Another few notes before we begin - printing with flexible filament is a tricky process! While this is certainly a budget option that can get you up and running, it takes tweaking and patience. Here are some tips for successfully printing with CoexFlex filaments.

• Print slowly. Start extremely slow. 15-30mm/s is an acceptable range of maximum printing speeds when printing flexibles. Start at the low end of the range and work your way up.
• Reduce or disable retraction. The name of the game when printing CoexFlex is to disturb the filament as little as possible. Part of this is turning retractions down significantly, or even disabling them entirely. We've found that disabling retractions (i.e. setting retraction distance to 0) makes for the most reliable printing experience with this budget direct drive setup, albeit a stringy one. 0.1-0.5mm of retraction is acceptable if you want to try to reduce stringing.
• First layer tuning. When printing with rigid filaments, it's often better to err on the side of too close to the bed rather than too far away as it could lead to prints separating from the print bed and failing. With CoexFlex, however, the opposite is true. If the print is too close to the bed, there will be increased backpressure in the hotend, which will cause the filament to bunch up in the extruder gears and your prints to fail. If your prints keep failing early in the first layer, increase your Z-offset until you get reliable extrusion. Ensure your bed is level as well, as inconsistencies in the first layer thickness could lead to failure.
• Be patient! Printing with any new type of filament is a learning experience, and CoexFlex is no exception. But with patience and fine tuning anyone can master it.

With all that out of the way, let's get into what you'll need and how to put together this direct drive mod!

3D Printed Parts

Surprisingly enough - there's only four 3D printed parts that are necessary for this mod. They can all be found on the Hero Me Gen6 Master Suite page. Specifically, the four files we used are:

• Direct Drive Base: HMG6 DD Base OEM-MK8-MS-BMS - Creality Single Gear Reverse.stl
• Gantry Plate Adapter: Ender 3V2 OEM-MK8-MS Gantry Adapter.stl
• Part Cooling Duct: HMG6-single-4010.stl
• Fan Guard: HMG6 Lightweight Fan Guard.stl (Any of the fan guards are acceptable, it is a purely cosmetic choice)

As recommended in the Hero Me Gen6 Printables page, the direct drive base and cooling duct will need supports (from the print bed only). Print the parts between 35% and 50% infill. The direct drive base itself will need higher infill, around 85%. The parts can all be printed in PLA provided you use a silicone sock on your hotend (which is the default for an Ender 3 V2).

Note that these parts are specific for the Ender 3 V2 and the modification we plan to do. The Hero Me Gen 6 suite has over 480 STL's for, quite literally, millions of possible combinations for nearly any printer!

Other Hardware and Tools

This mod does require some extra hardware, all in the form of simple M3 screws and threaded inserts. You can find M3 hardware assortments easily on Amazon and they'll likely have everything you need. The same can be said for M3 heat set threaded inserts that you can find here. You will need a soldering iron to install the threaded inserts. Specific soldering iron tips used for installing these inserts are available, but aren't necessary.

Here's a list of the hardware you'll need to complete this mod:

• 12x M3 Threaded Inserts. MediaMan3D specifies using inserts that have a 4.6mm outer diameter and either 4mm or 5mm in length, with 4mm being ideal. Ours were 6mm (oops) but they worked fine.
• 1x M3x6 SHCS Screw (Socket Head Cap Screw). For mounting the gantry plate adapter to the gantry plate.
• 4x M3x8 SHCS Screws. For mounting the direct drive base to the gantry plate adapter.
• 4x M3x10 SHCS Screws. For mounting the fan duct to the direct drive base.
• 4x M3x16 SHCS Screws. For mounting the fan guard and fan to the direct drive base.
• 2x M3x25 SHCS Screws. For mounting the hotend to the gantry plate.

Step 1: Install Threaded Inserts

All of the threaded inserts are installed on the direct drive base part that was printed.

To install the threaded inserts, first set the soldering iron to a temperature around 230°C. Place the threaded insert (with the smaller, tapered side down) slightly into the hole it goes into and then apply gentle, constant pressure with the soldering iron. As the insert heats up, it will melt the plastic and slide into place. Do not press too hard as you could push the insert in too far, or get the insert stuck on the soldering iron tip, causing it to back out when you try to remove the soldering iron.

Install all 12 threaded inserts as shown in the images below for the fan mounting, gantry plate adapter mounting and part cooling duct mounting locations.

Note that in the part cooling duct mounting locations (images 3 and 4) the threaded inserts are in the top hole for the location with two holes, and in the center hole for the location with three holes.

Step 2: Disassemble the Stock Extruder

Disconnect the extruder motor cable and fully disassemble the extruder assembly.

If your extruder is the stock plastic one, you will also need to cut off the cable management clip on the side of the extruder frame.

Here is how the part should look after cutting.

Step 3: Disassemble the Stock Toolhead

Next we'll need to disassemble the toolhead. Start by removing the M3 screw at the back of the gantry plate to be able to remove the hotend shroud.

Next, remove the two screws that hold the hotend itself onto the gantry plate.

Next remove the fans from the existing hotend shroud and remove the Bowden tube from the hotend. You should be left with all the hardware free from any of the existing shroud pieces.

Step 4: Measure and cut the Bowden tube to length

Next we'll cut a length of the Bowden tube to serve as the direct drive filament guide. The easiest way we found to do this was to insert the Bowden tube into the direct drive base, then down into the hotend assembly and cut it to fit. Leave a few millimeters of extra tubing at the top, as shown, and mark the tubing where it will be cut.

In our case, we ended up with approximately 2.5in (65mm) of tubing.

Once the Bowden tube is cut, reinstall the hotend back into the direct drive base just as was done for test fitting.

Step 5: Install the gantry plate adapter

Using the 4 M3x8 screws, attach the gantry plate adapter to the direct drive base as shown. Ensure the screw caps are flush with the backing plate adapter.

Step 5: Attach to the gantry plate

Line up the two holes on the gantry plate adapter with the studs on the gantry plate and press it into place. Use the 2 M3x25 screws to attach the hotend.

Install the M3x6 screw to secure the gantry plate adapter to the gantry plate.

Step 6: Reassemble the extruder on the direct drive mounting plate

Reassemble the extruder motor and extruder assembly onto the new direct drive plate as shown using the original hardware. Note that the countersunk M3 screw is not used and there is no spot for it in the direct drive base.

IMPORTANT: Ensure the connector on the stepper motor is facing upwards. If it faces to the left the cable will foul on the Z-gantry during homing.

Reconnect the extruder stepper motor cable.

Step 7: Attach the hotend cooling fan

Use the 4 M3x16 screws to attach the fan guard and hotend cooling fan to the direct drive base.

Step 8: Mount the part cooling duct

Attach the cooling duct using 4 M3x10 screws. Slide the cooling duct up along the grooves to ensure the duct outlets do not sit lower than the nozzle.

Place the blower fan in the slot in the part cooling duct housing and the assembly is complete! (Shown here with a BLTouch installed at a later time.)

Congratulations on assembling your very own Ender 3 V2 direct drive mod! We hope this serves as inspiration to give CoexFlex™ a try. We'd love to see any of your prints! Feel free to tag us, @Coex3D on Instagram and Twitter if you end up trying out CoexFlex™ - we'd love to see what you make!