Happy 2020: PrntrBoardV2 update

I’ve been busy over the holidays. Here is a summary of the recent progress with the PrntrBoard V2 3D printer controller.

I decided to give the JLCPCB SMT Assembly service a try and ordered some TMC2209 driver boards as well as some semi-assembled PrntrBoard V2 controllers. Overall I was quite happy with the results.

Here is a picture of the driver boards. I tested all of them and they worked flawlessly out of the box.

These are the semi-assembled controllers. I use semi-assembled, because only the SMT components were populated and I have to spin my soldering robot to work on the thru hole connectors.

Next I tested the sensorless homing capability of the TMC2209 drivers. After some tuning of the sensitivity parameter is works very well. You can see one linear rail axis homing with no sensors in this video:

I also decided to work on improving the mounting of the drivers to the board. The driver boards were not very stable in the PCI Express slots and I designed these little plastic holders to fix them in place.

They are bolted to the bottom of the controller PCB. The drivers are very well affixed in place.

While I was trying to get my 2004 LCD panel to work with the controller, I found that not all “standard” EXP1 and EXP2 connectors have the same orientation. At first I though that the SKR 1.3 board, just has them backwards, but I then found this article on the RepRap discussion forum. It appears that the original schematics had an error and now some boards/displays are just backwards. I quickly flipped the connector on my 2004 display and with worked, but this can be quite frustrating.

I made a small PCB that one can use to flip the polarity of the connectors. “To flip or not to flip” seems to be ongoing question.

Soldering machine progress

I managed to put together the chassis of the soldering machine. The bulk of it is made from parts for a Prusa MK3 3D printer. It provides a good start point so I can experiment further.

This is what is looked like in the beginning

I also put this mounting plate to hold the connectors that I need to solder for my test board. With this plate I can insert the connectors, place the board over and get it soldered quickly, then move to the next one.

Here is a video how the head would move along the Y axis

And another one along the X axis. This one needs to hop over the pins.

I used my PrntrBoard controller to drive the motors. This is a picture of the machine in it’s current variation. I added the Prusa LCD display, but have not connected it yet.

“mass” production

The demand for my CD-changer emulator is picking up, so I’m making several boards at the same time. Placing of the components on the board by hand and re-flow with hot air.

These 6 board take about 4 hours in this stage plus another 4 hours or so to solder the optical connector and other connectors. My hands feel tired after a while. I’ve heard that good scotch helps with this condition.

SMD stencil printer is so cool

If you can’t recognize what this is, here is an explanation.

When creating PCBs, one can order a stencil – usually from a thin sheet of stainless steel. On this stencil, there are cut small holes (with a laser cutter) where one is supposed to apply solder paste on the PCB.

So the operation is: you align the stencil on top of the PCB; then squirt some solder paste on top of the stencil; then use a flat “applicator” to smudge the solder paste over the stencil holes. In the end, you lift the stencil up, and you end up with the solder paste applied in a thin layer over the solder pads on the PCB.

To aid in this whole process is this contraption – a stencil printer. You align the stencil on the device and put come L shaped holders on the bottom to hold the PCB in place. The bolts on the bottom are to help to align the stencil and the PCB. When the alignment is achieved you put the PCB in the holder on the bottom; lower the stencil; apply solder paste; lift the stencil; remove the PCB. The whole solder paste application takes about 1 minute.

I should have gotten it sooner. My only regret is not getting a larger size printer, as you can see the stencil frame is a bit larger than the printer base – it still works though.