I was doing some larger almost full build volume prints (for the MP select Mini 3d Printer) on my tiny printer when I noticed the extruder stepper motor was clicking. You can see the print where I noticed this successfully completed in the image below. This is a housing for a PID temperature control and 25 Amp SSR that I will write up in another blog post.
This clicking sound is a sign of a skipping stepper motors. I was concerned my extruder was not to temperature, but upon checking and finding it to be at the correct temperature I considered other options. After a bit of online research this turned out to be something of a known issue with the MP select Mini 3D printer. What I found was that the motor driver heat sinks can over heat due to poor ventilation. Only the bottom panel of this 3D printer has any vent holes cut into it. I decided to add vent holes to the side panel where the PCB is located with the motor drivers.
Remove your side panel by unscrewing the 5 screws holding it in place. Tip: do no undo both the side and bottom panel at the same time. The 3D printer housing is a bit sprung. When you take both panels off you will find you need a clamp to squish it back into place in order to install all of the screws.
I have included the drilling template for the above as a PDF at the bottom of this post. You can download it to help you drill out the vent hole pattern.
Above is a side by side of the finished ventilated side panel with an unmodified one. These side panels are some pretty heavy sheet metal, 16 gauge steel I think. You can drill them out. I used my Roper Whitney hand punch as it was faster and involved less set up time. After printing the PDF out at “actual size” I cut out the outline of the side panel. I used some blue painters tape and a bright light to carefully align and mount the template to the side panel. I then center punched each hole using the printed template as a guide. This left nice punch marks in the steel which facilitated aligning my hand punch before squeezing to knock out the holes.Above you see an image generated of the template pdf which you can download below. Do not use the image as it will not be scaled correctly when you print it. Please use the pdf as it can be printed out as “actual size” easily.
The PDF for the template: MP select Mini 3D Printer – Side panel venting template.pdf
The first upgrade to the Monoprice Select Mini 3D printer has to be replacing the god awful input knob/button that came on the printer. This printer uses a standard rotary encoder with push button for it’s single user input. The UX is pretty miserable with the OEM knob/button. I designed a nice SLA printable version, and have included an FDM version as well for those without access to higher quality 3D printing options on printers like Objets or Formlabs. I printed mine in Formlabs Tough resin, because with the led lighting this translucent material looks magical on the printer.
This button upgrade is available for download for free on Pinshape here at this link: Link to Monoprice MP select Mini 3D printer upgraded button knob. Installation required me to bend some stiff wire with short 90 degree ends to get under the original button and pull it off. It takes a bit of force to remove the OEM knob/button but it comes off with some careful pulling/wiggling.
I hope you print one of these for yourself and it makes your mini 3D printer experience more enjoyable.
After my initial excitement of having a fully operational 3d printer waned, I used the printer to produce parts to upgrade itself. Making itself better, stronger, faster than it was before. (How cool is it that the printer can make parts to upgrade itself??) Mass of the moving components limits the speed at which they travel and increase printing time. Inertia has to be compensated for in acceleration parameters as well. In short, less mass equals faster printing. The primary goal of printing replacement parts was to reduce weight of the moving components, the x and y axis sleds. The Z axis moves very little and the mass is much less significant. This post focuses on the x axis upgrades. The above photo shows the x axis sled with side by side comparison of the original (on the left) and the upgraded (on the right) components. The left side is the original proof of concept machined aluminum bearing mounts and cross brace. The right side shows the upgraded 3d printed LME8UU linear bearing mount with a skeletonized machined aluminum cross brace that also lowers the print head slightly.
As you can see more clearly in the above photo, the 3d printed ABS plastic bearing mounts are considerably smaller then the original CNC machined aluminum design. My plastic bearing mount raps around the bearing 20 degrees beyond 180 on each side for positive retention and due to the flexibility of the ABS snap over the bearing with a perfect fit. The plastic mounts remove 18g of mass from each bearing. The skeletonized cross braces come in at 8 grams in aluminum vs 36g of the original aluminum parts. I did print them in ABS at 2g part weight, but they were a bit too flexible and I was concerned with heat from the making them softer still.
The upgrade of the linear bearing mount and cross brace resulted in 128g of mass removed from the x axis moving components. Also the bearing mounts applied a more uniform clamping pressure on the bearings then the CNC machined design, that when over tightened resulted in bearing drag. As is often the case when building something, you design and build using the tools you had on hand. I always planned to replace the machined bearing mounts. My original CNC machined aluminum bearing design was accurate but bulky, ugly, and heavy.
Above is a rendered image of my LME8UU bearing mount design. The mounting holes are tapped M3 after printing and 10mm between centers. Here is a pdf technical drawing showing the dimensions : LME8UU bearing mount technical drawing. I have added the linear bearing mount to Thingiverse.com as an STL and IGES file for others to use. Here is a link if you want to print your own 8mm linear bearing mount for a project: http://www.thingiverse.com/thing:142243
All was not 100% perfect with the bearing mount upgrade, I did not consider the limit switch contact points when designing them. I added a small aluminum plate using 2 of the 3mm tapped holes to solve this minor oversight. Eventually I’ll add a physical feature to the 3d model and print new bearing mounts for the two limit switches. My original purpose in designing these LM8UU linear bearing mounts was as a universal part so that I can use them in the future for other projects.
Along with the weight reduction I moved the wire support to a more centralized location on the back side of the sled. I felt this would help reduce strain on the wires during the repetitive movement along the x axis. I orient my parts when printing such that the bulk of the printing travel is done by the x axis. All in all, these improvements along with other upgrades (to be shared in future posts) have gone a long way to increase my printers speed, reliability, and aesthetics.