Why the Z-opto spring?

It seams to me that this is pretty useless.

BETTER would be to simply have 4mm threaded bar, the opto flag board attached to piece that is then on the threaded bar and held in place by the kabob effect used everywhere else on the Mendel for 8mm threaded bar.

The height/position of the opto flag board can then simply be raised/lowered by moving the 4mm nuts.

This is especially important if you want to try out different extruders and don't want to have to play around with the Z-flag.

Any comments on this thought?

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Why is it useless?

If you have two nuts you have to move both of them to make the adjustment. With a spring you only turn one bolt. Surely that is easier?

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[www.hydraraptor.blogspot.com]

Quote
nophead
With a spring you only turn one bolt. Surely that is easier?

You might have a valid point there!

BUT...

With a spring you have a limit as to how far it can compress, and being made out of extruded plastic how far it restores to it's original length.

With two nuts the top not is only for locking.
Adjustment is always done via the lower nut.

In other words, I move the top nut far away from the bracket and then adjust the bottom nut to the proper position. The top nut is then tightened to lock the position. This gives accurate position over the whole range of the bolt/rod.
The spring greatly limits the range of possible vertical positions.

Plus I didn't get a z-spring so I was looking for an easy alternative (of course I could always use a metal spring - I bought a box with different sizes in it).

Edited 2 time(s). Last edit at 04/14/2010 09:44AM by rhmorrison.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

I see, yes if you have a variety of extruders then it will not have enough range to accommodate all of them without changing the flag.

Actually I don't use it. I home to a limit switch at the top, which I just slide to the point where the extruder just clears the frame. Then I calibrate by jogging to 8mm above the bed and rolling an 8mm ground rod under the nozzle so that it just touches it. I then copy the actual z-position into my software's bed properties. I use the same technique for adjusting the bed springs to get it level.

I have a couple of buttons on my machine so jogging to find the position is easier than winding a bolt.

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[www.hydraraptor.blogspot.com]

Yes, I think your method of having the z-axis home at the top (away from the bed) is much safer. With your new Mendel do you really have to do your calibration for the z-axis 0 often. I thought that only your HydraRaptor had problems that the height would constantly change. With the Mendel it should be stable and only need calibration when the extruder/nozzle is changed.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Yes my Mendel only needs calibrating when I change the bed or the extruder. HydraRaptor varies by about 0.25 mm according to the weather.

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[www.hydraraptor.blogspot.com]

Although i see your point for future toolheads, I find the spring works well enough for existing technology.

I use the spring for fine calibration with a standard extruder/opto-endstop. I calibrate the spring position so that it's exactly the level i want to extrude my base layer at which is much easier IMHO then messing with raft-skeinforge settings as a percentage of layer thickness (which i like to mess around with independently in tuning my mendel).

Interesting idea, effectively is much better to home far from the bed and set "the height" to start from, then decrease z....
But how do you generate the gcode? Usually it starts from 0 and grows z...
Thanks

I don't drive my machine directly from g-code so it isn't a problem. My host software knows the distance from the endstop to the bed and subtracts the z value in the g-code.

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[www.hydraraptor.blogspot.com]