Converting a 3D Printer Bowden Extruder to Direct Drive

The grass is always greener, etc., etc.

I once bought a printer with a direct drive hot end design and then read online that the smart thing to do would be to convert to a Bowden configuration. The lighter gantry was supposed to make it print faster, improve print quality, etc. But after spending hours taking apart the hot end and then 40+ hours tuning the slicer profile, the printer didn't print any faster, but now I had a different set of print quality problems. 

It's called the Ikea Effect: people are more attached to products that required effort to build than to merely buying a product that did what they wanted in the first place. There's no clear winner in the Bowden vs. Direct Drive competition; after all, Prusa, one of the leading sellers of direct drive 3D printers, made their latest model a Bowden. And many high-end 3D printers use a Bowden configuration.

Despite the apparent convenience of buying the printer that's designed the way you want in the first place, there is an undoubted allure to tinkering. At 3DUPfitters, we want to support the DIY printer modification enthusiast along with the library that wants to stick an acrylic box over a stock printer. There are other modifications as well out there, including dry boxes, reinforcement bars, elongation kits, etc. 

Since 99% of our customers have stock configurations, we design the enclosures to fit the stock printer model with few modifications. So if you've modified your printer, you'll want to drop us a line so we can recommend the best way to accommodate your setup in an enclosure.

Direct Drive to Bowden Conversions

These are the easiest to support in a 3D printer enclosure. Since with a Bowden design, the filament feed enters at a fixed point; the user only has to drill a single hole, which is also the most convenient approach for adding a dry box. Most of the time, customers can handle this themselves, although we can make custom modifications as required. (Drilling a hole in acrylic does require care to avoid cracks.)

Bowden to Direct Drive Conversions

This is current our most common customer request since the Creality printers come with Bowden configurations and thus everyone wants to switch to direct drive.  (Except for the CR-10 V3 which is already direct drive.) These changes are trickier since the filament now has to get to the hot end, and before the enclosure only had to support reaching the externally mounted extruder.

The most straightforward printer configuration is the "bed flinger" design since the hot end only moves back and forth on a line. Putting a slit in the top will give a direct path to the hot end; it works in most cases, but weight could still be an issue. We reinforce the tops of enclosures intended for printers that store filament on top, but that may not be true of the modified printer.

In these cases, the best thing to do is upgrade the top to be 6mm thick. In the rare case where the weight would be more than a standard roll of filament, it may be necessary to reinforce the top with beams.  

The most challenging conversion to do is with H-frame 3D printers like the Ender 5 series from Creality. Now the head will be moving all around in the XY plane, so you can't just cut a slit in the top like with a bed flinger. 

The solution we've been successfully using is the "reverse Bowden" or "filament guide." The filament feeds from a specific spot on the top or side of the printer, and a PTFE tube protects the filament from the spool to the hot end, just like on a Bowden. The difference is that the extruder is now mounted on the hot end instead of the printer's side.

This approach has the added advantage of creating a constant pull on the extruder. It eliminates a significant source of degraded print quality with a direct drive: the extruder's changing forces as the hot end moves. 

Example:  Ender 5 Plus Direct Drive Conversion 

Here is an example of an Ender 5 Plus direct drive conversion using a kit from PrinterMods.com. Its main advantage is it's cheap and uses the existing extruder. If you were going to the trouble of switching to direct drive, this is a great time to upgrade your extruder and hot end. But it works well as an example, and the goal was to get this written over New Year's Day weekend.  I'm partial to the E3D Titan Aero, but there are other good options too these days like the Micro Swiss Direct Drive or the BondTech/Mosquito pairing.

I designed two parts to make this kit work inside an enclosure: a Bowden tube coupler holder directly above the existing filament detector and a Bowden tube connector holder just above the intake on the extruder. In an ideal world, you'd want to get a Bowden coupler-friendly extruder, but that wasn't possible with this particular kit.  

Here's the spool holder side of the design. The filament goes through the filament sensor like normal from the stock spool holder. But instead of going into the extruder, it goes directly into the PTFE tube instead.

Ender 5 Plus Direct Drive Conversion
Ender 5 Plus Direct Drive Conversion

 

On the other end, the extruder is now right next to the hot end. The best solution is a direct drive/hot end combination with a Bowden connector receptacle built-in, but in this case, I had to design a holder to fit right above the extruder. 

 

Creality Ender 5 Plus Direct Drive Conversion

Creality Ender 5 Plus Direct Drive Conversion

 

If you want to use these parts as a starting point for your own customization, here are the STL and Fusion360 designs.

Spool Side Bowden Mount

STL

STEP File

Fusion360 File

Hot End Bowden Mount

STL

STEP File

Fusion360 File