1/27/2026 - Researched components and frames

Researched quite a bit regarding different components, different sizes, and different styles of printers. I'm currently looking to make this a CoreXY-style printer with a 500x500x500-ish mm bed (mainly so it can fit large keyboards - particularly for pick and place and printing cases without splitting them into multiple parts)

The only real issue is huge beds are very difficult to find for a reasonable price. I've found are a heated bed for $90, and currently the best options for a magnetic bed are magnetic sheet(s) with adhesive for $30-50, and an actual build plate for another $50. I also found a ~$20-40 FR4 sheet (depending on thickness) - I'd much prefer magnetic so that 1) I can magnet stuff down to the bed when doing PNP, and 2) I don't have to worry about breaking a huge fiberglass panel lol, but given the cost it's not seeming very practical. Will see what's in the budget and what I can get away with towards the end though.

Also I've settled on most likely using the DRV8825 to drive the motors - it's fairly cheap, has a simple STEP/DIR interface, and is easier to solder than something like the A4988. If I need to handle more current I'll switch to an 8425 or 8424 instead.

1/28/2026 - Just a quick note

Just figured I should probably say Ender-3 compatibility is now less a concern - I'd like to go with a rail system more like this instead. Should be easy enough to modify the PNP model to mount on an Ender-3 - my only concern really is electrical compatibility for the vacuum bits.

2/14/2026 12 PM - Researched layouts more

Looked into my two options - corexy but not, and corexy. Apparently corexy but not is actually called box cartesian, and also corexy starts getting kinda bad around 350mm, but especially 500mm, so going with box cartesian. Easier to design too.

2/14/2026 9 PM - Looked into lasers and stuff, anadapter board for connectors

I'm aiming to have easy compatibility with lasers, with as little rewiring to switch out tools as possible, so I'm planning to have a board to adapt whatever's on the motherboard to easy wiring - for example, BL-touch to a single 5-pin connector, 2/3-pin laser to VDD + GND with PWM handled via a MOSFET on the board itself (will be 3 pin to support lasers that have PWM, can just use 2 out of 3 pins for standalone lasers), and connector for vacuum pump going to HE3.

Will also have 12/24V jumpers and buck converter for either voltage (for laser and vacuum pump), and will have an io expander connected via i2c for GPIO. Will also add general 12/24V power terminals for whatever.

Also some general resources relating to this cuz why not

• Octopus wiki thing: https://global.bttwiki.com/Octopus.html
• 3rd party diagram: https://gadgetangel.org/build/electrical/images/BIGTREETECH-Octopus-1.1-color-PIN.pdf
• Git repo (with manual and stuff): https://github.com/bigtreetech/BIGTREETECH-OCTOPUS-V1.0
  

2/16/2026 - Looked into mainboards and display

Was looking into the Octopus and Octopus Pro mainboards - apparently the Octopus Pro mainboard is only like $5 more, and it has sensorless homing, which if I can get that working will save some money, so I'm going with that instead. Plus it also has the amp required for PT100/1000 support, so this thing should be able to print up to 485 C if I do use that thermistor (or will at least be easily upgradable to do that).

Also I'm not very smort I thought the Octopus v1.1 didn't have EXP1 and EXP2, that's why I started looking for alternatives in the first place - nope it does, I just can't process images apparently.

P.S. this is gonna need a bulky external MOSFET for the bed, it's too high power. Bed is 350W, max is 300W.

2/21/2026 - Figured out pinout of the PCB

So uh after like forever I figured out the pinout of the PCB. JST ZPD is quite niche but will work perfectly, and isn't so niche that it's too difficult to find replacements, hence going with that for GPIO/I2C + power after much deliberation. LCSC's out of stock for female right-angle XT30 connectors, so instead I'm having to go with XT60, hence I'm having to make the GPIO connector much smaller. 26 pin would have fit (just barely), and would've allowed for 16 pins + i2c + 3.3/5/12/24V power, but XT60, so instead I'm having to reduce it down. 10 pin would've been fine - no GPIO, just i2c and power - but LCSC doesn't have those so I figured I might as well make it 12 pin and add another 24V pin for 4A total.

(also for context regarding the high pin count, every power pin has a matching GND pin so that's not limiting this, with just 1 it would be a max 2A power draw across everything)

(i also removed 2+2 laser support to clear up room - can rewire that very easily anyways)