Few industrial tasks look simpler than stacking finished cases on a pallet, yet the motion profile behind that deceptively calm dance is brutally demanding: long‑stroke lifts with hundred‑kilogram loads, high tip‑inertia wrist rotations, and a relentless 24 h duty cycle that tolerates neither dropped boxes nor line‑backing slip‑sheets. Palletizing robots live or die by the servo motors hidden inside each axis, and Bosch Rexroth’s MHD115C‑058‑PG1‑AA synchronous motor exemplifies why the right electromechanical heart makes or breaks a robot’s total cost of ownership.
Core Performance Figures That Matter on a Palletizer
The MHD115C‑058‑PG1‑AA delivers 70 Nm of continuous stand‑still torque and unleashes up to 231 Nm for short acceleration bursts, all while spinning safely to 6 000 rpm when axis gearing demands high wrist speed. A characteristic speed of 4 000 rpm keeps copper losses low in cruising motion, and a peak phase current of 371 A lets the controller tap the full magnetic headroom without demagnetising the rare‑earth rotor stack. The IP65 housing, 192 mm DIN 42948 flange, and 180 mm centring pilot withstand dust and stray stretch‑wrap while natural‑convection ribs shed roughly 3 % of output power as heat – no external blower required. Integrated digital multiturn feedback stores its own ID and parameter block, so a replacement drops in and handshakes with the drive in seconds.
Why Those Numbers Fit Real‑World Palletizing Joints
A modern four‑axis palletizer such as the Fanuc M‑410 iC or Kawasaki RD‑series must fling payloads from 80 kg to 185 kg across a two‑metre reach while holding repeatability better than ±0.07 mm. The wrist joints on these arms routinely demand 120–180 Nm during pick‑and‑place arcs; shoulder or lift axes can peak near 200 Nm when offset mass and inertia stack up. The MHD115C‑058’s 231 Nm ceiling therefore lands in the performance “Goldilocks” zone: high enough to cover worst‑case cartons and slip‑sheet grippers, yet still small and light (≈55 kg) so the robot’s overall inertia stays modest and cycle times stay sharp.
Equally critical is thermal endurance. A palletizer operates almost exclusively in S6 intermittent duty: bursts of full torque to yank a layer clear of vacuum cups, coasting as the arm slews, then braking hard to land accurately. The MHD’s 100 K over‑temperature rating means it can ride those pulses for years without cooking varnish, provided cabinet air remains under 40 °C and peak periods stay below the Rexroth‑approved 400 ms window.
Mechanical Integration Inside the Robot Arm
A palletizer’s lift axis often uses a 40‑ or 50‑mm pitch‑circle planetary reducer. The MHD115C flange mates directly to those gearheads, and its plain‑shaft‑with‑seal design resists pallet‑dust while minimising fretting at the keyway. For end‑of‑arm tooling, the same motor template can be flipped to drive a high‑reduction cycloidal gearbox on the “Theta” rotation, ensuring cable kits, mounting bolts, and encoder pin‑outs stay common across the bill of materials.
Bearing life dominates MTBF calculations once a robot crosses the 20 kg payload threshold. Because the MHD115C’s deep‑groove pair handles high radial loads, OEMs can mount a pulley overhang or belt‑drive a secondary axis without auxiliary outboard bearings; fewer parts mean quicker teach‑pendant jog checks after a motor swap.
Electrical and Control Considerations
IndraDrive C or Cs controllers recognise the MHD115C‑058‑PG1‑AA via plug‑in nameplate data; once the Sercos telegram identifies 70 Nm continuous torque and 0.95 Nm/A torque constant, the auto‑tune routine typically converges in one pass. Safe‑Torque‑Off (STO) wiring meets Category 3 / PL d without external relays, so integrators tie the robot’s e‑stop chain straight to the drive and still pass CE or UL audits.
When cycle times push the thermal envelope – for instance, 25+ layers per minute on a five‑axis gantry like the Festo heavy‑duty palettizing cartesian – engineers map the drive’s DC‑bus energy into a regenerative unit or sharing link so decel spikes bleed into the next motor instead of overheating the IGBTs. The Rexroth firmware’s real‑time current limiting then trims only the axis that exceeds its copper curve, not the whole arm, keeping stack rates steady even on hot summer shifts.
Example Sizing Walk‑Through
Consider a two‑box pick weighing 45 kg total at a 1 m wrist radius. Moment of inertia about the shoulder joint is roughly 45 kg × (1 m)² = 45 kg · m². To achieve 120° of lift in 400 ms, angular acceleration must reach 13 rad/s². Torque required is 45 kg · m² × 13 rad/s² ≈ 585 N·m at the output. A compact 7:1 planetary reducer drops that number to 84 N·m at the motor shaft, safely inside the MHD115C’s continuous 70 Nm plus 20 % headroom. Peak startup sees 231 Nm available, affording a 2.7× safety factor for rushed cycles or heavier mixed pallets.
Maintenance Payback
Daily washdowns common in food or beverage halls rarely touch a palletizing cell, but corrugated dust and stretch‑wrap static do their own damage. IP65 plugs and Viton shaft seals endure the lint storm, yet the weakest link is often connector gasket creep. Rexroth specs a five‑year replacement on the O‑rings; field data shows nine‑year service life when cabinets stay below 45 °C, illustrating how thermal discipline eclipses raw IP rating in the long fight against downtime.
Firmware logs switching events and heat‑sink hours; trend those counters against lift‑axis vibration signatures and you will usually spot a bearing nearing its L10 life six months before audible rumble. Wake Industrial’s exchange pool stocks fully rebuilt MHD115C‑058‑PG1‑AA units with encoder memory pre‑flashed, slashing mean‑time‑to‑repair to a single break in production. Remember, Wake Industrial supplies independent repairs and replacements and is not an authorized Bosch Rexroth distributor.
Beyond Articulated Arms: Gantry and Hybrid Designs
Hybrid palletizers mix linear rails and rotary wrists to cut floor space. A heavy‑duty Cartesian gantry lifting 200 kg at 2 m/s² asks the same mid‑hundred‑newton‑metre torque at its belt drum; hence OEMs often deploy the very same MHD115C frame on the Z‑axis while reserving fan‑cooled motors for long‑stroke X/Y carriages. Uniform motor families simplify spare‑parts shelves and let PLCs clone axis parameters, so change‑overs from a 100‑kg beverage case to a 50‑kg bag line become a recipe switch, not a mechanical rebuild.
Closing Thoughts
A palletizing robot succeeds when its motors straddle the tightrope between brute torque and nimble inertia. Bosch Rexroth’s MHD115C‑058‑PG1‑AA lands squarely on that rope: 70 Nm that never flinches under endless layer lifts, 231 Nm on tap for sprint cycles, and an encoder that makes swap‑and‑run maintenance a lunch‑break affair. Whether your cell is an articulated six‑axis, a five‑axis hybrid, or a high‑stroke gantry, choosing a servo in this performance envelope means faster stack rates, cooler cabinets, and fewer Saturday night crash calls.
Need to re‑gear a lift axis, trend a suspicious temperature alarm, or source a drop‑in replacement before the next shift? Talk to Wake Industrial today and keep your pallets moving out the door instead of piling up in front of the wrapper.
