How to Frame a Roto Mold
Rotational molding uses Microthene polyolefin powders, a plastics resin, to make hollow products of any shape or size. The frame allows the roto mold to rotate in a biaxial motion, while the resin is being heated. Making a frame for a roto mold requires fabrication and mechanical skills. You must make a frame capable of rotating in two directions at the same time. The size of the frame will depend on the size of the roto mold you are using.
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Things You'll Need
- 4 pieces of 24-inch steel box tubing (2-by-2 inches)
- 4 pieces of 30-inch steel box tubing (2-by-2 inches)
- 2 pieces of 40-inch steel box tubing (4-by-4 inches)
- 1/4-inch steel plate (36-by-36 inches)
- 1/4-inch steel plate (12-by-12 inches)
- 8 bushings
- Steel rod (1-inch diameter, 36-inches long)
- 2 gears
- Bolts
- Nuts (1-inch)
- Washers (1-inch)
- Drill press
- Hand drill
- Steel drill bits
- Tapping set (tools that thread rods)
- Wrench set
- Ratchet and socket set
- Tape measure
- Hacksaw
- Welder
- Welding rods
- 2-horsepower AC motor
Instructions
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1
Drill one hole in the center of two of the 24-inch steel box tubings large enough to fit bushings. Drill one holes in the center of three pieces of the 30-inch steel box tubing large enough to fit a bushing. Drill one hole in the center of one piece of the 30-inch steel box tubing large enough for the 1-inch steel rod. Drill one hole on the end of each 40-inch steel box tubing large enough to fit the bushings. Make these holes 4 inches from the end of the 36-inch steel box tubing.
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2
Weld the four pieces of 24-inch steel box tubing in a square shape, with the two pieces with center holes on opposite sides or parallel to each other. Weld the four pieces of 30-inch steel box tubing in a square shape, with the two pieces on opposite sides of each other.
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3
Mark a center measurement on either side of the 36-by-36-inch steel plate on opposite sides. Set one piece of the 4-by-4-inch steel box tubing on the center mark and vertically on the steel plate, with the outside of the box even with the edge of the plate. Weld the box in place. Repeat these steps and attach the other 4-by-4-inch box tubing on the other side, opposite of the first box tubing. Weld the end of the box tubing to the plate that does not have the drilled holes.
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4
Insert the bushings into each drilled hole. Cut the three pieces of the steel rod 8 inches long with the hack saw. Thread each end of these three pieces of steel rod. The rod must have approximately 2 inches of threads on each end. Thread the remaining 12 inches of steel rod on one end; the rod must have 4 inches of threads on that one end.
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5
Set the 24-inch steel box tubing inside the 30-inch box tubing. Align the bushings and slide a steel rod through each bushing. Tighten the nuts on each end of the steel rods, connecting the two frames. Turn the 24-inch box so it clears the inside of the 30-inch box tubing. Adjust if necessary so the smaller frame is evenly centered inside the larger frame.
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6
Attach both frames to the 4-by-4-inch box tubing stand. Place a nut on either side of the 30-inch box tubing that has the 1-inch hole drilled. Put a nut on the 12-inch rod and finger-tighten it all the way down to the end of the threads. Slide the 12-inch rod into the 1-inch hole of the 30-inch tubing. Put another nut on the end of the 12-inch rod and tighten down both nuts against the 30-inch tubing. The 30-inch tubing must not rotate on the rod.
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7
Install a gear on the outside end of the 12-inch rod. Press the other gear on the end of the drive shaft of the AC motor. Lift the motor up and match the gears. Mark a spot on the vertical 4-by-4-inch box tubing and weld the 12-by-12-inch steel plate on that mark, making a motor mount. Set the motor in place, aligning it with the gear on the end of the 12-inch rod. Drill motor mounting holes in the steel plate and insert mounting bolts. Tighten the motor in place.
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Tips & Warnings
Rotate the roto mold frame so the larger frame turns and the smaller frame turns inside the larger frame.
Lubricate the bushings with gear oil to prevent premature wear.
The roto mold can be connected to the smaller frame with C-clamps or other attachment devices.
Build a larger frame for a larger roto mold and use motor that has more horsepower to turn a larger roto mold.
Do not overload the frame with a roto mold that is too big for this assembly.
References
- Photo Credit Hemera Technologies/PhotoObjects.net/Getty Images
