The water cooling Part 3 and z-axis problem

Finally the last missing piece arrived.

When I screwed the fitting in the water pump I recognized that there is much play in the thread. One option is to use teflon tape, but this could split the plastic body from the pump if there is to much pressure on the threads.
So I decided to try an O-ring to seal the connector to the pump. I used a 10x1.5 mm o-ring that fits in the pump and seals towards the front of the pneumatic connector.


I had ordered an adapter cable with a plug that fits on the connector from the Water pump. As this is originally made for PC fans, this is pretty much standard. I was only interested in the part on the right in the picture, as this was hard to find.

As this is all standardized for PC fans, this is the pin layout for the 4 pin adapter. 

I want to run the pump always at full speed, so I don't need to connect the PWM signal(control). Anyway, I don't have any logic board to control it, I strongly recommend to not try to adjust the pump speed based on the water temperature. I explained this in detail in an earlier post.

The tacho signal(sense) will be used as input for the Einsy board, So the Einsy board will monitor if the pump runs, just like it usually does with the hot-end fan.

This is the logic diagram of the cable I made.

For the Temp/Fan control board I use a separate cable from the power supply.

This cable basically connects the ground from the power supply to the water pump and the fan 2 output on the Einsy board.

You will need a 3 pin Molex connector for the connection to the Einsy board. This cable need to be long enough to connect back to the Einsy board.

The 12 Volts DC from the power supply connects to the power (pin 2) on the water pump. The sense or tacho signal from pin 3 on the water pump connects to the fan 2 output (pin 3) on the Einsy board.

I also consider to use the 5V signal for the hot-end fan to switch the pump on/off. But I have not decided yet if I want to spent the effort. I guess then I would make sense to come up with a little perf board to connect everything together.
For now pin 2(middle) of the connector to the Einsy board fan 2 output is empty.

Make sure you don't mix up the pins, that might damage the Einsy board! You can see the 5V+, - and S(sense) for the fan  connections in the diagram below.

I have also made a small connector in the connection tot he power supply. So I can detach the cable from the power supply for my convenience.

This is the back of my printer now. I need to clean up the cabling a bit. The temperature sensor is just clamped between the radiator and the mount. I still need to find a better way to measure the water temp of the return flow. But the diameter of the sensor is 5, if it would be 4 or 6 I could simply use a T-shaped pneumatic connector.

Some words about the Molex connectors. I have got some from Aliexpress, but I cannot recommend them.

This is an original Molex connector. There is this little pin that locks the connector in the plastic housing.

On the ones I got from Aliexpress there is this pin missing. But you can bend over this part backwards to lock the pin in the housing. I am not sure if this intended to do so, but that worked for me.

But you should rather get the original Molex connectors. Usually you need an expensive crimp pliers, specially made for those Molex connectors. But with a little dexterity you can crimp them with some pointed pliers as well.

Not it was time to test if everything worked as expected. So I heated the hot-end up, but had the cable with the tacho signal not connected tot he Einsy board.

After some seconds the printer turned off the hot-end heater and displayed extruder fan error.
Just as expected and how it should be. This will be my fail-safe if the printer is on and the water pump is not running, the printer will automatically turn of the heater.

Then I connected the cable to the Einsy board and repeated this test. As you can everything worked just fine.

I was happy so far, but not with the "silent" water pump. This pump is anything but silent, at least when you run it on 100%. But see for yourself. I need to get a real silent pump or this thing will drive me crazy.

Now I wanted to see if I can run any of the calibrations of selftest from the original Prusa Software.

Here the problems began with the z-axis. While I can move tit around without any issues when I manually move the z-axis. Every attempt for full or just z-axis calibration the z-axis did not move, the z motors just hummed.
The problem is that Prusa uses no limit switches, even though the Einsy board does have connectors for it. The original Prusa software measures the motor current to determine that they reached a hard limit. They also seem to limit the current used for the upward movement during the z-axis calibration.
In my case this was not enough starting torque to get the motors moving. With a little help they started to move. So I tried white lithium grease on the z-axis shafts and the lead screws, then I moved the z-axis up/down over 20 times. But that didn't help much.
Then I loosened the upper mount for the lead screws and tried without them. Just to rule out that the width of the x-axis was ok and not bending the lead screws while moving.
Now it works every second try. But I have only problems with the calibration, if I move the z-axis from the menu everything runs smoothly. I guess the brurolls motors just need a higher current. I have read reports from other user that have problems with the Einsy board and the z-axis stepper motors. They reported to wire them in series and use just one output on the Einsy board improved the problem for them. At least with marlin they got it to work this way, but not with the Prusa firmware.

For the next build I am going to order the new stepper motors from LDO, same brand that Prusa is using. They announced an optimized version of motors that don't get as hot as the ones that Prusa uses on their original Mk3s.

So finally the printer started the z-axis calibration, but on position 3 of the bed leveling it failed again. But this time everything was ok, the P.I.N.D.A probe was already past the end of the heat bed.

As the x-axis calibration fails as well, I am not sure if I have the same motor current issue on the x-axis as well or if this is caused by the position of the P.I.N.D.A probe in the Titan Aqua mount.

The next time I am going to get the source code of the Prusa firmware and make the adjustments required for my Titan Aqua Klon hot-end. Then compile the hex file and test it on this printer.