Mendel Z-axis

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Mendel Build Documentation

You may find the Mendel assembly data sheet useful during assembly.


Leadscrew base

Total # of assemblies 2

Name Qty/assembly Total Qty Type
z-leadscrew-base-bar-clamp_2off 1 2 RP
z-leadscrew-base_2off 1 2 RP
624-bearing 2 4 Bearing
m4-nut 2 4 Fastener
m4-nylock 2 4 Fastener
m4-washer 8 16 Fastener
m4x40-cap 4 8 Fastener
m5-mudguard-washer 2 4 Fastener

RP parts



The bearings are used as idler pulleys with the large mudguard washers helping to hold the belt on the bearings.


Leadscrew base with optoswitch

One of the leadscrew bases needs an optoswitch.


Total # of assemblies: 1

Name Qty/assembly Total Qty Type
Optoswitch PCB 1 1 PCB
z-opto-bracket_1off 1 1 RP
z-axis-opto-spring 1 1 RP
m4-nut 1 1 Fastener
m4-washer 1 1 Fastener
m4x40-cap 1 1 Fastener
m3-capx20 2 2 Fastener
m3-nylock 2 2 Fastener
m3-washer 4 4 Fastener

Printed parts

Z-opto-bracket 1off.jpg Z-axis-opto-spring.jpg


The bearing screws are the wrong way round in the picture (sorry...). The heads should be on the bearing side giving an overall ordering of: nylock nut, washer, RP part, washer, bearing, washer, mudguard washer, screw head.

Slot the nut into the hexagonal cavity between the two bearings (underside in view). Put a spare 15mm M4 cap screw through a washer and tighten that on the nut to move it down the cavity - it should be a snug fit and not fall out. Undo the cap screw and return it to your collection.

This picture shows the assembly with the spring omitted for clarity (the opto-switch PCB is upside-down in this picture - sorry...):


And this one shows it in place:


Put a 40mm M4 screw loosely through the central holes in the spring just to locate it and screw it a few turns into the trapped nut. Then put the bearing assemblies together with their screws. The screw and nut on one of them that holds the spring goes through an over-sized hole. Adjust the spring so it is square by eye before tightening this.

Fit the PCB to its bracket and fit that on the spring. Don't tighten the M3 screws too tight, or you'll bend the PCB on the solder bumps sticking out the back (if you've got some, you can scalpel off two 2 mm lengths of 3mm internal-diameter silicone tube and use them as spacers; don't use metal washers - shorts).

Finally unscrew the cap screw running down the centre of the opto-switch spring, put a dab of super-glue between the spring and the opto-switch bracket, and reassemble the device. Make sure no glue gets on the screw, and that the opto-switch is square.

Motor bracket


Total # of assemblies:1

Name Qty/assembly Total Qty Type
drive-pulley_3off (alternative #1 #2 #3) 1 1 RP
z-motor-bracket_1off 1 1 RP
m3-capx20 4 4 Fastener
m3-washer 4 4 Fastener
stepper-motor-nema17-fl42sth47-1684A-01 1 1 Motor

Printed parts


Note: the latest design of pulley has a set-screw in a captive nut. This makes the pulley much easier to mount on the motor shaft. Get a motor with a flat on its shaft if you can, or - if not - file a flat where the screw will tighten.





Total # of assemblies 1

Name Qty/assembly Total Qty Type
z-tensioner_1off 1 1 RP
624-bearing 1 1 Bearing
m4-nylock 1 1 Fastener
m4-washer 3 3 Fastener
m4x40-cap 1 1 Fastener
m5-mudguard-washer 1 1 Fastener

Printed parts



The bearing screw is the wrong way round in the picture (you may see a pattern emerging here...). The head should be on the bearing side.




Note: there is a later improved design of this. It has two of the four pulley rims incorporated into the pulleys. For this design you need two pulleys and two rims.

Total # of assemblies 2

Name Qty/assembly Total Qty Type
stud-z-leadscrew (330mm) 1 2 Studding
z-drive-pulley-rim_4off 2 4 RP
z-driven-pulley_2off 1 2 RP
608-bearing 1 2 Bearing
m8-nut 3 6 Fastener
m8-washer 6 12 Fastener

Printed parts



Loosely load the lead-screw (1) to ensure studding comes flush with lower nut. Tighten the two nuts which surround the bearing. At this point make sure that the bearing still rotates freely, if the outer ring jams with the nuts tightened then it is either damaged internally or has a manufacturing defect; either way it's unsuitable for use in Mendel.

Remove the lower parts (2) and store - these will be re-assembled later.

The pulley rims will have one side that is slightly smoother than the other - the side that was against the flat base when the rim was being reprapped. Put the smooth sides on the inside.


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