Several months after completing my original Printrbot + Upgrades, I am now introducing the latest version of my improvements. These new components address several problems with the original upgrades and they are also much stronger, easier to assemble and they require far less material and print time.
- Minimal hardware required – assembly requires 22 zip ties and nothing more.
- Fewer pieces – the bridge consists of only two pieces instead of four halves.
- Easy access – the parts are more open for easy access to clean or replace the linear bearings.
- Increased strength – components are now much stronger where they need to be.
- Raised bed levelers to prevent interference with y-axis pulley.
- Improved bearing tolerances (Should work with LM12UU or LME12UU linear bearings)
- Thicker extruder mounting plate, no warping.
- Increased clearance between extruder mount and heated bed.
- Extended motion of the extruder mount with an adjustable x-axis end stop.
- Better alignment of the adjustable z-axis end stop with added nut trap.
- Designed for GT2 belts and pulleys.
Downloadable model here.
Available for purchase here.
Begin by cleaning excess plastic from the holes and corners of each part with a hobby knife. Assemble the three piece motor mount by aligning the pieces into the slots on the back of the left bracket. Only apply superglue to these three pieces, do not glue the completed motor mount to the back of the bracket. Completely assemble the six piece extruder mount with superglue.
Assembly the right bracket by securing the linear bearings and z-nut with five zip ties. Insert the pulley bolt and 10mm spacer before bolting the pulley into place.
Assembly the left bracket by securing the linear bearings and z-nut with five zip ties.
Secure the linear bearings to the extruder mount using four zip ties. Next mount the extruder and the 40mm fan into place. Feed the wires through the hole to the back of the mount.
Slide the left bracket onto the rods and bolt the x-axis stepper motor with pulley to the motor mount. Align the motor mount to the back of the bracket and pull through four zip ties around the x-axis smooth rods. It is not necessary to glue the motor mount to the back of the left bracket.
Complete the installation by sliding the extruder mount onto the x-axis smooth rods and securing the right bracket to the rods.
Secure the belt to the rear of the exruder mount. Note that the belt must be fastened to the bottom side of the loop. This requires that the travel of the x-axis stepper motor be reversed. To do so, locate the connection for the x-axis stepper motor to the printrboard. Remove any two wires from the connector and replace them in reverse order.
1) After removing the plastic skirt with a hobby knife, use a reamer or file to clean all of the bolt holes.
2) The X-bridge and extruder mount parts print with supporting elements between each bearing sleeve. This plastic must be cut away before installation.
3) Components that are not bolted together should be glued with CA glue (super glue).
4) The linear bearings should fit snug within the mounts. If there is too much play wrap the outer part of the bearing in vinyl electrical tape. If the bearings are too tight clean the edges with a hobby knife or carefully heat the plastic before inserting the bearings.
5) Insert the bolt and assemble the x-pulley to the x-bridge.
6) Thread the z-nut onto the threaded rod and slide the bearings onto the smoothed rod. Properly align the nut and bearings into the x-bridge before bolting the front plate. If the bearings are too tight clean any plastic from the edges of the sleeves or lightly heat the plastic before inserting the bearings.
7) Bolt all components together using M3 or 1/8″ bolts. Be sure not to over-tighten any of the bolts.
8) Insert the smoothed rods into one end of the x-bridge and slide on the x-carriage before bolting the other side.
9) Add the extruder and fan to the x-carriage. Tension all belts and secure with cable ties.
10) To adjust the z-endstop, carefully heat the plastic arm until it can be manipulated into alignment. Insert the z-endstop bolt for adjustment of the z-height.
After receiving my new Printrbot + from one of the original kickstarter backers, I promptly assembled the printer in hopes of having it printing as soon as possible. The printer went together quite smoothly and without any major issues. After reading of previous user’s experiences, I was a bit concerned how the quality of the printed parts and bearings would be. Fortunately, my kit arrived with no missing parts, in fact, there was plenty of extra hardware.
The quality of the printed parts that arrived with my kit were not the best, so after tuning in the printer and adjusting many settings in Slic3r, the first items I printed were some replacement parts. After weeks of use, three problems began to arise. The first was that I could not consistently produce prints that would stick to the build platform without curling at the edges. The second was that the tension of the belt along the X-axis began to warp the X-bridge, causing the Z-axis to slip along the right threaded rod. The third was the inability to level the plywood bed using the standard fixed mounts.
The first issue was quite easy to address. To correct the warping and inconsistent heating, I finally purchased an 8″x8″x1/8″ sheet of temperature resistant glass from McMaster-Carr. The first time I installed the glass I left the heated bed facing upwards with the silk screen printing on top. This didn’t produce enough heat to keep the prints on the glass, so I reversed the heated bed so that the bottom side faced upwards towards the glass. I also printed glass clips to secure the glass to the heated bed and keep it away from the exposed contacts at the rear of the circuit board. I would recommend printing the glass clips before going through the work of flipping the heated bed and securing the glass, otherwise you will need some way to temporarily hold the glass in place while the clips print.
To correct the second problem that I was having with the laser cut X-bridge, I decided to completely redesign the bridge and extruder mount. This process took many revisions before I finally had a working setup, but once complete, the improvements were very noticeable. My new X-bridge design corrected several of the problems I encountered with the original laser cut design, including:
1) Z-axis smoothed and threaded rod spacing was incorrect, causing the threaded rod to spread away from the smoothed rod when the bridge was lowered. This caused binding and slipping along the Z-axis that was difficult to manage. With my design the spacing of the rods has been corrected.
2) Placement of the threaded rod nut was too low on the bridge and poorly secured. With only a nut on the bottom of the left and right sides of the bridge, the bridge was free to move upwards unless secured by two additional nuts at the top. However, adding two additional nuts at the top often caused binding of the Z-axis. With my design a single nut is secured within the bridge mounts along each side. The nut is secured on all sides, preventing it from slipping and eliminating binding.
3) The laser cut X-bridge of the original design was made to hold the stress from the belt tension instead of taking advantage of using the smoothed steal rods as structural supports. This led to warping along the plywood parts and eventually slipping along the Z-axis. With my design the bridge mounts are made to use the smoothed steel rods of the X-axis as the structural supports that take the load from the belt tension. This eliminates the need for any other cross beam at the rear of the X-bridge and strengthens the mounts.
To correct my final problem, I redesigned the bed mounts so that I could adjust the height of each corner until the bed was level. These mounts use the same hardware as the original mounts with the exception of the spring. If you don’t have a spring, then you can put a nut on the top and bottom of the bed, but it will be more difficult to adjust. My kit came with two extra springs used to hold the extruder closed, so I cut each of these springs in half and used them on each of my bed mounts.
Although not entirely necessary, I made a final modification to my printer to improve the extruder mount. The mount has been redesigned to accept three linear bearings to prevent the wobble experienced with only two bearings. The extruder mount is very similar to the original mount, but it has an integrated 40mm fan attachment and a less bulky design.