jitsbuild-z-axis [Bukobot 3D Printer Instructions & Docs]

===jit's build:  Z axis===

(Go back up to [[jitsbuild|jit's build]])

======Parts======

Find these in bag 10, 16 + other parts:

{{wiki:jitsbuild:z-drive-kit.png?600}}

The eight M3x10mm button-head screws come out of the Z axis kit, along with most of these other things.  

=====Attach Two Stepper Motors=====

Use these screws to attach the remaining two stepper motors to the underside of the Z axis motor mounts:

{{wiki:jitsbuild:z-motor.png?800}}

The wires go out toward the back.

=====Z Couplers=====

Take out the four Z coupler halves, which are used to attach the stepper motors to the threaded rods.  Half of the holes have hexagonal outlines, indicating nuts go there.

Widen all of the holes to 2.5 mm (a 7/64" drill bit will do).  Put nuts into the holes that need them - note there are hexagonal shafts for nuts on one side, and round shafts for screw heads on the other.  If the fit is tight, use screws to pull the nuts into place.  Be careful;  it's not difficult to drive the screw heads through the plastic, which is not desirable.

{{wiki:jitsbuild:z-coupler-halves.png?800}}

Look at the flat sides of the coupler halves.  Each of the four pieces is identical, and each has the same asymmetry:

{{wiki:jitsbuild:z-coupler-halves2.png?800}}

The upper cavity, for the threaded rod, is wider than the lower cavity, for the motor shaft.

Match up a pair of coupler halves, making sure the larger cavities are at one end and the smaller cavities are at the other end.  Insert screws, and tighten them just until the ends of the screws are flush with the nuts.  You should be able to spread the two halves apart a few millimeters.  Do this for both pairs of coupler halves.

{{wiki:jitsbuild:z-couplers3.png?800}}

Put one coupler on top of a X axis motor shaft, with the larger cavity pointing up.  Tighten the two lower screws, a little at a time, keeping them matched.  After every tightening, spin the coupler around on the motor shaft, feeling how much friction there is to the rotation.  When you spin the coupler and it catches on the flat portion of the shaft, leave it in that position and tighten the screws a bit more.  The coupler should no longer rotate freely on the shaft.

Do this for both couplers:

{{wiki:jitsbuild:both-couplers.png?800}}

=====Z Slides=====

At this point, loosen the M5 screw holding the Z endstop holder onto the right frame piece and move it down to the bottom of the slot.  Tighten the screw.

Now get out the Z slide kit from bag 16:

{{wiki:jitsbuild:z-slide-kit.png?800}}

(Note:  some older versions of these parts don't have the center holes, and attach differently.)

Widen the center hole in each piece.  We won't be using the other holes.  Widen to 3 mm (a 1/8" drill bit should do).

Put a nut into each hexagonal hole.  Pull in with a screw if necessary.  Leave a screw in each nut, with the end of the screw flush with the nut.  This hardware should be below the surface of the slot tab for the next step:

{{wiki:jitsbuild:z-slide-recess.png?800}}

We will be applying special self-adhesive UHMW tape to this part (the upward-facing surface in the above image).  The tape will be adhered to three sides of the tab, and to the other two upward-facing surfaces.  For best results, these surfaces should be clean, so clean them with isopropyl alcohol and a cotton swab.  Let the alcohol evaporate completely.

The UHMW tape is actually transparent.  The blue stuff is the backing that must be peeled off.  Separating the two can be fiendishly difficult.  Basically, abuse a corner of the tape until you see the transparent layer starting to separate.  Grab the two layers with the edges of your fingernails and peel the backing off.  Throw the blue backing layer away immediately, otherwise you might later confuse it for another piece of unseparated tape.

Lie the transparent layer, sticky-side up, on a flat surface.  Try to get it to lie flat.

Pick up one of the Z slides by its screw and set it down right in the middle of the tape:

{{wiki:jitsbuild:z-slide1.png?800}}

Press down firmly on the back of the slide, along the centerline only.  Then pick it up by the screw and look at the other side:

{{wiki:jitsbuild:z-slide2.png?800}}

(The alligator clip seen extending to the left is not part of the build.)

The tape should be stuck along the tab, but not anywhere else.  If it is stuck anywhere else, pull the tape away from there.

The tape needs to fold over the sides of the tab, sticking to them, and sticking to the other two surfaces.  The best way to accomplish this in a symmetrical way is to push the tab into a slot in an aluminum extrusion.  Use the top slot in the frame bottom piece.  Lower the Z slide straight down into the slot and press it down firmly.  Push the Z slide against one edge of the slot, and then the other.  Then push down firmly again.

{{wiki:jitsbuild:z-slide4.png?800}}

Pick up the Z slide and examine it:


{{wiki:jitsbuild:z-slide3.png?800}}

Leave that Z slide sitting in the slot.  Repeat the above procedure with a second Z slide.

Remove the screws from the two Z slides, and insert them into the holes in the X axis right end:

{{wiki:jitsbuild:z-slide5.png?800}}

Make sure the ends of the screws are flush with the surface of the idler block.

Pick up the two Z slides, and press them into the front and back slots of the right frame piece.  They should be at the same height.  Hold them there with one hand, and pick up the idler block with the other.  Slide the idler block in from the right, enclosing the Z slides.

Holding the Z slides in position with one hand, hold the idler block with the other hand by pressing in on the two screws.  Slide the idler block up and down relative to the sliders until the two screws find the holes in the Z slides.

Holding the whole assembly and pressing the two screws with one hand, and pushing the idler block to the left against the frame, pick up the 2mm hex driver with the other hand and tighten the screws.

Slide the X right end up and down and verify that it moves easily and isn't trying to fall off the frame.  It may rotate a bit in the X-Z plane, but don't worry about that, it will be stabilized when the X axis steel rods are installed later.

If the slides aren't gripping the frame firmly, you may need to install a shim.  This is not shown here.

{{wiki:jitsbuild:z-slide6.png?800}}

{{wiki:jitsbuild:z-slide7.png?800}}

Now do the same on the left side with the remaining two Z slides and the X left end.  This is much easier if the motor and endstop are not installed while you do it.

Verify the movement of the X left end as before.



[[jitsbuild-x-axis|Next:  x-axis]]

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