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Rotational Casting machine home build

 
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clonesix
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Joined: 19 Jan 2007
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Location: california

PostPosted: Fri Feb 05, 2010 7:48 pm    Post subject: Rotational Casting machine home build Reply with quote

This has been on my mind for some time and I had previously believed it to be cost prohibitive due to the face that I don't own any of the required equipment. Upon dicovering that I can rent a metal chop saw and MIG weld for a very reasonable daily rate, this plan was in motion. I have gone on to locate a sheet metal shope capable of punching square holes for a cariage bolt, and a round hole for a 1/2" to pass through.

I am happy to announce that I have drawn this up and written up a cutting list for my 2X 2 rotocaster. My design allows for the machine to be mounted on casters for mobility, and disassembles for transport.

Thus far, I have just drawn this up. I have yet to order the list of parts I will need. I summed up all the bearings and gears and pulleys for under $200.

I just thought I would post it here. Pics to follow.
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stormtrooperguy
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PostPosted: Fri Feb 05, 2010 8:14 pm    Post subject: Reply with quote

Sweet! I have dreams of having a rotocasting machine some day!
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clonesix
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PostPosted: Sun Feb 07, 2010 5:16 pm    Post subject: Reply with quote

So far, I have been drawing this up and selecting parts from a catalog. I may have to alter my design if I can't figure out how to keep th etiming pulley stationary while the shaft running through it, turns.

Does that make sense? IN this model, http://www.youtube.com/watch?v=ArnzK6d6ugk you can see that the motor is turning the frame, but the sprocket on the shaft remains stationary. If it turned with the frame, the inner frame wouldn't turn.
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jdougn
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PostPosted: Mon Feb 08, 2010 8:22 am    Post subject: Reply with quote

clonesix wrote:
So far, I have been drawing this up and selecting parts from a catalog. I may have to alter my design if I can't figure out how to keep th etiming pulley stationary while the shaft running through it, turns.

Does that make sense? IN this model, http://www.youtube.com/watch?v=ArnzK6d6ugk you can see that the motor is turning the frame, but the sprocket on the shaft remains stationary. If it turned with the frame, the inner frame wouldn't turn.


What you're saying about the stationary pulley makes sense. My first thought would be that the stationary pulley has a larger shaft diameter than the drive shaft to the frame. The drive shaft passes through the stationary pulley without touching. It shouldn't be too hard to mount the stationary pulley to a metal plate or something fixed to the base frame. It's interesting that they used a gear reduction motor to get the low RPMs for the project instead of step pulleys.
DougN
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clonesix
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PostPosted: Mon Feb 08, 2010 9:27 pm    Post subject: Reply with quote

I fielded this question to several people thanks to the internet, and the answer came back universally to let the drive shaft pass through the timing pulley, and run a screw though the pulley, into the upright.

Yeah, that works for me. So I ordered all the parts and will make a stop off at the surplus yard for some steel. This project will soon get off the drawing board.

I don't know much about motors (or electricity, for that matter) and planned to hook up a dimmer switch to the drive motor to adjust the speed. Any dangers in that I should know about?

I know that I want the frame to rotate 1 - 2X/min.

I hadn't planned anything more than fishing through the motors at the surplus store, and grabbing 1/4hp out of the bin. Any advice?

Stay tuned for pictures.


Last edited by clonesix on Mon Feb 08, 2010 9:32 pm; edited 1 time in total
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stormtrooperguy
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PostPosted: Mon Feb 08, 2010 9:29 pm    Post subject: Reply with quote

clonesix wrote:

I don't know much about motors (or electricity, for that matter) and planned to hook up a dimmer switch to the drive motor to adjust the speed. Any dangers in that I should know about?


off hand, just make sure the dimmer is rated for the right amperage... don't use a 15 amp dimmer on a 20 amp circuit for example.
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Culvan
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PostPosted: Wed Feb 10, 2010 4:08 am    Post subject: Reply with quote

clonesix wrote:
I don't know much about motors (or electricity, for that matter) and planned to hook up a dimmer switch to the drive motor to adjust the speed. Any dangers in that I should know about?


It's been a long time since I studied AC motors. I believe it depends on the style of motor. I know it will work on some of them, and not others. I bought something to adjust motor speed from Harbor Freight recently. http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=43060

I suspect the motor in the video is geared down to run that slowly. Cordless drills have a gearbox to reduce speed and increase torque. I don't know how much strength you need, but a cordless drill could be one method of driving it. Cordless dril motors are DC so you would need to work out a power supply for that. An old PC power supply can be converted to do that (instructions are available through a google search.) If you chose to use a different motor, then the gearbox could be useful for slowing it down. For reference, Dewalt has a 3 speed drill with gear reductions of 47:1, 15:1 and 12:1.

Someone put together instructions to connect a different motor to the dewalt transmission. It's for a robotics competition, but it can give you a good idea of what's inside a cordless drill gearbox. http://www.chiefdelphi.com/media/papers/download/1589

Hope this helps.

Andy
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jdougn
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PostPosted: Wed Feb 10, 2010 8:25 am    Post subject: Reply with quote

clonesix wrote:
..... I don't know much about motors (or electricity, for that matter) and planned to hook up a dimmer switch to the drive motor to adjust the speed. Any dangers in that I should know about?
...
I hadn't planned anything more than fishing through the motors at the surplus store, and grabbing 1/4hp out of the bin. Any advice? ...


Yeah, I'm pretty sure Clonesix is correct when he says a dimmer switch will burn up most electric motors. A $20 variable speed router controller from Harbor Freight might work.
(http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=43060)
Although I'm not sure if it is designed for regular electric motors. The HF tech line might help.

Since you're salvaging anyhow, an old sewing machine motor might work since they are designed to be run variable speed. If all else fails just put a real little pulley on the motor and step up to a great big pulley on the rotational caster.

Clonesix had great ideas for using a cordless drill transmission that would be worth looking into.

hth, DougN
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clonesix
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PostPosted: Sat Feb 13, 2010 12:19 pm    Post subject: Reply with quote

Sad to report that the first attempt at welding was unsuccessful. I don't think the rented welder is powerful enough to weld the 16 gage steel that I got from the surplus yard. Its a Millermatic 135 115V MIG with flux core wire. So far, no good.

I am happy to report that the $65 chop saw from Harbor Freight, works fine. so I have pieces cut to size, but not drilled or welded.
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jdougn
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PostPosted: Sat Feb 13, 2010 7:54 pm    Post subject: Reply with quote

clonesix wrote:
Sad to report that the first attempt at welding was unsuccessful. I don't think the rented welder is powerful enough to weld the 16 gage steel that I got from the surplus yard. Its a Millermatic 135 115V MIG with flux core wire. So far, no good.

I am happy to report that the $65 chop saw from Harbor Freight, works fine. so I have pieces cut to size, but not drilled or welded.


What is the 16 gauge steel being used for? Most guys would usually use self-tapping zip screws for light gauge steel.

Here's a few 115v welder tips:
- It is assumed that necessary safety precautions are being taken to prevent blinded eyes, burned flesh, or catching something important on fire.
- Plug the welder in as close as you can possibly get to the breaker box. No extension cord unless it's as short as possible and at least 12 or 10 gauge.
- Get a bare metal to bare metal ground by roughing up the ground clamp with a file and the metal with a grinder.
- Grind clean and bevel both edges to be welded. NO rust or steel thats not been ground clean, including oily film or painted surfaces.
- Make sure the wire is the correct stuff. It should say on the spool.
- Crank the amperage way up on the welder or until it starts blowing through your steel then back it off a little.
- Lower the wire feed speed until the spark is maintained and the wire doesn't "bump" the steel you're welding after the initial spark.
- Use same thickness scrap to work all this out and get the hang of it before you start welding on the good stuff.
hth, DougN
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clonesix
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PostPosted: Sun Feb 14, 2010 5:30 pm    Post subject: Reply with quote

That was the problem jdougn: trying to weld dirty metal. I thought the flux core wire was enough. I put the $15 grinder to work and prepared the surface properly. The welding went better from there. WHile these are far from perfect, they are strong, and the rental of the welder was a good idea. I will now go buy the same model at Harbor Freight.


[img[/img]


Last edited by clonesix on Fri Mar 19, 2010 10:53 am; edited 1 time in total
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clonesix
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PostPosted: Fri Feb 19, 2010 9:23 pm    Post subject: Reply with quote

Add one more frame and I am moving right along. I still have some more work to do drilling holes and mounting bearings.

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clonesix
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PostPosted: Fri Mar 19, 2010 11:24 am    Post subject: Reply with quote

Test run done.
As you can see, it is held together with clamps. I must drill bolt holes before this is finished, and I have more work to do.

I also made a new mold of my helmet model. I made the mold to fit into this system. so far, it fits nicely and works well.









So I am off to weld and drill and add bolts. I hope to have it done by next week.
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