Sunday, 9 April 2017

Original Prusa i3 MK2 upgrade kit to full printer - extruder, LCD and electronics

I finally got my 625 bearings as was able to proceed with the build.

The extruder was a little fiddly but no real issues. Since the blower fan was self sourced the cables needed to be extended. I just made it the same length cables as the 30x30 fan cables. This needs a standard non locking 2 pin 2.54mm connector. The extruder needs a 5x16 shaft for inside the 625 bearing, this seems to be printed, probably in PET. I found a replacement.

I went to the local hardware store looking for something I could cut into a shaft, I sadly found almost nothing. In desperation I spotted some shelf pins with metal pins.

I chose to use the clear ones, as you can see the shaft doesn't have any ridges or other defects. I cut off the plastic with side cutters. The rod is a perfect 5mm x 16mm. The only down side is as its metal, this will make the extruder fractionally heavier. But fits well.

The LCD is an unknown as to what LCD electronics they use.  I used a geeetech 20x4. It fits well. The screen is in the correct place, the SD is in the correct place, the Knob and button are in the correct place, but somewhat short. The mounting screw holes are also in the correct place (about .25mm out, but not an issue)
I designed some small printed parts to make the MK2 lcd case work with my electronics.
You also need longer LCD cables, I made my own. These are 70cm long.

The heated bed went on without any issues, since I had tested the fit earlier.

The printer now looks quite good.
At least from the front. The back, needs work.
Lots of cables

I added the electronics enclosure, installed the electronics. Since everything has correct connectors and lengths, it really was just a case of plugging it all in and zip tie-ing it in place.

 The more observant of you will notice there is no power supply yet.

Saturday, 1 April 2017

Original Prusa i3 MK2 upgrade kit to full printer - electronics, firmware and LCD testing

I’ve tested out my Mini rambo with Prusa's latest firmware binary.

The first "got you" is the Mini rambo needs external power to power the atmega2560. So although when you plug the USB cable in this will power the usb/serial chip so your computer will see it. Without the 2560 you can't upload firmware.

I used the avrdude method to upload the binaries, the binary was downloaded from the normal place, at this time 3_0_10 is the current version

After numerous attempts avrdude eventually worked.  Best way I got it to work was power off the rambo and remove USB cable.. Power it back on, plug in the USB, as soon as you computer sets up a serial port give the avrdude command.

Second "got you" when the MK2 firmware first turns on the printer hasn’t been configured, you can not talk to it with pronterface or any control program.
Press the LCD knob button a few times till the following display is shown. After this point you can use pronterface. This wont be an issue after its been calibrated.


The avrdude command I used to upload the MK2 firmware binary and full log of output. On Ubuntu linux 16.04:

(your paths will probably differ) 

~/arduino-1.6.13/hardware/tools/avr/bin$ ./avrdude -C ~/arduino-1.6.13/hardware/tools/avr/etc/avrdude.conf -c stk500v2 -b 115200 -p Atmega2560 -v -P /dev/ttyACM0 -D -Uflash:w:/tmp/1_75mm_MK2-RAMBo13a-E3Dv6full.hex:i

avrdude: Version 6.3, compiled on Sep 12 2016 at 15:21:49
Copyright (c) 2000-2005 Brian Dean,
Copyright (c) 2007-2014 Joerg Wunsch

System wide configuration file is "~/arduino-1.6.13/hardware/tools/avr/etc/avrdude.conf"
User configuration file is "~/.avrduderc"
User configuration file does not exist or is not a regular file, skipping

Using Port : /dev/ttyACM0
Using Programmer : stk500v2
Overriding Baud Rate : 115200
AVR Part : ATmega2560
Chip Erase delay : 9000 us
BS2 : PA0
RESET disposition : dedicated
RETRY pulse : SCK
serial program mode : yes
parallel program mode : yes
Timeout : 200
StabDelay : 100
CmdexeDelay : 25
SyncLoops : 32
ByteDelay : 0
PollIndex : 3
PollValue : 0x53
Memory Detail :

Block Poll Page Polled
Memory Type Mode Delay Size Indx Paged Size Size #Pages MinW MaxW ReadBack
----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------
eeprom 65 10 8 0 no 4096 8 0 9000 9000 0x00 0x00
flash 65 10 256 0 yes 262144 256 1024 4500 4500 0x00 0x00
lfuse 0 0 0 0 no 1 0 0 9000 9000 0x00 0x00
hfuse 0 0 0 0 no 1 0 0 9000 9000 0x00 0x00
efuse 0 0 0 0 no 1 0 0 9000 9000 0x00 0x00
lock 0 0 0 0 no 1 0 0 9000 9000 0x00 0x00
calibration 0 0 0 0 no 1 0 0 0 0 0x00 0x00
signature 0 0 0 0 no 3 0 0 0 0 0x00 0x00

Programmer Type : STK500V2
Description : Atmel STK500 Version 2.x firmware
Programmer Model: AVRISP
Hardware Version: 15
Firmware Version Master : 2.10
Vtarget : 0.0 V
SCK period : 0.1 us

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.01s

avrdude: Device signature = 0x1e9801 (probably m2560)
avrdude: safemode: hfuse reads as D0
avrdude: safemode: efuse reads as FD
avrdude: reading input file "/tmp/1_75mm_MK2-RAMBo13a-E3Dv6full.hex"
avrdude: writing flash (201814 bytes):

Writing | ################################################## | 100% 32.32s

avrdude: 201814 bytes of flash written
avrdude: verifying flash memory against /tmp/1_75mm_MK2-RAMBo13a-E3Dv6full.hex:
avrdude: load data flash data from input file /tmp/1_75mm_MK2-RAMBo13a-E3Dv6full.hex:
avrdude: input file /tmp/1_75mm_MK2-RAMBo13a-E3Dv6full.hex contains 201814 bytes
avrdude: reading on-chip flash data:

Reading | ################################################## | 100% 25.85s

avrdude: verifying ...
avrdude: 201814 bytes of flash verified

avrdude: safemode: hfuse reads as D0
avrdude: safemode: efuse reads as FD
avrdude: safemode: Fuses OK (E:FD, H:D0, L:FF)

avrdude done. Thank you.


Monday, 27 March 2017

Core XY - failure

When I built my core XY one of the changes I had to make was to make it 2.85mm filament compatible. Since this is the size most of my filament is in.

The clone hot end "0.4mm E3D-V6 Metal 3D Printer Extrusion Head Exturder Nozzle With Fan" 
Has a 3mm option.


When it arrived I was quite concerned that the PTFE tube was ID=3mm, but OD=4mm  Ie very thin walls.  But I decided to give it a go.

Sure enough half way threw a print the PTFE tube tore off at the entrance to the extrude push to fit connector. Removal of the PTFE tube from the connector was also impossible.

I have now replaced the PTFE with some nice thick OD=6mm tube.

The tube on the right is the original complete with torn off end

 Hot end with new 6mm PTFE tube

This wasn't as simple as you would hope. The 4mm tube extends down into the hotend some what, So I kept a small bit for that and drilled out some of the 6mm to ID=4mm. This happens inside the PTF connector so the 4mm tube isn't being stressed at all.

Only time will tell if this will last

Sunday, 19 March 2017

Original Prusa i3 MK2 upgrade kit to full printer - progress thus far

The Y axis is assembled

And the X and Z
No X belt yet as I ran out of time.

A note on the provided belts: They are really nice and solid. Comparing it with stuff Ive had from china, their stuff is soft and lacking material (its almost like they use a filler vs what ever the belt is meant to made from) "Prusa" belts also have steel (at a guess) cores    

The extruder im still missing a few parts, the idler bearing and springs are the main hold up at the moment.

Also it would seem that m3x18 is a non standard size. Not available from my local supplier. Looks like another order from china is needed. Either that or ill have to make 17 odd of them from m2x20's

My Z axis was quite problematic. The lower plastics the holes in my alu frame are sloppy and I have lock nuts on the back side. The issue is you need to make sure the stepper rods are straight up and down, but the bolts are behind the steppers... So you cant loosen and adjust them when the stepper are in place and you need the steppers in pace to align the position of the lower plastics. Got there in the end. Wouldn't be an issue if I had a higher quality plate

Wednesday, 15 March 2017

Original Prusa i3 MK2 upgrade kit to full printer - checking Y plate

I checked that the old Y plate I have will fit on a new mk42 heated bed

Yes it will, once in the correct orientation all 6 holes line up nicely. (4 corners + 2 on Belt clamp)

Sunday, 12 March 2017

Original Prusa i3 MK2 upgrade kit to full printer - planning

I'm going to build a printer based on the MK2 upgrade kit

It will be as close as I can make it to the "Original Prusa I3 MK2"

I’m not going to worry about the colour of parts, ie threaded rods nuts and washers will not be black. Mostly because I can't find any source for such things at a reasonable cost or locally. Even M8 half height nuts seem to be rare here. So ill be using standard size M8 and M10 nuts

So far its all theoretical, but this is BOM so far.

Everything with a red background in the spreadsheet needs to be acquired.

This will be updated as I complete each section.

The provided spares bag with the upgrade kits has been a lucky inclusion,containing just enough of a lot of the required hardware.

If anyone wants to send me 10 of these "spares" bags, ill convert the nuts and washers to black. :)

Saturday, 4 March 2017

Core XY update 2.8, first print

I've leveled the bed close enough, and enabled mesh leveling to compensate for the remainder (its as close as I could get it without using a dial gauge)

I’ve also set the nozzle distance from the probe so Z0 is correct for the hot end.

First print!

Just a few seconds of a test cube (still on slow ADSL here, so uploads are painful!)

The bed is still cold aluminium, here I am attempting to print on glue stick with PLA. Seems to work for this small object

Finished first print looks great.

Now I have it working I have a few comments about the hypercube.

It is very much a build in place design. If you expect to change things later there may be lots of dissembling involved.

Not all tslot is equal, the tslot nuts in my extrusion are tight, as is will not turn freely to get into correct position. I find I need to force the nuts into the correct orientation with some long nose pliers then screw them down. Another person I know whom is building a hypercube his tslot is so loose in comparison that they work as designed, ie they self orientate on tightening.

The Z build height is only about 145 with current parts. (Z tslot 350mm)
This could be increased 15mm ish by dropping the bed onto the alu extrusion and letting auto be leveling take care of any offsets. (ie remove the springs), Make sure your bed is still electrically insulated from the alu if you try this)
Secondly the Y lm8uu holders could be modified so the bed is at the bottom of the part, this would also add about 20mm to Z (others have done this on thingiverse)

The current Y smooth rod mounts, the mounting screws end up behind the smooth rod (slightly offset) these are not fun to tighten.

Lots of parts stick out the sides...  making it very hard to stick any sides on the machine.

I’m now going to diverge from the standard machine.
Make some of the changes mentioned above and put the re-arm on this machine.