PUPS 10 | Complete Machine
To see all the calculations and work below as well as the problem and description head to my Transforming Table page.
Small apartments need furniture to be multifunctional and flexible. Who has space for a coffee table and dinner table and work table? What if the same table can transform between the three?
Manufacturing & Assembly
After manufacturing and acquiring all the parts described in PUPS9 I measured and assembled the parts, and they met my tolerance specifications, generally +/- 0.5 mm on size dimensions, hole locations, and clearance holes, and +/- 0.1mm on sliding fit or press fit holes.
The table is assembled! Everything went together as expected - I'm glad I spent time thinking about assembly during the design phase, because I didn't run into any unanticipated snags. A huge shout out to Maha Haji my shop buddy and peer reviewer who was a great teammate throughout and finishing up our tables together.
Operating the machine was smooth except for the wire management and motor control. For the demo day the table successfully moved up and down in a level manner 4 times!
During assembly, I cut wires approximately to length, threaded them through the wire spindle, and adjusted the length with the legs at their lowest point. I designed an additional adjustment on the pulley block for post assembly adjustment. Even with the grooves in the wire spindle, with depth and width calculated for the diameter of wire and number of wraps, the wire still slipped out of the grooves and wound around the base of the spindle creating a capstan effect (as described in the seek and geek). Thus, the day before the demos I created a wire guide to sit loosely around the spindle and constrain the wires to the height of their groove and keep the wires radially compressed. This worked well enough for the demos, but isn't a long term solution.
To finalize my table and make it really usable in my living room, I'm planning on switching from wire (which gets kinky and has a large bend radius) to 200 lb. dyneema braid fishing line, creating a new spindle for the smaller diameter line that has less height. I'm also going to change my simple switch that connects the motor with 12V to a buck converter which will output a high frequency PWM signal with a lower voltage to slow the RPM of the motor to provide more control, instead of ramming my carriage into the rail stops. After I made these few additions I'll be able to measure the accuracy, repeatability, resolution and stiffness of the final transforming table.