Applications
Machine Tending
Machine tending is the robotic loading and unloading of parts into and out of a production machine such as a CNC mill, lathe, press, or injection molding machine.
What it is
Machine tending puts a robot in front of one or more production machines to handle the load/unload cycle: pick a raw blank from an infeed, open the machine door or guard, place the blank in the fixture, clear the workspace, let the machine run, then pull the finished part and drop it on an outfeed.
It's one of the oldest jobs given to industrial arms because the work is repetitive, the cycle is well defined, and the hours are long. A single arm often tends several machines in a cell, staggering its trips so no machine sits idle waiting for a fresh blank.
How it actually works
The robot runs a fixed program keyed to the machine's cycle. It waits for a 'cycle complete' signal from the machine controller, enters through an open door or over a guard, and uses a gripper (often dual, so it can carry a finished part out and a blank in on the same trip) to swap the parts in the fixture. Handshake I/O between the robot and the machine controller gates every step: the robot won't reach in until the machine reports the chuck open and the door clear, and the machine won't start its cycle until the robot signals it has retracted.
Positioning has to be tight because the fixture, chuck, or mold cavity has little tolerance for a misplaced part. A mid-payload arm like the FANUC M-20iD/25 carries the gripper and part while holding taught positions to its rated repeatability, so a blank lands in the same seat every cycle. Part-presence sensing (a gripper switch or air-blow confirmation) verifies the robot actually has the part before it commits to the next move, which keeps a dropped blank from turning into a crash inside the machine.
How it differs
- Material Handling · General material handling moves parts between points; machine tending is the specific case where the destination is a production machine and the robot is interlocked with that machine's run cycle, waiting on its ready signals and gating its start.
- Palletizing · Palletizing stacks finished goods to a pattern at the end of a line. Machine tending feeds and clears the machine mid-process, and its cadence is set by the machine's cycle time rather than by a pallet pattern.
Where you meet it in the field
- FANUC M-20iD/25 · A mid-payload arm commonly deployed on load/unload cells where the gripper plus part stays within its rated wrist load.
- Setting the reference position · Tending cells depend on taught positions landing the part in the fixture every cycle, so the reference position has to be set accurately.
Common questions
- Can one robot tend more than one machine?
- Yes, and it's common. One arm parked between two or three machines staggers its trips so it's loading one while the others are running, which keeps the expensive machine tools busy instead of the robot.
- Why use a dual gripper for tending?
- A dual (or double) gripper lets the robot carry a fresh blank in one jaw while it removes the finished part with the other on a single trip into the machine. That halves the door-open time and the number of entries, cutting cycle time.
- What happens if the robot drops the part on the way in?
- That's why tending cells sense part presence at the gripper. If the confirmation signal says the part isn't held, the program should stop before the robot commits to placing into the fixture, so a missing blank doesn't become a collision inside the machine.