Video of the Vavle nozzle bench test.

Last night and yesterday i was rather industrious and made some good headway with my extruder, i tore it down after using it for a little bit for some preliminary testing, i would get close but then decide to add or change something so i would have to start again. This morning i have done a first test on the first nozzle, it also the first time i have tested a 0.25mm nozzle, there is nothing like changing only 1 thing at a time :D.

in this video you can see the valve work as the filament is pushed by the extruder the nozzle moves down and the valve slides out of the way ready for printing, there is one little problem with this profile of nozzle the step in the tip has two problem, A) the valve gets caught on the edge, this can be solved by forming the edge of the valve more, this may require a thicker but narrower valve. And B) the valve (if watch carefully) is pushing the nozzle back up into the extruder, this may or may not be a problem. Either way i am very happy with the way this works for a first try this is Awesome..

each time you hear the stepper feed its going slowly at a rate of 100mm/min and feeding 5mm of stock each time, tests will prove how well this actually works out, these valves are very crude, if i had better tools i would have made them 8mm wide and possibly attempted to put a V grove in the end to see if that helps with the riding up on the nozzle, i can see this riding action causing a problem down the path when the nozzle becomes worn from repeated opening and closing, but for a first attempt i am happier than a pig in mud..

My Powered Dividig Head

I  need a powered Dividing head for the Mill so i can make gears and drive bolts for the printer, i found  something close on ebay.. and i have since made up an frame for it to attach a stepper motor to the chuck..

 here is the chuck there is a locking screw that holds the back to tighten the jaws and while milling.

 Have i mentioned i am a lazy bastard.. I want to make gears with nice fine teeth and drive bolts for my printer with out breaking a sweat, done that too much already.. so i have devised a way to attach a stepper motor to the back of it and still maintain the ability to mount it either vertically or horizontally.  

I took a 12mm 1.25mm pitch bolt and drilled a hole in the end to match the steppers shaft, then i made a flanged shaft to attach the back of the chuck, on this i have a hobbed section that the bolt will run in, as it does the chuck will turn, but alas my measurements we off by 0.5-1mm and the drive bolt does not make proper contact with the flanged shaft. so i am going to have to print (slowly) a new worm and spur gear that i can use in this frame to mill a metal one out that will be able to turn while milling. the plastic one will require me to lock off the chuck when i make a cutting pass, i should be able to make the spur gear i need and the worm on the lathe. so many projects on the go it will be good to get some finished...

Update 10.. Valves are so rich and warm :)

My last post was a mess was downloading all the photos from my iphone so i jammed pics in later and they only sorta suit the words.. Meh...


I had to take apart my Extruder as i had a problem with the plastic building up above the nozzle and coming out the sides (must have been a lot of force up top there). to fix this i added tube to the top of the nozzles, these poke up through the carriage plate. while i had it in bits i thought why not see about my valves? see if they can work, i was going to just try them out separately while i was printing but the blobs up top forced my hand, thanks to my mate at work Dave, i got my paws onto some spring steel that was 10mm wide and i dunno how thin 0.5 at a guess, and bent them in to a Z shape that hugged the ends of my heater blocks..

 here you can see the valve made from spring steel bent. you can also see the brass tube on the top of the nozzle on the up turned carriage. it slides up inside the peek and goes thru the plate.

 see it fits :)

 here i have installed all three heater blocks, with resistors, these are held in place by a split brass tube. the nozzles are free to move up and down about 5mm, as they do they push the spring steel down and the taper on the nozzles push it to the side.

as the tips push the valves to the side the valves ride and spring up above the height of the print layer.and don't clip the print job.

here you can just see the tips of the nozzle poking down past the vlaves just enough to clear the print job.

 

these Nozzles will have to be leveled, i plan to do this by slapping down some emery paper or wet and dry sand paper on the bed and gcode it to go back and forth and hope they all end up at the same level. you can see that each of the nozzles have a different profile to their tips this was a bit of machinist error and when i saw it i thought hey i can claim its a test, wanted to see the best shape to get the valves out of the way, i need to model (somehow) how they move so i can get it perfect.

Between you, me and the lamppost my third channel may not work too well, i have something out of alignment and this can only be fixed by a complete rebuild, one of my mates who has helped with the build is now really excited about the printer, before he wasnt totally commited now he has volunteered to build the next prototype, once i have finished poking at this one. so far i need to shrink the camshaft motor (nema17 is beyond "Steven Segal styles" overkill), from playing with this unit the camshaft rolls so nice (even without rolled edges) in the bearings i can use a PM-20 stepper and some gears. i have these sitting here from old ticket printers. i might need to increase the spring tension or the the ratio of the tension arms so i get more grip on the plastic and try out a hyena style drive bolt but i need my CNC mill and the dividing head to be finished for that.. if my brass tube upgrade works i will be set :) then i have firmware and gcode scripts to sort out.. time to buff up on my python.

 

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.. Ausxmods.com.au 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..

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..

Progress Update 7

So i have been super busy of late. I landed myself a second job, it was only supposed to be to make a window demister, then that morphed into a second full time job once I found out what it was for. It was to help build James Cameron a Submarine that is capable of going to the bottom of the Mariana Trench. http://deepseachallenge.com More on these fun and games later <INSERT LINK>


So now that all those fun and games have settled down and i am not doing 100+ hours between my two jobs i can spend some time on finishing this printer off... and it will be about time too...

Here is a picture of the THREE hotends installed onto my extruder mounting plate.. there is a 50mm diameter piece of peek plastic that the three heater blocks get screwed into. these house the nozzles which are able to move up and down about 3-5mm.

In this picture you can see the cold end mounted to the mounting plate.

I have to take this apart yet again, i need to mill a hole in the mounting plate to allow the wiring loom to come straight up instead off to one side, this caused two problems, a) the loom kept getting caught in the frame when it moved all the way to the right of the bed. B) the loom would hang down into the printing area. so some thing may need to support the loom to keep it from falling. Having Three hotends is the cause of this problem, this leads to Three sets of wires for each filament.

More pictures once i take this apart and rebuild it with a bigger hole in the plate.
need to do some more cleaning up of the wiring loom and replace the bed glass, one time i was working on the printer and i dropped a spanner onto the glass bed and made it into several smaller beds :-( but at only $15/pc i dont mind that..