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The rotation moulder is a very interesting extension to the chocolate moulding project. It allows the pupils an insight into how many large plastic items are made. At Boxford we rotation mould the casing for the Duet machine, however many firms use the same technique for their products many garden play forts are made using this system and many exercise bikes have safety covers made using rotation moulding.
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The cutting order and the colours must following the following order and depths. All cutting is done with a 4mm cutter. First cut is set using the inside tag through or 12.4mm Second the magenta is cut to a depth of 6mm Third the red is cut using the outside tag to a depth of 12.4mm Once the pieces are machined the cradle can be hammered together with glue. The the axles or pins need to be made. The large rotating section needs a 5mm hole drilling across it's horizontal center and its vertical center. The smaller middle ring need two holes at the center of its long edge to allow the middle to rotate. The pulleys are made by gluing the two halves of the stepped circles together. Machine the axles as follows.
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Axle 1.
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Washer.
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Pin 2. Once the pins have been made the whole assemble can be finished. To pass the drive from the drive pins to the spinners the pins were drilled through in situ without going all the way through the wood. Small wood screws were then inserted to hold the pin in position and also transfer the drive. This may prove not to be a strong enough solution long term but as yet the system is holding out.
A handle was also machined for the crank.
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Once the mechanism is made then the moulds need to be manufactured. Using 3d Geocam the Dolphin STL file was made first in two halves from two pieces of model board.
Next machine a perimeter for the vacuum forming bay. The composition of the mould is a 6mm full size mdf board with a 6mm tray edge the edge is chamfered and cut to the size of the hole in the small hoop of the moulder. The angle is 60degrees from the 60degree router cutter. This angle is ideal for location and frees up perfectly from the moulded plastic.
60 Degree router cutter. |
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Two mould halves before vacuum forming. |
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The location of the master needs to be equal from the edge on both sides to make sure that the match up in the moulder. |
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Finished mould halves. Finally the two halves of the master are stuck together to ensure that the mould halves register correctly.
Place the master in the two halves.
The place neodymium magnets on both sides of the mould around the perimeter of the shape.
These are then glued into place so that as the mould are assembled they automatically snap into register. This could be achieved by other means if you don't wish to use magnets. When the unit was used it was found that the first half of the mould needs to be held in the machine securely before the second half is attached. The moulding material can then be poured in the fixed half before the second half is attached and the machine rotated.
To enable the holes to be drilled in the moulds a second middle was added to the plans with six holes drilled into it to be used as a drill template.
New upgraded design.
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Mould ready to spin.
Drawing Files and Lathe Profile Files - As a WinRAR File
Drawing Files and Lathe Profile Files - As a WinZIP File
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