Roto casting machine MacGyver style

E

erikv

Well-Known Member
[video]https://photos.google.com/share/AF1QipNm7OUbUha-HnTO96m_JTspV1AL7JdEc8xNwqNrjazz3cjF_Yypbd6gX-KhiPDdkw/photo/AF1QipOnBFlck30PyRV31lJuJfcKuKrqx5fmw5YuU-d-?key=MG5QZUxBM191RjF4VTIxbXg0UHlzbklDang3Z2Vn[/video]

got a bit tired of turning molds by hand so I MacGuyver'd this together.
I used 25mm aluminium angle bolted together, a few 8mm bearings, a couple of electric motors, a PC power supply and some chewing gum. To any real engineers out there I apologise but it works :)
 
I kinda just winged it so no plans as such.
The motors were a bit hard to figure just how powerful to get.
The first ones I got were under powered for the main frame so I upgraded, it is an electric window shutter motor. I used the smaller motors for the inner frame. I was going to run both the smaller ones on the inner frame but 1 turned out to be enough. I had to put the other one on for balance though.
The electric slip ring allows you to put power to the inner frame and saves messing about with pulleys and belts.
I put a potentiometer on each motor so the speed can be varied.
The power supply I had initially was also under powered so I re-purposed a PC PSU, i's a bit of a Frankenstein's monster but it saves my arms :)
20170815_200301.jpg
It worked a treat on my Deathclaw mold
If you need any help just let me know and I'll be happy to assist
 
Some of the parts used

Metal Gear Worm Gear DC Motor High Torque 12V DC 25RPM
12.5mm 300Rpm 6 Wires CIRCUITSx2A Capsule Slip Ring AC 240V
Stainless Steel Capillary Round Tube Bar OD 8mm x 6mm ID Length 250mm
Flexible Motor Shaft Coupling Stepper Motor Coupler Winding Connector
6V-28V DC 3A PWM Motor Speed Regulator Switch Controller Pulse Width Modulator
8mm to 35mm Zinc Alloy Flanged Pillow Block Self Aligning Ball Bearings
Worm Gear Motor http://www.motionco.co.uk/index.php?route=product/product&product_id=839
25mm Aluminium angle
 
Last edited by a moderator:
KeLorean said:
forgive my ignorance but why are you turning your molds?


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Rotocasting allows the use of less resin to be used on a cast but also allows you create a hollow object such as a face mask, vase, cups, bowls, domes, etc. Things that shouldn't be cast as a full object.

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PropReplicator2 said:
Rotocasting allows the use of less resin to be used on a cast but also allows you create a hollow object such as a face mask, vase, cups, bowls, domes, etc. Things that shouldn't be cast as a full object.

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thats amazing! just when i felt proud that i can cast bubble free clear urethane, now i feel like an amateur again. thanks for the info.


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KeLorean said:
thats amazing! just when i felt proud that i can cast bubble free clear urethane, now i feel like an amateur again. thanks for the info.


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Yessir! BTW, if you can cast bubble free urethane you can do anything;). I still have trouble with the pressure casting just cause of the wait time... Happy to help:)


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KeLorean said:
thats amazing! just when i felt proud that i can cast bubble free clear urethane, now i feel like an amateur again. thanks for the info.


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Which clear urethane do you use?

I want to roto cast a clear piece, but every resin I've looked at either has a prohibitively long pot life or is really nasty stuff.
 
smoothcast 326 from smooth-on. it has a 10min pot life and 1hr cure time. they have faster kicking ones BUT i like to work with my resin and im working in a hot garage so that speeds up my pot life some


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Zinger said:
Which clear urethane do you use?

I want to roto cast a clear piece, but every resin I've looked at either has a prohibitively long pot life or is really nasty stuff.
Click to expand...

actually, now that i think about it that isnt even the stuff they advertise as the crystal clear. i just use it bc it accepts color really nicely and usually after i make a mold i cast it clear just to see how the intricacies of my mold hold up. call smooth on or reynolds advanced materials, who have been a big help in my explanation of resin. they'll tell u the best urethane for clear casting and all of the ins and outs


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KeLorean said:
actually, now that i think about it that isnt even the stuff they advertise as the crystal clear. i just use it bc it accepts color really nicely and usually after i make a mold i cast it clear just to see how the intricacies of my mold hold up. call smooth on or reynolds advanced materials, who have been a big help in my explanation of resin. they'll tell u the best urethane for clear casting and all of the ins and outs


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I've been using 325 with about 1 drop of So-Strong white. 325 is translucent, so it gives me a milky white I'm fairly happy with.

But 325 is only semi-rigid. I'd like to try a clear resin that is also truly rigid.

Of the resins I've investigated, Crystal-Clear is nasty. It's a cat 2 or 3 hazard for inhalation, organ toxicity and aquatic life. EpoxAcast 690 is about as dangerous as house paint, but it has a 5 hour pot life. In tests I've done, I've had to rotate the mold for several hours after the pot life expired to keep it from slumping in the mold. That's not practical.

I might try letting the EpoxAcast 690 sit for 5 hours before putting it in the mold and rotocasting. By then, it's well gelled and might only need another hour or so of rotation.
 
erikv said:
I kinda just winged it so no plans as such.
The motors were a bit hard to figure just how powerful to get.
The first ones I got were under powered for the main frame so I upgraded, it is an electric window shutter motor. I used the smaller motors for the inner frame. I was going to run both the smaller ones on the inner frame but 1 turned out to be enough. I had to put the other one on for balance though.
The electric slip ring allows you to put power to the inner frame and saves messing about with pulleys and belts.
I put a potentiometer on each motor so the speed can be varied.
The power supply I had initially was also under powered so I re-purposed a PC PSU, i's a bit of a Frankenstein's monster but it saves my arms :)
View attachment 752178
It worked a treat on my Deathclaw mold
If you need any help just let me know and I'll be happy to assist
Click to expand...

Nice work. How big a mold can it hold?

I made mine based on plans from Make magazine. I had to scale it up to fit my molds.

https://makezine.com/projects/make-41-tinkering-toys/diy-rotocaster/

It works but it's finicky. It tends to tighten up during long spins causing the motor to stall.

I might try ditching the gear train and using your slip ring/two motor set up.
 
Zinger said:
I've been using 325 with about 1 drop of So-Strong white. 325 is translucent, so it gives me a milky white I'm fairly happy with.

But 325 is only semi-rigid. I'd like to try a clear resin that is also truly rigid.

Of the resins I've investigated, Crystal-Clear is nasty. It's a cat 2 or 3 hazard for inhalation, organ toxicity and aquatic life. EpoxAcast 690 is about as dangerous as house paint, but it has a 5 hour pot life. In tests I've done, I've had to rotate the mold for several hours after the pot life expired to keep it from slumping in the mold. That's not practical.

I might try letting the EpoxAcast 690 sit for 5 hours before putting it in the mold and rotocasting. By then, it's well gelled and might only need another hour or so of rotation.
Click to expand...

well, i havent experimented with much besides smooth cast 326, BUT the way i understand it is urethane resin is soft in general, so epoxy does sound like it's your best bet. have u looked into polyester or gelcoats? although im pretty sure those can get pretty noxious also.


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