Precision molding is the latest technology in the world of plastic injection molding. Precision molding is a type of plastics molding that is the most expensive and sophisticated process of mold design in the market.
Selecting Precision machines
Precision moluding machines should preferably be high pressure. This helps improve the quality and the overall precision of the plastic parts.
An injection pressure of around 392 MPa reduces the shrinkage factor to zero. Additionally, the mechanical strength of the part increases significantly when the injection pressure is kept around 392MPa.
Further, the efficiency of the injection rate improves when maximum injection pressure is increased.
Following are the main structural features of precision moulding machines:
Additionally, precision moulding machines should be able to manage the repeatability and accuracy of a product.
Selecting the areas within a mold that require precision
Precision molding is way more sophisticated and expensive than conventional plastics molding. This is the reason why it is important to understand the different aspects of your custom plastic parts and determine the ones requiring high tolerances.
It is also important to understand whether those tolerances can be managed through conventional injection moulding techniques. A plastic part may be created using both- conventional plastic injection molding process as well as precision moulding. An electronic part, may, for example, require precision works only for a small section of the piece and not the entire part.
Hence, understanding and determining the precision requirements will ensure a cost-effective solution that will meet your needs. Additionally, it will also help ensure that your parts are prepared with high quality and meet the production deadlines.
Selecting the right plastic material
Selecting the right plastic resins is an important factor for creating the right precision mould parts. The selection of material is one of the biggest determining factors in determining whether the plastic molded products will come out as desired.
Within the plastic material, shrinkage range is one of the most important criteria for creating parts with high precision. Narrow shrinkage ranges offer better chances of reaching tight tolerances.
Again, the requirement of shrinkage depends on the product being created. While a wider range of shrinkage is not preferable since it makes it hard to hit the right tolerance levels, it can still be used to create products that do not need to be of an exact size.
Polypropylene has a wider shrinkage range of +/- .014″ to +/- .022″. Acrylonitrile butadiene styrene (ABS) on the other hand has a narrower range but is still not in the category that fits the need for precision molding.
Polypropylene has a wider shrinkage range of +/- .014″ to +/- .022″. Acrylonitrile butadiene styrene (ABS) on the other hand has a narrower range but is still not in the category that fits the need for precision molding.
Usually, the shrinkage ranges required for molding a precision part is around +/- .001″ or +/- .002″
Choosing a plastic resin that offers low shrinkage is hence an easy way to get your materials right for precision moulding.
However, this may not always be a cost-effective option due to the high cost of the desired resins.
Various molders hence prefer to reach the high tolerance level by adding filler materials to the plastic resins. These include glass fibers, mica and other filler materials. The addition of fillers narrows down the shrinkage range and hence provides a better structure to the parts.