Eddie's Modular Hotend

Introduction

I use different hotends to print with ABS or PLA, and with various sized nozzles and various hotend designs. I want to change the hotend easily and quickly.

Most functionality is the same: movement, bed leveling, cooling. I only want to change the hotend, so I will physically separate the functionalities (Separation of Concerns).

The X-Axis Frame is connected to the bearing blocks and contains most of the common functionality. The Hotend Holder connects to the X-Axis Frame via one or two screws. The temperature sensor and heater wires have simple connectors. Of course you have to pull the filament guide out of the hotend and cut the filament flush. It’s quick and easy to replace the hotend.

The design has been developed over the last two years, and has been use on several 3D printers.

Overview

Here is an example, yours can vary. The X-Axis Frame (blue) is fixed to the X-axis smooth rods via bearing blocks (grey). It has many holes allowing various add-ons: bed level sensor (red), hotend radiator fan (green bottom), bed fan (orange), X-axis home trigger (green top), LED lighting (not shown) and of course, the Hotend Frame (yellow) and hotend holder (orange).

The composite STL file is to let you rotate it in 3D to have a good look at it.

An X-Axis Frame.

This has been made for a Mendel X carriage, but can be adjusted for other styles. The two M3 threaded inserts for connecting the Hotend Frame are pressed in using a soldering iron. The four raised blocks support the Hotend Frame, which rests on the shelf at the bottom. The holes are 4 mm to allow an M3 bolt to pass through easily. Notice that the position of the other holes is related to the size of the X-axis rod connectors.

The X-Axis Frame is screwed into the two bearing blocks on the X-axis.

The photos show the inserts, an X-Axis Frame screwed to a (Mendel) X carriage, an X-Axis Frame with attachments, ready for a Hotend Frame and a diagram of the hole positions.

The X-Axis Frame is general, but might need modifying for your specific X-axis connectors. I have made a SCAD version to make it easier to modify (rename to MainFrame.scad).

Hotend Frame for a cylindrical J-head/V6 hotend.

The hotend neck holder (orange) is in two parts and can be adjusted in height. There are two STL files of these, for 5 or 7 mm neck. Make sure you print TWO of the type you want.

This hotend didn’t have a PTFE coupler built-in, so it has a table to screw one in.

This Hotend Frame is also for a cylindrical J-head/V6 hotend that has a PTFE coupler built-in, so it has no table.

Use the hotend neck holder (orange) from above. Make sure you use the correct one.

Hotend Frame for a rectangular J-head dual hotend.

This can be the basis for other hotends that are fixed by a few screws.

Inductance bed sensor holder

Various probe holders for different positions, depending on the height and position of the probe. Choose the one you need.

BL Touch bed sensor holder

Holder for a BL Touch sensor.

Toothed belt clamp

A clamp for the X axis toothed belt. It can be screwed into the two outermost holes halfway down the X-Axis Frame. A spacer can be added for the correct position.

Spacer

Used to move the toothed belt clamp to line up with the toothed belt.

Fan bracket

Simple right angle to hold a fan or other add-on. Using just one screw allows the holder to be rotated.

X switch poker

Used to press the X-axis switch marking the leftmost X position. My switch is on part of the X frame, but I doubt if anyone else does that. Maybe this is useful as a starting point.

Fan holder

Simple holder to hold a fan and funnel or other add-on. Using just one screw allows the holder to be rotated.

Funnel

Allows the fan to direct the flow onto the freshly printed filament.

Some notes to help you:

• SCAD is a free program for creating models programmatically. If you haven’t used it, go and take a look. You can use it to make various geometric models, but it is excellent for parameterising models.
• The X-Axis Frame SCAD program is not simple. You can comment out function calls to see what they actually do. Different holes and structures are colour-coded to help. If you want to change it, make regular backups and document what you change.
• You can tuck the hotend wires between the frames, which helps keep them out of the way.
• A threaded insert can be pressed in using a soldering iron. When it’s nearly in, screw in a bolt to check that it’s at right angles to the frame.
• Position adjustment for each hotend can be set using M851 XYZ Probe Offset in the start-up script.
• M3 nuts and bolts are needed to connect different parts. Some parts, like the belt connectors will need much longer bolts. Check what you need first.
• Inserts can be found online. Search for M3 brass through-hole inserts.