Printrbot Simple Metal SKR SGEN_L adapter with exposed sd, relocated usb by ej0rge

Last crawled date: 3 years, 4 months ago

I picked up an old Simple Metal because of reasons. And of course, the printrboard was toast.
I had a spare MKS SGEN_L v1 kicking around that I had bought accidentally over a year ago. So i downloaded an existing adapter plate from thingiverse, printed it, and immediately hated it. So i designed my own. 40-some prototype prints later, I'm publishing it.
The SKR boards from Bigtreetech are designed to match the footprint of the Makerbase GEN_L exactly, and so is the Makerbase SGEN_L. So this adapter will work for any SKR, GEN_L, or SGEN_L, and probably any boards i haven't heard of that also mimic the GEN_L footprint.
I had watched the fintech repair shop youtube videos and i knew i had no interest in cutting a hole in the side of the chassis. Firstly because i'm terrible at that sort of thing, but secondly because it seems like a crime to mess up the metalwork.
By moving the board back toward the motors a bit, the micro sd slot on the motherboard is exposed where the printrboard usb port was. A little wall is provided to help you avoid pushing your sd card into the void between the motherboard and the chassis.
A micro-usb breakout board is mounted in the cutout for the printrboard sd slot and connected by soldering 3 wires to the back of the motherboard (just ground, D+, and D- since there is no reason to connect power).
The usb connector is clamped in place quite securely and it should be very difficult to break - and even if you do break it, it's just a breakout board and if you bought a pack of 5 (or 15) you could just replace it with another.
I have ordered some mini-b and regular B breakouts from china and will look into whether they could potentially fit if there is interest.
I have also noted that there are two kinds of micro-b breakout boards floating around both my workbench and amazon / ebay / aliexpress and the longer style will stick out a bit until i publish a new version that moves it back it 2mm. (Edit: I have uploaded a variation that will probably work for the longer breakout boards.)
In order to bring the board close enough to the chassis to expose the sd slot this adapter mounts flush to the chassis with tapered rings around the rivnuts that the printrboard was originally secured to, with the lip of the screw pressing down the ring.
No legs or feet are needed - even with very tall heatsinks on the stepsticks there is adequate clearance provided by the corners of the chassis. Very much unlike other adapters.
The screws that go under the motherboard MUST be M3x4mm button head, not socket head cap screws, probably not pan head either unless you use M3x4 plastic screws. This is to avoid shorting out against pins on the back of the board for the Y axis driver.
You could also just glue the adapter down - but I do mean glue, and make sure you clean the surfaces and use a strong adhesive.
If your print settings are not on point or if it turns out that the rivnuts varied a bit in their position you may need to scrape some plastic to get it to seat properly.
Aside from your motherboard, you will need the following:
Optocoupler for the Z sensor. The Z sensor won't work powered with 5v, it needs the same higher voltage that was provided by the printrboard. This is the most straightforward and simple way to handle that. If you switched to a capacitive sensor for a glass bed, this works for that too.
https://www.aliexpress.com/item/32719957788.htmlhttps://www.amazon.com/gp/product/B01L1OI1HC/
You can follow this diagram for hookup:
https://www.thingiverse.com/thing:2906283
If you don't have JST-XH parts and crimper, you'll need a JST-XH 3 position lead to connect the optocoupler to the motherboard. You can also use a JST-XH 2 position lead to provide power between one of the 12v/24v connectors on the motherboard and the optocoupler.
https://www.aliexpress.com/item/32996835431.htmlhttps://www.amazon.com/2-54MM-Female-Double-Connector-Wires/dp/B07XJMSZ2G/https://www.amazon.com/2-54MM-Female-Double-Connector-Wires/dp/B07XNTQK5M/
If you want to crimp your own cables, I recommend this crimper which isn't cheaper on aliexpress:
https://www.amazon.com/IWISS-IWS-3220M-Connector-0-03-0-52mm%C2%B2-Ratcheting/dp/B078WPT5M1/
And this kit of connectors has been adequate:
https://www.amazon.com/gp/product/B01MCZE2HM/
I also re-crimped my stepper motor cables, since new motherboards have JST sockets. It should also be possible to just shove the dupont connectors onto the JST pins, but you will want to hot-glue them in place because they will fall out very easily due to the shorter pins.
Shorter usb micro-b breakout: https://www.amazon.com/gp/product/B07KS1RPMP/
Longer usb micro-b breakout: https://www.aliexpress.com/item/4000216515466.html
You'll need at least three dupont jumper wires. Of course i made my own, but you can buy them ready-made.
https://www.amazon.com/GenBasic-Piece-Female-Jumper-Wires/dp/B077N5RLHN/https://www.aliexpress.com/item/1005001619905395.html
Or if you're getting into the crimping game, get a set of crimps and shells: https://www.amazon.com/Hilitchi-2-54mm-Headers-Connector-Housing/dp/B014YTPFT8/
If you don't have M3 hardware, get a set:
https://www.aliexpress.com/item/32907505613.html
or just get some M3x4 button head for the important spots:
https://www.amazon.com/iExcell-Stainless-Socket-Button-Included/dp/B08H2HCBQM/
The screws that attach the motherboard to the adapter can be up to 10mm long. The screws that secure the optocoupler shouldn't be longer than 6mm i think. Screws for the USB clamp should be in the 12-16mm range.
If you use an SKR motherboard, you will need to gently bend the blade fuses to make room for the power inlet. I also noticed that on the SKR I used after I burned out the SGEN_L, the solder job on those fuse sockets aint so hot, so I dabbed on some flux and reflowed them, which allowed me to reposition them further.
The SGEN_L and GEN_L do not have these blade fuses. Really, the better deal seems to be the SGEN_L v2 right now, since it is roughly equivalent to the SKR 1.4 Turbo with just a couple minor feature differences.
For extra safety, I trimmed the pins that might potentially touch the head of a screw and put some tape over the exposed metal. This might not be necessary but maybe do it anyway.
When printed in PETG the screw holes will self-tap with M3 machine screws. If printing in PLA you may find that you need to tap the holes. I like to use the combo drill-and-tap bits sometimes referred to as "power taps" in a screwdriver handle for that job.
I think i trimmed down one of these for cable management:
https://www.amazon.com/Viaky-Adhesive-Backed-Adjustable-Management/dp/B01M6U9Q9C/