Hydraulic mold clamps are not a single product. The hydraulic mold clamp family includes four distinct geometries, each engineered for a different platen layout, mold type, and engagement strategy. Buyers specifying a hydraulic mold clamp retrofit for the first time often default to the most-recommended clamp type without knowing the others exist. This article catalogs the four standard hydraulic mold clamp types KINGHOU manufactures, the engineering differences between them, and which hydraulic mold clamp belongs on which press.
Type 1: T-Slot Slidable Hydraulic Mold Clamp
The T-slot slidable hydraulic mold clamp is the most common variant installed on injection molding presses worldwide. The clamp body slides along the press platen T-slot during installation, then locks in position when hydraulic pressure is applied. The clamping arm engages the mold from a slot cut into the mold body.
- Force range: 5T to 60T per clamp
- Press tonnage suited: 250T to 4,000T injection molding machines
- Platen prerequisite: Existing T-slot bolster (standard on most injection presses)
- Mold-side machining: Standardised clamp slots cut per mold (one-time)
- Typical use: Default choice for hydraulic mold clamp retrofits on standardised mold inventories
Type 2: Dovetail Hydraulic Mold Clamp
The dovetail hydraulic mold clamp uses a dovetail-profile engagement instead of a flat clamp arm. The dovetail geometry distributes force across a larger contact area, reducing point-load stress on the mold clamp slot. Used most often on high-cycle injection molding lines and on presses where the same hydraulic mold clamp position handles a wide range of mold sizes.
- Force range: 10T to 40T per clamp
- Press tonnage suited: 500T to 2,500T high-cycle injection presses
- Advantage: Lower point stress on mold body, longer mold life
- Mold-side machining: Dovetail-profile slots required (precision machining work)
- Typical use: Premium injection molding lines where mold cost is high and clamp/mold contact stress matters
Type 3: Claw-Type Hydraulic Mold Clamp
The claw-type hydraulic mold clamp grips the mold from the outside edge using a hook-shaped clamping arm. The claw rotates around its pivot under hydraulic pressure, drawing the mold against the platen face. Used where the mold body cannot accommodate clamp slots — common on legacy molds or on customer-supplied molds where no machining is permitted.
- Force range: 5T to 25T per clamp
- Press tonnage suited: 250T to 1,500T injection molding machines
- Advantage: No mold-side machining required
- Tradeoff: Lower maximum force per clamp than T-slot or dovetail variants
- Typical use: Prototype injection molding lines, contract molders running customer molds, and short-run programs
Type 4: Arm-Type Hydraulic Mold Clamp (Long-Stroke)
The arm-type hydraulic mold clamp uses a long-stroke clamping arm that extends 50 to 200 mm beyond the platen face. Used on stamping presses where the bolster geometry differs from injection platens, and on injection presses with very tall mold height ranges where standard clamp stroke is not enough.
- Force range: 10T to 50T per clamp
- Press tonnage suited: 200T to 2,000T stamping presses and high-mold-height injection presses
- Advantage: Accommodates wide mold height range without clamp swap
- Typical use: Stamping line retrofits (see our stamping press quick die change engineering guide), and tall-mold injection programs
Hydraulic Mold Clamp Specifications — Standard Sizes
KINGHOU manufactures hydraulic mold clamps in 5 standard size classes, sufficient to cover 95% of injection molding, stamping, and die casting press tonnages. The size classes are:
- 10T hydraulic mold clamp: for 250T to 500T injection presses; small to medium die casting
- 15T hydraulic mold clamp: for 500T to 1,000T injection and stamping presses
- 25T hydraulic mold clamp: for 1,000T to 2,000T presses; standard for most retrofit work
- 40T hydraulic mold clamp: for 2,000T to 3,200T presses; larger automotive and EV lines
- 60T hydraulic mold clamp: for 3,200T to 4,000T+ presses; high-tonnage structural part production
For sizing calculation guidance see our hydraulic mold clamp sizing engineering guide.
Material and Seal Specifications
- Clamp body material: Hardened steel (typically 42CrMo or equivalent), heat-treated to 38-42 HRC
- Piston material: Hardened steel with chrome-plated surface
- Standard seals (≤80°C platen): Nitrile NBR primary, polyurethane rod seal
- High-temperature seals (>80°C platen, die casting, hot chamber): Viton FKM primary, Viton secondary
- Working pressure rating: 250 to 400 bar depending on clamp size
- Burst pressure: 4× working pressure (safety factor)
How to Choose the Right Hydraulic Mold Clamp Type
- Standard injection molding retrofit, T-slot bolster present: T-slot slidable hydraulic mold clamp
- High-cycle injection, premium molds, low contact stress required: Dovetail hydraulic mold clamp
- Customer molds without permission to machine clamp slots: Claw-type hydraulic mold clamp
- Stamping press or tall mold height range: Arm-type hydraulic mold clamp
- Die casting (cold or hot chamber): T-slot slidable with Viton seals
Conclusion
Choosing the wrong hydraulic mold clamp type is one of the most expensive mistakes a plant can make on a QMC retrofit. T-slot slidable hydraulic mold clamps are the default — but the dovetail, claw-type, and arm-type variants exist because the default is wrong in specific common situations. The decision matrix above is the version KINGHOU engineering uses on every survey before quoting a configuration.
Send us your machine tonnage and platen size. KINGHOU returns a hydraulic mold clamp specification with the right type, size, and quantity within 24 to 48 hours. Reach the engineering team via the contact form, by WhatsApp at +86 18051902698, or by email to kh020@jskinghou.com.
