|
Outside and inside views. To hold the top plate we use our smart nuts. These are nuts made from pvc that we machine to slide to position on the thread, and engage and lock by turning about 1 turn. They are much faster than wing nuts. One of the issues we've run into is clamping pressure. If there is too much pressure we find it closes the sprue holes and collapses the mold cavities. Our next incarnation will likely use an air piston to clamp the mold. That should be lots of fun to design. |
||
|
Creating the pattern Corel Draw was used to bring the design elements together. This shows the outline of Minnesota, a star, rope, lettering set around a circle and inside circle. The graphic on the right shows the finished piece. A black box is created around the design and all elements are turned white. The design is printed on transparency film to make the negative. It's printed on a 600 dpi laser printer. A base negative was also made to support the design. Register marks are added to align the front and back. |
||
|
A 95 shore-A durometer photopolymer pattern resin is poured right on the negative, the base negative is placed on top in register and a second glass plate completes the sandwich. There is a 1/16" self adhesive magnet on both pieces of glass. This makes the pattern 1/8" thick. Thicker to thinner patterns can be made by adding metal strips to the magnet or using clear plastic over the design to make it thinner. The resin turns from a liquid to a solid when exposed to ultraviolet light. This homemade light setup has two 20 watt F20T12BL fluorescent bulbs. A 1 1/2 minute exposure is made through the base and 2 1/4 minute exposure through the negative. The longer the base exposure the thicker the base becomes. If there is no base exposure, a pierced design is made. |
||
