In the previous post Printrbot – day1 we began assembly of the Printrbot Simple Metal Kit. This post continues where the previous stopped. We had assembled the X-axis and the bed on the base, plus inserted the vertical rods and the acme screw for the z-axis. We also attached the electronics board under the base. The board is the so called “printrboard”, which essentially is a glorified Arduino processor with integrated stepper motor controllers and more.
The next step in the process is to attach the various bits on the Y-axis. This includes the metal extruder assembly, the extruder stepper motor, the hot end and the Z-probe. The Z-probe is an inductive distance sensor that measures the distance to metal below it, it works as an end stop on the Z-axis in a way that compensates for a slightly unlevelled bed. It will require calibration later, but at this stage we simply assemble things roughly as shown below.
We are now starting to get a few wires to manage, such as power to the hot end, hot end thermistor, stepper motor power and the Z-probe wires. In order not to lose sight of what is what, it is a good idea to label them. This will make it easier to hook up things correctly to the printer board later.
After that, we start to assemble the Y-axis motor and drive assembly. This introduces another motor and the Y-axis end stop switch. Two more wires to manage and label.
The Y-axis motor assembly is then attached to the Y-axis rods via the very nice metal linear bearings. At the ends of the rods, delrin blocks are fitted. At this stage I made a slight mistake, I didn’t check the alignment of the screw holes on the Y-axis metal plate against the corresponding threaded holes in the delrin blocks before attaching the Y-axis GT2 belt. I therefore had to undo the belt attachment, hammer the blocks into place and then re-tighten the belt with new zip-ties. Another possible mistake here is to attach the zip-ties in a way that makes the zip-tie heads collide with the metal plate, when the Y-axis is all the way in to either side. If the zip-tie heads are positioned on the side of the belt opposite the metal plate, there is no collision problem. Lots of details to pay attention to….!
After attaching the Y-axis metal plate to the delrin end-blocks, the whole Y-axis assembly can be slid down the vertical Z-axis rods. The Y-axis motor assembly also has a delrin block (not shown) opposite the two white nylon standoffs. In this block there is a threaded hole, where the Z-axis acme screw goes. By rotating the acme screw, the Y-axis is lowered into place. The acme screw is coupled to the Z-motor axis via the axis coupler. During print jobs, the Y-axis is gradually raised as the Z-motor turns the acme screw.
The wiring now looks rather messy, and it is a good thing we have labelled everything. To make it look nicer, and also protect the wires from wear, the wires are fed through rubber grommets which are then inserted into holes on the base (under the Z-axis motor and on the back). Finally, we wrap the wires in plastic wire-wrapping and we then have something that starts to look much nicer:
It looks finished, but it isn’t. Nothing is connected or calibrated. But this looks like a good place to end the second day of assembly. More to come!