"LSD" Sovol SV06 Plus dual motor y-axis upgrade

I modified my original SV06 with dual stepper motors on the y-axis. The recommended acceleration from resonance testing almost doubled. People asked about doing the same thing on the larger SV06 Plus, and here it is.

The recommended acceleration from resonance testing went up from zv 3500 mm/s^s 30.8 Hz to mzv 8800 mm/s^2 54.6 Hz after adding these parts and strengthening the SV06 Plus' wobbly frame. 

This mod plus my frame enhancement helped my boost the recommended acceleration from resonance testing in Klipper from 3500 mm/s^2 up to 8800 mm/s^2. 

You will need:

• ability and desire to drill some holes in the frame
• a pair of stepper motors with long output shafts. I recommend 48mm steppers with output shafts that stick out by 24mm or more. 
• two F695 bearings
• two 20T pulleys for 9mm GT2 timing belt to fit 5mm output shaft of stepper motors
• some 9mm GT2 belt
• a bunch of M3 and M4 screws of varying lengths. I can't remember what screws came with the printer and which ones are new. 
• around twelve M3 threaded inserts
• approximately eight M4 threaded inserts
• some M4 nuts
• additional wiring for a second y-axis stepper motor

You will need to remove the front plastic panel. You will also need to drill two holes in the front aluminum panel for the M4 screws used to adjust belt tension. I designed a part that bolts to the aluminum panel and provided a pair of holes that can be used with a spring-loaded punch to mark the location of the holes. You could probably also use it as a guide to drill the holes. 

This design was inspired by brain-no-work's existing designs to accomplish similar goals. He also gave me the idea to add the new 2020 extrusions to reinforce the wobbly stock SV06 frame. 

You may or may not be able to piggyback the second stepper motor off the stepper driver for the existing y-axis motor; I did not try it that way. My printer has a non-stock motherboard with extra stepper driver slots for the second y-axis stepper motor driver. 

Sensorless homing still works on the y-axis after adding the second stepper motor driver. You probably should test and readjust the driver_sgthrs value for the stepper_y after performing this modification. 

All printed parts operate in close proximity to the heated bed, warm stepper motors, or both. I suggest printing all parts in ABS with a minimum of four walls, four top and bottom layers, and 20% infilll. I did my best during the design process to minimize overhangs, but you will need to enable supports for some parts. I suggest organic supports and checking the “on build plate only” option in your slicer. 

One of the belt interface parts has counterbores with design supports integrated into the model. You will just need to poke a tool through the hole to pop out the design support after printing. 

The bracket that connects the bed to one of the rod bearings of the y-axis must also be replaced in order to maintain full travel on the y-axis. 

Do not set the grub screws on the pulleys against the indentation on the stepper motor output shaft. You will need to adjust the stepper motor pulley when synchronizing the two motors. 

The drill guide is designed to allow you to screw it to the front panel with the stock screws. Once the guide is attached, use a punch to mark the locations of the three holes. Then remove the drill guides and drill the holes. I used a drill press. I included a photo to show the orientation of the drill guide. I suggest that you print all the parts and lay them out before drilling anything.