Injection molding and automatic deflashing.

A cost saving system developed by Altman Manufacturing combines injection molding and automatic deflashing. The example described in this article shows how one operator can produce production parts (molding) and at the same time operate an automatic die trimming machine in a cell. The unique aspect of this application is that the injection molding press is producing a molded pad of parts. Molding in a pad with controlled flash will decrease handling time, part removal time, mold maintenance cost and part finishing costs. This system eliminates moving parts to a deflashing area, cryogenic deflashing and inspection for thermo cracks, mixed media and loss of part quality, all of which produce added cost. This method of molding and finishing will produce parts of the highest quality with the lowest possible cost. Using the numbers from this example, 120,000 parts would be produced per day on a 24-hour basis, yielding 25,000,000 parts per year, in only a 21-cavity die.

Mapelli Rubber Technology (a division of Rutil), Fort Wayne Mold and Engineering, Burke Rubber and Airman Manufacturing have the ability to supply the equipment to produce large volumes of parts using automated mechanical trimming of injection molded parts. A section drawing of the molding system used is shown in figure 1.

[FIGURE 1 OMITTED]

Note that the injection sprues shoot into the center of parts, producing a rectangular pad of 252 parts. Fort Wayne Mold and Engineering has determined that a mold of the same size could have been optimized for about 350 cavities. The molding time has been estimated to be less than 180 seconds. When looking at the heat, one can see a repeating pattern down the length of the heat of parts. The flash is a repeating pad of controlled thickness, which when trimmed will leave a minimum of material. The flash consists of interlocking rings. The mold has small triangular stops to help control mold closure, as well as to lessen scrap. The weight of the scrap from this system is less than 5-1/2 ounces per shot of 252 parts. This includes the runner, which is also removed. This molding technique allows the rubber to easily flow across the sheet and fills out the mold completely. This type of mold is a Fort Wayne Mold & Engineering design, and could be expanded to fit specific customer parts and production requirements. This system will produce literally millions of parts without stopping. Note that this mold could be much larger with more cavities if necessary for production.

The automatic finishing machine (figure 2) is an indexing trimming machine, capable of finishing a heat as large as 32" square. Altman's system combines a hydraulic trim press with a feeding system to finish molded parts through a male and female shear type trim die. The die can deflash as many rows as needed at one time to match production needs. If production levels required, two pads of this size could be run through the finishing system at the same time. The rubber is carried on a mylar sheet that is moved very accurately so that the spacing of the mylar sheet and that of the molded heat of parts match. The parts are lubricated with a soap and water solution prior to trimming. This allows the rubber to move slightly to prevent wear.

[FIGURE 2 OMITTED]

In this example, the system is punching a long row of 11 and a short row of 10 at a time. The sheet requires 12 hits to remove all 252 parts, which will be trimmed in less than 26 seconds while using less than 10 seconds of the operator's time. This system could have been made even faster by trimming multiple rows at a time. Altman Manufacturing designs the system to match customer production volumes needed. If a customer were to mold on three or four injection presses at a time and finish in one automatic finishing machine, the labor rate is cut by three or four to one.

In today's marketplace, the bottom line consists of cost, quality and time. Equipment can be supplied to produce the lowest cost product possible. The process utilizes quality tooling, quick molding of rubber and complete finishing at the molding press. The parts are never moved or finished with the addition of more labor.