Rubber Molds

Yigal Sharabi

<div class="jnlc-container" id="jnlc-container"> <img src="http://static1.shopify.com/s/files/1/0014/5692/files/RubberMolds.jpg" width="360" height="200" class="floatLeft" /> Rubber Molds Rubber Molds are used for the purpose of reproducing a number of pieces from a single original model. Rubber is the ideal material. The specially formulated rubber used in mold-making is able to hold an impression of even the most delicate detail work. It is pliable, so that wax reproductions may easily be pulled from it. It is able to withstand the heat of the molten wax; and it is long lasting, so that many reproductions are possible from a single rubber mold. The rubber comes in strips, sheets, or rolls, and is individually cut to the correct size. Rubber is available in a variety of grades and in a sizable range of qualities. The shrinkage factor is dependent upon the grade and quality of the rubber and this is a crucial property to consider in mold-making. The denser the rubber, the less it will contract after vulcanizing. It is important to be educated about your materials because discretion and economics equal your profits. First the piece must be appraised by the mold-maker, not only for the quality of the rubber it demands, but also for the approach he will eventually take to cut it from the vulcanized mold. Then, the selected piece of rubber is cut to fit into an aluminum or zinc-magnesium frame. Next, it's packed down in layers until somewhat more than half the frame is completely filled with the rubber. The model, to which a spruce that looks like a golf tee has been soldered, is placed in the frame on top of the rubber. The end of the spruce should be touching the inner wall of the frame. More sheets of rubber are then packed down tightly on top of the model, sandwiching it entirely, until an equal number of rubber sheets have been placed on top and bottom of the model. The rubber, which rises one or two layers higher than the level of the frame, is ready to be vulcanized. A vulcanize is an electrically controlled device which resembles a cross between an etching press and something from the Spanish Inquisition. The aluminum frame containing the rubber-packed model is placed between two aluminum plates (rubber, like wax, does not stick to aluminum), so that the top plate just barely comes into contact with the topmost layer of rubber. The machine is turned on and the plates begin to heat up, melting the rubber at around 300oF. As the rubber begins to flow, a crank is turned to bring the two plates closer together. This causes the now-viscous rubber to become compressed completely around the model. It flows into all empty spaces and air pockets within the frame. This operation is repeated until the two aluminum plates come into complete contact with the aluminum frame and the rubber is compressed as much as possible between the plates. The mold is now done. After it has cooled, the now solid block of rubber containing the silver model within it, is popped out of its frame. It's then passed on to the person who slices open the rubber, liberates the model and creates a mold from which thousands of pieces of jewelry may be cast. Mold cutting is rubber-mold cutting and it’s quite simple. The rubber-mold cutter, after having appraised his piece, hooks the vulcanized block of rubber to the side of his bench -- usually with an ordinary beer can opener or bent nail -- and makes a few tentative cuts around the edges with a surgically sharp knife. He must free the model in such a way that the rubber falls into two halves that can be fitted together again easily and exactly. Once this has been accomplished, he can turn his attention to the primary work of cutting the model out of the rubber. The model is completely embedded inside the mold; there is no way of being absolutely certain just exactly where it is. The best that the mold-cutter can do is rely on memory and bend the mold open as far as it can go, stretching the rubber so that eventually the contours of the model start to show. Once the form of the model becomes discernible through the rubber, the mold-cutter may select the placement of the final cuts. However, unlike casting and vulcanizing, where a successful product is more or less guaranteed if you are careful, a good rubber mold depends upon the individual skill and experience of the mold-cutter. Anyone can slash the rubber mold into two pieces and free the model; only a true professional can do the job so that no difficulties arise later, either in casting or in finishing. <a href="/pages/manufacturing"><img src='http://static1.shopify.com/s/files/1/0014/5692/files/Back1.png' alt='' /></a> </div>

2008-07-17T13:16:18-04:00

rubber-molds 351392

2008-07-17T13:16:18-04:00

145692

Rubber Molds 2008-11-04T12:39:06-05:00 <notextile> <div class="jnlc-container" id="jnlc-container"> <img src="http://static1.shopify.com/s/files/1/0014/5692/files/RubberMolds.jpg" width="360" height="200" class="floatLeft" /> Rubber Molds Rubber Molds are used for the purpose of reproducing a number of pieces from a single original model. Rubber is the ideal material. The specially formulated rubber used in mold-making is able to hold an impression of even the most delicate detail work. It is pliable, so that wax reproductions may easily be pulled from it. It is able to withstand the heat of the molten wax; and it is long lasting, so that many reproductions are possible from a single rubber mold. The rubber comes in strips, sheets, or rolls, and is individually cut to the correct size. Rubber is available in a variety of grades and in a sizable range of qualities. The shrinkage factor is dependent upon the grade and quality of the rubber and this is a crucial property to consider in mold-making. The denser the rubber, the less it will contract after vulcanizing. It is important to be educated about your materials because discretion and economics equal your profits. First the piece must be appraised by the mold-maker, not only for the quality of the rubber it demands, but also for the approach he will eventually take to cut it from the vulcanized mold. Then, the selected piece of rubber is cut to fit into an aluminum or zinc-magnesium frame. Next, it's packed down in layers until somewhat more than half the frame is completely filled with the rubber. The model, to which a spruce that looks like a golf tee has been soldered, is placed in the frame on top of the rubber. The end of the spruce should be touching the inner wall of the frame. More sheets of rubber are then packed down tightly on top of the model, sandwiching it entirely, until an equal number of rubber sheets have been placed on top and bottom of the model. The rubber, which rises one or two layers higher than the level of the frame, is ready to be vulcanized. A vulcanize is an electrically controlled device which resembles a cross between an etching press and something from the Spanish Inquisition. The aluminum frame containing the rubber-packed model is placed between two aluminum plates (rubber, like wax, does not stick to aluminum), so that the top plate just barely comes into contact with the topmost layer of rubber. The machine is turned on and the plates begin to heat up, melting the rubber at around 300oF. As the rubber begins to flow, a crank is turned to bring the two plates closer together. This causes the now-viscous rubber to become compressed completely around the model. It flows into all empty spaces and air pockets within the frame. This operation is repeated until the two aluminum plates come into complete contact with the aluminum frame and the rubber is compressed as much as possible between the plates. The mold is now done. After it has cooled, the now solid block of rubber containing the silver model within it, is popped out of its frame. It's then passed on to the person who slices open the rubber, liberates the model and creates a mold from which thousands of pieces of jewelry may be cast. Mold cutting is rubber-mold cutting and it’s quite simple. The rubber-mold cutter, after having appraised his piece, hooks the vulcanized block of rubber to the side of his bench -- usually with an ordinary beer can opener or bent nail -- and makes a few tentative cuts around the edges with a surgically sharp knife. He must free the model in such a way that the rubber falls into two halves that can be fitted together again easily and exactly. Once this has been accomplished, he can turn his attention to the primary work of cutting the model out of the rubber. The model is completely embedded inside the mold; there is no way of being absolutely certain just exactly where it is. The best that the mold-cutter can do is rely on memory and bend the mold open as far as it can go, stretching the rubber so that eventually the contours of the model start to show. Once the form of the model becomes discernible through the rubber, the mold-cutter may select the placement of the final cuts. However, unlike casting and vulcanizing, where a successful product is more or less guaranteed if you are careful, a good rubber mold depends upon the individual skill and experience of the mold-cutter. Anyone can slash the rubber mold into two pieces and free the model; only a true professional can do the job so that no difficulties arise later, either in casting or in finishing. <a href="/pages/manufacturing"><img src='http://static1.shopify.com/s/files/1/0014/5692/files/Back1.png' alt='' /></a> </div> </notextile>