helix insert that mixes the resin on they way to its destination.
These helical mixing tubes are commonly used in robotic application of industrial resins. I worked on a project about twenty years ago that required a two part foam in various cavities. The resins came in drums and were pumped to the mixing tube with a parallel piston pump. The piston stroke was adjustable to get proper ratios.
The foam system worked well once the operators learned how to maintain it. The mixing tube is removed as part of the shut-down. Each start-up requires a new one. Keeping resins off everything (and everybody) is the hard part.
Sorry about the delay chaps, been a little busy.
So, there is no really feasible way of building a dispensing system for a curing/solidifying liquid other than building in a disposable component?
Originally Posted by doug6949
Is there nothing in the idea of a cylinder with a plunger that forces almost all of the material out of the chamber?
You mean along these lines?: 1100962 - Static Mix Nozzle; 9.98 inches long; 11.2 mm square I.D; 20 elements; 7/8 - 9 threaded end. (3 pack) | Henkel
Originally Posted by doug6949
I looked at the .DXFs but they don't explain much beyond what you have said.
I have a mixing solution in mind that will likely (tests on the way) ensure the results I am looking for, involving a vacuum chamber and a simple mixer driven with a servo motor.
My intention was to utilise disposable parts with the mixer and the vessel that holds the resin while it is being mixed, so I suppose the dispenser shall probably have to be the same.
It may be inelegant, but I feel it conforms reasonably well to Murphy's Law concerning problems with bubbles in the casting process.
Concerning dispensing, I was thinking it may be that the simplest way to control the flow of resin might be to have a door above an open channel, both of which could be replaceable.
I would make the aperture quite narrow to avoid a messy impact, and perhaps an incline too.
The door could close inwards so that the vacuum would strengthen the seal. Perhaps I could have a pneumatic actuator that rotates to close it while the chamber is under vacuum?
Does anyone take any issue with that notion? Might there be a better way?
Thanks for your contributions so far!
P.S. I'm having real trouble find a retailer in the UK that supplies low cost hydraulic dampers, preferably low force or adjustable, to be used with something like this:
But with a rather longer stroke, about 10cm I'd estimate. If anyone has any ideas, I'd be much obliged, thanks!
Might require too much force though.
Look into miniature shock absorbers, most of the leading pneumatic suppliers do them. There not cheap but like most things are darn good. If all else fails look into 1/10th scale rc shock absorbers, there dirt cheap and are incredible value for money, especially the cheap alu ones from china on ebay might have to buy a set of 4 though :-)
Static mixes are the long tube with the helix in, there dirt cheap in qty and available in lots of options. Paddle stirring and vacuum degas, is not the way to go. Don't try and automate the hand process, use the industry proven automation. If the resin goes into the mixer gas free it will come out that way after the first bit. Then you want to warm it to kick the cure speed up, mould it and dump the part and be able to mould the next one with the same static dispenser full of much slower setting cool components to fully mixed but still cool resin. Or you need to run multiple moulds
Alternatively have you looked into simply getting the parts injection moulded? There is a lot of heat softening elastic compounds out there that you can simply injection mould. Equally there's a lot of companies out there that specialise in low run mouldings.
As to the plc, i don't know i don't get to play with them that oftern, 99% of what i do is repairs - mods to existing equipment.
Ah, excellent, I was having the devil of a time trying to source those, I'll try looking more specifically for what you have recommended.
Originally Posted by adama
Evidently. :S I've been looking around and they do seem cheap, but how to stop the resin solidifying in the tube?
Originally Posted by adama
Does the resin have to be continuously sent through?
If so, I'll have to make some pretty fundamental changes to my design.
That was my original intention, but to have them all running in parallel, perhaps I need to have them all running asynchronously, which would invalidate a good part of my machine design.
Originally Posted by adama
I did look into that, but it isn't appropriate for the kinds of designs I'm doing, undercutting and very fine detail are a bit of a necessity.
Originally Posted by adama
Thanks for all your assistance adama, a lot of unknowns have been revealed to me now.
P.S. You stated before that there were companies who could cast resin parts, do you have any specific companies I could look at?
Running lots of moulds at once in parallel does not help with cure times, in series one after another does. Keeps the dispensing system liqiud, keeps molds ready to be decast, just makes things flow.
Try this see if it helps.
Let me google that for you
Just to add you need to try diffrent companies if your after specific resin feed stocks. If there already buying that resin - compound in bulk and your only after a few - smaller parts it could end up being a lot cheaper.
Hello Chaps, thanks for all of the help, but my feeling is that I overreached the resources I have at my disposal in considering whether I could produce the required volume in house.
I'm pretty sure I'll be outsourcing the manufacturing to some company somewhere, and I'm currently speaking to some individuals about the legal ramifications of that (protection of intellectual property and so on).
Unless anyone has any advice on how to conduct myself and what to expect in that event, I'm quite sure that I'll have no reason to bother you any longer!
Own the tooling, only leave it with them for production to be returned after the job is ran is my best advice.
I see, so in my case, using a resin casting process (which I prefer regardless), I should own the moulds and the master?
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