Motion control for printing and converting machines

In short:Modern printing and converting machines are shaftless: every print unit, roller and cutter has its own servo motor, synchronised by an electronic line shaft, with high-resolution encoders holding register to hundredths of a millimetre. Digital and large-format printers add linear motors and linear encoders on the print head axes. Specify from the register tolerance at the web, then work back to encoder resolution, control cycle and drive.

Typical requirements

Machinery we specify motion for

• Digital inkjet printers
• Flexographic presses
• Offset presses
• Rotogravure presses
• Large-format and flatbed print head positioning
• Rotary and narrow-web label presses
• Labelling machines
• Web converting: slitting, die-cutting, folding, forming
• Colour register control
• Screen and membrane printing XY gantries

What printing and converting demand from motion

Printing is a synchronisation problem. Every colour, every die-cut and every fold must land in the same place relative to the others, on a web that may be moving at several metres per second and stretching as it goes. Converting machines, which slit, laminate, die-cut, fold and form printed material, face the same problem with knives and folders in place of plates.

The UK print sector is large: a BPIF summary from 2019 put it at about 8,000 companies, 112,000 employees and £14 billion turnover, and called it the world’s fifth largest producer of printed products. The machinery ranges from compact digital printers to large rotary presses, and HEIDENHAIN supplies encoders across that range, from prepress to postpress.

Shaftless presses and the electronic line shaft

Older presses tied every unit to one mechanical line shaft through gears. Shaftless presses give each cylinder or roll its own servo motor and synchronise them in software. The published benefits are well documented:

• Synchronisation. A Machine Design review of servo label presses reports synchronisation within 0.5 arcmin (0.008°), including during acceleration and deceleration ramps, and pressure-roller matching of 0.01 mm across print stands.
• Makeready. Units can be set up at the same time instead of one after another. On a press with a spare print unit, plates can be changed at full speed in a few seconds with only a few dozen copies of waste.
• Waste and maintenance. A shaftless press article reports paper savings of up to 15% in some cases and notes that gear transmission error and wind-up disappear.
• Electronic gearing. Each axis runs at a ratio of the master speed; draw rolls can be trimmed in 0.01% steps on one published system to control tension.

Where motion components sit on a press or converting line

Servotecnica’s slip ring catalogue lists digital inkjet, flexographic, offset and rotogravure printing among converting uses, with through-bore designs up to 500 rpm and Gigabit Ethernet options.

Digital and large-format printing

In inkjet printing, motion and imaging are the same problem: the head fires when the encoder says it is in the right place. Renishaw’s Flora Digital case study describes wide-format UV flatbed printers up to 5 m wide printing at up to 315 m²/h in two-pass mode, with print heads firing at around 30 kHz and resolutions up to 1,200 dpi. The scan axis uses an optical linear encoder at 1 µm resolution, rated to 15 m/s, with total cyclic error below ±300 nm.

For those axes, specify:

1. Constant-velocity window. Speed ripple shows as banding. Ironless linear motors give the smoothest motion.
2. Turnaround time. Shorter turnarounds raise throughput but need more force and stiffer structures.
3. Encoder resolution and cyclic error relative to the dot pitch. At 1,200 dpi the dot pitch is about 21 µm.
4. Cable management and cooling for a carriage that never stops moving.

See the linear actuators hub for motor types and how to size a linear actuator.

How to specify register control: a worked example

Take a flexo press with a 600 mm circumference plate cylinder, a register tolerance of ±0.05 mm and a maximum web speed of 300 m/min.

1. Angle tolerance. 0.05 ÷ 600 × 360° ≈ 0.03°.
2. Encoder resolution. Aim for at least ten counts inside the tolerance: about 0.003°, or 120,000 counts per revolution. A 17-bit encoder (131,072 counts) meets that; 20 bits or more gives a smoother servo loop.
3. Synchronisation check. A synchronisation error of 0.008° equals 0.008 ÷ 360 × 600 ≈ 0.013 mm at the web, comfortably inside the tolerance.
4. Speed. 300 m/min = 5 m/s. The cylinder turns at 5 ÷ 0.6 ≈ 8.3 rev/s, about 500 rpm. A direct-drive torque motor or a servo motor with a low-backlash gearhead both work; direct drive removes gear transmission error.
5. Timing. At 5 m/s the web moves 5 mm every millisecond. A register mark sampled on a 1 ms PLC scan could be 5 mm out. Capture mark positions with hardware latch inputs or timestamps on the drive or controller, and run the network cycle at 250 µs or faster.

The timing point is where many retrofits fall short: the encoder and motor are fine, but the mark capture is too slow.

On a retrofit of an older shafted press, the same numbers decide whether to keep the line shaft and add servo register correction on each unit, or go fully shaftless. Keeping the shaft is cheaper but leaves gear error and wind-up in place; going shaftless means one servo motor and drive per axis, an encoder on every cylinder and a motion controller acting as the line shaft. Either way, ask suppliers for interpolation error and mounting tolerance on the encoders, not just resolution, and confirm the controller’s mark-capture latency in writing.

Converting: die-cutting, slitting and flying knives

Converting axes mostly follow the web through an electronic cam. A rotary die-cutter must match web speed exactly during the cut, then speed up or slow down between cuts when the product repeat differs from the die circumference. A flying knife or flying shear accelerates to web speed, cuts while synchronised, and returns. The motor sizes on the acceleration between cuts, not on the cut itself, so calculate RMS torque over the full cam profile at the shortest repeat and highest web speed.

Rodless belt actuators such as the B3W are used for high-speed flying cut-off on lighter cuts, while rotary knives use servo or torque motors. Slitter knife positioning, by contrast, is slow and infrequent: stepper or small servo axes with absolute feedback set the knives for each job. Labelling machines use the same principle as die-cutters: the label web is dispensed in step with the product, so the dispensing axis is cammed to a product sensor and conveyor encoder. The packaging and food page covers labelling and wrapping in more depth, and servo vs stepper helps with the smaller axes.

Things that catch engineers out

1. Sampling register marks on a PLC scan. Use latched or timestamped capture.
2. Ignoring cylinder inertia. A large cylinder on a small motor makes the loop sluggish; check inertia ratio or use direct drive.
3. Gear backlash in print units. Any lost motion shows as register error on reversal or speed change.
4. Ink mist, solvent and paper dust on encoders and slip rings. Specify sealing and cleaning access.
5. Web tension zones fighting each other. Coordinate draw rolls in the motion controller, not with independent loops.
6. Low-level signals through slip rings. Load cells and thermocouples need shielded, low-noise rings.

What to send an engineer

• Machine type, web width, maximum web speed and repeat range.
• Number of print units and axes, cylinder diameters and inertias.
• Register tolerance and mark sensor type.
• For digital printers: carriage mass, stroke, scan speed, turnaround time and dot pitch.
• Controller, fieldbus and encoder interfaces.
• Environment and safety functions, including threading speed limits.

Our specialist engineering and supply partners can propose matched servo, encoder, drive and controller sets; start in the spec builder.

Standards to have in view

• EN 1010-1 (printing and paper converting machines: common safety requirements)
• EN 1010-2 (printing and varnishing machines including pre-press)
• ISO 13849-1 (safety-related parts of control systems)
• IEC 61800-5-2 (drive safety functions: STO, SS1, SLS)
• EN 60204-1 (electrical equipment of machines)
• 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.