This is the sixth stage of our 3D printer kit build. For the background to the project and details of the kit we are using, take a look at the introductory page here, or click here to see all our posts about this project.
After an unscheduled hiatus while we waited for a replacement part, here we are back with the next part of our 3D printer build. We hit a problem when installing the X-Y rods as one of our rods was too wide, so after raising a support ticket with the kit manufacturer we received a replacement X-Y rod from Velleman along with an improved version of the pulleys that secure the belts on the X-Y rods (the original version had only a single grub screw whereas the new improved version has two grub screws to help keep the pulleys secure) so we’re now ready to go again.
In this part of our printer assembly, we:
- finished mounting the X-Y rods and the print head
- mounted the belts and pulleys and tensioned the belts
- Time for this step: 2 hours
- Total build time: 13 hours 50 minutes
The first step was to partially install the X-Y rods without any belts or pulleys and add the print head carriage rods and print head assembly. This allows fine tuning of the distance between the carriage rod clamps.
The aim is for the print head to slide easily over its full travel when the printer is tilted at 45 degrees, without any binding or stiffness. Sometimes the print head moves easily in the centre and then binds in the corners, which means the clamps are too close together. In this case, tapping them lightly with a hammer (using a piece of wood or plastic in between the hammer and the clamp to protect it) can help to move them slightly apart. It is worth spending time on this step as free and easy movement of the print head is absolutely vital to a well functioning printer.
Once we were happy with the print head movement, we partially pulled out the X-Y rods and removed the print head carriage rods so we could mount the pulleys and belts. It is easier to put the grub screws loosely into the pulleys before installing them into the printer as they need to be screwed in perfectly straight to avoid stripping the fragile thread, which is a lot harder to do when the pulley is installed into the printer.
After pushing the X-Y partially through the frame and adding the belts and pulleys for one side, the print head assembly and print head carriage rods can be introduced and slid through the X-Y rods. The carriage rods are not equal length so need to be oriented the correct way (the small fan at 90 degrees to the print head faces the front panel). Care must also be taken to ensure the carriage rod clamps are facing in the correct direction so the small protrusions will fit through the X and Y endstops.
Once all the rods were installed, we began positioning the belts and pulleys. The small belts connect the X-Y rods to the stepper motors for each axis, and the long belts connect each X and Y rod with the opposite rod and move the print head carriage rods. In the two corners with motors both belts sit on the same pulley, and we had to carefully position the belts so that the motor belt is nearest the side panel and the longer belt sits against the outermost flange of the pulley.
Belt positioning in progress:
Correct positioning of the motor belt:
When all the belts and pulleys were installed, we could now install the belt clamps/tensioners. These pieces clamp part of the belt to the carriage rod clamps so that the carriage rods move in step with the X and Y rods, and are also used to adjust the tension of the belts. The tensioners screw into the top or bottom of the carriage rod clamps, where there are captive nuts to hold them in place. We found it a little difficult to engage the screws into the captive nuts and found that tilting the printer to 45 degrees so that the nuts slide to the outer edge of the clamp helped. At this stage we only did up the screws in the tensioners enough to hold them in place as we now need to calibrate the carriage rod positioning.
We now began the process of aligning the rods. For the printer to produce accurate prints, the X and Y rods and the corresponding print head carriage rods must be perfectly parallel. The assembly manual suggests aligning the carriage rod by measuring the distance from the side panel with a caliper, but this is not really an ideal method as the panels can bow out slightly. The method we used, as suggested by the user-maintained Vertex Wiki, is to fix two identical objects (in this case bicycle cone spanners) to hold the X or Y rod and the corresponding carriage rod parallel while we tightened the grub screws on the four pulleys parallel to the rod and the belt tensioners attached to the two belts. There is a 3D printed tool exactly designed for this task available on Thingiverse but of course you need access to a functioning printer to be able to print it, so we used what we had available.
Using our improvised alignment tools:
Belts installed and tensioned. The tension on the X and Y belts should be as loose as possible without the belt coming out of the tensioner, as excessively tightened belts can lead to the printer missing steps (so called X-Y axis shifting). The motor belts though should be as tight as possible, and once the other belts and pulleys are all calibrated and clamped in place the motor mount screws can now be fully done up to tension the motor belts.
In the next step we will install the filament feed tubes and begin to assemble the Z axis stage which will move the build platform up and down.
Keep an eye on the 3D Printing section for all the posts about our build, post questions in the comments or tweet us at @dannynic or @sarah_nic.