diyplus: a new and improved version compared to FFF

this version features a custom heatsink combined with the bottom plate, suitable
for aluminium CNC milling. the construction provides a better heat dissipation
compared to the DIY (FFF) version.

see all details in the readme.

README.md

@@ -40,6 +40,59 @@ assembled. the property is configured from the same asmsheet.
 
 > TODO: insert here acceptable 3D printer specs and an assembly guide
 
+## DIY+ (plus)
+
+this version features a custom heatsink combined with the bottom plate, suitable
+for aluminium CNC milling. the construction provides a better heat dissipation
+compared to the DIY (FFF) version.
+
+   |
+---|---
+![DIY+ assembly unboxed exploded](diyplus/assembly_ub_exp.png) | ![DIY+ unboxed assembled](diyplus/assembly_ub_imp.png)
+![DIY+ assembly](diyplus/assembly.png) | ![DIY+ assembly boxed](diyplus/assembly_boxed.png)
+
+<img alt="DIY+ temperature during IBD" src="diyplus/ir_1166.jpg" align="right">
+the baseplate serving as a heatsink brings down the main CPU temperature
+from around 70℃  to 50℃. when measured externally while doing bitcoin initial
+blocks download, an IR camera showed around 36℃.
+
+the main file [diyplus.FCStd](diyplus/diyplus.FCStd) contains all parts
+as well as the assembly. other files in the [diyplus](diyplus/) directory are
+exports from the main file, such as baseplate DXF, STL, STEP and drawings.
+
+a complete assembly BOM is as follows.
+
+**off the shelf parts**
+
+- [raspberry pi 4 model b][rpi4]
+- [waveshare 4.3inch DSI LCD][lcd]
+- [sandisk portable 1TB SSD sdssde30-1t00][ssd]
+- 90 degree angle [USB-C adapter][usbc90deg] 3.1 gen 2, 10Gbps
+- adhesive gasket/seal tape for LCD, 1mm thick, 10mm width, L370mm
+- 3 thermal pads 1.5mm thick, 424mm sq total area - see baseplate drawing
+- 7 screws M2.5 L10mm
+- 4 adhesive bottom pads Ø5mm, 3mm+ thick
+
+[rpi4]: https://www.raspberrypi.com/products/raspberry-pi-4-model-b/
+[lcd]: https://www.waveshare.com/wiki/4.3inch_DSI_LCD
+[ssd]: https://www.westerndigital.com/en-in/products/portable-drives/sandisk-usb-3-2-ssd
+[usbc90deg]: https://www.delock.de/produkt/65915/merkmale.html
+
+other parts, harvested from the above list:
+
+- 2 self-tapping screws 2.9mm L3mm (from the SSD)
+- 1 screw M2.5 L5mm (from the LCD)
+- 4 PCB standoffs M2.5 L30mm (from the LCD)
+
+**custom parts**
+
+- [baseplate](diyplus/baseplate_techdraw_c.pdf), CNC milled from aluminium
+- [enclosure box](diyplus/box.stl), 3D-printed
+- [SSD support plate](diyplus/ssdsupport.stl), 3D-printed
+- 3 [spacers](diyplus/spacer_3x2.4mm.stl) Ø3mm hole, 2.4mm thick
+
+> TODO: assembly instructions
+
 ## assets
 
 various files are placed in the [assets](assets/) to use in an assembly composition.