Granted, machining powder metal parts presents challenges. Some manufacturers use this as an excuse to use more wasteful manufacturing methods such as copper infiltration or resin infusion. In fact, these limitations can be overcome with a thorough understanding of powder metal materials and the forming process.
Net shape minimizes the need to machine powdered metal
When manufacturing powdered metal parts, your supplier drops precise amounts of powder into a mold or cavity. The powder is then compacted with a punch, ensuring that every strand of the mold is filled. After release, the compressed part enters the furnace for sintering. This fuses the powder particles to form a hard-finished or semi-finished part.
Compared with traditional processes, net shaping has at least four advantages, but it also has limitations. The axial compression imparted by the punch moving into the die means that certain features cannot be formed. Either the powder will not migrate into the mold, or if it does, the subsequent release of the part becomes difficult or impossible. These features include: cross holes (these can be formed with some newer compactors, but in general this is usually true), undercuts, threads, and reverse taper.
Harder materials are more difficult to machine (i.e. stainless steel vs. aluminum, etc.), but powdered metals present their own challenges. The overall hardness may not appear particularly high, but don't underestimate the wear effect of porosity within the part. Low levels of porosity are inherent (and often desirable) in powdered metal parts, however, this can result in microscopic intermittent cuts that can lead to chatter, reducing cut and machine tool life.
In summary, when machining powdered metal parts, cutting forces are generally higher and tool life is shorter. Also, chatter can be detrimental to surface finish, especially if aesthetics are important to your component.
NingBo GSK Powder Metallurgy Co., Ltd. is a belt tensioner pulley factory, which manufactures MIM-Lock Case, powder metal pulleys, etc. Welcome to inquire.
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