blender

For the past couple of months, I’ve been working on building a 6502-based computer from scratch.

In a previous blog post, I wrote about designing a 3D-printed enclosure for this project in Blender.

During this build, I needed to wait for some parts, so I had some time to see what I could do with the 3D models of the case and circuit board. I ended up animating the assembly process, and learned a couple of tricks along the way.

Splitting components and PCB

I already had a 3D model of the circuit board and components. This was initially exported from KiCad, in STEP format. I then used FreeCAD to convert it from STEP to STL, which I imported into Blender for designing the case. I also repeated this export with some different footprints, since I needed sockets and microchips.

It is a challenge to make this look good, because the circuit board and all components come in as one object, and have lost all of the detail from the KiCad 3D view.

I spent a lot of time splitting objects, then selecting faces so that I could assign different materials. I’m using a free BlenderKit account for materials, and using procedural materials where possible.

I also modeled the DC barrel jack and slide switches, which were the first of many components which were missing from the original KiCad export. Still, something was missing.

Adding missing details

I thought that the PCB in the previous image was too bare. The real PCB uses plated through-holes, and almost every hole in a real PCB has a shiny solder pad around it.

To fix this, I exported the front solder-mask layer from KiCad as an SVG, which looks something like this:

I imported this SVG into Blender, scaled it to fit the PCB, extruded it, then went through a series of boolean modifiers. This resulted in a new object which contained every part of the PCB which was not covered in solder mask. I assigned this a shiny metal material.

After this was applied, I subtracted this from the original PCB model, giving the parts of the PCB which are covered in solder mask.

Showing both of these at the same time, I have a PCB with solder pads and plated through-holes.

Importing the silkscreen

This still was not right. On the real PCB, everything is labelled.

I exported the front silkscreen layer from KiCad as an SVG. This layer looks something like this:

I then used InkScape to change this to white text on a transparent background, before finally exporting it as a PNG. I mixed this into the procedural texture which I was using for the PCB, using the transparency as the mix factor. As a final touch, I also exported the front copper layer, and used this as the displacement input for the final material. The nodes are shown in the screen capture below.

This allows me to render a PCB which looks a lot like the real thing.

UV unwrapping everything

In the earlier render, all of the chips had clear surfaces, while real chips are covered with text and logos.

I created small transparent/brown PNG images for each chip, using Inkscape, then UV unwrapped the chips. I mixed the logo into the texture, much the same as I did for the PCB.

I also UV unwrapped each resistor, in order to paint on the correct colour codes. This was perhaps the most egregious waste of time in this whole thing.

Adding final parts

There were plenty more parts which I couldn’t export from KiCad, and needed to model from scratch. I used the bolt factory add-on to create screws, nuts, and hex standoffs (both a screw and a nut, combined).

I also added power and reset buttons (which are partly threaded), plus the speaker. I decided not to add wires, since it would be beyond my skill at the moment.

When everything is displayed at once, a lot of this detail is hidden behind other objects.

Animating

With that last render, I decided to see if I could make an animation of all of the parts coming together. I’ve never animated anything in Blender, so I had a lot to learn.

I added a tracking constraint to the camera, which is panning around an invisible object on the table, and animated everything using key-framed movement. Parts are raised out of view with slightly randomised rotation/location before falling into place.

Rendering

I exported the animation from Blender as 360 separate 1920 x 1080 images, to be played back at 30 frames per second. I would normally use ffmpeg to convert an image sequence into a video, but I wanted to try adding an audio track.

I imported the rendered animation into Kdenlive, which can process image sequences (the button is “Add clip” / “Import as sequence”), fetched a track from the Free Music Archive (Scanglobe – Current. CC BY-NC), and rendered the project.

Wrap-up

I wanted to get a textured, 3D model of this entire project so that I could easily illustrate documentation and project pages. I definitely achieved this, though working with the exported circuit board and components in Blender was tedious.

The version of Blender used here is 2.93, and the files were exported from KiCad 5.1.10.

I recently built a small 6502-based computer on a custom PCB, which I designed in KiCad. This blog post is about the process of building a 3D-printed case to house this project, using Blender.

This is my first ever 3D print, so I had a few things to learn.

Quick background

My effort on this project has been focused on making a design which works, then transferring that design to a PCB. Since this is my first electronics project, I’m working sequentially, and have completely ignored the need for a case until now.

I could have saved some time if I positioned the ports and mounting holes to match pre-made electronics enclosures, but I’ll take that as a lesson for my next project.

The requirements for the enclosure are simple:

Ability to mount the PCB inside the case
Cut-out for power input
Cut-outs for cable routing to expansion ports
Cut-outs for power and reset buttons

My PCB design files are in KiCad, and I decided to design the case in Blender, since I already know how to use it. Blender is not a CAD tool, but it is excellent for general-purpose 3D work, and will do just fine for this task.

Getting scale

My first challenge was to get the PCB into Blender at the correct scale, so that I could build a model around it. This is mostly just juggling file formats, but also note that Blender works in metres by default. I’ve set it to millimetres, with a scale of 0.001. There are guides on the web about how to set this.

I tried two different methods.

Method 1: Image import

In KiCad, I added two “dimensions” to show the distance between the centre of the mounting holes, then plotted the front copper layer as an SVG.

I used Inkscape to convert from SVG to PNG. I then used GIMP to add cross-hairs to the centre of the mounting holes.

In Blender, I added a single vertex at the origin, then extruded it on the X axis to match the measured dimension. I then added a reference image (the PNG file exported above), and scaled/moved the reference image until the cross-hairs lined up with the vertex.

Method 2: Model import

KiCad can export its 3D model to a STEP file. I imported this file into FreeCAD, then exported it to STL.

Lastly, I imported the STL into Blender.

The scale is correct with both of these methods, because I can align the image and model.

The second method produces much larger .blend files, but has less room to make undetected errors, so I’ll be using it in future.

Building a box

I modeled out the case as a lid and base with 3mm walls, and used boolean modifiers to cut out spaces for buttons and cables.

One challenge was rounding the corners without the two pieces intersecting. I built the box as a square, then beveled it in wire-frame view. The spaces are larger than necessary, and I will try using modifiers slot the pieces together with a fixed tolerance if I need to do this again.

The result was two pieces which sit together but do not attach, with rounded corners and no sharp overhangs, for ease of manufacturing.

Manufacturing and test

I exported the STL files, and sent them to a local manufacturer, since I don’t have my own 3D printer. The print is black PLA, printed with fused deposition modeling, with an 0.2mm layer height and 30% infill.

When I received the parts, I first checked that the two pieces fitted together, then placed a blank PCB over the base to check that the holes lined up. PLA shrinks as it cools, but this aligned perfectly, which is either good luck or correct calibration.

The computer’s board will be installed on standoffs, which are secured by a nut on the other side. I like the idea of using heat-set inserts instead, but I don’t want to try too many new things at once, so I’ve skipped the idea for now.

Next steps

At the time of writing, I’m still waiting for some parts to assemble this computer with a power/reset button, which will be the end of the hardware side of this project.

I’m quite happy with how this turned out as my first ever 3D print. If I need to make enclosures for future projects, I’ll take another look at open source parametric CAD tools such as OpenSCAD and FreeCAD, which are more targeted to this kind of work.

The STL files for this case are available on GitHub at mike42/6502-computer, critique is welcome.

Tag: blender

Rendering my 6502 computer project in Blender