Machine Tending Retrofit: The Interfaces That Decide
Direct answer: Verify five interfaces before specifying hardware: the pick and place itself; how parts are presented and buffered; what state the machine control can report, such as cycle complete, door open and workholding released; how start permission is granted and who holds it; and how the safety interlock suits the real layout. On older machines those signals often have to be brought out deliberately, which belongs in the application review.
Who this is for: Written for engineers planning to add robot loading and unloading to machine tools that are already in production.
Scope: This EVST guide covers the interfaces between a robot and an existing machine: pick and place, part presentation, machine state signals, start permission and safety interlock. It does not quote cycle times or availability figures.
The pick is the visible interface, and the easy one
In the reference footage robots tend two different machines, loading parts in and taking them back out. Door position, rack height and grip attitude are different on each.
Gripper and rack design is the part of the job everyone can see, and it is usually finished first. Retrofits rarely stall here.
What a machine tending retrofit has to resolve
The robot needs to know when the machine has finished, whether the door is fully open, and whether the workholding has released. Without those states it can only wait on a timer and guess.
Guessing costs both cycle time and reliability, and it fails in exactly the situations that matter, such as a cycle that runs long or a door that sticks.
Older machines may not expose the signals
On machines that predate the retrofit, the state signals often are not brought out to a terminal at all. Whether they can be, and by what route, is a question for the proposal stage.
Leaving it to commissioning is where retrofit projects lose weeks, because the answer sometimes involves the machine builder rather than the integrator.
According to IEC 60204-1:2016, the electrical equipment of a machine has defined requirements for interface conditions, which is what makes bringing state signals out a design task rather than a field improvisation.
Start permission and who holds it
Someone has to decide when the machine may start its cycle: the robot, the machine, or a cell controller between them. That choice shapes the whole sequence.
It also determines what happens after an interruption, which is the case worth designing for rather than the clean cycle.
Safety interlock comes last and is not optional
When the robot enters the machine’s working space, how the door is interlocked, and how the cell stops when someone enters, all follow from the real layout. ISO 10218-2:2025 covers integration and ISO 12100:2010 the risk assessment behind it.
The guarding visible in the footage is one arrangement among several; yours follows from your own assessment rather than from a photograph.
According to ISO 10218-2:2025, the interlock arrangement follows from the integrated layout, so a guarding scheme copied from another cell is not evidence for yours.
According to ISO 12100:2010, the assessment starts from the intended use and the reasonably foreseeable misuse of the cell as installed.
A short checklist before you specify hardware
Pick and place; part presentation and buffering; machine state signals; start permission; safety interlock. Five items, in that order.
A retrofit that has answers to all five can be specified. One that has answers to the first two is a gripper project, not a cell.
In practice an application review begins with project inputs rather than with a robot: the machine list, the signals each control can give, and the part range. Selection follows from that evidence, and acceptance is written around the five interfaces above.
| Interface | What it covers | What closes it |
|---|---|---|
| Pick and place | Gripper form, approach, part orientation | Part drawing and grip study |
| Presentation and buffer | Rack, tray or conveyor, and where parts wait | Part range and batch size |
| Machine state | Cycle complete, door open, workholding released | Available signals on the control |
| Start permission | Who allows the next cycle and after a stop | Sequence agreed with the machine owner |
| Safety interlock | Door interlock, entry stop, safeguarded space | Risk assessment for the real layout |
Frequently asked questions
Can any machine be retrofitted with robot tending?
Mechanically, usually. What decides it is whether the machine can report its state and accept a start permission, and whether the door and workholding can be interlocked safely.
Does the robot have to match the machine brand?
No. What has to match is the interface: the signals available, the voltages and the safety category.
What if the machine has no spare signal points?
Then bringing them out becomes part of the project scope, and it belongs in the proposal rather than in commissioning. It sometimes involves the machine builder.
What should we send to get a useful answer?
The machine list, the signals each control can provide, and the part range with weights and outline dimensions.
Project inputs for an application review
To have your machines assessed rather than a generic cell, send:
- machine list with control type and available signals
- part range with weights and outline dimensions
- current loading method and operator involvement
- cycle requirement and shift pattern
Send the machine list and the signals available and it can be worked through one interface at a time. Related reading: industrial robot product range, robotic factory integration.