Can the machine shell charged 24VDC？

Hi all,
A supplier give us a new tooling for a machine. They connect 24VDC power to the tooling itself to detect whether there is a component. And when we install the tooling to our machine, the whole machine has 24VDC voltage.
Can anyone tell me whether this method is OK?
Or if not OK, are there any standards objecting it?
Thanks very much.

In a situation like this there should be some kind of isolation. No, your machine frame should NOT have 24VDC going to it. The reason machine frames are grounded is so that if the frame becomes energized it will trip a breaker / blow a fuse and open the circuit as quickly as possible. Imagine if this was a motor frame and was carrying 20A or 30A of current. Operator Joe goes to open a door and is at the same time grounded, he would become a part of that circuit and could easily suffer electrocution. Now it is really unlikely that the 24VDC circuit is going to kill you, but it is possible, and the machine's motors don't run on 24VDC, so you need to get this issue resolved before there is a dangerous short on the machine.

I would contact them about this and see what is wrong as well as find out why the fuse that powers that 24VDC circuit is not tripping like it should be.

24 VDC, relative to what? Is it isolated or grounded? I would assume it's through a resistor, limiting current.
Interesting article on Electric Shock.

If the whole machine has 24VDC on it I would say not only is the tooling wrong but your machine isn't grounded properly either.

I wouldn't worry too much about the 24VDC hurting someone, possible but <50V is generally considered 'safe.' However, consider for a moment that a 400VAC feeder comes loose inside the machine, now your machine has 400VAC to ground and that is bad news.