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I have a prototype machine with mechanical moving parts (all contained inside a transparent interlocked enclosure) to review. Single-phase AC power enters at the rear via a fused IEC 60320 C14 inlet, through a rotary isolator switch (adjacent to the inlet at the rear) to a front-mounted emergency stop switch and then on to the rest of the unit.

The main unit is controlled via an LCD display with a rotary turn and click encoder for navigating menus. Selecting a task and starting / stopping it is achieved via this interface - effectively implementing a software Start / Stop switch. All stops are uncontrolled - i.e. a shutdown signal is sent to the motor drivers causing an immediate loss of power to all moving parts (they have minimal inertia).

In many machines with simpler functionality (pillar drill, band saw) I see this same topology but with the addition of a series contactor controlled by a pair of mechanical Start and Stop switches. Obviously, in this case there is no need for a complex LCD + encoder control system, so the start and stop switches are both necessary and sufficient. But in the case of the system I have described , does the LCD control described provide compliant control of the system, or is an additional pair of mechanical Start / Stop switches required for compliance with EN60204?

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  • \$\begingroup\$ So the only way to shut it off is to go through the menus or pull the plug? Imagine your finger gets caught in the machine, now in extreme pain you have to use the other hand to navigate the LCD display and shut the machine down? Typically systems I design all have an E-Stop button that is push/pull or push/twist and it cuts all power. \$\endgroup\$ – Ron Beyer Jul 8 at 16:20
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    \$\begingroup\$ @RonBeyer : from the original post: "Single-phase AC power enters at the rear via a fused IEC 60320 C14 inlet, through a rotary isolator switch (adjacent to the inlet at the rear) to a front-mounted emergency stop switch and then on to the rest of the unit." The machine includes an E-Stop for exactly this purpose, mounted at the front of the machine. I am specifically interested in whether EN60204 requires mechanical Start and Stop buttons for standard start and stop procedures, or whether soft features are sufficient. \$\endgroup\$ – stefandz Jul 8 at 16:24
  • \$\begingroup\$ You say the moving parts are all contained in an interlocked enclosure. Does this mean that it is physically impossible for the user to come in contact with any moving part while the device is powered? That it is impossible to get "your finger caught in the machine"? \$\endgroup\$ – Elliot Alderson Jul 8 at 16:52
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    \$\begingroup\$ @ElliotAlderson Yes - these interlocks are in series with a low voltage DC rail that power all of the moving parts, so it is physically impossible (without defeating the interlocks). In addition there is a physical emergency stop (E-Stop) switch at the front of the machine, easily accessible from the whole machine front for emergencies. My question really revolves around what EN60204 requires re: mechanical Start / Stop switches for standard start and stop procedures. \$\endgroup\$ – stefandz Jul 8 at 16:56

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