This is my Scuddy Dual Z upgrade for the Ender 3. It's a mix of my own designs and one remix part. My whole goal was to design a well thought out and cheap dual Z upgrade for the Ender 3. I upgraded mine for about $35 in parts.
IMPORTANT: Use this Z Axis Motor Holder (https://www.thingiverse.com/thing:3189649) to correctly adjust and align your stock lead screw FIRST. Otherwise your lead screw will NOT correctly line up with my bearing support bracket. Individually test each lead screw for smooth operation.
(1) T8, 2mm pitch, 400mm long lead screw with brass nut -
(2) GT2, 8mm bore pullies - https://amzn.to/2EtU4L0
(1) GT2 3mm bore idler pulley - https://amzn.to/2EuUK2I
(2) 688zz bearings - https://amzn.to/2XgPFTj
(1) GT2 belt - https://amzn.to/2Xmv5AU
I used Hatchbox Silver 1.75mm PLA for my build - https://amzn.to/2XoeFrx
I highly recommend eSun PETG if you want something stronger https://amzn.to/2IC6HYC
UPGRADE PART DESCRIPTIONS:
Dual Z bracket (Print 1) - Two versions are available. One has slots to capture M3 lock nuts. This makes adjusting the lead screw brass nut much easier later. Mount this bracket with (3) M5x42mm screws and the stock lock nuts. You will use the spacers bellow to space the bracket from the stock v-slot wheels.
Z Bracket Spacer (Print 3) - These spacers help mount the Z bracket and align it perfectly with my custom top bearing supports.
Belt Tensioner (Print 1) - This is optional if you make your own closed GT2 belt to size as I did in my pictures.Otherwise this tensioner mounts at the top of the printer with (2) M4x6mm screws and t-nuts. It allows you to adjust and apply tension to a looser GT2 belt driving the second lead screw. You will also need (1) GT2 idler pulley and (1) M3 screw with lock nut.
Pulley Lead Screw Spacer (Print 2) - One will space your second pulley from the top bearing support. It should sit on top of the bearing. The second spacer goes under the bearing support and is held in place by a lock collar. The lock collar will keep the lead screw from riding up.
Top Bearing Support (Print 2) - This custom part will support the lead screw and pulleys. Insert a 688zz bearing into each and secure them with (2) M3x6mm screws.
Ender 3 Front/Rear PSU Brackets (Print 1 each) - These custom brackets will offset the Ender 3 Power Supply Unit, to allow room for the second lead screw. Use (4) M4x6mm screws and t-nuts to mount these. Do not over tighten.
SCREW PURCHASE LIST:
(1) M3x20mm with lock nut for the belt tensioner.(optional if you cut your belt to size)
(8) M4x8mm screws with t-nuts to mount the tensioner, top bearing supports and PSU offset brackets.
(1) M4x6mm screw to secure the front PSU bracket to the PSU. You can't use the stock mounting screw because it's too long.
(3) M5x42mm screws to mount the second Z bracket. You will reuse the stock M5 lock nuts.
(4) M3x6mm screws to secure the 688zz bearing to the top bearing support brackets.
(2) M3x6mm screws with lock nuts to secure the lead screw brass nut to to the second Z bracket.
ADDITIONAL RECOMMEND PARTS:
Print and use this jig to help you cut and create a custom closed loop GT2 belt. You will need CA glue to join the belt. The one pictured I made to size. I do have to loosen a bearing support bracket on one side to get my belt over it. That’s how long or how munch tension is in it. https://www.thingiverse.com/thing:1827260
This is the stop collar I used (https://www.thingiverse.com/thing:2940715) to secure my second lead screw. It will keep the lead screw from riding up the bearing support bracket. If you decide to use it, space it away from the bearing support bracket with one pulley lead screw spacer. Please see the image for an example.
Use my clamping lead screw control knob to help you manually adjust your x-axis gantry. I noticed after installing the second lead screw there was too much tentsion to manually move the x-axis gantry. This lets you do it easily. https://www.thingiverse.com/thing:3459199
UPDATE 2/27 - New version of the rear PSU bracket has been added. I incorporated a cap into the back of it to fully cover the frame extrusion and take the guess work out of how far back the PSU should be.
UPDATE 2/26 - Top bearing support bracket (V5) has been updated with a thicker mounting area and bigger opening on the bottom to allow the collar spacer direct contact with the rotating bearing instead of the bottom of the bearing support bracket.
By using my designs, you are doing so at your own risk and agree not to hold me liable for any misuse, injury or damage to property or life that may inadvertently result.
It takes time and effort to develop things. You can contribute by tipping me, the designer.