Download SPI Mold Standards
SPI Mold Classifcations (Standards)
SPI's book, "Classifications of Injection Molds for Thermoplastic Materials" was created over 30 years ago in the mid to late 1970's. The purpose was to level the playing field for both mold makers and those wishing to purchase molds for their specific production requirements.
Prior to the standards being written there were no guidlines that stipulated what was considered to be a "Class A" mold or any other class for that matter. As an example there were mold makers that would say they could build a "Class A" mold from aluminum while most would say it had to be made from hardened tool steel using the highest and best manufacturing techniques. This of course presented a problem for those gathering quotes as well as the competitive nature of the business.
Now that standards are in place for the construction of injection molds those looking to purchase tooling can get quotes based on the number of cycles they need the mold to last as well as what materials they will be made from. This enables an "apples to apples" vs "apples to oranges" approach to the quoting process.
These standards are to be used as guidelines but do not ensure you will get the "perfect" mold. They do not cover very real design issues that can and will effect part quality and or cost. For example every mold will require individual gating scenario's, balancing of runners and potential hot runner designs. For these you need to be sure that you are using the experienced mold makers and molders who will be your trusted advisers guiding your through the ideal scenario for you and your injection molding requirements.
For the condensed story of how the standards were created click here.
To get a copy of the SPI Mold Classifications you can download it at the top of the page.
You can also go SPI's (Society of Plastics Industry) website to attain the most recent revision.