After assembling the basic frame of the prusa and realizing that all of the parts I had previously printed before upgrading Pronterface were not going to be good enough I decided to attempt reprints of the Z motor mounts, these worked remarkably well and were immediately useable with no manual remodeling required at all (Cool) once again proving that software is king when it comes to quality prints.
As these 2 Z motor mounts came out so clean and accurate compared to previous attempts I thought it best to bite the bullet and go for new X carriage end as well, rather than just reprinting the standard ones I had a good look at the alternatives on Thingiverse and found some great looking advanced versions (ref) that appeared to use less plastic, have bolt in LM8UU bearing holders for the Z axis smooth rods and a much improved way of clamping the X carriage rods in place (rather than the captive nut method which is ok but quite fiddly to assemble.
I went for the motor end first as this was the one I was having most of the problems printing with the old software version/configuration, I was stunned by the result it printed perfectly and the quality puts my other parts to shame, buoyed by this success I followed up with the idler end same design, at this point my Darwin decided to remind me that it was not a happy bunny and began to rear its ugly mechanical failure head again!
First off the X axis end stop decided to fail (whilst I was demoing to an interested friend (embarrassing) this was a simple re-soldering job.
Secondly (and more critically) over half way through the X idler end (4.5 hour print on the slow old Darwin) the X axis began to slip mechanically, affected a repair and tried again, same problem half way through this large print and again the X axis slipped ruining the print, (at this point I am beginning to worry again about how much plastic I am wasting and wondering if I have enough left to finish the 1st child.
Attempted another repair and broke the captive nut completely out of the resin cast X carriage drive gear (whoops) luckily there as already a second grub screw hole drilled so I used this instead and tried again ~(in fact this was about my 4th attempt at fixing this X axis slippage issue each time wasting a lot of plastic and time) but to my relief the 4th attempt worked like a treat and my perfect looking X idler is now sitting proudly on the build bed waiting for me to crack it off and carry on with the prusa build.
The more I use the Darwin the more it reminds me of an old car, it requires constant maintenance and really needs replacing or upgrading but at the same time it has the feel of a solid piece of engineering hardware and is remarkably forgiving of the number of bodge’s I have affected to make it print.
Although I can’t quite describe it as “Old Faithfull” due to the constant maintenance, when treated well it responds with great prints.
I have spotted a number of parts remaining to print for my 1st child, namely the Z motor mount bar clamps x 2, end-stop holders (I haven even decided what sort of end-stops to use yet!) also I have only just remembered that in order to get the Darwin printing I used one of the steppers from the Prusa for the geared extruder on the Darwin, this leaves me short 1 motor, I think that I will just remove the entire geared extruder from the Darwin when the Prusa is ready for it and once the Prusa is printing I will probably buy 1 or more new Nema 23’s for the Darwin and other printers/projects.
Although at first this seems a fairly expensive hobby, my total build cost for both printers bearing in mind that I was gifted the old nonfunctional but essentially mechanically complete Darwin is running at about £300-£350 not including purchased tools.
I think that this is damn good value for a system that can essentially print anything in plastic in a matter of hours.
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