Guide
MIM or Press-and-Sinter Powder Metal: Which Fits a Small Steel Part?
MIM or press-and-sinter powder metal is a choice between two ways of making a small steel part from metal powder: injection molding a powder and binder feedstock, or pressing dry powder in a die. The deciding factor is geometry, because press-and-sinter works along one pressing direction and MIM forms three-dimensional shapes.
By Saola Manufacturing engineering team · Published · Updated
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Are MIM and press-and-sinter the same thing?
No. Both start with metal powder and end in a sintering furnace, but press-and-sinter compacts the powder in a rigid die, while MIM molds a powder and binder feedstock in an injection mold and removes the binder before sintering.
MPIF defines conventional powder metallurgy, also known as press-and-sinter, as mixing elemental or alloy powders with lubricants or additives, compacting the mixture in a die and sintering the compact in a controlled-atmosphere furnace (MPIF, Conventional Powder Metallurgy). MIM mixes fine powder with a binder into a feedstock, molds it in a conventional injection molding machine, removes the binder in one or two stages and then sinters (MIMA, Process Overview). PickPM groups MIM with other near-fully dense processes, whose residual porosity is often under 1%, and treats press-and-sinter as the other principal category (PickPM, Consolidation Processes).
The distinction matters because the two processes have different shape limits, different material standards and different cost structures, and a drawing that is ready for one is not automatically ready for the other.
How do MIM and press-and-sinter compare on density, strength and cost?
MIMA rates MIM at about 98% density and conventional PM at about 88%, with higher strength, ductility and complexity for MIM, and rates PM as the lower-cost process. The price of MIM’s better properties is a higher cost per part.
The table reproduces MIMA’s own comparison. These are the association’s ratings across the whole industry, not a guarantee for a particular part, but they set the shape of the trade-off. MIM gives you near-full density, which supports higher strength and ductility and a better surface finish. Press-and-sinter gives you a lower-cost process for simpler shapes, with porosity that you manage through material choice and density target.
Note that MIMA is the MIM association, and PickPM is an MPIF design center for the press-and-sinter side, so each source has a stake in its own process. That is why this guide uses both, and why the rule below comes from the geometry each source describes, not from either source’s sales pitch.
| Property | MIM | Conventional PM |
|---|---|---|
| Density | 98% | 88% |
| Tensile strength | High | Low |
| Elongation | Medium | Low |
| Complexity | High | Low |
| Surface finish | High | Medium |
| Production volumes | High | High |
| Range of materials | High | High |
| Cost | Medium | Low |
| Material standard | MPIF Standard 35-MIM, ASTM B883 or ISO 22068 | Not ISO 22068, which excludes press-and-sinter parts; MPIF Standard 35-SP covers structural PM parts |
Which geometries suit press-and-sinter, and which need MIM?
Press-and-sinter works in one pressing direction, so profiles with steps, flanges and gear teeth along that direction suit PM, while cross holes, undercuts and fully three-dimensional features suit MIM. Side holes in a pressed part are made by machining after sintering.
PickPM says holes in the pressing direction can be round, D-shaped, keyed or splined, that undercuts perpendicular to the pressing direction are not possible because they block ejection, and that side holes must be produced after sintering, usually by machining (PickPM, Design Considerations). It also says small steps and flanges can be formed by machining a shelf into the die. Those are the features that make a part a pressing: a gear with a hub, a bushing, a cam profile that is the same through the thickness.
MIMA lists cross holes, internal threads, undercuts and cantilevers as geometries suited to MIM, and says MIM offers the same design freedom as plastic injection molding (MIMA, Designing with MIM). A pawl with a cross pin hole, a latch with an angled slot and a small housing with internal features are MIM shapes. The decision rule is simple: if every feature can be formed along a single axis, quote PM first; if the part has features off that axis, quote MIM or accept machining after pressing.
What limits do wall thickness and part size put on each process?
Each trade body publishes a recommended range: PickPM for pressed walls, MIMA for molded walls. The ranges come from different sources written for different audiences, so read them as guidance to discuss with the fabricator.
PickPM recommends walls of at least 1.52 mm (0.060 in.) and says that at a length-to-wall-thickness ratio of 8:1 or higher, uniform fill needs special precautions and density variation is unavoidable (PickPM, Design Considerations). MPIF adds that most conventional PM parts weigh less than 5 pounds (2.27 kg), and that compaction pressures run from 138 MPa (10 tsi) to 965 MPa (70 tsi) depending on density requirements (MPIF, Conventional Powder Metallurgy). For MIM, MIMA gives preferred wall thicknesses of 1.3 to 6.3 mm (0.05 to 0.25 in.) and says exceptions in both directions are possible (MIMA, Complex Designs with MIM).
These figures do not make one process thinner-walled than the other; they come from different sources written for different audiences. What they show is that both have a recommended range and that a drawing outside it should be discussed with the fabricator before tooling is cut.
How do the material standards differ for MIM and press-and-sinter?
ISO 22068 covers MIM materials only and states that it does not apply to press-and-sinter or powder-forged structural parts, so a pressed part must be specified to a different standard. Quote the right one on the drawing or the supplier will have to guess.
ISO 22068:2012 sets requirements for the chemical composition and the mechanical and physical properties of sintered metal injection-molded materials, and was published in June 2012 (ISO 22068:2012, Standards Council of Canada listing). ASTM B883 covers ferrous MIM materials, and ASTM lists B883-19 as historical with B883-24 as the active version (ASTM B883 store page). MPIF publishes Standard 35 for the MIM materials as well (MPIF Standard 35-MIM listing). These documents are sold, and this guide does not reproduce their values.
What to put on the drawing: the material designation, the standard and edition it comes from, the heat treatment condition, and the density or hardness you will accept. Do not copy a press-and-sinter designation onto a MIM drawing or the reverse; they use different documents and different property tables.
How do you decide for a gear, cam or latch?
Start with the geometry: a part formed along one axis with steps goes to PM, and a part with off-axis features goes to MIM. Then check whether the strength and surface requirement fits PM’s lower density, and add machining if only a few features break the rule.
Gears are the clearest case. A spur gear with a hub is a classic pressing, since the tooth form runs along the pressing direction, and PickPM discusses gear teeth and hubs in its design guidance. A cam with a through-thickness profile is the same. A latch with a cross pin hole, a hook and an undercut is a MIM shape, and forcing it into PM means machining those features afterwards.
When it is close, ask for both quotes with the same finish-machining scope. A pressed part with side holes machined after sintering and a MIM part that needs only a finish-turned bore may land close in cost, and the better answer then depends on strength and the finish requirement. Saola places MIM and PM through a partner plant it manages and finishes critical faces and threads by CNC, so a drawing can be quoted down both routes. See the MIM and powder metal capability page and the CNC milling page.
Frequently asked
Is MIM just powder metallurgy with injection?
It is in the powder metallurgy family, but the forming step is different: MIM molds a powder and binder feedstock and removes the binder before sintering, while press-and-sinter compacts dry powder in a die. The shapes, tolerances and standards differ as a result.
Which is cheaper, MIM or press-and-sinter?
MIMA rates conventional PM as the lower-cost process and MIM as medium, so press-and-sinter is cheaper when the geometry suits it. MIM wins when PM would need multiple machining operations to finish the shape.
Can press-and-sinter make a part with a cross hole?
Not directly. PickPM says side holes must be produced after sintering, usually by machining. If the part has several such features, MIM may be the better route.
Do I need a different standard for a pressed part?
Yes. ISO 22068 states that it does not apply to structural parts made by press-and-sinter or powder forging, so the pressed part needs its own material designation from the standard that governs it.
Which has better density and strength?
MIMA rates MIM at about 98% density and conventional PM at about 88%, with higher tensile strength and elongation for MIM. Press-and-sinter density can be raised by re-pressing or other steps, so ask for the density the supplier will guarantee.
Sources
- MIMA, Designing with MIM, Metal Injection Molding Association, accessed October 2026 (page copyright 2026)
- MIMA, Process Overview: MIM, Metal Injection Molding Association, accessed October 2026 (page copyright 2026)
- MIMA, Complex Designs with MIM, Metal Injection Molding Association, accessed October 2026 (page copyright 2026)
- PickPM, Design Considerations, MPIF powder metallurgy design center, accessed October 2026
- PickPM, Consolidation Processes, MPIF powder metallurgy design center, accessed October 2026
- MPIF, Conventional Powder Metallurgy (Intro to PM), Metal Powder Industries Federation, accessed October 2026
- ISO 22068:2012, sintered metal injection-molded materials, specifications, ISO, published June 2012 (Standards Council of Canada listing, accessed October 2026)
- ASTM B883, Standard Specification for Metal Injection Molded (MIM) Materials, ASTM International store page, B883-19 listed as historical, B883-24 as current (page updated 2024)
- MPIF Standard 35-MIM listing, Metal Powder Industries Federation, accessed October 2026