Dip molding mandrel prototype

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Dip molding mandrel prototype

Postby Randy » Sun Feb 06, 2011 9:13 pm

This is a prototype/feasibility model for a dip-molding mandrel for a small air duct. The concept is, dip the mandrel in liquid rubber, let the rubber harden, trim the ends and pull the part off the mandrel. It is a technique for flexible parts that are a difficult shape to mold conventionally (rubber gloves are all made this way) This will be a duct that goes between a small fan and a heatsink.

I did the part as two 2-sided jobs with the stock and STL rotated 90 degrees between them, because of the extreme asymmetry of the part. Roughing was .250" ball-end, finishing was .125" ball-end and pencil finishing on the rib was .0625" flat-end mill. I edited the penciling toolpath to eliminate all but the rib itself, otherwise MC wanted to trace all the hard edges which the little mill wouldn't reach (and the rib had the only inside hard edges anyway). Material is aluminum, and I squared and measured the blank before running the MC jobs to assure I had the right size entered in the stock definition.

The socket at each end (the parallel parts) will only be 1/4" or so long, and I made them plenty longer to allow for trimming. I'm planning to try coating this with silicone caulk for my prototype, after rubbing the mold with somthing slippery as a mold release. It's something I've never tried before, but MeshCAM did its part of the process admirably. :)

Randy
Attachments
ductmold3.jpg
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ductmold2.jpg
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ductmold1.jpg
ductmold1.jpg (98.41 KiB) Viewed 7796 times
All opinions in this post are mine alone. I am not a MeshCAM employee, I do not have a financial interest in MeshCAM, nor do I speak for MeshCAM. MeshCAM user since Beta 5 in 2003. viewtopic.php?f=11&t=15333 :ugeek:
Randy
 
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Re: Dip molding mandrel prototype

Postby jeffD » Mon Feb 07, 2011 4:55 pm

Randy.

It should work. Maybe radius the corners. I have made pen parts using a mandrel and dipping into hard wax. Inside dimensions were critical but then I let MC play with the outside art. All machining done while still on the mandrel. First attempt worked really well, no repeats required. Novel experience :o

jeffD
I have no financial interests in MeshCam. Nothing I say here has had any approval from MC. Any errors or omissions are mine alone. Use at your own risk.
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Re: Dip molding mandrel prototype

Postby robgrz » Mon Feb 07, 2011 6:07 pm

I've never heard of dip molding before but it's a technique I'll have to keep in mind. Be sure to post the results

Glad to see you've got the mill back up and running.

-Robert
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Re: Dip molding mandrel prototype

Postby Randy » Tue Feb 08, 2011 6:22 pm

The first duct came out better than I could have hoped for. [EDIT]Actually a do-over after removing the silicone caulk stuck all over the mandrel--I'm ignoring that try... :o [/EDIT] Plasti Dip has nominally .008-.010" per dip, with a setting time of 30 minutes between dips. I dipped the mandrel 5 times, hoping for .050" thickness, but it came out a little thin. No problem pulling the duct off the mandrel, and no residue left behind. Total win! :D

Randy
ductmold4.jpg
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ductmold5.jpg
ductmold5.jpg (149.62 KiB) Viewed 7762 times

ductmold6.jpg
ductmold6.jpg (190.05 KiB) Viewed 7762 times

ductmold7.jpg
ductmold7.jpg (198.84 KiB) Viewed 7762 times
All opinions in this post are mine alone. I am not a MeshCAM employee, I do not have a financial interest in MeshCAM, nor do I speak for MeshCAM. MeshCAM user since Beta 5 in 2003. viewtopic.php?f=11&t=15333 :ugeek:
Randy
 
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Re: Dip molding mandrel prototype

Postby Randy » Fri Mar 11, 2011 1:59 am

This isn't MeshCAM related, but I have more experience to relate in case any of you try dip-molding with Plasti-Dip.

The material has an open-can life of about a week unless you wrap vinyl tape or similar around the edges of the lid to seal it after using. The supplied plastic lid will warp from the evaporating solvents and not seal tightly after a couple of days.

The completed dipped part should remain on the mandrel for about a day to let it firm up from the continuing solvent evaporation (the majority solvent "flash off" occurs in the first 30 minutes) but after 3 days the material is so tough that it is very hard to trim and pry off the mandrel if there is any kind of reverse draft to the mandrel. I would suggest not leaving on the mandrel over 48 hours.

Randy
All opinions in this post are mine alone. I am not a MeshCAM employee, I do not have a financial interest in MeshCAM, nor do I speak for MeshCAM. MeshCAM user since Beta 5 in 2003. viewtopic.php?f=11&t=15333 :ugeek:
Randy
 
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