Jim Heinrich, at Mittler Bros. Machine & Tool asked:

I would like to know if it is acceptable to use only a light curtain and part present switch to initiate an assembly or test machine cycle. I would like to eliminate the Cycle Start switch, to save part to part cycle time and reduce repetitive motion for the machine operator. Are there any standards that address this with OSHA or ANSI? Thank You

SafetyMan says:

What you are talking about is PSDI. Presence Sensing Device Initiation, using the make/break detection of the safety light curtain to initiate a new machine cycle. OSHA refers to this in CFR 1910.217, the standards for presses. Unfortunately, this is the only location where this is referenced. I am assuming that your machine is not a power press. In 1910.217, OSHA requires that a third party validates the application. At this point, there are no third party validators, therefore, you cannot achieve the requirements of OSHA's Standard at this time. If it is not a power press, now we need to look at the requirements of control reliability as stated in ANSI B11.19. If the components that are used meet the requirements of this standard, your personnel have been trained in the proper usage, and the system is hardwired and not controlled by a solid state device such as a plc, then we must assume that it is safe. Until OSHA or ANSI gives us further guidelines on PSDI, this is the best we can do. Meanwhile, I will mention that where this has been implemented, CTD's have been sharply reduced!