Magnetic rods kit

[printednest]

Hello everyone,
Do you know where to buy magnetic rods kit for max v2?
Efector, no needed. This seems wuite great, but too expensive: http://www.spiderbot.eu/en/shop/upgrade ... etail.html" onclick="window.open(this.href);return false;

I need just carbon tubes, magnets and steel balls, all other parts will be printed. Dost it matter how long the tubes are? Do i need to corect lenght in EEPROM or printer settings? If length will be different from original ones?

[bubbasnow]

i made my own with carbon fiber arrow shafts, magnets from k & j and traxxas ball ends

[printednest]

Is final length important? I mean, if it will be little bit shorter of 1-2 cm, should I correct this somewhere? Does it affect something?

[Polygonhell]

You need to get accurate measurements for both the arm length and the horizontal offset which is the horizontal distance pivot to pivot when the platform is centered.
If either one is incorrect in the firmware, you get domed motion of the effector. If both are incorrect, you can get motion that looks like a saddle.
You can incrementally address one by starting with an approximation, it's hard to separate errors in both.

[Jimustanguitar]

It's more important to make them exactly the same length than it is to make them a specific dimension. As Polygonhell mentions, you can easily change the dimensions in the firmware.

Some of the threads on the forum have referenced a technical paper about the inverse kinematics of Delta machines, and that work suggests that longer arms will translate less dimensional error into the print. We're talking about thousandths of a millimeter though, so not anything that most of us could even measure.

[626Pilot]

You will want to assemble the rods on a very tight, unforgiving jig so that they all wind up E-X-A-C-T-L-Y the same length. You do not want to deal with what happens if there is even a tiny, 1mm variation. The inverse kinematics depend on the effector being completely flat in the physical world. That flatness depends on the arms forming perfect parallelograms. If they aren't the same length, the parallelograms aren't perfect and the effector is not completely flat; in fact it may twist some way in one location, and another way in another location.

[printednest]

Thanks for your feedback.
Question is, is it worth to make this upgrade?
Is there any big difference in quality of prints??
I am asking, because I did just a few prints, and surface seems quite nice...
Yes with magnetic rods, its easier to change, clean effector...Do you have magnetic rods?

[Polygonhell]

I personally get very good quality out of my original V1 arms, I probably wouldn't see a significant increase in quality from magnetic arms.
The only thing that tempts me on the magnetic arm front is the ease of changing too platforms, and only then because I currently run a kraken, and removing it requires messing with the water cooling lines.

[Generic Default]

I'm on my 4th iteration of magnetic arms right now. They will give your prints a much smoother surface on the sides; there are no more ripples.

With that being said, they really do have to be almost perfect. If the arms are different lengths, the platform will tilt to different angles across the build plate. And your prints will come out trilobal, so for example a circle would be more elliptical if one set of arms is longer than the other two. I don't have a jig so I just use 12 inch calipers to adjust the arms to within 0.05mm. That 0.05mm shows up in concentricity of circles, which isn't noticeable by eyeball, but it binds in rotating parts.

So if you decide to make your own arms, just make sure that they are exactly the same length, they have low friction, high holding force, high rigidity, and they don't lose alignment over time.


Check out my thread in the Mods and Upgrades section.

[imagebuff]

Whoah! The very symmetrical ripples going down the walls of my prints are due to the arm mechanism? I really assumed this was just due to delta movement calculations, etc..

Chris

[Nylocke]

How consistent are the TL arm lengths? I know they were made on a jig, but I seem to get oblong holes. Not sure if its my delta correction settings or the arms..

[Eaglezsoar]

How consistent are the TL arm lengths? I know they were made on a jig, but I seem to get oblong holes. Not sure if its my delta correction settings or the arms..

I have found that the Trick Laser arms are very length consistent and have read no reports of this forum to the contrary.

[AxmaG]

Hey can you give an update to what you ended up doing, I am considering purchasing the magnetic arms kit from spiderbot aswell. All the current designs of delta robots are using the magnetic ujoint solutions seems like an ancient solution.