dzach's Hadron build

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Re: dzach's Hadron build

Postby dzach » Thu Jul 12, 2012 1:58 pm

New hotend made and installed:
CuHotE_milled.jpg
Hand milled a pocket for the wires on a drill press with a 3mm fluted bit. Not very nice but functional.

CuHotE_heater.jpg
Nichrome wire installed and high temperature cement cured.

CuHotE complete.jpg
Thermally insulated.

CuHotE complete_installed.jpg
Mounted on the new extruder plate made from scrap aluminum. It's about 10mm longer than the old one to make space for safer heater connections


Drilling 1mm holes on copper is not an easy task. The thermal capacity of copper raises the temperature quickly and the bit sticks or brakes very easily. So instead of the nice angled holes that I planned, I ended up with straight holes and 2 broken bits left in the heater's body. It does its job, but doesn't look as great as I wanted.

EDIT:

This is a thermal response graph of both old and new extruders:
alu_copper_comparison.png
Thermal responses
dzach
 
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Location: Athens, Greece

Re: dzach's Hadron build

Postby dzach » Fri Jul 13, 2012 11:33 am

I have been avoiding to print large parts with ABS due to problems with warping. Here is my first take at a heated bed which might help minimize this problem:

heated_bed__layout.jpg
Nichrome wire sandwiched between kapton tape

heated_bed_insulation.jpg
Glass fiber insulation. All held together with adhesive aluminum tape.

2012-07-13-141657.jpg
Heater installed under a 5mm aluminum plate which distributes the heat evenly.


This is a low power heated bed, since it is only about 80W.

heated_bed_thermal_response.png
Heated bed thermal response

The thermal response graph shows that it would be impossible to reach 150°C with this power. It takes 24' to reach 83°C.
In the next iteration I'll make the heater with two nichrome wires in parallel.
dzach
 
Posts: 180
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Location: Athens, Greece

dzach's Hadron printing @300mm/s

Postby dzach » Sun Jul 15, 2012 9:10 pm

Here is a video with my Hadron printing a test object at 300mm/s with the new heater. I don't see much of a difference with it except that it takes more than 3 times longer to reach extrusion temperature.
dzach
 
Posts: 180
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Location: Athens, Greece

Good-bye Z-axis wobble

Postby dzach » Sun Jul 29, 2012 12:55 am

One of the few problems remaining with my Hadron has been Z-axis wobble. Not wanting to go the ACME lead screw way, I gave my best trying to align the coupler. I even run a dial indicator on the coupler, inserted shims in the coupler bore, and added more set screws at 120° angles:

2012-07-29-030244.jpg

Finally I managed to get the coupler dead centered and the threaded rod with now wobble at all. Alas, this didn't stop the motor from wobbling on its semi-flexible bracket, which unfortunately showed also on the surface of the prints.

Today I tried Nophead's Prusa Z-coupling from Thingiverse:

2012-07-29-004533.jpg
Nophead's Prusa Z-coupling. Notice the artifacts on the surface of the coupler, due to Z-axis wobble.

The coupler requires the installation of a plastic tube on the motor axis to take some of the angular wobble. Not having the recommended plastic tube, I settled for 3 layers of heat-shrink that I happened to have:

2012-07-29-005106.jpg


The diameter of the axis after the heat-shrink was about 7.25 mm:

2012-07-29-005247.jpg

This is a test @0.33mm layers, printed at 150mm/s using the new couplers:

2012-07-29-024325.jpg
I didn't even bother to use ABS juice or heat the bed. ABS does warp when given the opportunity.

The problem is gone.

The rods do still wobble a little but the motors are absolutely still. To align them, I tighten the coupler screws lightly, loosen the motor bracket and derlin nut holding screws and run the z motors up and down a number of times, one or two are not enough. The couplers align themselves nicely. I knew I was done when the motors stopped wobbling. Tightening the screws back needs to be done gradually not to upset the optimal alignment of the system.
dzach
 
Posts: 180
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Location: Athens, Greece

Re: dzach's Hadron build

Postby orcinus » Sun Jul 29, 2012 1:34 am

I've tried the heat shrink method with Bart's couplers as well as a flexible alu clamp-type coupler that had the wrong diameter.
It works awesomely at first, but be advised - it deteriorates over time.

The heat shrink starts slipping and gets torn to pieces eventually.
Might just be the kind i've used.

I've switched to spiral-cut clamp couplers (proper diameter this time), aligned everything and for the first time, i'm getting zero wobble without fear of it all flying loose after a high-acceleration Z move.
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Re: dzach's Hadron build

Postby dzach » Sun Jul 29, 2012 9:10 am

Thanks orcinus.

It looks to me like most of the z-axis wobble effects are due to the angular component, which makes the motor wobble. This is what the plastic tubing seems to be curing.
Hopefully the heat shrink sleeves will not have the fate of the ones you used with Bart's couplers, I'll report it if they do. Maybe it was the set screw that damaged the sleeves initially and then they failed.
I'll try to find some proper plastic tubing, just in case, cause I'm not going back to the z-wobble days, no matter what.
dzach
 
Posts: 180
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Location: Athens, Greece

Re: dzach's Hadron build

Postby orcinus » Sun Jul 29, 2012 12:51 pm

Oh, yeah, it does away with the angular misalignment and steppers rocking on (or with) the mounting plates.
But you still get some eccentricity between the motor shaft and the threaded rod. Not initially, but as the sleeving gets squeezed/torn, and you keep tightening the set screw (or the clamping screw), the layers of sleeving can become uneven. One caveat, though - i had to use 3 layers to get to the wanted diameter, so your mileage may vary :)

BTW, i found a nice, simple way to align the rods to the motor shafts. Mount the coupler on one of the steppers and unscrew the rod out of it so it hangs above the coupler. Poke the threaded rod with your finger a little, get it to hang loosely (which it will, unless your delrin nuts are unused, because the threads do wear out rather quickly initially). Unscrew the stepper plate T nuts a little - enough to move the stepper freely, but leave it tight enough so it keeps position. Look down the threaded rod and see where the end... ends. And move the stepper along with the plate and the coupler until the coupler hole is dead center under the rod end. Tighten the stepper plate (carefully, while watching the rod, so you don't rotate it away again with your wrench), screw down the rod into the coupler with your fingers and tighten. Rinse and repeat for the other side.

Edit: Obviously, you need to have the coupler on the other side too while doing one side, but the point is, it doesn't have to be perfect, you just need it to keep the gantry up. Also, it helps immensely if you adjust the gantry so it's level and immobilise it while doing this, becase there's usually enough leeway in the left and right Z to have it at enough of an angle for the threaded rod to end up hanging at an oblique angle.
orcinus
 
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Re: dzach's Hadron build

Postby dzach » Sun Jul 29, 2012 3:41 pm

I do align the axes in a similar way, have a look at the picture above with the digital calipers, where the rod is hanging right above the shaft :) . I did that from the beginning but it didn't eliminate the wobble effects.

Listening to the sound of the motor also helps find if there is a misalignment, the more it sounds the worse the misalignment.
dzach
 
Posts: 180
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Location: Athens, Greece

Re: dzach's Hadron build

Postby orcinus » Sun Jul 29, 2012 8:48 pm

Yeah, i never really got rid of the sound, but it's now created by the bend of the rods.
Goes a bit like zeet-zeet-zeet-zeet :lol:

It mostly gets transformed into whipping of the rod tops now.
Which is fine as long as i don't go all the way to the top of the Z travel.
orcinus
 
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Re: dzach's Hadron build

Postby dzach » Tue Dec 18, 2012 12:50 am

I've been happily printing since the start of the summer, when I replaced the Z axis couplers with nophead's z-couplers as described above. Today, I printed an 100mm tall car roof rail profile, to use it as a guide for some brackets.
2012-12-17 13.46.59.jpg
100mm tall profile. 200 layers of 0.5mm thickness @ W/T = 1.9


After it finished printing I measured the height, it was supposed to be 100mm but it came out 101.91, that's ~2mm taller than expected or ~2% off.
2012-12-17 13.52.53.jpg
Off by 1.91mm, that's ~2% !

I calibrated the z axis long ago (Spring '12) with the Z resolution given at the time in the wiki : I believe it was 2599.75. Now, I've just revisited that page and I see that the calibration data has changed: Z axis resolution is now 2560, for a M8 threaded rod. Aha! 2599.75 / 2560 = 1.016 ~= 1.019.

Obviously I need to correct the Z resolution to 2560.

Note: The pimples in the ABS print are because I used higher than usual nozzle temperature, to make the layers bond better. Higher nozzle temperature combined with a Width/Thickness of approx. 2 really makes me stronger parts.
dzach
 
Posts: 180
Joined: Sun Feb 19, 2012 12:47 am
Location: Athens, Greece

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