Kraken thread

[pyrophreek]

You are correct about the software needing to know the correct values to travel in a plane, but even if it is off, the entire print head will still remain parallel to the print be as it travels out of plane. This would result in all of the nozzles lifting/crashing rather than individual nozzles shifting with respect to each other. I am printing something now, but when I am done I will try to take some pictures to show what is happening.

[mhackney]

EDIT: removed incorrect statement.

[mhackney]

EDIT: This is NOT how the nozzle moves with a misconfigured delta radius. As long as all of the arms are the same length and parallel, they effector and nozzles should remain co-planar to the bed.

[pyrophreek]

Are you sure? the way I understand it, what keeps the effector level to the print bed is the inherent geometry of the system. Thus, no matter what the drive belts are doing (which is all that software control is able to change) the effector should remain level to the bed. This is a result of the dual-arm nature of the rostock system.

I believe what I am seeing is a result of a slight twist in one or more towers, or difference in arm lengths on one or more arms.

[pyrophreek]

So as I understand it, your drawing is incorrect. The boxes should all be horizontal, it is just the position that follows the arc. If your drawing were correct, then if you moved to one of those positions after fixing the software settings, you would still be at that angle (which is what is happening to me) as this would be equivalent to following that path with the incorrect software settings.

[mhackney]

Yes, you are correct, the drawing is wrong. So, you have something else odd going on.

[mhackney]

So in your situation, you are correct that the nozzles should both be the same distance from the bed if you zeroed both of them, say at the center. Do you have backlash in any of your arm joints or carriages? That might account for what you are seeing.

[pyrophreek]

What is happening to my printer is what is shown in your drawing (or the inverse ie. the box would rotate the opposite direction as you go farther from the center, I forget which). As I mentioned before, I believe this may be an issue with the towers being slightly rotated or a slight difference in arm lengths. I am having difficulty finding exactly what the problem is, and I am hoping someone else has found a good way to solve it.

[pyrophreek]

I don't think so, I have the belt tensioners installed, so there is very little play. Actually now that you mention it, I just noticed that one of the carriages appears to be a little loose. I am going to try and tighten that up and see if that is the problem. Any slight wobble in the carriages appears to wiggle the heads slightly so this might be the culprit.

[mhackney]

First we need to figure out what the problem is! How much difference is there say, 10mm to the left of center? 100mm?

[mhackney]

Belt tension is only part of the story. If the wheels are not adjusted properly, the carriages can wiggle around.
Check the arm joints too.

[pyrophreek]

I tightened up the loose carriage, and checked all the rest to make sure they were also tight. This seems to have made it a little better, but there is still some height difference between the nozzles as I leave the center. I redid a careful calibration to make sure all of the towers were calibrated, turned out one was off a little. This also seems to have helped a little bit, but still there is some rotation in the effector.

Right now the differences in nozzle height are very predictable. Anytime I leave the center, the outermost nozzle(s) are higher than the inner nozzles. Thinking about how the setup works, this actually seems to make sense to me. As the effector moves towards an edge, the carriage(s) on the tower(s) it moves towards goes up. This means any minor slop in the arm linkages will be less and less a factor of how that edge of the effector sags. The opposite is true for the arms that are going more horizontal. Any slop in their connection will result in a larger sag on that side of the effector.

The result of this is what I think I am seeing: the inner nozzle essentially dropping (which I am inadvertently compensating for with printer radius) due to the rotation of the effector, and the outer nozzles not. Unfortunately this may mean I am SoL in terms of trying to solve this problem without switching to some form of zero backlash arms such as magnetic ball joints.

Anyone have any other ideas?

[Renha]

Hi there. As I can see, some of Kraken-users use heater cartridges. What length of cartridge itself is preferred? I have seen photos of 20mm cartridges not fully fitted in, so isn't good idea to order 15mm ones?

[mhackney]

The heat cartridges come with the Kraken. These are a "standard" 3D printer cartridge and are about 7/8" long.

[Renha]

thank you for reply, it's wonderful.

Does anybody uses thermocouples with Kraken? Is it possible to drill it's heating cube to use m6 thermocouples?

[mhackney]

Not sure if there is enough metal on the Kraken hot end for a thermocouple - but I haven't used these. I did drill and tap M2.5 for a threaded thermistor. That worked fine. But M6 is a little large.

[Renha]

could you give a link to a thermistor you have used?

[mhackney]

This one: http://www.ebay.com/itm/Modular-Screw-o ... 4ad175c679

[Captain Starfish]

Could also grab a non-threaded thermocouple, drill out the axis of a M2.5 screw to 1.5mm and just thread the wire junction thermocouple down the guts of it...

[Renha]

Thank you again mhackney, that one is not sendable into Russia, but i have found same thing I think, little bit more expensive, but sendable. I wonder why aliexpress has no such things. I would be needed to learn how to tap, never have done that before

[Renha]

Not sure if there is enough metal on the Kraken hot end for a thermocouple - but I haven't used these. I did drill and tap M2.5 for a threaded thermistor. That worked fine. But M6 is a little large.

Is it ok to drill through the wall until out at nozzle slot?

[Renha]

my threaded thermistors are M3 and they are longer than mhackney's, that's why previous question is pretty actual

[mhackney]

I don't quite understand what you are asking Renha. Perhaps a photo or drawing would help.

[Renha]

I'm sorry for that, my English is very bad... Image is [img]http://i.imgur.com/TYIxy9n.png[/img], question to it: is it ok to drill like Renha's (red) path shows? (without nozzle inserted while drilling, of course)

[mhackney]

Yes, that should be fine. I did something similar by accident. When the nozzle is put in, it seals the hole.