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Assembling The Ponoko RepRap Z Frame

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First off, let me don my "Mr Safety" hat and point out that there is a high probability of an accident in putting this framework together. You do not want to see a sight like this coming at your retina at speed:


Please put something on top of the pointy-up poles you are about to install so that there is no room on top for an eyeball:


You will need these parts from the lasercut kit, and the following hardware:

  • 4 off 8mm bright steel rod, 500mm long
  • 6 off M8 nut
  • 8 off M5 nut
  • 8 off M5 8mm grub screw

It is really, really handy to have a 2.5mm ball-ended hex key to put the grub screws in with. Using one without a ball end is likely to result in cracked acrylic.


Placing the four jigs on the ends of the lowest bars, prop up the Lower Frame and slide the <part>4 8mm diameter 500mm long bright steel rod</part>s into the holes in the outside corners. Have the rods poking out about 45mm from the bottom surface of the corners.


<repeat count="2"> Using an <part p="4">M5 grub screw</part> and <part p="4 M5">nut</part>, fix the vertical rods in place. Do not tighten the grubs more than is necessary to hold the rods firmly. Fit grubs to the upper and lower segments of the Corner Assemblies. </repeat>


Fitting grubs under the Z Motor means you'll have to take it off.


When all the vertical rods are secured, it should look like this.


Wind a pair of <part p="2">M8 nut</part>s 35mm down the shaft of the Z Idler and lock them off as shown.


Either fit skate bearings (if you're using them) or remove the retaining bolts (if you're using the BB-loaded assemblies) from the bearings in the Lower Frame. Slide the Bed Mount over the vertical rod, and put the end of the Z Idler into the bearing in the Corner Assembly. Do this for all 3 Corners.


Remove the 3mm thick disc from the end of the Z Motor Assembly.


Now we assemble the Z Drive Rod. You'll need the remaining Bed Mount, the disc from the operation above and the following hardware:

  • 290mm M8 studding
  • 3 off M8 nuts
  • 1 off M8 half- or press-nut
  • 2 off M8 washers
  • Length of 11mm compression spring

Caught without an M8 half-nut? You might get away with a full one. If not, hacksaw time.

If you're using an NEMA 23 motor, then one of the M8 400mm studding only needs to be 290mm long. If you're using a NEMA 17 motor, then the length is currently unknown, but is likely to be longer. Fit the Bed Mount to the studding as before. Wind an <part>M8 nut</part> on so that 10mm of thread is left exposed.


Put an <part>M8 washer</part> on the studding, followed by the disc, another <part>M8 washer</part> and the <part>M8 half-nut</part>. Tighten.


Slide the Bed Mount over the vertical rod near the Z Motor. Fit the disc back on top - you will probably not be able to fit the washers unless they are very skinny ones. Oh well.


<repeat count="4"> Grab an extra <part>2 M8 nut</part>s and lock them off on the top of the Z Drive Rod with 35mm of thread protruding. Do the same to the Z Idler rods. </repeat>


Now to assemble the top part of the Z Frame. You will need the Top Corner Assemblies, the Opto Holders with Y and Z written on them and the following hardware:

  • 4 off 500mm bright steel rod, 8mm diameter
  • 2 off M5 nuts
  • 2 off M5 8mm grub screws


Slip the bearings out of the Top Corners.

Slide the Top Corners onto the <part>4 8mm diameter 500mm long bright steel rod</part>s much as per the Lower Frame, but don't forget to add the Opto Holders as shown. Get them the right way up - the Y Opto Holder is on the left in this photo. The flat side should be on the same side as the 3mm pieces, and the long side of the Z should point in, while the long side of the Y should point out.


Here are the X and Y Opto Holders on their own (no Z, silly me, must redo photo. But the Z and X ones are exactly the same size). They are etched, and the Y one is longest.


Once more, use the jigs to space out the rods before tightening the screws.

As you have removed the bearings, you can flip the frame over to tighten the screws on the underside. If you forgot to remove them, it will rain BB's.


Fix the Opto Holders in gently with the <part>2 M5 grub screw</part>s and <part p="M5">nut</part>s, just to hold them out of the way.


Fit the bearings onto the tops of the Z Idlers, and put the safety cap back on.


Now lower the Top Frame onto the Z Frame Assembly. The 8MM corner parts go up and the 3mm corner parts go down. Orient the Top Frame so that its lower rod points in the same direction as the Bottom Frame's lower rod. The Z opto holder should be adjacent to the Z motor.

To get the spacing right, use a jig and then tighten the nuts on the Z Idlers to position the bearings into the underside of the Top Frame.

If your jig does not have an 8mm hole in one end (sorry early adopters) then drill one so that the upper and lower frames are separated by 375mm.

The hole fits on the Top Frame stubs like this...


...and clips on the Lower Frame like this:

Secure the Top Frame as you did the Lower Frame using <part>8 M5 nut</part>s and <part>8 M5 8mm grub screw</part>s. Now, loosen all connections in pairs of X, X and Y, Y, and re-check the spacing with the jigs. The corners will naturally hold everything at right angles, but only when everything has been tightened down. To prevent concentrated stress on any one acrylic part, you loosen all the connections and tighten them up in more accurate positions. Double-check every dimension with the jig.

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-- Main.VikOlliver - 14 Dec 2008