The wooden parts of the frame are nearing completion. Six orders from Aliexpress remain in-transit. All in all, this is going swimmingly… albeit the anticipation of the linear bearings and stepper motors arriving is just driving me crazy. I’m nearly able to start assembling. This post may be low on photos. I didn’t stop to take many.
One refund has been confirmed (for an order that wouldn’t pass ‘security’ ?!) and the replacement order has been made from a different supplier. Another order that arrivied with parts missing (they fell out a hole in the packaging during shipping) has been in dispute, and should have replacements shipped this week. Since I don’t have a high-degree of confidence in that happening, I ordered replacements from Amazon. I’ve also purchased a quantity of small square M3 nuts from Fastenal, which is the only supplier domestically I’ve been able to find that stocks M3 square nuts 1.8mm thick.
In the way of the frame, the 1/4” router bits I ordered from Amazon did the trick. They’re cheap, they dull quickly, and one of them already broke from metal fatigue and heat. This is why name-brands don’t make 1/4” bits bearing topped for flush-trim work. I’ll have to try a more traditional flush-trim bit with ABS templates in the future. However, the PLA templates worked for this instance. I drilled out the holes in the frames using #14 and #40 drill bits, and test-fittings of M3 screws in the #40 holes work fantastically. The frame has been filled with putty, sanded, primed, puttied again, primed, and sanded again. Most of the parts took two or three layers of sprayed top coats before I was happy with them. The extrusion facimilies, front and rear plate, and Y carriage are ‘done’. The frame was nearly done, but the last coat on one side has runs, so I’m going to have to sand and re-spray that tomorrow after the paint has a long night to cure. Once the frame is dry and I’m pleased with it, I can start assembling the Y axis.
For the extrusion facimilies, I laminated a bunch of 1/2” thick plywood with wood glue, then cut them down to the proper width and height. I used a keyhole router bit to route 8mm wide channels in two sides, up to 12mm deep. With the keyhole bit I can use T-bolts or design some plastic nut housings that could hold captive metric nuts (hex or square) and slide them into the channels if I want to add things to the carriage later. I’m probably going to put a sheet of baking parchment or silicone-coated paper underlyament between the ends of the extrusions and the front and back faces of the frame. That’ll give me the option to cleanly remove them at a later time. To drill the holes in the corners, I used a #29 bit in the drill press, with stop blocks and squares to ensure direction. I marked the initil drilling locations using a marking gauge and a spring-loaded awl, so that the bit wouldn’t wander as much. I plan to use M4 cap head screws, rather than the M5’s called for in the original plans. This is due to the use of wood instead of metal – I fear the wooden wall betwen the outside of the piece and the OD of the M5 hole would block out too easily. As it is, I’ve carefully test-fit the M4 screws in the #29 holes several times, and I think it’ll be ok.
Today Sam brought the ABS back to the office, where I’ve printed linear bearing holders for the Y-carriage (printing the part was cheaper than sourcing u-bolts to hold them, and it’ll be more reliable than zip-ties) and customized couplers for the Z-axis TR8x8 lead screws. I’ll use eight M3 set screws to clamp the lead screws and the motor shafts in place. Sure, you can order 5x8 anodized aluminum couplers for a couple dollars, but again, printing the part is cheaper and will be ‘more in the spirit’ of this project – and more accurate in color coordination.