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Technical note
Pick-and-place with soft landing with 48 V DC servo drives
If your machine needs to know how hard it pressed, you need a force signal, not just a position counter.
What the motion looks like
Classic Z-axis approach. The interesting engineering is in the transition — how the axis decelerates from approach speed into contact speed, and how the force setpoint is applied without the machine feeling the step.Does it need force control?
If the machine must know how hard it pressed, a position counter is not enough. You need a force signal that is available before, during and after contact, sampled fast enough to catch the peak.What to look at in the specification
| Question to ask | Why it decides the drive |
|---|---|
| Does the tool need to know the peak contact force, or just hold a force? | Peak detection needs a fast loop; holding a force is easier |
| How much stroke does the soft-landing zone need? | Soft landing usually needs more stroke than the nominal travel |
| What is the part's mass and inertia? | Determines the current rating and therefore the model |
| Which bus does the machine run? | EtherCAT if there are multiple synchronised axes; Modbus or pulse otherwise |
A selection checklist you can send to your engineer
Send this list to whoever is doing the mechanical work. If the answers come back with specific numbers rather than adjectives, the drive selection is half done — and so is the quotation.- Does the tool need to know the peak contact force, or just hold a force?
Peak detection needs a fast loop; holding a force is easier - How much stroke does the soft-landing zone need?
Soft landing usually needs more stroke than the nominal travel - What is the part's mass and inertia?
Determines the current rating and therefore the model - Which bus does the machine run?
EtherCAT if there are multiple synchronised axes; Modbus or pulse otherwise
Common mistakes I see
- Treating the approach as a position-only move with a slow final speed. If the tool must seat into a feature, position alone will not tell you whether it seated or jammed.
- Applying force control to a part that does not need it. A rigid part on a known stop does not need force control — it needs good positioning, and force control adds commissioning effort for no benefit.
Cycle time and settling
On cycle time, the fast traverse dominates and is where most of the optimisation effort goes. The contact phase is short by design — a soft-landing dwell of a few tens of milliseconds is normal, and lengthening it to look thorough usually costs more yield than it gains. The place where a soft-landing machine quietly loses time is the settle before the Z axis retracts. If the tool is still moving when the pick logic releases it, the placement inherits that motion. Multi-segment trajectory control in the drive shortens the loop from command to output, so the axis reaches a confirmed stop sooner and the retract can begin earlier.Where I would start
Starting point: UF series, -P variant if the contact force genuinely matters.. That is a starting point, not a finished selection — the deciding inputs are the motor model, the bus interface, the payload or stroke, the axis count and the ambient temperature. The parameter reference lists what each family covers, and the documents library has the cable tables and application notes your engineer will want.Key takeaways
- Where I would start: UF series, -P variant if the contact force genuinely matters.
- Compare the current-loop and sampling specifications, not the force headline — the force number alone does not decide these applications.
- If the axis never touches the workpiece, say so. Position-control criteria are the right ones to judge on.
- Send the checklist to your mechanical engineer before choosing a model — most wrong selections start as an incomplete brief.
Common questions
Is a 48 V DC servo drive the right choice for pick-and-place with soft landing?
It depends on whether the axis makes contact and on the thermal environment. My starting recommendation for pick-and-place with soft landing is UF series, -P variant if the contact force genuinely matters. — but the motor model, payload, bus type and ambient decide it properly. Send me those four and I will give you a specific answer.
Do I need force control for this application?
If the machine must know how hard it pressed, a position counter is not enough. You need a force signal that is available before, during and after contact, sampled fast enough to catch the peak.
Can one drive cover several axes in this machine?
For synchronised axes on one bus, the G-series multi-axis units cover pairs and six-axis groups over EtherCAT. If the axes are independent, separate drives are usually simpler and cheaper. Tell me the axis count and which axes must move together.
Which communication interface should I specify?
EtherCAT if you have multiple axes that must move together, or if you need STO. Modbus-RTU or CANopen for simple point-to-point axes where the motion is self-contained. Pulse/direction when you are retrofitting into an existing controller. One warning worth repeating: STO exists on EtherCAT models only, so if your safety case needs it, that decision forces the bus choice.
How do I validate the choice before committing to a quantity?
Run the drive on your own part, not on a test piece. The ForceControl Application note in the documents library describes the setup, and the current-loop and sampling figures in the parameter reference tell you what to look for in the force signal at the moment of contact. If you would rather have someone look at your data with you, send me the traces.