Wednesday, 25 April 2012

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...

Wednesday, 18 April 2012

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..

Sunday, 15 April 2012

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. 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..