WOOT I'm so happy i'm squirting... plastic all over the place

    I have spent the last 36 or so hours poking at my printer trying to get it to play nice..  Last night i was so close to getting nice results out of the beast...

    After printing and tweaking and printing and tweaking and printing some more, I just couldn't get it right. the first layer was too thick the middle layers were too thin and the top layers too thick, then i decided to check what i was working with, turns out what i thought was a 0.5mm nozzle was actually a 0.35mm nozzle.. after that things went pear shape, so i went to bed, that was about 5am..

   when i woke up i had another stab at it. looking at what i had done made no sense, the firmware changes i made were gone, or wrong... so i started fresh, looked at the output and started to make some progress. i found that i needed to install the Z min endstop, to get a bit of repeatability out of the printer, once this was done things started to get better, i got the printer to start printing nice, then they wold fail due to the print job lifting up off the print bed... once i adjusted the temp of the bed to get 110'c on the surface of the glass, and the fans to blow at the right time, things started to come together really well. well enough that i could get to chasing down some print quality.

    With Repraps and Repstraps the fun and games really start when you start calibrating, and chasing print quality. You could be starting the print too close to the bed, (is there backlash in you z axis), adjust your Z offset in the slicer to test this then adjust the hardware to zero this out. then you need to make sure you are putting out just the right amount of plastic. When things don't come out  as expected there are a variety of causes, are you moving your axis enough, or too much for a desired gcode command.  I got to the point where the side of my test cube were nice but the corners where the print head lifts up and down between layers were not really pretty, there were random blobs, not on every layer, this is because Slic3r has a feature to randomize the starting point of each layer. i got the blobs small but it wasn't as good as i wanted, then trouble started, i got something stuck in the nozzle, i tried the lazy way out and created more work for myself, i tried to clear the hole by drilling the hole out to 0.5mm but ended up snapping the drill in the nozzle and stuffed it..

     Tomorrow is A Long weekend  here in Australia so i am going to spend the day at my mates workshop and knock up another three new 0.5mm nozzles, if time is going well i will make a bunch of blanks up as spares then when the 0.25mm & 0.35mm drills arrive from ebay i will drill them out. to do this i might have to re-face the jaws on my dividing head, while making my hyena style bolt up i noticed that depending on where the job is inserted into the jaws it can wobble, this didn't affect my bolt as i used a tailstock steady on the job.

Here you can see the results of my 36hour printing session.... on the left lots of worms. the back row, some niceish blocks. and in the middle you can see a print with a missed step. and on the lower right the nicest print so far.. that crease in the top is from where the extruder clipped it while it was still soft when i was trying to move the print head out of the way..  this is not perfect it still has a few blobs here and there but its on the way to being nice.. cant wait to make some more nozzles..

I still have some ptfe tube and brass left over from the last time when i made the first lot. this time i will make them a little longer and see if that helps with some of the problems have been having. and this time i have the CNC mill working enough that i wont have to hand crank the drill bit in and out to peck drill the hole to prevent snapping.. its a pain as you have to pull the drill bit all the way out of the job to check you have not snapped it, a 0.5mm drill bit doesn't give you very much if any feedback, and if you snap a drill when blind drilling or are unsure, you can waste drill bits trying to drill out the hole that is now blocked by a drill. will have to make some sort of depth ring for the drill bits to make my life easier..

for now its a bit of TV and Bed for me..

I need a Extruder with grip!!!

I finally got around to testing out my printer last night and all is not well.
Its not all that bad either, i have a problem where the hobbed drive bolt in my extruder is slipping more than its gripping. so when i try to print i get very very inconsistent  feed/flow rate of plastic.

to get around this problem i have a few options:-

 one is to get a bigger spring - the problem here is i am confined to a small space the springs can be no wider than 10mm this is the biggest limit of making this design smaller..

two would be to change the tension arm design to make better use of the spring tension that i have avail to me now, this is a possible option, not too hard to do but a little fiddly and will make the extruder heavier..

the third option to to try and attempt to improve the bolt that i have. this can be done a few ways, re-make it with a different more coarser thread tap to get better teeth and thus grip, or go to what reprappers know as a hyena drive bolt. this is a CNC milled bolt, unfortunately due to the triple filament design the stock off the shelf bolts are not useable in my extruder, so i will have to make my own..

To do this the easy accurate repeatable fashion a CNC mill is required to take repeated and evenly spaced notches out of the profile of the drive bolt. I have been distracted from my printer in the last few months as i got a second job and that took up all my time, but it also filled the bank account enough that i went and bought a X2 Milling machine and i am in the process of CNC'ing that. there is not too much left on that build, all i need to do is mount the electronics in to a box and mount my end stops.

What is also needed to make the hyena style drive bolt is a dividing head, this is a lathe chuck that allows you to hold a job and rotate it by a preset angle. i have a non powered one that i bought off ebay and will be powering that to be able to perform the milling require to make the drive bolt teeth.

to cut the teeth i am going to require a special/custom cutter, so i have ordered some carbide tool steel from ebay to make the cutter. once i have all this up and running i will be able to progress more on the printer.. i am hoping that this weekend i will get a chance to make the box and bolt it all to the mill and get the last stepper mounted..

so the printer is on hold for a little while until i can finish off the mill..