Metal Injection Molding (MIM) and Powder Metallurgy Parts for Locks

Net-shape steel components for lock cylinders, cam mechanisms, gear trains and security hardware. Complex geometries in a single sintered piece, hardened and finished, from pilot batches to mass production.

MIM and Powder Metallurgy at Hydroforce

Hydroforce Engineering manufactures metal injection molded and powder-metallurgy components for the lock and security hardware industry. This is established production capability: the same toolroom, sintering line and inspection process that runs our regular PM and MIM programme supplies cylinder plugs, cams and gear sets to European lock assemblers, and delivers MIM parts for hand tools, electromechanical actuators and small-arms components.

MIM is the natural answer to a problem that conventional machining cannot solve economically: a small, intricate steel part — under fifty grams, full of cross-holes, pockets, gear teeth, undercuts and threaded features — that has to ship in tens or hundreds of thousands of pieces, all interchangeable, all hardened, all to print. Lock manufacturers consolidated on MIM in the 2000s for exactly this reason, and the cylinder plugs, levers, cams and shackle frames that move through our line every week are direct evidence of the volumes the technology was built for.

Why MIM and PM for Lock Components

A modern cylinder lock is a small package of high-precision steel. Pin chambers, key channels, lever interfaces, retainer grooves, threaded mounting features and anti-pick geometries are crowded into a body twenty to thirty millimetres long. Producing that geometry by milling and turning requires several setups, custom fixturing and a generous machining envelope; tolerances drift with tool wear, and the unit cost climbs with batch size in the wrong direction.

MIM takes the opposite approach. A feedstock of fine metal powder bound in a polymer matrix is injection-molded in tooling almost identical to plastic-injection dies. The green part already carries the final geometry — cross-holes, fillets, pockets, gear teeth, knurls — formed in a single shot in seconds. After binder removal and sintering, the part shrinks isotropically by about 15 to 20 per cent and reaches 95 to 99 per cent of theoretical density: a fully metallic part, not a porous compact, with mechanical properties comparable to wrought steel and the same response to heat treatment.

Conventional powder metallurgy (press-and-sinter) handles the simpler, larger pieces in the same family — bushings, washers, retainer plates, flange backings — where the geometry can be uniaxially pressed and the density required is lower. Between MIM and PM we cover the full lock-hardware envelope from a 2-gram lever to a 250-gram base plate, in steels, stainless steels and tool steels, all hardened and finished to drawing.

Capability

We deliver MIM and PM components to customer drawings across the typical industrial range:

Series sizes range from a few hundred pieces for prototype validation to millions of pieces per year for established lock platforms. The same tooling, sintering programme and inspection plan run unchanged from one production batch to the next, so the part that ships in year five is dimensionally identical to the first-article submission.

Production Examples

The components below are representative of our regular MIM and PM output for lock and hardware customers. Each one demonstrates a geometry that would be uneconomical to machine in series and that benefits from the heat treatment and surface options open to a sintered steel part.

Lock Cylinder Plug

The body of a high-security cylinder lock, produced from low-alloy steel in a single MIM shot. The rectangular key channel, the four pin chambers on the upper face, the cross-bore for the cam pin, the head flange and the external thread on the rear shank are all formed as-molded; only the thread and the keyway are finish-sized after sintering. The part is case-hardened and black-finished. A milled equivalent would require four setups and roughly three times the cycle time per piece.

Compound Gear with Integral Pinion

A two-stage gear for the drive train of a motorized cylinder or an electromechanical lock, produced from sintered low-alloy steel. The large spur and the smaller pinion sit on the same axis as a single piece — no hub joint, no pressed assembly. Tooth geometry on both diameters is formed in the mold and meets the gear quality grade specified on the drawing after sintering, with no post-machining of the teeth. Through-hardening and tempering bring the tooth flanks to the required hardness for the application.

Disc-Detainer Rotor

A rotor disc for a disc-detainer cylinder lock, with the characteristic ribbed perimeter and a central key-bore. Each disc in the stack carries its own gate cutout and must rotate to a precise angle for the sidebar to drop into the gates — geometry that has to repeat to a few hundredths of a millimetre across every disc in every lock. MIM in low-alloy steel reproduces the gate position and the rib profile in one shot, sintered, then case-hardened for wear resistance against the key.

Cam Lever with Forked End

A mechanism lever for a multi-point lock or window-handle gearbox: a precision bore in the pivot boss, a forked actuating slot at one end and a ball-shaped detent at the other. The three functional features sit on three different axes, joined by a tapered web — a single-shot MIM part that would otherwise require turning, milling and a slot operation. The as-sintered surface accepts a passivation or black-oxide finish directly, with no intermediate grinding.

Cylinder Cam Insert

The cam insert that translates plug rotation into bolt drive: an oblong engagement slot at the head, a thin actuating web with a cast-in drive lug and a stepped cylindrical foot that runs in the lock case. Three functional zones on one part, formed by MIM in a hardenable low-alloy grade. The drive lug is the wear point — after sintering the part is through-hardened and tempered so that the lug holds geometry through the rated operating cycle count of the lock.

Multi-Bore Base Plate

A back plate for a lock case, with seven through-holes of different diameters, four of them counterbored on the visible face. The plate carries the mounting interface for the cylinder, the screw fixings to the door frame and the seating for two internal mechanism pins. Press-and-sinter PM in a low-alloy grade gives the part the load-bearing density it needs while keeping the cost low; the counterbore depths and the chamfered edges come out of the press die ready for assembly.

Twin Shackle Frame

A two-element shackle frame for a security padlock, produced in 17-4 PH stainless and shown here in the as-sintered state. The interlocking U-profiles, the keyway slot at the top and the heel cutout at the bottom are all molded; only the engagement surfaces are sized after solution treatment and ageing. The combination of 17-4 PH stainless and the precipitation-hardening cycle gives the frame the hardness required for cut-resistance while keeping the surface naturally corrosion-resistant — no plating required.

Production Process

Every MIM order runs through the same four-stage core process, with PM parts skipping the binder-removal step. The whole flow is contained on a single line:

1. Drawing review and feedstock selection. The drawing is reviewed for moldability, gating, parting line and shrinkage allowance. The customer’s grade is matched to a powder–binder feedstock — typically 17-4 PH for stainless features, Fe-Ni alloys for case-carburizing, M2 for tool-steel hardness, or low-alloy steel for the bulk volume work.
2. Tooling. Steel injection molds are produced with shrinkage compensation built in (the cavity is roughly 1.18× the final part size). Cores, sliders and ejector pins are laid out to release every undercut and cross-hole in a single shot.
3. Injection molding. Feedstock is heated and injected into the closed die at controlled pressure and temperature. Cycle times typically run from 15 to 45 seconds per shot, depending on part weight and wall section. The green part has the full external geometry of the final piece.
4. Debinding. The polymer binder is removed in two stages — solvent or catalytic primary debinding, then thermal debinding in the front of the sintering furnace — leaving a fragile “brown” part of bound metal powder.
5. Sintering. The brown part is heated under hydrogen, nitrogen-hydrogen or vacuum atmosphere to 1,200 to 1,400 °C, where the powder particles fuse and the part shrinks isotropically by about 15 to 20 % to its final dimensions. Sintered density reaches 95–99 % of theoretical. For high-melting-point grades we also run ultra-high-temperature sintering cycles.
6. Sizing and secondary operations. Critical dimensions are coined or sized to pull the part into the tightest portion of its drawing tolerance. Threads, undercuts or features unsuitable for MIM are added by CNC machining where required.
7. Heat treatment. Through-hardening and tempering, solution + age for precipitation steels, case carburizing or nitriding per the drawing — applied to the full batch in tray furnaces or controlled-atmosphere lines.
8. Surface treatment and inspection. Passivation, nickel, zinc, black oxide, phosphate or PVD per specification, followed by dimensional inspection and packaging.

Quality Control

Every order ships with a documentation file matching the part, in line with our ISO 9001 quality system:

• Material certificate for the powder lot used, traceable to the feedstock batch
• First-article CMM dimensional report against the drawing
• Sintered-density verification (Archimedes method, with cross-section on request)
• Hardness report — bulk and case where applicable
• In-process dimensional sampling across the production batch
• Surface-treatment record (coating thickness, passivation lot)
• Visual inspection for sintering defects, surface porosity and finishing

Tooling drawings, injection parameters, debinding profile and sintering program are retained for every part, so a repeat order ships against the same baseline as the first article — five or ten years later, with the same dimensions and the same metallurgy.

Ordering

Send your drawing or 3D model to office@hydroforce.ee. We respond with a tooling and per-piece quotation, a recommended material grade, a heat-treatment route and a suggested finishing path. Pilot lots and prototype tooling are welcome — the same documentation package follows the part from the first piece into series production.