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  MOLDS As the applications of plastics become more sophisticated, so must mold designs. When designing a mold for a difficult part there are resources available to the moldmaker and molder to confirm the best mold design. For these designs it is recommended that a computer aided flow and/or cooling analysis be performed. These programs may help determine the best mold design, saving time and cost of design rework. These classifications are for mold specifications only and in no way guarantee workmanship. It is very important that purchasers deal with vendors whose workmanship standards and reliability are well proven. Mold life, because of variations in part design and molding conditions, cannot be guaranteed. This guide will attempt to give approximate cycles for each type of mold (excluding wear caused by material abrasion, poor mold maintenance and improper technique). Maintenance is not the responsibility of the moldmaker. Normal maintenance, such as replacement of broken springs, broken ejector pins, worn rings or the rework of nicks and scratches should be borne by the molder. Mold rework costs should be closely considered when deciding which classification of mold is required. CLASSIFICATIONS OF INJECTION MOLDS UP TO 400 TONS. The following contains a brief synopsis of the various mold classifications and the detailed descriptions of each mold class. Class-1 Mold: *Cycles: One million or more   Description:  Built for extremely high production. This is the highest-priced mold and is made with only the highest quality materials. 1. Detailed mold design required. 2. Mold base to be minimum hardness of 280 BHN. 3. Molding surfaces (cavities and cores) must be hardened to a minimum of 48 R/C range. All other details, such as slides, heel blocks, Guide ways, wedge blocks, etc. should also be of hardened tool steels. 4. Ejection should be guided. 5. Slides must have wear plates. 6. Temperature control provisions to be in cavities, cores and slides wherever possible. 7. Over the life of a mold, corrosion in the cooling channels decreases cooling efficiency thus degrading part quality and increasing cycle time. It is therefore recommended that plates or inserts containing cooling channels be of a corrosive resistant material or treated to prevent corrosion. 8. Parting line locks are required on all molds.    Class-2 Mold: *Cycles: Not exceeding one million Description:  Medium to high production mold, good for abrasive materials and/or parts requiring close tolerances. This is a high quality, fairly high-priced mold.   1. Detailed mold design required. 2. Mold base to be minimum hardness of 280 BHN. 3. Molding surfaces should be hardened to a 48 R/C range. All other functional details should be made and heat treated. 4. Temperature control provisions to be directly in the cavities, cores, and slides wherever possible. 5. Parting line locks are recommended for all molds. 6. The following items may or may not be required depending on the ultimate production quantities anticipated. It is recommended that those items desired to be made a firm requirement for quoting purposes: a. Guided Ejection b. Slide Wear Plates c. Corrosive Resistant Temperature Control Channels d. Plated Cavities Class-3 Mold: *Cycles: Under 500,000 Description:  Medium production mold. This is a very popular mold for low to medium production needs. Most common price range.   1. Detailed mold design recommended. 2. Mold base must be minimum hardness of 165 BHN. 3. Cavity and cores must be 280 BHN or higher. 4. All other extras are optional. Class-4 Mold: *Cycles: Under 100,000 Description:  Low production mold. Used only for limited production preferably with nonabrasive materials. Low to moderate price range. 1. Mold design recommended. 2. Mold base can be of mild steel or aluminum. 3. Cavities can be of aluminum, mild steel or any other agreed upon metal. 4. All other extras are optional. Class-4 Mold: *Cycles: Not exceeding 500 Description:  Prototype only. This mold will be constructed in the least expensive manner possible to product a very limited quantity of prototype parts. May be constructed from cast material or epoxy or any other material offering sufficient strength to produce minimum prototype pieces.  
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