Stratasys Mojo Retrofit

Stratasys has ended support for their Mojo 3D printers, and you can no longer purchase parts or filament for them. This project aims to retrofit them with off-the-shelf parts to extend their lifespan.

Parts

Here is an example parts list that may be used for this conversion. This assumes that you repurpose the old printer's ATX power supply and CoreXY mechanics. Minmimal irreversible changes are made to the machine, although that doesn't really matter at this point!

I converted two printers at once for $300, a slight cost savings due to higher quantity of GT2 pulleys resulting in a lower individual price, as well as the endstops comkng in packages of six.

You'll also need some assorted M3 screws. I use them standard across all of my designs now and just bought a little box of a few size off of Amazon. Your local hardware store might be better though!

3D Printed Parts

In the cad/ subdirectory, I have included designs in both Fusion 360 and STEP formats for you to customize and export. STLs and potentially Printables links coming soon!

Note that the Z Endstop Mount design is currently not suitable for the conversion. It doesn't allow the bed to move up enough to reach the hotend. Future revision will correct this, however, I just use hot glue and software offsets in the meantime.

Buildplate

@mebillica has improved the accuracy of my build plate design used in the PrusaSlicer model preview to the point that it can be printed and used in the abscence of OEM buildplates, an increasingly prevalent issue with Stratasys Mojo machines after their discontinuation.

Here's a link to his model on Thingiverse, which also includes the Fusion source if you need to make further modifications. The Fusion design and STL file are also mirrored in this repo, in the cad/Fusion/Build Plate and PrusaSlicer/buildplate directories, respectively. If you'd prefer the Printables download, that is available as well.

Stratasys OEM buildplates are made of some some sort of ABS plastic so that their ABS filament fuses to them. This makes them non-reuseable unless you cover first with transfer tape (and a glue stick). However, if you're looking to print PLA using a machine retrofitted according to this guide, you may have success printing these plates out of other materials.

PrusaSlicer should now show this new buildplate design in the Plater tab when setting up your prints, giving you an even better idea of where your model lands relative to the 5" grid as well as locking mechanism.

Laser Cut Parts

If you have access to a laser cutter, it can be really useful for quickly making the following parts out of acrylic:

• LCD frontplate
• LCD backplate
• Control board backplate
• Control board standoffs
• Control board fan mount

However, a laser cutter is not required and these could easily be made manually with careful marking, a drill press, and a jigsaw, or 3D printed if you're willing to run a relatively long print.

These design files are not yet included.

Assembly

Removing original hardware

I'd suggest using a drill with the clutch limited to about 5 (attached to an appropriately sized socket head) to remove all of the screws. Probably you'll want a magnetic screw dish as well.

1. Remove the metal backplate after unscrewing all of the screws marked in red in the below image
2. Remove the two side panels after unscrewing all of the screws marked in blue in the above image
3. Unplug every connector from the original I/O board, including the power cables and all ribbon cables
4. Unscrew each screw keeping the I/O board in place, then remove it
5. Carefully bend the metal tabs previously holding the I/o board in place out of the way. Ideally all should be in a flush position, save for the small bump where they are attached.
6. Unscrew and remove both filament buckets. There's four obvious screws on the top, but also one hidden one that I had to use a screwdriver plus shaft extension on:
7. Remove the original hotend carrier. This takes some work, and many screws that I don't (yet) have documentation photos for. This is a general guide and it took at least an hour of messing with it the first time I did it.
   1. First, try unscrewing the PCB on the back
   2. Remove the belts from their tensioning system and unscrew the back from its slider
   3. Remove the clip holding the front on, and I think you can take out the entire assembly

Installing new hardware

In lieu of a full assembly guide (right now), I'll just add some notes.

• If you're not using a heated bed, just power the control board off of the power supply's PCIe power
  • Snip off the last couple of inches of the header
  • Twist together the three yellow wires, then separately twist together the three black wires
  • Maybe put a blob of solder on the twists to keep them in place while inserting into the control board's screw terminals
• When viewing the printer from the back, the left motor should be plugged into the X connector and the right motor into the Y connector
• You'll need to drill some ~1" holes through the side panels and filament buckets to accomodate a dowel rod for the filament spool
  • Alternatively, for a no-damage installation, print first one of the filament spool holder designs that uses bearings and rollers to support the filament and allow it to spin freely
• Your Y axis endstop should be on the right side when viewed from the front or left side when viewed from the back, a couple of inches towards the back away from the front block. You can identify the right position by pushing the Y axis all the way forward, then placing the endstop in a position so it is well depressed.
  • Depending on your printer, you may be able to screw down one or both of the endstop's mounting holes. I used a 1/8" drill bit and, after marking the position, drilled through the metal with a shop vac for cleanup only
• All endstops need some insulation on the bottom to prevent shorts. Either heatshrink the whole thing, which would hide the LED :(, or, as I did, liberally apply hot glue to the bottom
  • Then, for all of the endstops, use more hot glue to affix in place as necessary
• The Z axis endstop now has a custom mount consisting of a U-shaped bracket that slides over the Z axis block and a separate plate that the endstop mounts to and slides up and down on to adjust the zero offset. The U-shaped bracket probably should be glued down once everything's all set
• Don't forget that ATX computer power supplies require their PS_On pin (#6 on a 24-pin connector) to be jumped to ground to activate them. As I have not implemented power supply control, please use a short piece of wire to connect PS_on (also denoted by the green wire) to any black ground wire.

Firmware

The firmware for the prototype single extruder system is based on Marlin 2.0.9.7 LTS which is not recommended for use with "modern" boards. For that machine, I was reusing an old mega2560 MKS Base v1.4 control board, but I could have used a newer Marlin version, and I'd suggest you update the config to do that.

The dual nozzle version is currently based on Marlin 2.1-bugfix as of 5 April 2024, but I intend to upgrade it to 2.1.3 when that becomes available. I'm using the MKS Eagle (basically Robin Nano with builtin drivers) for the production version, so the config files and binary reflect that.

Build and Upload

As this was my first time dealing with a 32-bit control board, the process for uploading firmware was initially foreign to me. Here's the process I found to be best for quick iteration:

1. Clone or download makerbase-mks/MKS-EAGLE
2. Clone or download this repository (for easy access to the Marlin configuration files)
3. Download and extract the appropriate version of Marlin from this page
4. Copy the configuration files from the appropriate subfolder of the firmware folder in this repository, and paste them in the Marlin subfolder that you extracted. You should see in the same directory the folders lib and src in addition to the file Marlin.ino if you're in the right place.
5. Install Visual Studio Code using the download link for your platform
6. Set up Auto Build Marlin according to these instructions
7. Customize the example configuration
8. Build using the Build button in the Auto Build Marlin window
9. Find your mks_eagle.bin output file. It should be located in `../.pio' folder (one level outside of the Marlin folder)
10. Copy mks_eagle.bin to the DFU-upload folder downloaded from the MKS-EAGLE repository. Overwrite the mks_eagle.bin that's already there.
11. Ensure that your control board is entirely unpowered, then move the board's power jumper (near the USB Type B port and microSD slot) to USB power (on)
12. Press and hold the BOOT0 button on the board, then plug it in to your computer using the included cable. Once it's plugged in, release the button.
13. Download and run the latest version of Zadig, which will help install necessary USB drivers.
14. Once Zadig is running, click Options then List All Devices then select from the top dropdown a device like STM Bootloader
15. Set the driver in the right-side combobox to WinUSB, and then click Replace Driver. This process can surprisingly take a few minutes to complete.
16. In the MKS-EAGLE/DFU-upload folder, run DFU-Upload-firmware.bat
17. Once flashing is complete, unplug the board and change the power jumper back to off (so no USB power)
18. Turn on your power supply and test the firmware!

Slicer

I selected PrusaSlicer for its robustness and ease of customization, however, I believe that derivatives such as SuperSlicer or OrcaSlicer will also work. Or, if you prefer Cura, as I do for my other machines, the configuration should be easy enough to replicate.

1. Install PrusaSlicer.
2. Copy the PrusaSlicer folder from this repository
3. Navigate to C:/Users/YOUR_USERNAME/AppData/Roaming in your file explorer. You can do this easily by typing in the directory bar %APPDATA% and pressing Enter.
4. Paste the PrusaSlicer folder, and select Replace the file in the destination if prompted. This will install the filament settings, print settings, and printer settings I have tuned for the Stratasys Mojo conversion.
5. Open PrusaSlicer and navigate to Printer Settings.
6. Ensure that Expert mode is selected by pressing the button in the top right.
7. Navigate to General > Bed Shape.
8. Load the Mojo Logo.png file from the PrusaSlicer/buildplate folder you copied as the bed texture.
9. Load the Accurate Mojo Build Plate.stl file PrusaSlicer/buildplate folder you copied as the bed model.

Usage Instructions

I created a guide with instructions for a novice user to prepare a model for printing on one of these converted machines. That document is available here: Stratasys Mojo Instructions

TODO

• [x] Update to 2.1-bugfix
• [x] Implement M16 in print profile to ensure that the right profile (dual vs single extruder) was used
• [ ] Figure out feasibility of ATX power supply enable / disable and standby power
• [ ] Consider MPC temperature instead of PID
• [ ] Consider S-Curve acceleration
• [ ] Consider nozzle clean
• [ ] Enable linear advance
• [ ] Consider sensorless homing
• [ ] Create X axis endstop mount
• [x] Create both extruder mounts