Custom Rubber Molding Compression: Transfer: Injection
At Vip we utilize three main processes for custom rubber molding: compression, transfer and injection.
Each process is different and allows us more flexibility when choosing which process might be best for our customers. The goal is to create quality parts efficiently, while keeping costs down. Each mold project is closely evaluated to determine which process should be used.
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Rubber Compression Molding
Although compression molding is the oldest of the three processes, it is still highly valuable. Compression molding is really quite simple in theory, however it takes wisdom and experience to properly load the mold cavity without wasting any material. Our trained operators preform uncured material to the correct amount and weight. Preforming is preparing the rubber into smaller amounts so it is precisely what is needed for your part. This process helps eliminates any waste, which then reduces cost.
Basic Steps of Compression Molding
A. Vip operators calculate how much material is needed for each cavity, and preform the uncured rubber to this measurement
B. Rubber is placed into the mold cavity
C. The mold is closed over the material
D. The mold is placed under heat and pressure for a predetermined amount of time
E. When time has elapsed, the mold is opened and your part, fully cured, is removed, and the next part is ready to be made.
F. Any excess flash will be trimmed if necessary, by hand, or in the cryogenic deflasher
Advantages of Compression Molding
Molds are lower in cost
Less material waste due to careful preforming
Typically better for larger or less complex parts
Disadvantages of Compression Molding
Difficult to get consistent part repeatability (parts may differ slightly)
More flash than other processes
Slower production time
Rubber Injection Molding
Injection molding is the most complicated and sophisticated process of the three. Typically reserved for higher quantity needs, injection molding is a valuable resource and can be used for very small to quite large parts. The Vip team has over half a century of experience in the rubber industry and can guide you in choosing which method is best for your part.
Basic Steps of Injection Molding
A. Uncured rubber is placed into the machine using a screw feeder system. There is no need for preforming with this process.
B. The injection machine, via the screw feeder, will bring in the exact quantity of material needed for the mold. There is no guesswork with rubber injection, and therefore no material waste.
C. The rubber material moves into the barrel, where it is heated and becomes pliable, and is then pushed by a plunger into the runner system.
D. Material will fill the mold cavities and begin to cure. As soon as the curing process is complete, parts can be removed and the process can begin again.
Advantages of Injection Molding
Fast production and cycle times
No need for preforms (reduced labor, less material waste)
Good for complex parts
Less flash / Less post-production labor
Good part repeatability
Disadvantages of Injection Molding
Not suited for all compounds
Higher Tooling Costs
Rubber Transfer Molding
Transfer molding can be seen as a combination of compression and injection molding and is great for high-quantity needs. This process also allows for metal inserts and other custom options to meet specific needs. Vip is a custom manufacturer and creates new solutions daily for customers.
Process of Injection Molding
A. Uncured rubber is preformed by our team into the specific amount needed for your part
B. The preformed rubber is placed into a portion of the mold (not directly in the cavity)
C. The mold is closed and placed under pressure
D. The rubber is then pushed through a small opening (sprue) where it will fill the cavities
E. The mold remains closed, heated, and under pressure while the parts cure
F. When ready, the mold is released and parts are removed
G. The process is ready to begin again
H. Excess flash is trimmed by hand or parts are placed in the cryogenic deflasher
Advantages of Transfer Molding
Molds are lower in cost
Good for complex parts that require tight tolerances
Good part repeatability
Disadvantages of Transfer Molding
Increased need for mold maintenance
Molds can be complex, and therefore costly
Some material waste
Vip Mold Department Overview
EQUIPMENT: Press plates from 6"X 6" to 48" X 72", ability to mold as small as one gram to hundreds of pounds.
SPECIAL PROCESSES: Mold to metal, mold to plastic, mold to fabric, custom engraving, metal inserts, plastic inserts
SPECS: MIL-R, MIL-PRF, AMS, BMS1-57, BMS1-72,
A-A-59588, Aircraft, Automotive, Railcar, Military, Customer Generated Custom Compounds
CERTIFICATIONS: AS9100, ISO9000, ITAR, Boeing Approved
MOLDED SHEET: 12 X 12 : 24 X 24 : 36 X 36
RUBBER COMPOUNDS: Silicone, Fluorosilicone, EPDM, Natural Rubber/Polyisoprene, Neoprene/Chloroprene, Nitrile/NBR, HNBR, Fluorocarbon/FKM, SBR, Butyl, Custom Compounds
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