Practice missions
Practise in
0 XP
Practice missions
Mission 49 · Pro PLC programming exercise

Both hands, every time

Write two-hand control for a press, with an interlocked guard.

Start a stroke only when both palm buttons are pressed within 0.5 s of each other, with the guard shut and the ram at the top. Return the ram if either hand lets go or the guard opens.

This mission is part of ProTry the full course, every mission and the expert challenges free for 7 days. No card needed.
The 3D two-hand control press this mission runs on Pro mission
Test replay

A full stroke

Test 1 of 4
Set by the testChecked by the testStep 10 of 10 · 1.3 s
Level
Applied
Time
About 30 min
Reward
+350 XP
Rig
3D two-hand control press
Siemens editors
SCL, LAD
Rockwell editors
Structured Text, Ladder
Course stage
27. Machine lab 2: memory, timing and sequences
Automatic tests

What the tests check

  1. Both buttons within 0.5 s start a stroke; slower does not.
  2. Letting go of either button returns the ram.
  3. No stroke with the guard open; opening it mid-stroke returns the ram.
  4. Both buttons must be released before the next stroke.
  5. PartCount counts strokes that reach the bottom.
  1. Try it Use the buttons below the model and watch the rig respond.
  2. Test solution Every check runs on your code in one press.
  3. Replay If one fails, step through it one scan at a time to see why.
Why it matters

Where you’d see this on site

Every hand-loaded power press follows rules like these, set by EN ISO 13851 and checked by the insurer's inspector.

Without the 0.5 s window, one button can be taped down and the press run one-handed. Without the release rule, holding both buttons repeats strokes while the operator reaches in.

Where you'd find thisKeep both hands on the buttons, and out of the tools

Presses are among the most dangerous machines in any factory. Two-hand control keeps the operator's hands on the console while the tools close, and an interlocked guard stops anyone reaching in.

  1. LoadGuard open, blank in
  2. Close guardInterlock made
  3. Two handsStroke downYou are here
  4. UnloadDrawn cup out
On a real site: places, parts and safety
  • Metal pressing and deep drawing
  • Riveting, staking and crimping stations
  • Assembly presses in electronics and automotive

In real machines these rules are enforced by safety relays or a safety PLC, so a programming mistake cannot defeat them. Here you write them to understand why they exist.

Tying one button down to run with one hand is the classic way operators are hurt: that is why both must be released before the next stroke.

The sizes, timings and cutaways are teaching choices, not a drawing of any one real installation.

Keep going

Next in the course