Automatic Take-away

Greetings Gurus!

A common desire (read 'fixation') among my engineers is the idea of an automatic loading mechanism from certain manual operations.

For instance, we have a project where operators will manually sonic-weld plastic clam-shell packages at a stand-alone welder, then load these onto an automatic labeller. The expressed desire is for the labeller to "know" the pack has been loaded, do it's job, then shuttle the pack to the next station, all without any kind of operator input.

I know a light curtain could do this, but frankly, they aren't trustworthy enough for me. A safety device should, I feel, be a safety device and nothing else. Making it do any kind of double-duty compromises its real function.

Personally, I think the automatic station should be set up with some kind of operator initiation, preferably palm switches, but at least a foot pedal. Something where the machine moves when the human tells it to, and not on its own.

How have you guys handled this in the past? Any good, safe auto-load schemes in operation? Am I being too cranky on the light-curtain-real-job thing?

What sayest thou?

TM

Timothy.
My company uses light curtains in exactly the kind of application that you describe.
On your machines the operator can select EITHER to let the sequence continue the moment the light curtain "senses" that the piece is inserted following that the hand is clear, OR the sequence waits until the operator presses a "continue" button (and the light curtain is uninterrupted of course).
The faster setting of automatically continuing the sequence is used when it pays off in terms of produced pieces per hour.

Go with the light curtain

Tim,
We also use light curtains as part of cycle intiation. The operator loads a part and hits an opto-touch to start the cycle. Halfway through the operator needs to manipulate the part and after they pull out of the light curtain, the cycle continues.

Or instead of using a light curtain you could use a fiberoptic thru beam.

TimothyMoulder said:

I know a light curtain could do this, but frankly, they aren't trustworthy enough for me. A safety device should, I feel, be a safety device and nothing else. Making it do any kind of double-duty compromises its real function.TM

Click to expand...

That is why they have a non-safety monitoring output. However, I agree in not liking to have a process initiated by a light curtain. I that what you mean by not trustworthy? I hope you can trust a safety device for safety.

A foot pedal scares me.

On our machines, the operator loads parts through a light curtain while the rest of the stations are cycling. (The load stations is mechanically isolated from the other stations) Once loaded, the operator hits an opto-touch button to "pre-set" the machine. The part is clamped and the indexer waits. Once the rest of the machine is done cycling, the index is free to move without operator intervention. If the curtain is broken during this wait, the operator must hit the button to re pre-set the machine.

This works well and is very efficient, as the operator can go do other things instead of waiting for the machine.

We also use the light curtain to initiate things like fixture wash and other non-critical functions.


They make non-safety light curtains also, If you feel the need. I am pretty sure http://www.sti.com has some.

Use a foot pedal if you want to but your operators may complain and it really is the least safest choice. Operator has to place all of their weight on one leg for a short period and that is not very ergonomic.

Your operators will love you if you use the light curtain and you can satisfy the safety issues. Add a another opto-touch too but thats one extra step most operators would prefer not to make.