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| Re: A Magic Mushroom [message #42351 is a reply to message #42323 ] Fri, 20 January 2012 18:46 UTC |
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Injection molding typically only pays off when running large quantities (larger than 1000 units) because the cost of the molds is quite high. Unfortunately, a quantity of about 1000 units is kind of in no-man's land between the benefits of rapid prototyping (high unit cost but no tooling) and a good fit for injection molding (low unit cost but high initial investment in tooling).
My question is, why do you need 1000 made? The best part about printed parts is that they are made on-demand; you can print them as you sell them. Perhaps you need to keep a small stock (20 parts?) on the shelf to keep the lead times down, and then just replace your stock as sales are made.
Or are you shooting for 1000 just to bring down the unit cost? In that case, my guess is that you won't find a price break at that quantity for molded parts.
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| Re: A Magic Mushroom [message #42368 is a reply to message #42351 ] Fri, 20 January 2012 21:16 UTC |
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One of the reasons that i'm going for a 1000 is to bring to cost down.
The other is that i think this item is a bad candidate for 3D printing. Besides the printed parts, it requires 13 small magnets, an o-ring to make the seal watertight and some other smaller parts. It also needs assembling, but that is quite easy as the various bits lock together. Also the cost of printing it is very high even if i use WSF, which is not smooth enough for the locking mechanism and so it has to polished.
Based on a few quotes i got so far, i estimate the cost of injection molding vs 3D printing to be 1/10 at quantities greater than1000. As the quantity goes up, so do the savings but i think 1000 is pushing it even if it sells ok.
This is my first attempt at designing something to be produced via injection molding. I know the basics, but i have virtually no experience in this industry and this is why i'm asking for help and feedback here. I assume a lot of people using shapeways are industrial designers or work in a similar position and so they could point me to the right direction.
Dinos
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| Re: A Magic Mushroom [message #42374 is a reply to message #42368 ] Fri, 20 January 2012 21:49 UTC |
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I forgot to mention that you have a very cool looking locking mechanism, judging by the videos. Good luck!
It is hard to tell, but are there undercuts in your parts that would make injection molding difficult? I don't know of any good resources for small run IM, but maybe you can take a look at http://www.firstcut.com. They are fast and high quality (at least for the metal parts I've gotten from them in the past), and best of all, they do offer a price break for quantities. You could probably get the bulk of your parts machined in lots of 100 at a reasonable discount, and there is a wider selection of materials than Shapeways. And of course, no investment in the molds. The only problem I forsee is the rather large cavity in the "trunk" of the mushroom, you are machining away a lot of material. Worth a look though.
[Updated on: Fri, 20 January 2012 21:50 UTC]
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| Re: A Magic Mushroom [message #42418 is a reply to message #42374 ] Sat, 21 January 2012 10:11 UTC |
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Thanks.
Their http://www.protomold.com site looks more interesting than firstcut as they can perform injection molding. I'l upload a couple of parts and see how it goes.
Dinos
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| Re: A Magic Mushroom [message #42440 is a reply to message #42432 ] Sat, 21 January 2012 16:02 UTC |
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I've never heard of Rotational Moulding before, but it looks very interesting. The shape of the mushroom could be a good fit for the process. I'll definitely check it out and see where it leads me.
Dinos
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It is printed in black and white detail and its fully functional. You must see the videos to appreciate the way it locks at: 
