Hey all,
I have a 3 phase advance lift table that I am using (manually) to load plywood onto a CNC router. It is a hand remote with 2 switches. Up and down and a disconnect...(see attached diagram).
What I am trying to figure out is, I would like to build a control box with a Hand Off Auto switch where hand works as it does currently, and auto would affect up only. In auto Either an eye or mechanical switch would open/close after the top sheet of plywood was removed it would then wait 20-30 seconds and raise the table up 3/4", retripping the switch and stopping with the next sheet in position. Is this possible? Probably wouldnt hurt if an estop was added as well. Thanks in advance for your help!!

 

Welcome to AAC.

You can certainly do this, but, for safety reasons open loop timed operation where there are people working is not good practice. Some sort of confirmation that are no hands present is critical to safe operation.

I don't mean to be a wet blanket but auto-start operation of a large motor driven mechanism where people's hands are potentially in the area just isn't something I could help with.

 

I agree with the previous post. A timer removes the action / reaction relationship, which unless globally considered, introduces safety concerns.
I suspect you are handling the sheets by hand? Would initiating ‘advance to location’ not be sufficient, as I suspect the time to advance to the next sheet would not be a time penalty. A timer has more cons than pros, unless there is a specific scenario.

 

I don't mean to be a wet blanket but auto-start operation of a large motor driven mechanism where people's hands are potentially in the area just isn't something I could help with.

Typically in these applications, safety Palm Buttons are used, both buttons have to be pressed for any action to occur, the industrial variety are fairly expensive as they have fool deterrents such as laying an object on one of the switches and pushing the other does not work.
Just two PB in series would be the cheaper minimum.

 

the industrial variety are fairly expensive as they have fool deterrents such as laying an object on one of the switches and pushing the other does not work.

I assume that is done by requiring that both buttons be pressed within a short time interval to be valid.

 

Typically in these applications, safety Palm Buttons are used, both buttons have to be pressed for any action to occur, the industrial variety are fairly expensive as they have fool deterrents such as laying an object on one of the switches and pushing the other does not work.
Just two PB in series would be the cheaper minimum.

Yes, though unfortunately the safety feature seems to be incompatible with the TS's desire for automatic feed. I surmise he wants to speed up production. Maybe a proximity sensor could prevent movement until the operator leaves the area with the sheet he's taking away.

 

I assume that is done by requiring that both buttons be pressed within a short time interval to be valid.

Most work this way, often used for machines such as a press etc, where an item is loaded and the cycle is only initiated when the operator is clear.

 

During operation there wouldnt be a need for an operator to be on this end of the machine at all. The previous sheet is dragged onto the table via the cnc gantry and the vacuum suction cup handler i made.
Once finished cutting a sheet the gantry goes "home" while the operator unloads the peices, vacuums the table. He then starts a new cycle by pressing a button which raises the locator pins, lowers the vaccuum cup rail and pulls the new sheet on, locates via air cylinders on 2 sides, actuated locating pins on the other. The camera on the gantry checks 0,0 status then begins cutting. I actually like the safety aspect you speak of, i have several new Sick light curtains that could guard the only 2 points of entry (the rest is fenced off). Adding those in series to the E-stop circuit I would assume?
Right now the operator has to walk to the other side and push the button between cycles each time to raise the next sheet the 3/4".

 

Relocate the button? What logically drives the vacuum transfer system?

 

The ones I mention aren't usually in the E-Stop circuit, mainly in the machine sequence, IOW, it holds up sequence until buttons pressed.

 

Plc runs the feeder and pins, i am out of I/O's. The lift is 48"x72" and able to be used on a different router that is set up Identically to this one whith the exception it cuts 1.125" plywood.
The point is to make it as automatic as possible. We have already purchased a robot to unload the machine, (by looking at the lead time so has everyone else) moving the current button with no limit switch wouldnt prepare for the next step.
I can assure you that the safety committee and safety manager will have to approve the operation of the table prior to it being released in production. The table will either be light curtained or cabled at poe.
They sell tables, unguarded, that do exactly as i describe. You can view them in operation on you tube running an auto processing cnc router. Hint company name starts with L.
I just #1 already have these tables and #2 would prefer 4K lift cap vs 3.2K #3 trust American ingenuity above the others

 

Plc runs the feeder and pins, i am out of I/O's.

Most PLC's have expansion I/O capability.

 

Not sure what tables you are referring to, but I've seen many configurations in the field.
If your lift is positioned up to an unload station, could you borrow functionality from the unloader, extending safety circuits via a connector. 'Enabling' the auto height of the table during some unloader state might be possible? How do you envision reloading the table? is that auto as well? One system I worked on had the fork truck place the bundles on a transfer chain which then fed into the hoist.

 

The lift will be manually lowered to the floor a fresh pallet of plywood placed on it 3/4" = 44 sheets. After resetting the light curtain/entry cable faults the operator will bring it up to the correct position (switched indicator light) then put it back into auto to cycle the other 43 sheets. Our goal is 40 sheets per day so it is basically a once daily procedure.
My personal goal is to keep both the lift table on the load end and the conveyor on the unload end, running as tgeir own entities. Reason being, if for instance we shell a hsd spindle motor or a servo, and are down for 2 weeks, we can readily automate one of our machines currently running slower jobs. Put the safeties in place, hook up 4 wires. Flip the disconnect and back running again. Since ya never know if it will be there more than 90 days, hardwire it in so it complies with 1910.

 

If you google SmartShop Autoloader you will see what I am trying to accomplish with my table.

 

Pretty straight forward. Why do you need a delay?

 

My thought was just to give options for placement of the eye. Depending onwhere it is located, pulling longways it may move too soon?