Bushing insertion · Light bearing pressing · Snap-fit riveting · Locking · Multi-speed pressing · Position + stall dual verification · No PLC · A fraction of a servo press
Bushing insertion, light bearing pressing, snap-fit riveting, plastic part locking — the process requirements of this class of pressing boil down to two things: press to position (depth tolerance around ±0.1 mm) and press tight (enough force, part never falls out). Building a servo press with force sensor and data system for these two requirements is over-capability at over-budget.
This solution is built on the SD6 integrated drive & control closed-loop stepper driver plus a lead-screw press head: multi-speed pressing (rapid → press → hold → retract) is stored as path parameters; pressing depth is guaranteed by position control; the pressing result is verified by stall detection — when the head reaches the mechanical stop and current rises to the set level, the part is pressed. No PLC, no programming, and the entire control cost is a fraction of a servo press.
Depth is set by the mechanical stop, force by the current limit — neither "accuracy" depends on a program
A complete pressing cycle is four segments, each independently set for position, speed and accel/decel (example values):
| Seg | Type | Position / Action | Speed | Notes |
|---|---|---|---|---|
| Seg 1 | Motion | Rapid to 2 mm above the part | High | Saves cycle time on air travel |
| Seg 2 | Motion | Press down to the stop | Low | Low-speed pressing — no shock, no bounce |
| Seg 3 | Wait | Stall hold 0.5～2 s | — | Current limit reached = press force settled, joint stabilizes |
| Seg 4 | Motion | Retract to origin | High | Clears the space for the next cycle |
Press force ≈ 2π × stall torque × screw efficiency ÷ lead — force is one current-limit percentage; changing products means changing one number
| Signal | Direction | Function |
|---|---|---|
| Two-hand start | DI inputs | Two-hand trigger for pressing (safety compliant) |
| Light curtain | DI input | Stop on obstruction — operator protection |
| Origin switch | DI input | Power-up homing, re-establishes the depth datum |
| Up/down limits | DI inputs | Hard travel protection |
| Press done | DO output | Releases the line to proceed |
| Out-of-tolerance alarm | DO output | Stall timeout = wrong part or missing part — audible/visual alert |
Terminal definitions per SD6 specification; input active level NO/NC selectable
| Item | Pneumatic + PLC | Servo Press | SD6 Integrated Solution |
|---|---|---|---|
| Force control | Air pressure, fluctuates | Precise & tunable | Current-limit tunable, sufficient for light duty |
| Depth control | Mechanical stop | Program + curve | Mechanical stop + closed-loop position |
| Force-displacement trace | None | Yes (choose it for QC-required pressing) | None (this solution targets process-grade, not QC-grade pressing) |
| Device cost | Low | High | Low to medium |
| Commissioning | PLC programming | Specialist setup | Parameter configuration, no programming |
Honest boundary: safety-critical pressing that requires force-displacement archiving belongs on a servo press — this solution serves "press to position, press to tight" process-grade pressing
Depth is set by the mechanical stop (±0.02 mm class once calibrated); system deflection under load adds only microns in light duty — comfortably inside ±0.1 mm class process tolerances.
The driver current limit determines stall torque, converted to force through the screw: F ≈ 2π × T × η ÷ lead. Calibrate two points on site with a force gauge — linear in between.
The multi-segment path resolves it naturally: rapid segment saves time, low-speed segment protects the joint, hold segment settles it — force and takt live in different segments.
Multiple path sets are stored: each product has its own "position + current limit" combination, recalled by segment number on the panel — ideal for multi-model OEM machines.
Parameters are calculated and calibrated in the office; on site there is only loading and verification