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..

Victory is Near... so near i can taste the plastic!!

Had a hard day at work trying to make some soothing sounds from a PIC micro and a mosfet driven speaker, feeding it a square wave at varying frequencies to make a bleep and a bloop sound for good and bad report. I was eager to get to the mill, as soon as i sat down at home i rang my mate to see if he has finished work for the day, and he was, so i scooted out there as fast as traffic would allow. I got there at about 6:30ish and proceeded to setup the mill to enable the Y axis as i am still waiting on the replacement stepper drivers, so i am plugging the A axis into a axis that is not required, this time i needed the Y axis, first time i needed to use it so i had to calibrate the axis and document the backlash.  after about and hour or so and nice hunk of chicken i had the axis' setup and ready to roll.

i whipped up some gcode to make the teeth that i need, forgetting my notebook that i scribbled the formula in last night i had to go off memory and plain forgot how many teeth i wanted and some how ended up only cutting 18 teeth on the first groove so i manually cnc'd the last two teeth.

%
G21
G91
o100 repeat [20]
G1 Y-2.6 F25
G1 Y2.6 F50
G1 A18 F1000
o100 endrepeat
%

this fed the cutter into the groove nice and slowly then retreats to clear the job and rotates 18' and repeats. simple code. i then manually cranked the X axis to line up with the next groove and let it rip and repeated this for the last groove. the teeth are a little off center to the grooves but that shouldn't affect anything as i pre-grooved the job.

so now i need to go to jaycar.com.au and buy me a 10 tooth gear to mesh with the worm drive and mount that. i will venture into hobbyco in the city to latch onto a new set of skateboard bearing ( i know i have four fresh ones here somewhere but meh) then i will be all set to start a print, i seem to have lost one of my nozzles, probably hiding with the bearings so i might order some 0.25mm & 0.35mm drills and make a new set or two, now i have the mill under control they wont take so long to make, well at least i wont have to crank it by hand to peck drill them out, last time it was a PITA, might have a better look in the work room.. once i have the hardware sorted i will have to find out what the best firmware will be to use, i haven't been in #reprap for a while..

here is a vid or two of the bolt being machined on my cnc X2 Sieg mill with Dividing head..

 here you can see the cutter making the teeth for the drive bolt for my 3d printer. its cutting 20 teeth.

 this is the cutter that i made from a piece of 5mm hss tool steel that i bought off the internet for about 1$au each, bought 10 bits in the buy it now sale, so $10 delivered, i have posted about a company that will make/does make, cutters that would have done the job but i am an impatient sort of person and wanted to try and see if i could do it, as it turns out its not that hard i used a 6inch angle grinder with a 1mm cutting disc to form the profile then turned it to an angle of about 30' in the tilting vice to cut the cutting edges/flutes.

 my iphone doesn't seem to like taking photos of things up close but the videos are not that bad..

the cutter seems to have survived enough that i will probably use it to make the new extruder with any improvements that i can think of. i would like to see if i could make this thing printable and post it to thingiverse.com, that reminds me i should update my existing things i have posted to reflect the progress that has been made. 

Progress on the printer..

Finally i have the mill working enough to attempt to make a Drive bolt for the triple extruder. as i blew up a few channels on the Stepper control board for the mill and am waiting for the replacements to arrive from digikey.com. They should be here just before the weekend :). I currently only have three channels/axis' working on the mill, XYZ, i was moving the mill and pinched the stepper wires and let out the magic smoke on the other two channels AB. i have ordered 10 replacements (not expecting problems but not wanting to get stuck) and it makes the fedex charges ($30aud) worth it.

Today was spent setting up the mill, plugging in the steppers, i dont need the Y axis to make the bolt i can make do with XZA. then YZA to cut teeth. i also documented the backlash in the mill and entered those into EMC2 and tuned the acceleration to avoid the missed steps. I haven't quite got my head around the speed settings and stopped once things were working good enough for now. finer tuning can wait for when i have all the axis running.

The other weekend i purchased a 2m length of 1/2in Brass Solid bar for about $40aud and cut off a short length of about 100mm. placed that in the lathe and machined a 6mm wide 8mm diameter step to fit a skateboard bearing that i had placed in a Steady i made for the dividing head. plan is to put a cone shape coupling so stepping the job piece is not required but that can wait and a shoulder will work for now. i then proceeded to write me some gcode. while i was doing the expected cut and paste job in a spreadsheet i got to thinking there has to be a better way, so i had a quick peek at what gcodes i had at my disposal and found the while loop and do while pages in the linuxcnc docs and rushed ahead and developed some code that would repeat the tasks required then when checking the syntax i found a neater command, repeat [n]] ; other commands ;endrepeat this doesn't require any external variables to be setup. soon after i had some code ready to run.

%
G91

; 12.7 - 8 = 4.7/2 = 2.35
;2.35 / 0.25 = 9 & .1

o120 repeat [ 9 ]
        G1 Z-0.25 F35
        o125 repeat [362]
                G1 A1 F1000
        o125 endrepeat
o120 endrepeat

G1 Z-0.1 F35
        o126 repeat [362]
                G1 A1 F1000
        o126 endrepeat

G1 Z2.35 F50
G1 X30 F300

o130 repeat [ 9 ]
        G1 Z-0.25 F35
        o135 repeat [362]
                G1 X40 F300
                G1 X-40 F300
                G1 A1 F1000
        o135 endrepeat
o130 endrepeat

G1 Z-0.1 F35
o140 repeat [ 40 ]
        G1 X1 F300
        o136 repeat [362]
                G1 A360 F1000
                G1 A-360 F1000
        o136 endrepeat
o140 endrepeat
%

this code takes a 1/2 inch rod of brass and machines two shoulders for the bearings to run on.
have some more code that levels off the center area that actually grips the filament. this code is very similar to the above code in the way it uses repeat to loop.

after this i attempted to make the semi-circular grooves that should have lined up with the pinch rollers but i didn't quite get the gcode right, i forgot to lift the head up when moving from one groove to the start of the next and stuffed it up really bad. it has big fat grooves where it shouldn't be :(

So tomorrow I will try and get away from work early and scoot out to my mates shop where the mill is located and start on a new bolt. i have plenty of material and i hope i have all the kinks out of my code and should be able to make a bolt with out too much trouble.

here you see the grooves (that shouldn't be there) between the rings (that should be there) this is where i was missing a line of gcode

G1 Z1.5 F50

if i had that between the loops i would have been okay. as it turns out i noticed that the chassis of the extruder was not parallel, the sides tapered inwards and was throwing my measurements all of the shop, now i have massaged that out of the way i can get to making the drive bolt. without errors.

to make sure i get it right this time i will take the job out of the mill and place it in the extruder before i make the rings and mark exactly where the rings are to go then i will cut the teeth into them individually with the dividing head, i was trying to keep the bolt in the chuck of the dividing head for as long as possible to try and keep the run out to a minimum.

Armed with the knowledge that i learn today i should be able to get this bolt done and all three materials working on the printer, once this bolt is done i have all the mechanics done and then it time for firmware, or some creative g-coding.

before i go i have to say i set the mill up and left the factory to go get food and came back and the job was still ok, the cutter was still ok and there were no big holes in the chuck or the bed, my mate was there doing his thing and would have stopped it if he heard it lunch a tool or something but it survived, i am getting a little more confidence that this project will get finished and actually exceed my initial expectations, i am really happy with the repeatability of the axis' movement now i have the backlash under control :0

Springs Springs Springs.. then things went wrong...

Seeing as thou my extruder was lacking in the grip department i had planned to get the mill up and running so i can make a hyena style drive bolt. but being struck down with some food poisoning of some sort, i was stuck at home unable to play with my mill at my mates workshop, i started to clean up the work room and found some springs, these were smaller in diameter and a bit longer than the ones that i have in the extruder and this got me thinking will these fit??

I pulled the cold end of my extruder off the printer, this was a pain, i took out the cam shaft and drive shaft to remove the springs then sized up these new springs for fit, but they were about 5mm too long.

then playing around between donations to the porcelain gods i noticed that these two springs would just screw inside one another, so i tried to jam this combination into the extruder but it would not fit until i got out the big side cutters and lopped off 5mm from the ends, this allowed the springs to fit in just enough that with a G clamp i managed to get all three pairs compressed enough to  install the camshaft, its a tight squeeze very little space to move the camshaft into place once, the original springs were just short of fully compressed, there was no way the longer ones with more turns was ever going to fit without being cut down. and the way they are inside the other this keeps them all spaced correctly.

the bigger springs are from a packet labeled C-624 the inside springs are labeled C-614  they have 1mm wire thickness and now are 28mm long when not compressed. this new double spring combination seems to have enough grip on the plastic..i would be able to say for certain but would you believe it, i had a Mosfet die on me for some reason it became short. then i replaced that. then my arduino crapped pants and no longer talks to the usb bus :( !Not Happy Jan!
so i have not been able to fully test this out yet but i am pretty sure it will work.. I have ordered a new Mega off ebay buy it now for $32 delivered in 7 days if i am lucky. i also ordered 2 new atmega 2560 chips and 2 atmega8u2 chips all from different suppliers and they are all going to take 5-7 days to arrive at best :( really not happy i want to print now......

While i wait i guess i will get to finish off the milling machine,  not too much to go on there for a basic CNC setup. need to add lcd and touchscreen. then work out the accessories pcb that interfaces the air compressor coolant pump and endstops and servos for speed control etc.. then it will be time to build the tool changer.. i have just about completed the dividing head just have to cut a worm drive and that will be ready.  but i want to print :( damn it...

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..