It’s been a few days since the last post – we went to the Oregon coast with some friends for a long weekend. Good company, good food, good weather, and good times. That doesn’t mean there hasn’t been progress, however! In fact, I’m pleased to say that the X-axis is finished. I would guess that that means that the mechanical construction is about 10% complete. As I look forward in the instructions, it continues to be daunting, but I’ll keep plugging away. Anyway, on to some new pictures:
This is the completed x-axis. You can see the wires leading to the stepper motors that drive the extruder and x-axis carriage, as well as the z-axis stop flag (hanging down from the right end) and the red x-axis opto-stop board at the top left.
This is the same view, but from the back.
This shows the underside of the end containing the x-axis carriage drive motor. The four gold washers have bearings underneath them, and you can see the toothed belt that wraps around them. If you look closely, you can see the stepper drive gear below and in between the two middle gold washers. Below this, you can also see the hole containing the captive 8 mm nut that rides on the z-axis leadscrew behind the three bearings arranged at 120 degrees to one another. This three bearing arrangement allows the z-axis guide rail to be fully captured and removes play from the system.
An interesting technical problem arose with the toothed belt and the bearings it rides on. The BOM calls for a 5 mm wide belt, but the belt from McMaster (suggested by the BOM) is actually about 6 mm. This means that the suggested bearing arrangement of small washer, bearing, small washer, fender washer did not leave enough room for the belt to move smoothly without rubbing against structure. Since I had to buy a bunch of extra fender washers anyway, I changed this order to fender washer, two small washers, bearing, small washer, fender washer. This leaves plenty of room for the belt to ride smoothly on the bearing between the two fender washers, completely isolates the belt from rubbing against structure, and nicely captures the belt to keep it in place.
Next you can see the other end of the x-axis:
This time, there is no motor gear to route the belt around, so there are only the two corner bearings. You can once again see where the leadscrew nut is, this time between just two bearings. Since alignment is provided by the three bearing set on the other end, only two opposed bearings are used allowing the z-axis rail to float a little.
Finally, this is an “overhead” view of the x-axis, showing the positions of the motors. Note here that the toothed belt makes a loop around the entire axis and is clamped off at the carriage (top center of the part I am holding onto). The short piece of belt sticking up is a little extra that I grab onto with pliers when I am trying to tighten the belt.
There is more to talk about – all of the z-axis assemblies are complete – but I’ll write about them and show pictures next time. I’m having some trouble getting the thick stock parts laser cut, and will be working on getting that done this week. I’m hoping I don’t have to do it by hand on the bandsaw. The first of the laser cut parts is needed at the end of the y-axis assembly, so I need to make a decision on fabricating them pretty soon.