Pole pitch is the single most-asked question we get when injection plants in India, Southeast Asia, and the Middle East spec their first magnetic platen. Pick the wrong pitch and the platen still works — but you leave 15–30% of available clamping force on the table, and small molds slide on the surface during high-speed runs.
This guide explains what pole pitch is, how to match it to your mold back-plate set, and the three pitch options KingHou ships for injection molding presses 100T to 4,000T.
What is pole pitch on a magnetic platen?
An electro-permanent magnetic platen is a grid of magnetic poles. Each pole pairs with a counter-pole to create a closed magnetic circuit through the steel back-plate of the mold. Pole pitch is the center-to-center distance between adjacent poles on that grid — typically 50 mm, 75 mm, or 100 mm on industrial magnetic platens.
The pole pitch decides three things:
- Effective clamping force per square meter: finer pitch = more poles per area = more force. A 50 mm pitch platen can deliver ~160 N/cm²; a 100 mm pitch platen delivers ~80 N/cm².
- Minimum mold back-plate size that engages: the smallest mold the platen can hold securely. A 50 mm pitch handles back-plates as small as 150 × 150 mm; a 100 mm pitch needs at least 300 × 300 mm to engage enough poles.
- Maximum mold back-plate thickness: magnetic flux penetration depth. Larger pitch reaches deeper into the back-plate. 100 mm pitch can clamp through 25 mm of steel; 50 mm pitch maxes out around 15 mm.
How to choose pole pitch for your mold set
The right pole pitch is decided by the mold set you actually run — not the press tonnage. Start with the smallest and largest mold back-plates you change between.
50 mm pitch — small to medium molds, thin back-plates
- Mold back-plate size: 150 × 150 mm to 600 × 600 mm
- Mold back-plate thickness: 8–15 mm of structural steel
- Typical press: 100–500 T injection molding machine
- Best for: high-mix plants running many small precision molds (medical, electronics housings, optical parts)
75 mm pitch — the universal mid-range
- Mold back-plate size: 250 × 250 mm to 1,000 × 1,000 mm
- Mold back-plate thickness: 12–20 mm
- Typical press: 400–1,800 T
- Best for: general-purpose injection molding plants. 75 mm pitch is what we recommend when a plant doesn’t yet know its full long-term mold mix — covers the widest range with one configuration.
100 mm pitch — large molds, thick back-plates
- Mold back-plate size: 400 × 400 mm to 2,500 × 2,500 mm
- Mold back-plate thickness: 15–25 mm
- Typical press: 1,500–4,000 T+ (automotive bumpers, large appliance shells, EV battery trays)
- Best for: large-mold plants. Our 2,800 T magnetic platen install for an EV battery tray molder uses 100 mm pitch with 18 mm back-plates.
Mold back-plate material spec
The magnetic platen clamps through the back-plate, so back-plate material matters as much as pitch. The plate must be ferromagnetic structural steel with consistent thickness across the clamped area.
- Recommended: S50C, P20, 1045, or equivalent medium-carbon steel
- Acceptable with reduced force: mild steel A36 / S275
- Not compatible: stainless steel (austenitic 304/316), aluminum, copper — magnetic flux cannot close through these
If your existing molds have aluminum or stainless back-plates, the solution is a steel adapter plate, not a different magnetic platen. We ship steel adapter plates with KingHou platen orders when needed.
Three sizing mistakes plants make with magnetic platens
- Picking pitch by press tonnage instead of mold size. A 2,000 T press running mostly 400 × 400 mm precision molds wants 50 mm or 75 mm pitch — not 100 mm. The press tonnage decides the platen’s outer dimensions, not the pole grid.
- Forgetting back-plate thickness varies in the mold fleet. If 80% of your molds have 15 mm back-plates and 20% have 22 mm, the magnetic platen must clamp the 22 mm ones reliably. Size to the thickest back-plate, not the average.
- Skipping the safety zone calculation. Magnetic clamping force degrades at the platen edges (last 50–80 mm). A mold whose back-plate fits exactly at the platen edge loses 20–30% of expected hold. Always leave a margin equal to one pole pitch on each side.
How magnetic clamping compares to hydraulic mold clamps for your mold mix
If your plant runs many different mold back-plate geometries — different sizes, hole patterns, flange types — magnetic platens are usually the better answer. They clamp any back-plate shape that fits within the platen footprint, no per-mold tooling required. Hydraulic mold clamps are still preferred for plants running a few standardized molds, where the per-mold flange interface is consistent.
We typically install magnetic platens on injection lines with 20+ active molds and a mold-change frequency above 2 per week per press. Below that threshold, hydraulic clamps usually return faster ROI.
Frequently Asked Questions
How long does it take to switch a mold with a magnetic platen?
The clamping operation itself is 1–2 seconds — a single button press energizes or de-energizes the platen. Total mold change time (release, transport, position, engage, restart) is typically 60–90 seconds with a mold change cart, compared to 6–20 minutes manual.
Does the magnetic platen need power to hold the mold during production?
No. Electro-permanent platens are energized only during the clamp/release operation (200–400 ms). During production the mold is held by permanent magnets — zero power consumption, and no risk of release if power fails mid-cycle.
Can I retrofit a magnetic platen to an existing injection press?
Yes. The magnetic platen mounts to the existing fixed and moving platens via adapter plates. The press itself is not modified. Installation typically takes 3–5 days on a 500–1,500 T press, 7–10 days on a 2,000 T+ press.
What working temperature can a magnetic platen handle?
KingHou platens are rated to 180 °C continuous, 200 °C peak. Covers all standard thermoplastic processing. For engineering resins running at higher temperatures (PEEK, PPS at 250 °C+), we ship high-temperature platens with NdFeB grade adjusted to maintain force at temperature.
Get a magnetic platen pole pitch spec for your mold set
Send us your smallest and largest mold back-plate dimensions, back-plate thickness range, and press tonnage. Our engineering team returns a pole pitch recommendation within 24 hours.
WhatsApp engineering audit (24h reply): Open WhatsApp → Send back-plate spec
Full engineering proposal: Request complete magnetic platen configuration with ROI projection
