Mould Creation Time


banjeed

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Please don't flame me to oblivion for this as I have tried searching for the answer prior to posting. If the answer is obvious and or posted already, please stomp this with a one hit post.

I'm wondering why it takes a month to make the case mould. I work with 3D graphics on an everyday basis and my company has access to various 3D scanners and model optimizers. I can't think of a single scan that took longer than a few hours to reproduce as an optimized 3D nurbs mesh. From there, it's not hard to 1:1 the model to plastic through various companies. I'm not talking about rapid prototyping. I'm talking about injection moulding. I'm sure I'm missing something. Is it that the companies are backed up?
 
I think making the case itself is not hard - getting it right is.

You have to consider some things:
- The company doing the moulds is in china. This adds delays through shipping and timezones
- The case is very complex
- The case must be stable and must be changed when the board changes a bit
- The board has wifi on it which requires special work on the case
- ...
 
I think you might be confused as to what kinds of manufacturing are available, blow moulding is pretty fast and easy, you might be thinking of that, or maybe resin casts with rubber moulds, even hobbyist`s can do that, so some plastic moulding techniques are fast and easy, but the Pandora case is injection moulded, you use really high pressure to force the plastic into the moulds and leave no air bubbles, and I mean REALLY high pressure, to prevent the mould popping apart before the injection is finished they have to be clamped shut, in the industry the clamping pressure standard unit is the ton, so the mould can`t be flimsy.

so they have to create a really strong mould out of solid steel thats highly polished and will not bulge during injection, then they have to allow for "sink", when the plastic cools it shrinks a bit, if the plastic at one spot is really thick then when it cools lots of plastic=lots of shrink, so you are left with a dimple on the product or a too short support post etc, so they may have to modify the mould to prevent that (thats why sometimes you see products where the internals are made from two or three parts rather than cast in one, so now you know why they did it the "hard" way)

then you have to think about production speed, the mould has to be water cooled so that once the part is cast it can be removed from the mould as soon as possible rather than waiting a hour or so for it to harden, to do that you have to model the heat distribution in the product and then place water channels in your solid steel mould too cool it down without warping the thing being moulded, all the while remembering the immense pressure used during injection.

THEN you have to get the thing out of the mould, that means ejection pins so that when the mould unclamps and opens, the product will just pop out, rather than you having to go get a screwdriver and lever it out <_<

so a mould is a multi ton resistant, solid steel, internal pressure resisting vessel, water cooled, with sliding ejection parts, that self dismantles to allow the product to be removed, highly polished, and made slightly oversize to allow for shrinkage, you don`t make one of those in a couple of days, thats the reason why many small manufacturers and electronic kits use ready made cases, it`s cheaper and easier, the stuff you are talking about is probably cast resin or blow moulded, neither require fancy, high precision moulds, either that or your firm pays a premium for fast tracked manufacture.

http://www.toolcraft.co.uk/index.htm

linky thing, very informative

remember, an initial order for 4000 components in an industry that makes more than that from one machine in a day will not be getting preferential treatment, they have to stop whatever the machines making, change the moulds, run off 4000, (one minute injection cycle and four cases per mould == 1000mins work == 16 hrs or two shifts on one machine) then stop the machine, change back to something more profitable (say 20,000,000 Wii controler cases) then restart the machine, they will probably fit it in where they can, plus we probably only have the one mould, most firms I work with charge for the moulds unless the contract is very big (when it in all probability gets factored in on the product price), interestingly, at least here in the UK, when you are charged for the mould (and most customers are) that means you own it, so if you want you can take it and send it to another firm if you want.


edit: reading my own link, I see the linked to firm uses alloy moulds, I guess steel is for larger production runs where wear or heat distortion is an issue, either way, carving a case and its negative (the inside) from solid metal, is not that quick or easy, even in alloy.
 
In addition to hobbyman's excelelnt and informative post, the manufacturer who is making the mould and the final case is not sittling idle waiting for OpenmPandora to say the word "GO!". They are a busy, constantly-working factory constantly making "new stuff". So each time OpenPandora say "GO! Do it!" what the factory does is allocate OpenPandora a slot in the queue, to be actioned when their turn comes around.

Add to this that, this time, they are taking on extra responsibility in tweaking the case/mould design to suit the full product design (they're putting extra work to ensure that the case produced will actually FIT the final motherboards as well as possible and actually WORK rather than just being a very close near-miss). every bit of work takes time, and when projects cross departmental boundaries (as this would seem to) delays get built into the schedule.
 
Thx for the great informative post hobbyman II. It does seem like a really precise and complex process. Hopefully the Chinese case maker know what they are doing and won't be too much trouble.
 
Apologies for this as it's kind of hijacking, but as we're on the subject of moulding, and hobbyman seems extremely knowledgeable on the subject, I was wondering if it would be feasible to have a company mill a custom arcade joystick case to my design? Or would it be incredibly expensive and a waste of time...
 
Apologies for this as it's kind of hijacking, but as we're on the subject of moulding, and hobbyman seems extremely knowledgeable on the subject, I was wondering if it would be feasible to have a company mill a custom arcade joystick case to my design? Or would it be incredibly expensive and a waste of time...
only if you're making more than 1000.
 
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Apologies for this as it's kind of hijacking, but as we're on the subject of moulding, and hobbyman seems extremely knowledgeable on the subject, I was wondering if it would be feasible to have a company mill a custom arcade joystick case to my design? Or would it be incredibly expensive and a waste of time...
I think that depends on your definition of expensive, and what constitutes a waste of time. Personally, I think you should get one of these (and then let me play with it): http://store.makerbot.com/cupcake-cnc.html :D
 
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Sugar_Kane, You'd probably want to contact a local plastics shop.
This article might be helpful : http://www.ides.com/articles/plastic_prototyping.asp

You'll have to find a shop that specializes in small batches. Many places won't want to waste their time on a batch of one or two pieces, but other places specialize in making prototypes for engineering companies. (They charge more.)
 
Also depends on your goal; I just buy real arcade joysticks and use them in my cabinets, but have also turned them into little handheld controllers for consoles. Course, a plastic project box or wodden box with a arcade stick in it is sort of clumsy, but awesome-clumsy!

jeff
 
Thanks guys. I've already made three for myself out of wood and perspex, and swapped out the parts of a dreamcast and a namco ps1 stick. I had dreams of having my own design tooled for me but I guess it really would cost 1000's. I wonder if craig and co would be interested in the possibility of an official pandora arcade stick? It would be awesome for tv-out play and I'd love to do some designs.
 
and swapped out the parts of a dreamcast and a namco ps1 stick.
You mean that you put real arcade controls into the case of a dreamcast "arcade" stick? That's pretty cool. How did it fit, though? Real arcade joysticks have pretty bulky bases.
You have to trim out some of the plastic casing and drill some new screw holes for the stick to fit, which was nothing compared to the buttons, which you need to take a metal file to the front plate for, because they are a couple of millimetres bigger than the standard buttons.
 
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Man that video was awesome! Makes you appreciate how much has to go into in to get it right. Now we are only up to the machining phase like Gruso said. So there is still a possibility that we could have the same problem as those buttons in the video. Hopefully the machining is done perfectly from the get-go.

I wish we could see a video of the Pandora cases being cranked out. Would be so sweet. OP Team do you have any estimates from the Mould company? When should the machining be done? The Unofficial estimated completion date for the moulds is next week, so the machining has to be done relatively soon right?

Hope to hear good news.
 
cant wait till you finish guys.. i will definatly buy one as soon as i see one finished completley. i was gonna invest in a gp2x but im gonna hve to wait.. hopefully not too long

looks beutifull im well impressed
 
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