I'm planning my next woodworking project which will be a dining table with a recessed vault for boardgames.
The typical boardgame table is just that, but I'd like to add a mechanism to be able to raise and lower the platform and I'm thinking about using stepper motors to do that, so i have many questions
My idea is to install 4 steppers (one in each corner) and have those rotate a threaded rod to do the job, just like the z-axis of most 3d printers or cnc, but with 4 steppers instead of just one.
Something like that (not my image, but it represents what I am thinking)
Is it a good idea to have 4 steppers working together like that? What are my chances to have them perfectly in sync? Should I be worried about mis-steps ?
My other question is about required torque. I dont have actual numbers right now, but my lifting platform would be pretty large, around 30"x60" I'd say, so probably at least 25-30 lbs plus whatever is sitting on top. Would some quality nema 17 do the job?
Anything else I am missing? Any other idea for my use case?
Quite possible to get something like that to work, but ONLY if you get all 4 to start at the same point of the screw each time you start the steppers. A much more practical design is to connect ONE stepper to pulleys with a cog belt. Plus a tension adjustment of some sort.
If you use separate stepper drivers for each motor, you could wire the STEP and DIR signals together for all the drivers, and treat them as one. Or you could have separate pairs of STEP & DIR pins for the 4 drivers and have the code send identical signals on the separate pins.
@Paul_KD7HB's suggestion of mechanically synchronizing the actuators is good.
If you size the motor(s) properly, they should be able to handle the load with no missed steps.
Mechanically, the system looks overdetermined with 4 actuators versus 3 degrees of freedom (up-down, pitch, & roll), and it could be possible to bind the system and cause skipped steps if they get out of sync. How well it works could depends on a lot of missing information about the threaded rods
There is always the most interesting problem of computers and mechanical stuff. That is the "initial conditions" that are present when you first power up the system. There is zero certainty that each stepper will start up its initial position at the identical position it had when power was turned off.
If you want it work anytime soon don't use steppers. Use 1 DC motor + 1 spindle + 2 limitswitches + 2 diodes + 2 buttons + 1 decent linear rail (however that is constructed). These kind of mechanisms are around since ages in furniture building, so you might want to peek there. If you insist on 4 spindles use 1 timing belt for all and one (central) motor.
I know that using a single motor would be better, but due to the large platform, it's not very practical, I'd need a really (too) long belt.
I was thinking maybe adding limit switches to each corner, both top and bottom and then simply running each motor independently until it hits the limit switch would be a good idea, but then I guess I don't exactly need stepper motors anymore, DC motor would probably be good enough,
