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Choosing a Finish When designing a part for injection molding, it is important to keep in mind the relationships between surface finish, moldability, cost and lead time.
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Table 1 contains the list of standard surface finishes available through Protomold's rapid injection molding rvice, listed in order from lowest to highest cost. Figure 1: List of available standard finishes
Higher
Cost
PM-F0:
程滨PM-F1:
Non-cosmetic —finish to Protomold discretion Low-cosmetic —most toolmarks removed SPI-C1:
SPI-B1:
600 grit stone, 10-12 Ra 600 grit paper , 2-3 Ra PM-T1:
PM-T2:
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Protomold texture, SPI-C1 followed by light bead blast Protomold texture, SPI-C1 followed by medium bead blast SPI-A2:
Grade #2 Diamond Buff, 1-2 Ra
"PM" in the table signifies a surface finish adjusted to fit the rapid injection molding process, where SPI (The Society of the Plastics Industry) denotes an industry-standard finish. The photographs shown in Figure 1 illustrate the difference in cosmetic appearance for a few of the options on some example parts.投保英文
Figure 1: Surface finish examples
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If the part will not be visible to the end ur, you will probably choo to specify either PM-F0 or PM-F1 using the
drop-down menus on your ProtoQuote (e sample). But many times your design will require a more cosmetic surface finish. In the cas there are two key things to keep in mind:
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• Polishing: Smoother part surfaces are achieved using manual mold polishing techniques. Consider a part
the bestwith tall, thin and curved ribs which need to have an SPI-A2 finish. In this ca you should expect a significant cost increa becau it is very time consuming to polish deep, narrow slots in molds. And such lengthy polishing times may also affect the lead time for your parts, potentially making it impossible for Protomold to accept your order for our famous 5-day turn.
•Texturing: Given the line-of-sight nature of bead blasting, it may not be possible to texture the sides of minimally drafted ribs on a part becau the mold surfaces may be inaccessible. In addition, if the walls of your part are textured it may have an adver effect on the ability of the part to relea from the mold, potentially resulting in unsightly "drag marks". For the reasons we recommend that texture be specified only on areas of the part that are drafted at least 2-3 degrees. And in fact, if your
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part does not have sufficient draft your ProtoQuote may not even offer the textures as options for you to lect (contact your Customer Service reprentative if this ever becomes an issue).
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