Hadron Ord Calibration Help

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Hadron Ord Calibration Help

Postby justingray » Sat Nov 30, 2013 12:03 am

I'm building my Hadron after a long wait. I bought one of the first ATI kits about two years ago (before they bumped the price a little bit). Here's my setup:

ATI Hadron Ord Kit (original one, from before the price bump... two years ago)
Z-axis flex couplers
bart's z-axis wobble fix
rambo 1.2 electronics
ez-struder
J-head
Mk2a heated bed
HomeDepot glass build surface.
RepRap discount LCD

I'm running the latest repetier firmware with repetier-host and slicr.

I've made my first few prints today, just calibration cubes. I'm please to admit that they do look (mostly) like what they are supposed to. However, I have a few issues that need to be resolved and I'm not really sure where to start.

My first print was of this: http://www.thingiverse.com/thing:5011
Image

The print came out "ok", but has a number of problems. There is a lot of wobble in the layers. My bridging settings are clearly not ideal. Also, the first few layers seem to be wider than they ought to be.
Image
Image

I tried printing a simple open top cube, but much smaller. The same layer wobble showed up as well as the wider first few layers.
Image


Im not really sure where to start. However, here is what I have tried so far. I tensioned the belts to a lot. My motor mounts are a bit flimsy (the first ATI kits were made of thin aluminum, but I think they've fixed this), and there is enough tension that they flex a little bit. I've made the necessary mods to the z-axis to mediate the z-axis wobble issues. However, the layering issue I'm seeing looks like this problem anyway. I played around a bit with extrusion temperatures, but that did not seem to help.

I am currently planning to try and figure out the uneven layering issue first. As that one seems the most serious. I suspect some kind of mechanical issue here, though I don't know what it would be... Then I want to try and dial in my slicr settings. Can anyone share the slicr settings that have worked well form them with the j-head on the ord bot?

Thanks in advance for the help.
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Re: Hadron Ord Calibration Help

Postby cvoinescu » Sat Nov 30, 2013 12:28 am

You have some backlash, probably from loose belts or loose pulleys, which is why the infill does not touch the perimeter. Check that your V-wheels are tight, too, and adjust the eccentric spacers.

The uneven layers happen because the Z screws aren't perfectly aligned with the motor shaft, and/or they aren't straight. The nuts constrain the screws, so they exert a sideways force and/or momentum on the shaft (depending on the coupler). This causes the Z brackets to flex; because they're attached at one edge, flex translates into vertical movement, so some layers get compressed and some expanded. The two-piece modification of the nut should take care of most of this effect. It's still worth spending some time making sure that the axis of the screw is the same as the axis of the Z motor shaft (both angle and eccentricity matter). Depending on your coupler, it may help to wrap the ends of the screws with some tape before putting them in the coupler, to help keep them centered.

It's hard for me to say why the first layers are wider -- it could be that the effect of loose belts grew bigger, or it was dependent on speed and the first layers were printed more slowly; or it could be that you started the first layer too close to the plate and/or with too much plastic, and there was a knock-on effect on the few layers on top of it.

All in all, not a bad first print, and I'm sure you'll have nearly-perfect prints in short order, with some tinkering.
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Re: Hadron Ord Calibration Help

Postby OliverK » Sun Dec 01, 2013 12:22 am

You have addressed all the common problems (with Bart's Z wobble fix, etc.). Here are some outliers that might be worth checking:

1. Check that your filament feed is smooth and consistent. High resistance can pull the X-carriage and head up very slightly, resulting in higher layers. When the resistance reduces, the head moves down again squishing the layer. The result looks very similar to Z-wobble. Filament pools are not balanced. Mount your filament spool on ball bearings, then add just enough rotational resistance so the filament doesn't unspool by itself. Avoid kinks or sharp corners in the filament between the spool and the machine.

2. Constrain the top of the Z-rods (http://www.thingiverse.com/thing:119997) to stop them moving around when using the floating Z-fix with Z couplers if you haven't already done so. Not much impact on build parameters, but stops them wobbeling too much during travel and getting knocked around when working on the printer.

3. The necking-in (narrowing of part after first layers) happens when the part cools down too fast. Create a draft shield around the bed. Ensure the bed stays hot during the whole build.

4. Experiment with your Slic3r variables, including travel speed (slow it down - try 40mm/s, with your first layer at 50% speed), extruder calibration (http://reprap.org/wiki/Triffid_Hunter's ... tion_Guide), and don't be afraid to adjust your e-steps/mm manually. In Slic3r you can also increase/decrease material volume/width for particular build sections, e.g. first layer, perimeters, fill, etc. in the Printer Settings/ Advanced tab (leave that for real fine tuning though).

5. Change belts and pulleys from MXL to GT2 to eliminate all remaining backlash - this only creates a very marginal difference though, noticeable only if your machine is already very well tuned.

6. Go back and tighten everything, again, and again. Just be careful with the Delrin wheels as the material creeps under constant load and will develop flat spots. If they are not too severe, they disappear again. If you won't be using the printer for a while, loosen the eccentrics.

7. Experiment with different filaments - just when your printer is working like a dream, you try another filament and it it will need e-steps, temps, retraction and extra-length-on-restart variables tuned.

8. A final non-scientific observation: I could swear machines need a decent run-in time before things stabilise and run consistently... give it time and keep trying.
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Re: Hadron Ord Calibration Help

Postby flurin » Mon Dec 09, 2013 1:52 pm

Take a look here: http://cisana.net/extruder-calibration/

It's only one of several settings but it may help.
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