When you need to injection mold complex plastic parts or assemblies, you must understand what SPI standards are. We will discuss a series of questions with you before production to better understand your project needs from multiple perspectives (design, purpose, and goals), which involves an important measure – the SPI standard.
So what is the SPI standard?
The American Society of Plastics Industry (SPI AN-102-78) divides molds into five categories. These five types of molds have different requirements and standards, and this mold classification is suitable for molds with injection molding machines of 400 tons or less. In addition to this, SPI specifies 12 finish grades, divided into four categories ranging from glossy to matt. Each level has different requirements for the perfect allowable deviation. The smaller the number, the smaller the deviation, and the larger the number, the larger the deviation.
5 Types of Die Standards
- SPI Class 101 Molds：(Rated for one million or more cycles) Mold design required. The mold base should be a minimum hardness of 280 BHN. Molding surfaces (cavities and cores) must be hardened to 48 RC. All other details, such as slides, heel blocks, gibs, wedge blocks, etc., should also be of hardened tool steels. Ejection should be guided. Slides must have worn plates—temperature control provisions to be in cavities cores and slides wherever possible. Over the life of the mold, corrosion in the cooling channels decreases cooling efficiency, thus degrading the part quality and increasing cycle time. Therefore, it is recommended that plates or inserts containing cooling channels be of corrosive resistant material or treated to prevent corrosion. Parting line locks are required on all molds.
- SPI Class 102 Molds：(Rated for no more than one million cycles) Molds design required. This mold is identical to type 101 with the following items not required: guided ejection hardened slide wear plates plated water channels and wear plated cavities. All other extras are optional. This tool is a medium to high production tool good for abrasive materials and close tolerance products.
- SPI Class 103 Molds：(Rated for under 500000 cycles) Mold design recommended. The mold base should be a minimum hardness of 165 BHN. Cores and cavities must be 280 BHN or higher. All other extras are optional.
- SPI Class 104 Molds：(Rated for under 100000 cycles) Mold design recommended. The mold base can be of mild steel or aluminum. Cores and cavities can be aluminum mild steel, or agreed-upon metal. All other extras are optional.
- SPI Class 105 Molds: (Rated for no more than 500 cycles) The mold base may be constructed from cast metal, epoxy, or any other material offering sufficient strength to produce the minimum prototype pieces. This tool is for prototype purposes only. All other extras are optional.
SPI Finish Grades:
Finish Type | Description | Roughness Averaging | standard |
A-1 | grade #3 diamond buff | 0-1 | for mirror or optical finishes |
A-2 | grade #6 diamond buff | 1-2 | most time consuming and costly finishes to achieve |
A-3 | grade #15 diamond buff | 2-3 | steel grade important to results (D-M-E No.3 or No.5 steel recommended) |
B-1 | 600 grit paper | 2-3 | removes all tools and machining marks |
B-2 | 400 grit paper | 4-5 | provides good mold release |
B-3 | 320 grit paper | 9-10 | light reflecting finish on molded part,some sheen |
C-1 | 600 stone | 10-12 | removes all tools and machining marks |
C-2 | 400 stone | 25-28 | provides good mold release |
C-3 | 320 stone | 38-42 | mute finish on molded part,no sheen |
D-1 | dry blast glass bead (8″ distance at 100psi;5 secs) | 10-12 | for decorative finishes |
D-2 | dry blast #240 oxide (5″ distance at 100psi;6 secs) | 26-32 | helps hide shrink marks and other imperfections |
D-3 | dry blast #24 oxide (6″ distance at 100psi;6 secs) | 190-230 | dull non-reflecting finish on molded or cast part |
Keyanng’s Injection Molding Services
We have extensive experience in custom injection molding, and our factory allows our services to maintain high quality and fast turnaround. For injection mold standards, keyanng usually produces long-life molds of class 101 and 102 to produce high-quality injection-molded parts. For more information, visit Injection Molding Services.
