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Metal DMLS, Polyurethane casting, metal inserts: recommendations on production methods? [message #55114] Wed, 10 October 2012 00:32 UTC Go to next message
avatar thomashuang.net  is currently offline thomashuang.net
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Registered: September 2011
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I'm thinking of taking my products from on-demand to mass-production to lower the production cost and increase part complexity, but I'm not knowledgeable in all the different possible manufacturing processes, and I'm hoping someone could point me in the right direction to find out more.

What I'd like to find out is what process should I consider to focus on that would be cost effective with accurate results?

My products are used for taking panorama photographs, which require shooting 4-6 shots rotated around a very exact position with a maximum 0.5mm deviation. So far, SLS polymide has been very accurate. There has been some sagging around the holes in z-axis, but other than that, center points are accurate.
http://thomashuang.net/products/nps75/nps75.html
http://www.shapeways.com/model/730954

My "rotational" part design is extremely simple, where a coupling nut slides into the lower part, and the upper "ring" part rotates freely around it. Teeth keep them engaged, and a screw on top keeps them together. The reason why I've done this is that the SLS can't make threads this small, and can't create perfectly round holes and tubes that can rotated within each other.

But people are complaining about how they have to unscrew, lift, turn, lower, and screw again each time they want to rotate the camera.

So now I'm thinking about making a more complex rotator using metal inserts. The metal inserts would be designed to allow for the advantage of smooth rotations with an easy locking mechanism.

I think injection molding would be too expensive for a short run of 200-300 units. I've read that polyurethane casting is a good way to produce small runs, with the possibility of having metal inserts cast directly into the plastic. The only problem is that my designs have so many undercuts, I don't know how it would be possible to remove the molds after casting. But if I resolve the undercuts, would casting be much cheaper than SLS?

I am thinking about the possibility of making this out of metal. It would look like this:
http://www.shapeways.com/model/731440

I'm not sure about metal casting, but it sounds expensive, especially out of aluminum. I looked at Shapeways and i.materialise 3D printed stainless steel but according to the process description, my unsupported rings would break or deform before getting to the furnace for hardening, and it would not give me the accuracy that I need.

I looked for digital metal laser sintering, and I see that i.materialise has Titanium using EOS M 270 DMLS printers. Searching Youtube also comes up with videos of DMLS prints, and it looks like "real" direct printing. But the i.materialise Titanium quote was 420 euros.... which is not cost effective.

So the question I'm trying to answer is, what process would be cost effective while allowing me to create more complicated moving parts while staying accurate to 0.5mm?
Re: Metal DMLS, Polyurethane casting, metal inserts: recommendations on production methods? [message #55125 is a reply to message #55114 ] Wed, 10 October 2012 06:38 UTC Go to previous messageGo to next message
avatar mkroeker  is currently offline mkroeker
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Registered: June 2012
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Similar thread already running here in the General forum.
For that last metal part, stamping might be a technical alternative, but the cost issue will be the same as for injection molding - the tool will in all probability be too expensive for runs of just a few 100 pieces. (But the coolness of a blank strip of metal running through a few feet of apparatus and coming out as precisely cut and folded pieces is similar to that of seeing a 3D print materialize. Smile )
Re: Metal DMLS, Polyurethane casting, metal inserts: recommendations on production methods? [message #55128 is a reply to message #55125 ] Wed, 10 October 2012 09:35 UTC Go to previous messageGo to next message
avatar BillBedford  is currently offline BillBedford
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Casting in aluminium would normally be a lot cheaper than any 3D print, but you would have to work closely with a foundry to ensure that there was no distortion. Have a look at this site, I'm not recommending them as they use hard moulds to produce the waxes, but the site will give you an indiction of what is possible.


Bill Bedford
Re: Metal DMLS, Polyurethane casting, metal inserts: recommendations on production methods? [message #55129 is a reply to message #55128 ] Wed, 10 October 2012 11:46 UTC Go to previous message
avatar thomashuang.net  is currently offline thomashuang.net
Messages: 83
Registered: September 2011
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Thanks for the info.

After looking at that foundry website, I noticed the use of removable cores to cast cavities. This could probably be done with the plastic resin casting, to get my original "double ring" design. The 2 halves of the mold could close in onto the removable core, which solves my problem with the internal cavities/undercuts.

I think I need to show my 3D printed model to someone who is familiar with all the possible production techniques to tell me how practical the processes and costs are for each possibility.

I'm currently in Cologne, Germany, possibly Hamburg next week (living on a bicycle), but it's difficult finding information here as I don't read or speak German. Anybody know of a prototyping/manufacturing company around this area that I could visit?

The information I need affects design questions, such as whether I should use all metal parts, or 1 part metal 1 part plastic, or all plastic with metal inserts. And whether the loss wax casting or all machined metal parts is more practical will affect the decision to use inserts or all metal parts. One issue is the creation of threads. If loss wax casting still requires the machining of threads, wouldn't an all machined part make more sense using the same process in a single run?

 
   
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