Motion control for plastics, rubber and tyre machinery

In short:Plastics and rubber machines are moving from hydraulics to servo-electric drive: roller-screw actuators and servo motors on injection, clamp, ejector and thermoforming axes, high-torque gearboxes on extruder and winder drives, and slip rings on rotating blow-moulding wheels and winders. Size each axis at the two corners of its cycle, maximum force at low speed and maximum speed at low force, then check heat near barrels and moulds.

Typical requirements

Machinery we specify motion for

• Electric and hybrid injection moulding machines
• Blow moulding machines (extrusion and stretch)
• Extrusion lines, haul-offs and winders
• Thermoforming machines
• Plastic film and bag making
• Part ejection, mould positioning and sprue pickers
• Tyre building and green tyre transfer
• Rubber cutting and calendering
• Ultrasonic welding presses

What plastics and rubber machinery demands from motion

Plastics and rubber processing combines heat, high force and relentless cycling. An injection moulding machine may close, inject, hold and eject several times a minute, every minute, for years, with molten polymer at a few hundred degrees a short distance from the actuators. Extrusion and film lines run continuously for weeks. Tyre and rubber machinery adds heavy loads, sticky compounds and tight synchronisation.

The UK industry is substantial: the British Plastics Federation puts it at about 5,700 companies and around 160,000 people directly employed. Much of that capacity runs injection moulding, extrusion and thermoforming machines that are steadily being replaced or retrofitted, and every replacement is a chance to rethink the drive system.

Electric vs hydraulic: what the evidence says

The case for electric drives rests on energy, repeatability, cleanliness and noise. The energy figures vary widely, so treat them carefully:

The honest conclusion: replacing an old fixed-pump hydraulic machine saves a lot; replacing a modern servo-pump hydraulic machine saves less. The other benefits, shot-to-shot repeatability, no oil near the mould, lower noise and less cooling, often decide the case on their own. Our hydraulic to electric actuator guide walks through a conversion.

Where motion components sit on plastics machinery

Servotecnica’s slip ring catalogue lists blow moulding, plastic bag making and extrusion as plastics uses, and Exlar reports Dukane chose its GSX actuators for an ultrasonic welding press line.

How to size a thermoforming platen actuator: a worked example

Take a vertical forming platen with 120 kg moving mass, a 200 mm stroke completed in 0.35 s and a 15 kN forming force at the top of stroke, at 30 cycles per minute.

1. Motion. A triangular profile gives peak speed v = 2 × 0.2 ÷ 0.35 ≈ 1.14 m/s and acceleration a = 4 × 0.2 ÷ 0.35² ≈ 6.5 m/s².
2. Acceleration force. Lifting: 120 × (9.81 + 6.5) ≈ 1,960 N.
3. Lead choice. For 1.14 m/s a 25 mm lead screw turns at 45.6 rev/s, about 2,740 rpm. A 10 mm lead would need about 6,840 rpm, too fast for most screws and motors.
4. Torque at forming force. With the 25 mm lead and an assumed efficiency of 0.85: 15,000 × 0.025 ÷ (2π × 0.85) ≈ 70 Nm. During acceleration: 1,960 × 0.025 ÷ 5.34 ≈ 9 Nm plus rotor inertia.
5. The two corners. The axis needs high speed at low force and high force at nearly zero speed. Check both points against the motor’s torque-speed curve. A large servo motor with about 120 Nm peak could do it directly, or a servo-driven toggle can give force multiplication near the end of stroke so a smaller motor runs faster.
6. Heat. If the forming force is held for 0.5 s of each 2 s cycle, that alone gives an RMS torque of about 35 Nm. Size the motor’s continuous rating with derating for the hot machine environment.

The same two-corner check applies to injection units (fast fill, then high hold pressure) and clamp units (fast close, then full tonnage). See how to size a linear actuator and ball screw vs roller screw.

Injection moulding axes in detail

An all-electric injection moulding machine typically has four main servo axes: clamp (often through a toggle that multiplies force near lock-up), injection (a screw driving the plasticising screw forward), screw rotation for plasticising, and ejection. Some add nozzle touch and core-pull axes. Each has a different duty:

• Clamp. Fast open and close at low force, then full clamp tonnage held during injection and cooling. The toggle does most of the force multiplication; the motor sizes on speed and the brief lock-up peak.
• Injection. A fast fill at high speed, then pack and hold at high force and nearly zero speed. This is the most demanding two-corner axis on the machine.
• Screw rotation. Continuous torque during plasticising against back pressure. Size on RMS torque.
• Ejection. Short, fast moves with moderate force. A ball screw actuator usually suffices.

Hybrid machines keep hydraulics for the clamp and use servo drives elsewhere, or drive a hydraulic pump with a servo motor so it only runs when needed. When choosing between them, list each axis with its force, speed and duty, then decide axis by axis: the linear actuators, servo motors, gearboxes and servo drives hubs cover the options for each.

Extrusion, film and winding lines

Extrusion lines are continuous, so the motion problem is synchronisation and tension rather than force. Haul-offs set the pull speed, flying cutters match line speed for each cut, and winders control tension as the roll diameter grows. Servo motors with gearheads or direct-drive motors run these axes; encoders on measuring wheels set cut length. Winders with turret spindles need through-bore slip rings for power and signals. Heated rolls need a slip ring rated for the roll temperature, such as the High & Low Temperature Slip Ring range, published from -55 °C to 250 °C.

Rubber and tyre manufacturing

Tyre building machines rotate building drums, transfer the green tyre between stations and apply plies and treads in synchronised steps. The loads are heavy and the compounds sticky, so axes need high torque at low speed, stiff gearing and protection from contamination. Rotating drums carrying sensors or segment actuators need slip rings, and transfer rings use servo or electric linear axes. Specify drum inertia, index and acceleration times, and the synchronisation needed between drum and servers.

Things that catch engineers out

1. Sizing only at peak force or only at peak speed. Check both corners of the torque-speed curve.
2. Ignoring heat from barrels, moulds and heaters. Motors, encoders, lubricants and cables near the tool need derating or relocation.
3. Hold time. Holding pressure or forming force heats motors as much as moving does.
4. Thermocouple signals through slip rings. Low-level signals need clean contacts, shielding and separation from heater circuits.
5. Lubricant contamination. Food, medical and optical mouldings may need food-grade or sealed actuators.
6. Regenerative energy. Fast clamp and platen decelerations return energy; plan for it.

What to send an engineer

• Machine type, axis, and the force and speed at each step of the cycle.
• Stroke, cycle rate, hold times and moving mass.
• Ambient temperature at the mounting point and any heat sources nearby.
• Cleanliness, food-contact or medical requirements.
• Controller, fieldbus, encoder interface and safety functions.
• For conversions: hydraulic cylinder bore, rod, pressure and stroke.

Our specialist engineering and supply partners can propose matched actuators, motors and drives; start in the spec builder.

Standards to have in view

• EN ISO 20430 (injection moulding machines: safety; developed from EN 201)
• EN 422 (blow moulding machines: safety)
• EN 1114-1 (extruders and extrusion lines: safety)
• EN 12409 (thermoforming machines: safety)
• ISO 13849-1 (safety-related parts of control systems)
• IEC 61800-5-2 (drive safety functions, STO)
• Regulation (EU) 2023/1230 (machinery; applies from 20 January 2027)

Which standards apply depends on the end product and its market. Your engineer will confirm what the component itself needs to meet.