Thursday, 25 January 2018

Prusa MK2s Bed thermal runaway issue

Well It had to happen sometime. My MK2s developed an issue! Hard to believe but true!

I was printing something in ABS (bed at 100C) and suddenly the printer just stopped!

I look at the LCD and it says "Bed thermal runaway"

I did some quick testing and sure enough the bed was reading a lot lower temperature than the infrared thermometer was telling me. (yes these infrared thermometer are notoriously inaccurate, but I know mine is close enough, especially on a black surface like the printed bed)

So I removed the heated bed and this is what I found

Lets take a closer look at that thermistor

It has come free from the tape and it hanging in mid air!
So I pealed back the capton tape, no issues.But the alu tape just tore to bits. So I removed it

I contacted Prusa support, but unfortunately they could not tell me anything about the aluminium tape.
Luckly I had Kapton and Aluminium tape
I added a bunch more tape... to try and stop that happening again.

What I don't know is if the adhesive on my Alu tape will be able to handle the temperature. Ill find out soon...

So what actually happened here? My best guess is that the spiral wrap grabbed the cables and pulled the thermistor out with repeated Y movements. All the cable was pulled threw and sitting the in the electronics enclosure.

I suspect this has happened to others, as looking at the build instructions for the Mk3 they now say the wrap the thermistor cables around the heated bed cable. Which I will now do to my machine.

Sunday, 24 September 2017

Core XY update 3.3

Still not quite 200 in Z, but I am determined

So I tried a bunch of sizes for my Z rod clamps and settled on Moving the Z smooth rods 5mm In on the Y and 15mm Down on the Z

This enabled the Build plate to descend the entire length of the rod (there is a plastic bump around a screw head that sticks out level to the end of the t-slot, so it not all wasted space between the bearing holder and the side)

Next I mounted the power supply under the machine using
Now on thingiverse
They seem to do the job.

Next is the re attach the Z Stepper and lead screw
I use the same mounting bracket for the stepper but turn it upside down. So the stepper is completely below the t-slot

There is now about 2 mm space between the Power supply and the tslot.
The power supply also has to be positioned between the two heated bed mounts. 

Monday, 11 September 2017

Core XY update 3.2

Winter is passing and I have awoken from hibernation.

This is my second attempt to get 200 mm in the Z axis on my hyper cube.

I have lowered the aluminum cross bars as far as possible, and moved the 90 degree brackets to the inside.

This of course caused an issue where smooth rods and Z stepper motor now sits below lowest point of the printer.

I created new legs for the printer to raise it up again.

I have put the model for these legs on thingiverse and the openscad. Its parameterized so if you want to change anything you just have to edit the variables.

The printer now looks like this.

With a ruler and eye balling it, It looks like I may now have 200 In Z. I wont know for sure till I re install the electronics.

With all this space under the printer I am also looking at mounting the power supply and electronics under the printer. There should be about 60mm under the bed when its fully down.

Monday, 26 June 2017

Original Prusa i3 MK2 to MK2S upgrade kit - contents

I got this kit to make my machine even closer to a factory MK2s. In particular the smooth rods I used for my machine I borrowed from another machine with the intention of replacing them, then they released this kit and I thought problem solved.

So what exactly is in this kit, lets see

You will note there are no replacement printed parts, instead they give you filament and your meant to print your own!  They do provides models and even pre-sliced gcode for the main parts

In some ways I like this idea, but not in others, what if you have a power cut or some other failure? You can't get this filament, you cant just try again. This color "Safety orange" is made special for Prusa. Also the pre sliced only replaces the main parts, the extruder mainly. But if you look at the mk2s parts nearly every single part has been modified. Notably absent are new X ends, where the nut traps have been strengthened.

Also just how are you meant to print from an unspooled roll without making a mess? 

At this stage I have not printed these upgrades. 

Wednesday, 3 May 2017

Core XY update 3.1

I upgraded my Z rod holders on the hyper cube

The way my rods are mounted the smooth rod covers the t-slot screw head, making it very difficult to tighten the screw or align the rods. So I created my own part with two offset screws for much easier access.

This can be found on thing:2167139

This also gave me an idea, the current lower Z rod clamps are not at the end of my Z rods.
So I could extend the mount downwards to hold it lower. Like this.
This should give me a little move Z travel? Yes it did, but there is a issue.
The lm8uu holder on Z hits the middle nuts. It used to hit the old part also. My solution, remove that screw. Now it moves as far as it can until it now hits... The Z stepper mount

So ultimately having the lower Z mount achieved nothing as you can't move down that far, but swapping the original mount for my new mount did enable me to remove that screw and give me full Z movement. Untill the Stepper mount is hit.

I'm now wondering about mounting the the Z stepper motor back at the top with the lcd screen elsewhere so it is not blocked by the stepper motor. 

Wednesday, 26 April 2017

Core XY update 3.0

I've  Printed a few replacement parts for my Hypercube

Some parts you may recognize.
On the left are standard Hypercube e3d mounts and fan duct, but now in ABS.
In the middle, these parts are replacement bed mounts that are much lower, giving me 15mm more Z axis. Files can be found @ thing:2272127  (These are adjustable in scad)
The last part is a very simple mount for my power supply. I'm not sure I am happy with it, so no files at this time.
 E3D mount installed

New lower bed mounts installed

Power supply mount installed. Really need to tidy up those wires sometime...

Sunday, 23 April 2017

Original Prusa i3 MK2 upgrade kit to full printer - Power supply and test prints

I've temporarily (Will probably never be changed) attached my power supply to the frame.

Since there are no power supply mounting holes on my frame, and I'm not 100% sure where it is meant to have holes I opted for a more make shift solution

Yip, good old zip ties. Two of them to form a crude box shape so they sit flat on the front so as to not catch the X axis. There is also some strong double sided sticky tape between the power supply and the frame.

The MK2 is complete (well close enough) :)

Now for some test prints.

I grabbed the pre sliced examples from the mk2 site.

All printed fine. There are two "PRUSA" as one is ABS and the other PLA, the simple color changing eg (Prusa bottle opener) worked well, but I ran out of red PLA so ended up doing two filament swaps.

As a final stress test, I printed one of the 6 hours examples. NB it really took over 7!

It a little stringy in places, but nothing that couldn't be picked off later.

Over all very satisfied with this printers performance.