13. Mechanical Design¶
This week is machine week, and we worked on a machine as a group. Inspired by the presentation of the Blot plotter during the 24 March 2025 machine building recitation, we chose to use that as the basis for our machine building.
Our inspiration: the Blot plotter
We decided to recreate this plotter, while working to reimplement all the pieces, including local designs. As a group, we divided tasks between Magnus, Evert, and Albert.
With guidance from our instructor, we decided to have both Evert and Albert reimplement the machine control boards. As part of this the boards will have integrated power delivery, based on Nicolas Decosters QC-Hack, which will provide the 12V necessary for running and controlling the motors. We decided to have redundancy for PCB building, as that was anticipated as a difficult step, which could be prone to failure. Both Evert and Albert designed PCBs for the project, and their efforts are documented on Evert’s and Albert’s pages.
Magnus was tasked with designing the mechanical aspects of the Blot plotter. The Blot is open source and design files are available, though as STL files. Magnus elected to reimplement the Blot plotter as a parametric design, which allows for construction of the machine to different dimensions than those specified via the original files. Details on his adventure are fully described on his page for the week.
While detail on building steps can be found in the individual pages, we started by sketching out a work plan. Starting on Thursday after the lecture, we planned to work each through Sunday, hopefully completing the machine in four days.
We sketched out a plan on a lab white board, and got to work. In short the first day was designated to design, the second to part construction, the third to assembly and initial testing, and the fourth to final assembly and machine completion.
The starting plan
Largely, we hit all the targets, only needing to do final demonstration on the fifth day. This last day allowed us to take hero shots, and also make the custom hero program (see video).
To give an overview of our process and machine, we have the following one minute video regarding our build and machine.
Building a Blot (plotting) machine
Bill of Materials:¶
| Part Name | Quantity | Description |
|---|---|---|
| USB-A Cable | 1x | USB-A Extension Cable for power |
| USB-C Cable | 1x | USB-A to USB-C or USB-C to USB-C for RP2040 power and data |
| PCB | 1x | The board with RP2040 and Stepper drivers. |
| 5mm Plexyglass Pieces | 10x | Bottom Plate with Hex holes, Second bottom plate with circular holes, 4x top pieces with hex holes and 4x top pieces with circular holes. See production/design files below |
| 3D Printed PCB Mount | 1x | See production/design files below |
| 3D Printed Tool-Head | 1x | See production/design files below |
| 3D Printed Belt-Clip | 1x | See production/design files below |
| 3D Printed Legs | 2x | See production/design files below |
| 3D Printed Carriage Rail | 1x | See production/design files below |
| 3D Printed GT2 Pulley | 2x | See production/design files below |
| 130 cm GT2 Belt | 1x | Single long belt, We initially purchased two shorter ones by accident. |
| Stepper Motor | 2x | Nema 17, 42 x 42mm, 38mm tall. Cables needed if not included, 20mm |
| M3x10mm Bolts | 10x | Button Head, 4 for each stepper face and 1 for each pulley |
| M3 Nuts | 2x | 1 for each Pulley |
| M5 T-Nut | 5x | The original blot used 12 pieces but the 3D printed parts hug the extrusions well enough that I only used 8 as they can be a pain to install |
| M5x12mm Bolt | 8x | Go into the T-Nuts. |
| 5x16x5mm Bearing | 6x | Used instead of the flanged bearings. 4 for the main carriage and 2 for the carriage rail |
| M5x30mm Bolt | 4x | For the main carriage assembly |
| M5x25mm Bolt | 1x | For the Carriage Rail |
| M5 Nut | 17x | 16 for the carriage, 1x for the rail |
| 250x20x20mm V-Slot Extrusion | 2x | Make sure to check for dents/scratches from shipping. One of ours was a bit beat up |
| 3D-Printed “Flanges” | 10x | See production/design files below |
| SG-90 Servo | 1x | We used a “TowerPro Micro servo 9g SG90” |
| M5x40mm Bolt | 12x | These were for the wheels and the tool head, Knurled knob ends and the last 10mm are smooth with no threads. Probably not necessary but nice quality of life for adjusting the wheel tension and making sure the bearings don’t catch on the threads. |
| 3D Printed 6mm Standoff | 8x | See production/design files below |
| 625zz V-Wheel | 11x | 8 of these on the central carriage, 3 on the tool head |
Design Files¶
Here are the design files for parts that were changed around. If not listed here, Refer to the original HackClub Blot
| Filename | Type | Description | Link |
|---|---|---|---|
| CarriagePlateAssembly | .f3d | The Lasercut 5mm Plexyglass version of the Carriage Plate Assembly, This is the one we ended up using. | Link |
| CarriagePlateAssembly3D | .f3d | The 3D-Printable version of the Carriage Plate Assembly, Requires 4 6mm standoff pins | Link |
| GT2Pulley | .f3d | 3D Printed GT2 Belt Pulley, Original Design Credit goes to @bequ3 on Printables.com | Link |
| ToolHead | .f3d | This one was surprisingly tricky due to the wheel spacing. | Link |
| BeltClip | .f3d | I tightened the teeth and “Sharpened” them by decreasing the diameter of the circle | Link |
| PCBMount | .f3d | The center gap for the extrusion is 21mm. If you’re confident in your printer you can set it closer to 20mm. This part is hard to print and I definitely want to make a support-free version but I ran out of time. | Link |
| 6mmStandoffPin | .f3d | These fit into “ScrewHoleDia” in the other files. | Link |
Production Files¶
Here are the production files for everything. If not listed here, Refer to the original HackClub Blot
| Filename | Type | Description | Link |
|---|---|---|---|
| 5mmPlexyPiece | Cut on Epilog Fusion, Speed 2%, Power 100%, Frequency 100% | Link | |
| 6mmStandoffPin | .3mf | Print as oriented. I added a brim for better adhesion. | Link |
| BeltClip | .3mf | Should print without supports, Make sure the teeth are printing cleanly | Link |
| CarriageAssembly3D | .3mf | Might require supports for the underside Hex slots, If using this version, Print 4 of the 6mm Standoff pins | Link |
| GT2Pulley | .3mf | Worked fine on a .4 nozzle with no support. Make sure the layer heights aren’t too course. | Link |
| PCBMount | .3mf | Requires some tricky support usage. I used PrusaSlicer’s paint-on supports inside on the outside overhangs and inside the hex slot. | Link |
| ToolHead | .3mf | Printable with no supports. | Link |