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Let your UM Original gain some weight

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It's widely known that the UM Orignal print quality may suffer from vibrations due to the relative low weight of the z stage (see e.g. http://umforum.ultimaker.com/index.php?/topic/3755-horizontal-banding-elimination-thread/).

Quite some people put additional weight on their z stage below the building plate. This has the disadvantage that the the front part of the z stage lowers continuously due to the induced torque.

There is another unused space in the z stage which is less problematic to be filled with some weight. It's at the back left and right of the threaded rod. Unfortunately this space has no bottom. Well, let's make one:

weight holder view 1

It's actually not a house... ;-)

And this is it what it looks like when mounted and filled with four quadratic steel bars of 70mm length:

weight holder view 2

And in terms of quality? Let's put it that way: it's non-negative. On my machine it's hard to judge as the quality was quite good before, but I have a regular pattern (most probably coming from a fault in the brass z nut) which I never got rid of completely but which is now the least pronounced ever.

 

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Bloody brilliant!!!!

Although, I would think that the opposite would be the way to go. The z-stage should always be the same distance from the from the print head in all three axes during printing when the head moves.

The movement of the head doesn't move the z-stage directly. Instead, the shifting of the frame is then translated into the z-stage. If the shifting of the z-stage doesn't exactly match that of the rest of the frame, the relative positioning of the stage to the head will have error.

I would think that the way to reduce this error is to make sure the z-stage stays in sync with the shifting of the frame.

There are two ways to do that. Make the z-stage LIGHTER or prevent the frame from shifting by making IT heavier and more rigid.

I guess I should read the other thread.

 

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I agree on making the frame heavier would be a good thing. But my present approach is rather to decouple vibrations from the frame as far as possible.

However, I think it's not possible to get the z stage to vibrate/oscillate in phase with the frame as the two systems are coupled with springs; not only the four springs below the building platform but also the whole wooden construction of the stage which can oscillate.

 

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Well to me it seems that is the opposite of what you should do in my uneducated opinion. If you decouple then you can have the platform moving in one direction due to a lag in it responding to a previous frame movement because of its increased mass and the frame moving in the opposition making the error much larger.

I would think that the three axes should be as strongly coupled as possible so they move as one unit due to the shifting mass of the hotend or the XY axes should dampened by the frame so that vibration between the XY and Z don't occur.

However, I have little mechanical engineering or experience with 3D motion systems so there is probably something I don't understand deeply enough.

I think there might be something to increasing the weight of the platform AND the weight of the frame. The Z stage has a lot of "slop" in the vertical axis. It's possible that it is bouncing up and down slightly as the z-screw moves. Weighing it down probably helps it settle more forcefully and accurately when the z-screw attempts to move it down.

 

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That's a great idea.. must go find weights! I've always felt the thing was quite a bit more shakey than it should be. Especially the front seems super light compared to the back... you think it would help to put more weights near the front of the machine to balance out the back as well?

Does the machine struggle at all with the additional weight on the platform?

 

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you think it would help to put more weights near the front of the machine to balance out the back as well?

 

Interesting question. I would not see it as a problem as long as it is not on the verge of tipping. From a vibrational point of view the weight asymmetry might even be an advantage as symmetrical systems have a much higher tendency to oscillate.

 

Does the machine struggle at all with the additional weight on the platform?

 

No, it doesn't. I even have more weight on the z stage as I have a heated bed with a basalt slab. The friction between z nut and the threaded rod might be a bit higher but the z motor should be more than strong enough for it.

 

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