Safety in the machine ...

Safety questions,
An external company is integrating a machine in our factory,
I do not agree with the safety...

1. When changing something in manual mode, and I press AUTO, then everything is setting back because the current step is activated. Dangerous I think. It Should be (I think), when entering manual mode, operands are zeroed, even when coming back in AUTO, after hitting start operands should be enabled again. ?

2. Servo's and other motors can be controlled manually, even with the doors open ? Is this allowed ? I think that drives may not send pulses to their IGBT's when a door is open ?

3. When changing a servo setvalue in manual, the machine follows the new entered value, there is no confirm, when entering a wrong number... hope that nothing brakes ?

Combo. Here is my take.

Combo said:

1. When changing something in manual mode, and I press AUTO, then everything is setting back because the current step is activated. Dangerous I think. It Should be (I think), when entering manual mode, operands are zeroed, even when coming back in AUTO, after hitting start operands should be enabled again. ?

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I'm not sure I understand exactly what you are saying here, but if you are talking about position states, like whether a cylinder is extended or retracted, for example, I believe it should be set up one of two ways (or some combination of the two); either the machine has a "HOME" position where everything must already be set in order to initiate an AUTO START or the devices stay where they are until a controlled move signal is initiated. In short, this means nothing simply moves on its own just because you have entered AUTO mode.

Combo said:

2. Servo's and other motors can be controlled manually, even with the doors open ? Is this allowed ? I think that drives may not send pulses to their IGBT's when a door is open ?

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I don't see this as a problem ASSUMING that a dead-man switch style control is used. The key, of course, is that in manual mode a human being must be in control of all movement at all times. This is the same way robots are controlled in TEACH mode.

Combo said:

3. When changing a servo setvalue in manual, the machine follows the new entered value, there is no confirm, when entering a wrong number... hope that nothing brakes ?

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I agree with you completely on this. No setting should be immediately taken - a confirmation step needs to exist.

As a standard practice, I recommend creating a Safety Standards spreadsheet that details each condition to which all machines must conform. Everything you have talked about here should be on it and proper operation should be described. Typically this document would be supplied to a machine builder or integrator in advance of the contract, but in your case, I suggest going ahead and introducing it now. If you are working with a decent integrator, they should happily accept this and, where applicable, make minor modifications at no additional charge. In some cases, though, there will be additional costs involved and reasonable explanation to justify them.

Steve

On 1, agree with Steve completely.

On 2, I'll add that I've seen machines where running servos in manual, with guarding open, is possible if a safety keyswitch is made; if the servos drop to a very slow speed with guards open; or with both. It's awfully hard to set up, test, or troubleshoot the servos otherwise. In the case of large systems, or robots in workcells, then the deadman switch is ideal. The newest robot we have has a three-position deadman - you have to hold it in the middle position, or the robot disables. Let go, or squeeze too hard, and the robot stops.

On 3, you might be able to bound the range of allowed values. This doesn't help, though, if the machine setup is just wrong for the product and nobody notices. It is certainly possible to modify the HMI so that each setup has a unique range - if that would help - but you'll doubtless pay extra for that. How do you know that the value is "wrong" in the first place?

Paul T said:

How do you know that the value is "wrong" in the first place?

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If for no other reason - maybe it was not the number you intended. Maybe you wanted to key in 10 but fat-fingered 100 instead - both of which could easily be in the "limited" range you describe. That's what I was thinking about anyway.

Steve