Nozzle Fun and games..

Today was spent hanging out eating with the family, yay nephews and the niece running around screaming, it was a change from the drone of the printer or the mill :). After that was over with i went to my mates workshop and proceeded to make some new nozzles for the printer..

  First i took a length of 5/16ths brass rod that i had from a previous nozzle session and proceeded to center the piece in the lathe which resulted in a 7.8mm rod 30mm long, i then made a shoulder 6mm in diameter and 22.5mm long, i then cut that off at 28.5mm long.

I turned the nozzle around and pushed a 3.5mm drill bit into the piece to a depth of 25mm, i then took the nozzles to the mill and proceeded to setup to peck drill the 0.5mm hole to form the nozzle, this was a total bust I snapped two drills in the process, so i decided to attempt to drill the next one from the outside to the inside so i could see what was happening, turns out that this was not that hard a process, i placed the blank into the drill chuck and moved the bed with the vice mounted on it until the blank nozzle was touching the jaw of the vice, this took a little bit of back and forth on the handles to get it just right, using a set of feeler gauges to find the point where both corners of the V groove. i then tightened up the vice and released the chuck, then in went the 0.5mm drill, then some manual gcode to lower the head in 0.25mm steps, i noticed the amount of swarfe that was generated from a 0.25mm plunge of the drill was quite significant given the diameter of the drill i was using, i found that my previous gcode didn't clear the swarfe from the drill leading to breakages.

Using this method of drilling from the outside to the inside was actually quite easy, as long as the tip of the nozzle is formed dead flat the drill doesn't wander any noticeable distance, i had tried not to do it from this end because i was worried that i would end up with a nozzle that flared out due to the need to use a centering bit first ( on the lathe this was needed) with the bed of the mill being so nice and tight i didn't need to center drill the blank first.

One thing i noticed was that when you have a 0.5mm drill bit in the chuck of anything you gotta be very very careful, if you even think a bad move it will snap.. i broke a drill before i even started by issuing a bad gcode command, the command itself wasn't bad just the results. the spindle wasn't moving and the drill was a lot closer than i thought..

 

here you can see a partially completed nozzle installed and two placed in just for the photo. they still need the ptfe liner and the brass riser tubes and nozzle tips formed before they are ready to use.

The result of a half a days playing on the mill and lathe.. i have still to shape the end of the nozzle to a point, this will be done later once the riser tube and ptfe liner is installed.

 here you can see the blank nozzle with its 0.5mm hole this is in the retracted position.

here the iphone decided the flash was need, you can see the nozzle in the extended position. once i have the first channel of the extruder working nice i will duplicate the settings across to the other two channels, then it i will see if the spring loaded nozzle flaps/valves can be remade to suit the new nozzle length, i increased the length of the nozzle to see if i can get a more positive closing and opening action. the original nozzles and valves seems to work quite nice but haven't actually printed with them installed i was having a bit of trouble getting started again so i removed them to make cleaning of the nozzle area much easier, on that note i think i may run into some clogging issue of the valve area, in that if the nozzle doesn't snap shut i may end up with strings hanging and these could end up above the flaps and cause problems, with the longer nozzle length i should be able to avoid some of these problems.  they may not be a problem. one thing i did notice when i was playing with the nozzle retracting was the amount of pull the filament puts on the nozzle isn't that great, i have a plan to crowd in the end of the brass riser tube at the bottom. this sits about 5mm above the melt zone with the ptfe tube extending towards the opening of the nozzle. i am hoping this crowding of the brass tube will grip the plastic a bit more on the retract and pull the nozzle up more. with the longer nozzles i will also be able to put a bend on the leading edge of the valve as i did notice the nozzle was starting to wear due to the valve scraping the brass away and this will eventually lead the Z height issues.

once i form the nozzle tips i will have to install all three nozzles and mount a strip of emery paper to the printer bed and drag the tips of the nozzles until they are even in length when the are fully extended. this will ensure one nozzle doesn't pump out plastic at a different heights and cause layering issues.

While i was attempting to peck drill the 0.5mm hole i discovered that my mill had developed a loose Z Axis Rack gear. this is because its held in place with two countersunk screws about 5mm in diameter, they don't hold up well when you have the Z axis Quill clamp engaged and you try to crank the Z axis, the cast iron in the main post just caves to the stress. I devised a solution, i took some 19mm wide strips of steel 3mm thick, one is about 200mm long the other is about 60mm long, these were then drilled to match the other holes in the post. the top one was close enough to the top that i managed to place a nut on the back of it and some loctite to make sure it stays tight with out the fear of stripping this hole too. the bottom strip rests on a step in the rear post that out of sight, this setup ensures there is nowhere for the rack to move when too much force is put on the axis. this makes sure my backlash stays at 1.83mm in Z axis.

Victory is Near... so near i can taste the plastic!!

Had a hard day at work trying to make some soothing sounds from a PIC micro and a mosfet driven speaker, feeding it a square wave at varying frequencies to make a bleep and a bloop sound for good and bad report. I was eager to get to the mill, as soon as i sat down at home i rang my mate to see if he has finished work for the day, and he was, so i scooted out there as fast as traffic would allow. I got there at about 6:30ish and proceeded to setup the mill to enable the Y axis as i am still waiting on the replacement stepper drivers, so i am plugging the A axis into a axis that is not required, this time i needed the Y axis, first time i needed to use it so i had to calibrate the axis and document the backlash.  after about and hour or so and nice hunk of chicken i had the axis' setup and ready to roll.

i whipped up some gcode to make the teeth that i need, forgetting my notebook that i scribbled the formula in last night i had to go off memory and plain forgot how many teeth i wanted and some how ended up only cutting 18 teeth on the first groove so i manually cnc'd the last two teeth.

%
G21
G91
o100 repeat [20]
G1 Y-2.6 F25
G1 Y2.6 F50
G1 A18 F1000
o100 endrepeat
%

this fed the cutter into the groove nice and slowly then retreats to clear the job and rotates 18' and repeats. simple code. i then manually cranked the X axis to line up with the next groove and let it rip and repeated this for the last groove. the teeth are a little off center to the grooves but that shouldn't affect anything as i pre-grooved the job.

so now i need to go to jaycar.com.au and buy me a 10 tooth gear to mesh with the worm drive and mount that. i will venture into hobbyco in the city to latch onto a new set of skateboard bearing ( i know i have four fresh ones here somewhere but meh) then i will be all set to start a print, i seem to have lost one of my nozzles, probably hiding with the bearings so i might order some 0.25mm & 0.35mm drills and make a new set or two, now i have the mill under control they wont take so long to make, well at least i wont have to crank it by hand to peck drill them out, last time it was a PITA, might have a better look in the work room.. once i have the hardware sorted i will have to find out what the best firmware will be to use, i haven't been in #reprap for a while..

here is a vid or two of the bolt being machined on my cnc X2 Sieg mill with Dividing head..

 here you can see the cutter making the teeth for the drive bolt for my 3d printer. its cutting 20 teeth.

 this is the cutter that i made from a piece of 5mm hss tool steel that i bought off the internet for about 1$au each, bought 10 bits in the buy it now sale, so $10 delivered, i have posted about a company that will make/does make, cutters that would have done the job but i am an impatient sort of person and wanted to try and see if i could do it, as it turns out its not that hard i used a 6inch angle grinder with a 1mm cutting disc to form the profile then turned it to an angle of about 30' in the tilting vice to cut the cutting edges/flutes.

 my iphone doesn't seem to like taking photos of things up close but the videos are not that bad..

the cutter seems to have survived enough that i will probably use it to make the new extruder with any improvements that i can think of. i would like to see if i could make this thing printable and post it to thingiverse.com, that reminds me i should update my existing things i have posted to reflect the progress that has been made. 

BNZ's Hotend - Triple Extruder BNZII

Today I Finished my design for my new hotend this will take three power resistors and three thermistors or thermocouples, The power resistors will be fire cemented into short (15mm long) sections of thin walled brass tube, this will then be installed into the hotend, one for each nozzle. with a little heatsink paste.

the nozzles slip into place from above and will also have a interference fit, and some heatsink paste, i will be trying out a variety of nozzles so this hotend is fairly easy to remove once i complete the mounting plate for it.

Below are some screenshots from solid works showing the construction of the pieces, this section is by no means printable.

the height of the hotend is 29mm this is 4mm more than the height of SC10UU linear bearings that i have used for my X cariage. this wastes no Z axis movement.

 side view of the hotend,  the top greenish piece is peek 10mm thick as a thermal barrier and also to hold the slip in nozzles tight.

here is a cross section view from the side. you can see the nozzle section and the heater resistor cavity and on the right is the thermistor point. might not be drilled that deep in reality but meh.

 here is a bottom up view of the Hotend, the nozzles are 10mm apart and the white holes are mounting holes M3 will probably counter sink them to help clear the printed plastic. The grey holes range from 1mm to 3.5mm (except for the 5mm that power resistor's home) are to try and keep the heat from wandering between the nozzles, a probably feeble attempt but hey, this is going to be CNC machined from brass as there is no hope i could get all those holes right in a drill pres.

 here is a front view if the three nozzles the model has 0.30mm holes but we will see what works

 here is a semi exploded view of the three nozzles they have a 9mm OD flange (heheh i typed FlangE)

 here is a cross section of the exploded view

and the cross section view of the three nozzles, so far the rebuild of the extruder has saved about 10mm of wasted print height


Here is the New extruder  mounted onto the X carriage. its not fully mounted i will decide how that happen when i build the prototype,  i have to raise the axles up 3 or 4 mm more from the plate to allow for the 20toothed gears that will be used to drive the axles.

in this Design all running surfaces have been replaced with tiny 703, 7mm OD 3mm ID bearings that i get from the hoby shops at a ok rate for 2 at a time, this design will require 9 of these and 4 1608 bearings. but the wont wear too fast. this design is also missing the springs that will push down on each of the tension arms. the plate that the springs will press against is not in the drawing but will be added later.

here are the screen grabs.

this is a side view, looking along the X smooth rods.i will be able to bring the motor in a little more maybe 5mm before they will start to interfere with the filament too much. the area outside the worm drives is where the belts will run, i have to make a new idle axle and some extenders for the X axis to spread the belts to all this to mount up.

 this is a front view of the extruder mounted on the X carriage  i could have mounted it the other way but i prefer this way, i also get to shorten the X carriage length.

A 3d angle shot to help you get the picture. the two motor are not exactly in line with each other, this was done to give me a little more leverage on the camshaft.

i will be driving both the filament and the filament select camshaft with Nema17 2300g/cm stepper motors ( with a 20:1 worm drive reduction to get enough torque..)  they will be driven by a pololu stepper driver. with 1/16th the motors have 200 steps per rev and 2300g/cm so that's
64000 steps per rev, and ~46Kg/cm of torque if an can convert half of that into grip  i will be off to a good start. thats for both the feed and the camshaft which should be suffcient.


Update : The pictures here show a single piece heater block, the idea here was that there would be holes drilled between each of the three sections of the block to provide simple mounting and thermal isolation between each heater, this is too hard to manufacture for my liking, all those 0.5 and 1.0mm holes are a PITA to get right with out a decent MILL and plunge bits. so i have changed the design to use three separate pieces of brass, one for each nozzle, that will be 8mm thick this will give me 2mm of air gap  between each of the heated sections that can be packed with ceramic insulation tape if required, this does complicate the installation of the nozzles but simplifies changing of the nozzles as each one can be removed and replaced/repaired without disturbing the others, one drawback to this is that each nozzle can be installed into a slightly different position if the mounting holes are not the perfect size.