How to Vend Sheets

So I recently proposed to a group of members a thought challenge, and I figured I’d bring it online.

How would you vend sheets of things, like plywood, acrylic, steel etc?

Some design criteria:

  • Cheap mechanisms, no ‘stepper per board’ solutions.
  • Supporting different sizes in the same machine, the more axis dimension changes you support, the better. (ie, any thickness, one point. any depth, one point, any height, one point. [any height is the hard one])
  • Able to vend addressably, rather than delivering the top off a stack
  • Must protect against casual theft but does not need to protect against outright vandalism
  • Simpler mechanisms are better


  • Payment is not a design consideration, start the thought process at ‘a user is able to be vended a sheet’

I’ve got my own ideas obviously, but lets hear yours first! If your idea is awesome, we might actually build it!

Could a open large rectangular tube with a fabricated screw top and bottom driven by geared motor work?

It’d contain any sheets that physically fit in the unit, with ease to adjust size (adjustment holes for the top screw and just spacer plates on the sides where you only need to ensure the gap is less than the sheet width. Each unit one only vend one type of item, by capacity is only limited by “depth\ (max allowable sheet thickness + sheet gaps + motors)”, so for something like 20mm thickness limit a 1m deep enclosure could hold like 30 sheets to vend, and only needs to be as wide as smaller height\width dimension largest allowable sheet with the machine wall either side and enough gap to move.

Control wise it just needs to turn a given amount per “vend” operation, so it should be heaps simple to set up.

Would a turntable with holders (and a slit between the holders ) work?

The idea is
1)Rotate the turntable until the sheet is in the correct place
2)Slider underneath reaches up through the slit and pushes the sheet out.

2a) Alternatively the slider comes from the center of the turntable.

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I can’t picture your description, you may need to draw it :smile:

I think it fails the ‘cheap’ requirement though, a motor per sheet is expensive. It also has a low score for only being able to vend like items.

I’m keen to see a drawing and how you solve the above problems.

Again, you’ll probably have to draw it. :smile:

It sounds like you’re aiming to move sheets via mechanical motion. I think this will lose feasibility quickly as you try to vend things like 25mm thick full size plywood sheets. The user should be able to use their own muscles to remove the sheet (its cheaper, less failure modes)

What about a small push to push it out so the user can then grab it? I

For two motor options I see two classes of designs.

1)Move a pusher that pushes the sheets out
2)Move the sheets in front of the pusher.

@devians will draw it for the 7th, but busy this week due to modifyre.
BTW its 2 motors per sort of sheet, regardless if you have 2 or 50 in a rack.
Regardless what you decide to do, good luck, I picture many good uses for a sheet vending machine near the lazer cutter.

How are you going to load it? I have a couple of ideas but they depend on if its a forklift load or are you restocking it by hand?

It would take up a lot of space, but I still have an old rotary 50-CD stereo stacker that could be upsized to accomplish this. The base spins around which enables you to add/remove CDs from the stack. Have an access gap only wide enough to access one slot, and a door that unlatches when it’s reached the right slot. To meet the guidelines preventing casual theft but not outright vandalism, a sheet of fabric could be installed as dividing material.

This would be pretty cheap and low-tech meaning it would be reliable and easy to build/repair, would only need one geared motor + lazy susan bearings and a solenoid for the door latch, would support whatever different sizes/thicknesses physically fit in a slot, supports fully random sheet removal as well as random sheet restocking rather than simple LIFO/FIFO, plus a payment system would be pretty easy to add to the slot selection controller. Its only downside is its physical size is hardly the most compact design.


I think looking at CD stackers and jukeboxes for inspiration is a good starting point.

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That is pretty much what I was thinking with the turntable.

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I’m not sure a turntable will work, not only is it a really inefficient use of space, but once you load it up you’ve gotta somehow stably turn something that weighs quite a lot. a 25mm full sheet of plywood is about 45kg. lets say you can fit 20 of these things in. Thats 900kg, that you have to spin/support etc.

Well, we don’t have a forklift, so I assume by hand :slight_smile:

OK that helps. This will be one hell of a large machine that would also need a lot of room around it.

My concept is that you have an arm that would reach the back of the sheet. Pull the arm and hooks on the end grab the back of the sheet allowing you to slide it forward to grab.
What i haven’t worked out yet is the front part would need a slot to allow 1 sheet to slide through and that slot would need to drop after every purchase

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this would only ever vend the top sheet off a stack? It would work I guess but it’s very limited.

Would something like this work ?

With vertical dividers and motorized doors.