RAMPS D8 and D9 mixed up

After the accident with the first RAMPS I bought new one and it arrived couple days ago. I moved jumpers, steppers and wiring to it from the old one but I could not get it to work properly. The fan at D9 and heat bed at D8 were somehow bridged and worked at the same time. I didn't see any obvious soldering mistake on the back side of the board so I was quite puzzled. Some searches on the RepRap forum gave me a hint and the problem turned out to be MOSFET heat sinks touching and messing up the logic. Only a little bending was required and now the printer is operational again.

10 tips for RepRap P3Steel builder

These are my tips for anyone building a P3Steel printer. I did not purchase a kit so some of these might not apply for kit printer builders.

1. Get plenty of LM8UU bearings. Tolerances vary a lot so it is better to order at least 2x the required amount. They are cheap after all. Or use alternatives like IGUS.
2. Try to get printed parts in good quality and as a dedicated set for P3Steel. Using some generic Prusa i3 parts is possible but requires more manual work. Also, think about using upgraded parts like Toolson edition straight away.
3. For heat bed I have been using ordinary 4mm glass. It is cheap and available at local glass shops. So far I haven't had any heat related issues with PLA temperatures.
4. Plan for cable management. There is plenty of wiring going around and some of it is moving around with hot end etc. So you'll need also cable sleeves, heat shrink etc. 
5. Be careful with 8mm rods. Especially longer lengths can be bent when handling or hammering in to the frame.
6. After couple initial test prints, go around and tighten up all the screws. I have had screws falling of from flexible couplings and belt pulleys.
7. Purchase enough M3 screws in various lengths. Not only you need plenty for the frame assembly but you will also need them to put together cooling fan supports etc.
8. Z end stop setting needs to just close enough. No need to go mental as the fine tuning can be done in software.
9. Print from SD card in order to avoid connection issues and pauses with USB
10. Zip ties and hot glue. Shortcut to get first print out :-)

Enclosure controller

As mentioned in an earlier post I have a plan to add an Arduino Uno based controller for enclosure. Its responsibility is to monitor temperature, control ventilation fan speed and switch on the main relay. It also has a simple 1602 LCD display shield for temperature and other information. At the moment I haven't planned any use for the keys of the display shield.

So far I have been testing the design on a breadboard in order to get temperature reading and relay control working. I have plenty of 100k Ohm NTC 3950 thermistors so I used one to measure temperature using voltage divider circuit and Steinhart–Hart equation in the Arduino code. There are plenty of examples online how to wire this up.

The main relay is an automotive 40A relay with integrated fuse socket. The funny thing was it actually came with a 30A fuse. That should be enough, though. In order to energise the coil of the relay I used BC548 NPN transistor. I also added 1N4148 as a flyback diode.

Adding a PWM controlled 12V should be straightforward. I will use BC548 or BC639 but I might add a capacitor to smooth out the fan control. After I have that sorted out on the breadboard I'll solder everything together.

Polarity matters

I was reorganising the cabling after I installed the cooling fans next to the hot end. I checked there were no loose ends and everything seemed to be fine. But as soon as I turned the PSU on there was a faint popping sound and no lights on the LCD. I managed to connect wires from PSU to RAMPS wrong way and that instantly fried RAMPS.

Looks like the LCD and MEGA are okay though, I was able to turn them on with USB power and use different features on the controller. However, none of the steppers move and the hot end wont warm up. Just to make sure I decided to order new RAMPS, MEGA and stepper drivers again. This will mean couple weeks pause with printing but I'll use that to design and build an enclosure for the printer.

Toolson improvements

The plastic parts of my P3Steel are quite a mismatch and I have started to print new ones. I chose very nice selection of essential parts and improvements called Toolson edition. It can be found from http://scheuten.me/?cat=9.

So far I have printed parts for Y axis but I haven't installed them yet. I need to wait new bearings to arrive as it uses smaller flanged bearings. I also have bunch of other stuff on the way including cable sleeves, Kapton tape, 40mm fans etc.

Printrun issues with USB connection and OS X

I spent quite some time trying to get Printrun to connect my RAMPS board. The fix was to set the baud rate lower with #define BAUDRATE 115200 both in Marlin Configuration.h and in Pronterface user interface.

The screenshot below shows necessary details:

But the while I was testing some models there were long pauses in the print. Those were long enough to clog the hot end as the heating was on but no filament was pushed through. After couple attempts I started to use SD-card reader on the LCD display unit.

First print!

After doing some ugly hacks with zip ties and hot glue I got end stops in place and the printer was ready for its first print. At that point there were plenty of issues waiting to be fixed but I wanted to see if anything usable would come out.

First proper print

Leveling the bed was pretty difficult as I didn't have enough clamps to secure the glass on the PCB. I ended up using some painters tape to hold it for a moment. But that is pretty bad idea. Also, finding the Z level for the first layer took quite a while.

After couple days I managed to find clamps for the glass so I could do the levelling properly. With this essential fix in place I started to print more parts for the printer including a box for LCD, RAMPS fan support,  finger guard for the 80mm fan and some smaller bits.

Wiring done

Wiring was pretty easy to get done but it looks pretty messy. I have to wrap wires somehow together and think some clever routings. It is important to make sure cables have enough length for the whole movement of the axis. I almost snapped the end stop of from X-axis because I didn't remember it moving higher as the Z increases.

While I was testing the cabling I could not get extruder stepper working. I thought I had burnt driver but in the end it was the 'cold extrusion prevention' feature of the firmware. Simple fix this time. Also, some of the axis were moving to wrong direction but I fixed that in the firmware configuration.

Heatbed thermistor

I was planning to get a silicone pad heater and machined aluminium plate but I could not find a nice plate with decent price. So I had to go with a traditional PCB with glass plate. I ordered PCB Heatbed MK2B and a bunch of NTC 3950 thermistors. I will use the rest of the thermistors with my environment control unit.

The power wires were easy to solder but I might have bought a bit too heavy wire for it. I use 4 sq mm wire between RAMPS and heatbed. That is pretty much the thickest fitting in the RAMPS screw terminals but it isn't very flexible and might cause me headaches when I try to clean up the wiring mess.

Most of the instructions use Kapton tape to attach thermistor to the heatbed. Unfortunately, I have none here so I had to improvise. I soldered the thermistor to a longer wire with heatshrink and thermal protective sleeve. Then I placed the thermistor in the PCB with some heat resistant grease as I did not have any thermal paste either. I secured the wire in place with some masking tape and then I added good amount of bathroom silicone on the wires. According to the label the silicone is good till +180 C degrees.

Not very pretty but seems to hold pretty well. I hooked up the wires to RAMPS and heated the bed up to 95 C degrees and everything worked ok. In any case this part is hidden so the appearance does not really matter.

XYZ complete

The second batch of LM8UU bearings arrived and I was finally able to assemble both X and Z axises. Y axis was completed earlier. The second set of 12 LM8UU bearings was not much better but I was able to find enough bearings with suitable tolerances.

X axis ends and carriage were some 3D printed parts I got from a friend. I also had another set but this one seemed to fit better. In any case I am planning to replace those and X belt bearing with better ones as soon I get the printer productive.