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Redesign of the Mega Hub PCB

The external connections of the 3d-printer are neither very robust, nor do they offer much flexibility in respect to upgrading/changing the printer. From the original distribution circuit board a new board was designed which has both the original and D-sub connectors.

The original circuit board was analyzed using a flatbed scanner:

Original Anycubic I3 MEGA distribution circuit board
anycubic_distribution_pcb.pdf anycubic_distribution_pcb_annotated.pdf

Then with KiCad schematics were drawn.

From the schematic diagram a new circuit board was designed, which consists of two parts and can be separated by breaking-off using so-called mouse-bites. The small circuit board is meant to be located at the other side of the printer. With this the wiring underneath the printer for the X-stepper and Z-stepper-L can be tidied up and organized much better.

I3 MEGA HUB-II distribution circuit board
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The schematic diagram and pinout of the board can be downloaded from here:

The meaning of the annotations on the circuit board are:

Label Description
X stepper for X-axis
Y stepper for Y-axis
Z stepper for Z-axis (right)
E0 stepper for filament
E1 stepper for Z-axis (left)
HEATER0 power for the extrusion head heater
FAN0 fan at the extrusion head for print cooling
FAN2 fan at the extrusion head hotend cooling
D42 Z-endswitch (left)
HUB Connections for thermistor and Z-endswitch (right), filament- and X-endswitch

Specially for adding a cable chain to the printer, a further redesign of the circuit board (I3 MEGA HUB3) was made:

The improvements are mainly that the connections for the X, Z (right) and E0-steppers (filament) were placed on the right side, making a single cable chain with all necessary wires for the steppers easier to realize. The wires for the left Z-axis are still placed on the left side, as these do not have to be running through the cable chain.

Cutting holes

For cutting the holes in the metal casing, the following file can be helpful:

This file contains the following drawing:  Drawing to facilitate positioning of holes.

To start, first unscrew/remove everything which is attached or mounted on the main metal casing. It is better to prevent any metal dust getting onto the circuit board and/or power supply or anything else. When done, for the large cutout, draw with a pencil horizontal and vertical lines on the metal casing, using the position of the press-in nut, which is visible from the outside, like shown on the picture below:

Then place the printed drawing with some double sided sticky tape on the metal casing, using the drawn lines as guides:

Using the printed drawing, do the following:

  • Use a punch tool to mark the centre of the two holes (here visible on the right) for mounting the pcb. These need to be drilled to 3.0 mm.
  • Use a sharp knife to draw lines, which mark the shape of the metal cut-out as can be seen below.

First drill the two 3.0 mm holes and counter-sink them. Then drill with a larger diameter several holes to roughly cut out the major part of the metal. Finally use a file to complete the cutout. The result should look like this:

For the other side of the metal casing, the positioning is much easier, since we do not need to take into account any existing mounting points. Therefore place the drawing from above roughly as shown in the image below:

First drill the 4 holes on each side and counter-sink them. Continue with cutting with a sharp knife some lines of the cutout in the metal casing. Then use a drill to cut out the majority of the metal and use a file to finish the rectangular shape.

The result should look like the following:

Mounting circuit boards

Mount the large circuit board using the following spacers:

  • 4x 2.5mm for additional distance at the 4 existing press-in nuts.
  • 2x 6.0mm for the 2 mounting points at the right.

With some heat shrink and glue the 2.5mm spacers can be added more permanently to the existing press-in nuts, preventing them from falling off when trying to mount the circuit board.

The small circuit board needs 4x 6.0mm spacers for mounting.

From the inside the circuit boards should look like the following:

Main HUB X-stepper/Z-stepper-L
Main HUB X-stepper/Z-stepper-L

Wiring the new circuit boards - internally

Internally the following cables need to be made:

  • todo.

Wiring the new circuit boards - externally

The following parts have been acquired. Supplier was Farnell (Develektro)

Position Part Manufacturer Manufacturer code Farnell Description
1 D-sub Connector Backshell MH CONNECTORS LTD. MHDVSL9-K 2532964 DMHDVSL Series Zinc Angled
2 D-sub Connector Backshell MH CONNECTORS LTD. MHDVSL25-K 2532963 DMHDVSL Series Zinc Angled
projects/3dprinting/anycubic_i3_mega/redesign_hub_pcb.txt · Last modified: 2020/03/08 21:39 by admin