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..

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