Saturday, 12 May 2012

Update 9.Victory is near....

Having received my new Arduino Mega and installed it i started to play around with my printer..

I got impatient waiting to finish the mill so i thought i would see what i can do about the grip issue.. i cleaned the hobbing on the bolt and gave it a whirl, and what do you know, i could feed filament at 140mm/min into the hotend, then the motor would stall..
Talking to the peeps on #reprap i decided to ignore what they were saying and install a stronger motor.
$30 later including postage i was waiting for a new 62oz stepper motor...  this arrived very promptly.. i cut the wires nice and short and installed  a header onto the motor and a socket on the loom, it was a pain to re-wire the whole carriage to replace a motor..

So i have been printing quite nicely YAY.. i still have a lot of little settings that i need to tweak with slic3r or Skeinforge to get some nice printouts but i keep adding things so i never actually get to a happy point where i can claim complete victory..  See the "Things I have printed" page for the results..

To stop the extruded plastic from curling up and deforming i have a heated bed this was not enough, i had to also add a fan, i made one fan shroud that was ugly but encouraging, so i made a new one and this one is sweet the holes where the air come out have been reduced to only where i want them, but opened up more so i get better air flow, as sweet as this one is i think i need a second fan on it, i do have a problem i have a the fan driven off the arduino mega's pin 11 according to the screen printing on the board, the documentation and numerous websites pin 11 is PWM capable, i have exactly the same mosfet driver circuit as my hot ends, which are optically isolated and driven from a separate 12V PSU, with the hot end resistors are 4r7 so if i drive them all at 100% at 12v i will take 7.5amps, currently i am only experimenting with one hot end, but will have to keep that in mind later, until then i have no idea how to get his fan to PWM, wont spin until i give it a S value of 255. so i cant slow it down.

ok so it not perfect but it does the job, have a plan to print a nicer one, cuz its so big i need to add some LEDS to it, i bought some from jaycar and paid to much for them if you ask me.
i found that my extruder being all Alu needs a fan to keep it cool so i just hotglued one on top to blow air on the frame. the intake for the air that gets blown on to the print job is drawn too close to the bed and is to warm i think. the middle shot is of the old shroud the new one covers the bearings, they both blow air past the smooth rods so i will have to make some socks up to cover them to keep dust out of my bearings while i am at it i will make some socks for the other smooth rods too.. velcro should do the job.

The new stepper on the extruder makes a big difference i could only retract the filament @2mm/s before the motor would stall.. and i noticed a strange thing, when i have 0.25mm of retract with the new stepper i get nice prints if i turn the retract up any farther it gets worse.. but i dont care about that for now i have other problems with the extruder..

my plastic was melting above the nozzle inside the peek block this area/void was to be where the nozzle was able to lift up so it was out of the way and the valve can close.. I made a mission to Kellets hobbies (they are nice guys as long as you dont get there right on closing) to see if they
 have some ptfe tubing, forgetting that i have some on the Mill as air lines for the piston, and i bought some brass tubes that range in diameters all around 3mm. some metric some imperial. got that home and pulled apart my printer, took the  extruder off the carriage and removed the hot end, had to first heat the hot end up to break the blob of plastic off, then use a hammer and knock out the plug of plastic that built up above the nozzle. i then cleaned out the nozzle the best i could and drilled 5mm into the top with a 3.5mm drill, cut a piece of brass tube that has a OD of 3.55mm and a ID of 3.05mm and hammered the tube into the top of the nozzle see the pics.

this should stop the plastic from building up in the area above the nozzle and allow the filament more grip on the brass to lift the nozzle up so the valves can close.. if i move the fan to the front of the extruder the thin tube will poke up above the aluminium plate that my carriage is made out of, and will get cooled a little and stop it melting too high up.. (i hope)

 here is the first decent print i have done. this was/is vodka tight. i thas a seam line up the back you can see in the pic, i have since been trying to get rid of that, came close but ended up changing stuff and have to re-tune the settings..

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