Cupcake Z Stage Assembly

This page is part of the Cupcake CNC build sequence.

Summary

Assembling the Z stage mechanisms will take you about two hours.

Parts list

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Set aside the following parts:
  • Lasercut parts
    • Z stage
    • 4 bearing brackets (labeled 'bb')
    • 4 Z guides (labeled 'zg')
  • 8 608 skate bearings
  • 22 M8 nuts
  • Z belt (the longest of the three toothed belts)
  • Z Small Idler/Drive pulley (the one with the smaller bore)
  • 4 Z rod stepper pulleys
  • 2 Z idler pulleys (the ones with no metal insert in the bore)
  • 2 M8x50 bolts
  • 4 1' M8 threaded rods
  • NEMA17 stepper motor
  • 4 M3x10 bolts
  • 32 M3x16 bolts
  • 32 M3 nuts

The lasercut parts are in the Cupcake CNC Lasercut Parts box.
The skate bearings, pulleys and belt are in the Belt, Bearing and Pulley bag.
The M8 and M3 bolts and nuts are in the Hardware Burrito bag.
The threaded rods are in the Drive Rod Kit.
The NEMA17 motor is bubble-wrapped with the other NEMA17 motors.

Assembly

Prepare the Z stage

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  • Remove the protective paper from both sides of the acrylic Z platform.
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  • Use 4 M3x16 bolts to bolt a Z guide to one corner of the platform. Make sure that the Z guide is bolted to the top face of the platform (the side with z-stage printed on it), and that the slot is facing towards the side of the platform, in the same direction as the slot cut in to the platform.
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  • Add Z guides to the remaining 3 corners in the same manner.
  • Put the Z stage aside. You'll install in the machine later in the build process.

Assemble the Z rods

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  • Take one of the Z rods. Thread an M8 nut on to one end. Then add a bearing and another nut. Keep all three close to the end.
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  • Using two wrenches, tighten the bolts against each other until they do not move and the bearing is locked in place, but still spinning freely. You may want to put some Loctite or other thread locking compound on the nut closest to the end as it can loosen due to vibration and cause the rods to become misaligned, especially if your rods are not perfectly straight.
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  • On the other end of the rod, thread one nut about halfway down the rod. Then thread another nut, another bearing, and one more nut. Do not tighten any of these. Make sure you have two nuts threaded on below the bearing! One will be used to hold the bearing in place; the other will move the Z platform up and down. Now would be a good time to spray the rods with bikechain lubricant or some other such compound just to ensure smooth operation. coat the central area of the rods not the ends.
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  • Insert the rod into the body so that the tightened bearing fits in the socket at the bottom, and the top of the rod protrudes from the matching hole at the top. Note that the amount of protrusion is determined by the mounting of the belt mechanism shown in later instructions, below. Adjust the nut below the top bearing so that it holds the top bearing flush with the top of the top panel of the body. Once the bearing is properly positioned, screw down the top nut and tighten the nuts to hold the bearing in place.
  • When you're done, the rod should rotate freely around its axis, and you should have one free nut that slides up and down the rod.
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  • Take one of the bearing brackets and mount it over the top bearing. Use four bolts and nuts to secure it.
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  • Prepare and mount the remaining three rods.

Assemble the belt mechanism

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  • Mount the motor on the underside of top plate with the shaft facing upward. Be sure to use 10mm long bolts, not 16mm long bolts! Using the wrong bolts can jam or damage your motor. Orient the motor so that the cables face the right side of the machine.
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  • Place the four Z rod pulleys on the tops of the Z rods, with the end containing the set screw facing upwards. Do not tighten the set screws yet! Leave the pulleys freely sliding on the rods.
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  • Prepare the two idler pulleys by sliding the large idler pulleys on to the M8 bolt. Point the collar of the pulley towards the head of the bolt. After the pulley is on, thread an M8 nut on to the bolt as far as it will go and tighten it. The pulley should still slide freely.
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  • Place the idler pulleys into the slots on the top panel. Use an M8 nut to loosely secure the pulley to the bot.
  • Loosen the set screw in the Z drive pulley(Small Idler) and place it on the motor shaft. The set screw and collar should point down.
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  • Wrap the Z belt around all the Z rods and the drive pulley. Thread it so that the idler pulleys meet the back of the belt, pulling it to the interior of the bot.
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  • Adjust the height of the rod pulleys and the drive pulley so that they are all level. Make sure the rod pulleys are high enough that they do not scrape the bolts that hold on the bearing brackets. Once you've got them to the right height, tighten the set screws.
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  • Slide the idler pulleys forward in their slots until the belt is snug, but not too tight. Turn the motor pulley by hand to make sure that the belt is still loose enough to let the belt turn smoothly. Once you've tensioned it, tighten the nuts beneath.

That's it! You've got the Z stage assembly ready to go.

Next Step: Cupcake XY Stage Installation

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