Sunday, 20 January 2013

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 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.


; 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

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