Z axis

I have a request. If anyone has made the Tantillus with the Spectra 'Z' option instead of the lead screw, could you please post how this is put together? I would rather use the cable version, as it should be smoother. Thank you in advance.

Milt

Have you read through the Cable Z thread already? [forums.reprap.org]

It gives a list of parts needed and gives general assembly instructions. Is there anything in particular that you are unsure about?

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It sucks getting old. Thank you very much.

Milt

No worries. Let us know how it goes and if you have any issues do not hesitate to ask.

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OK, I am not able to get the routing of the cable done. Just a quick pencil drawing of how the cable is to be run.

Milt

How about these.

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Got it!!! Could not figure out how I would drill a hole in the drum with the stepper shaft running through it. Now I know I do not have to. Thanks bunches.

Milt

OK, I have to admit stupidity. I have tried this the way the drawing is made, and the drum just spins inside the cable. Shouldn't the cable be attached to the drum in much the same way the cable is attached to the smooth rod on the X,Y axis? So that the drum creates a pull, pull action on opposite rotations of the drum? As I stated, the drum just rotates under the cable and does not move the Z axis at all. Sorry to be such a pain.

Milt

No worries. The cable has to be really tight. When you pluck it, it needs to play a high pitch note (musically tight). Basically you need to have the tensioner as loose as possible while making the cable as tight as you can using knots at that point. Then tighten the tensioner bolts to get the cable musically tight. You may need to release the tensioner after tightening and add some knots and retension until it stays musically tight.

Also it turns out the holes may not be necessary even on the upper metal rods as long as the cables are tight enough. Ingentis (a derivative of Tantillus) does not use holes in the upper rods.

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Hello all and thanks Sublime for the continuous effort you put in improving this little marvel.

I am attempting my own build and I was wondering why you did not wind the spectra line directly on the Z motor shaft as, based on my very little knowledge of mechanics, it should give a better step/mm rateo.

Thank to anyone that will take the time to explain this to me.

I'll take a crack at it...

Guess 1), using sound linear motion design practice, the other side of the shaft should be supported by a bearing in that application, most motors that are readily available to rep-rappers world wide come with too short a shaft, or the shaft has a flat on one or both sides.

Guess 2), the distance that you can move an axis using cable drive is limited by the amount of cable you can spool on and off of your "bobbin". As the diameter of the shaft gets smaller for a given ammount of travel the number of wraps increases, until you reach a point where the wraps become both unmanageable, and they dramatically increase the angle at which the cable is deflected from where it attached to the carriage. If the angle becomes too great then the cable tension increases as you reach the end of both sides of your travel. This can do anything from causing your axis to deflect, to causing the motor to skipp stepps, to snapping the cable.

In looking at the diameter that sublime chose for the spool/bobbin it appears to me that the z-axis upgrade was designed to manage the cable angle for 150-200mm travel.

Anyway that's my best guess.

Quote
cns1
I'll take a crack at it...

Guess 1), using sound linear motion design practice, the other side of the shaft should be supported by a bearing in that application, most motors that are readily available to rep-rappers world wide come with too short a shaft, or the shaft has a flat on one or both sides.

Guess 2), the distance that you can move an axis using cable drive is limited by the amount of cable you can spool on and off of your "bobbin". As the diameter of the shaft gets smaller for a given ammount of travel the number of wraps increases, until you reach a point where the wraps become both unmanageable, and they dramatically increase the angle at which the cable is deflected from where it attached to the carriage. If the angle becomes too great then the cable tension increases as you reach the end of both sides of your travel. This can do anything from causing your axis to deflect, to causing the motor to skipp stepps, to snapping the cable.

In looking at the diameter that sublime chose for the spool/bobbin it appears to me that the z-axis upgrade was designed to manage the cable angle for 150-200mm travel.

Anyway that's my best guess.

The travel is not limited, as whatever line you reel in, you reel out at the same time on the other end.