Having a dual motor setup involves adding a second stepper to the gantry to ensure there is no play (or "wiggle") to the gantry's movement. In a standard single-motor setup, the far side of the gantry just follows along (but c.f. Drive Shaft).
Inventables Project Status
The dual drive kit is the first official Shapeoko upgrade available from Inventables.
Reversing One of the Motors
Note that in most Dual Y setups that employ a belt, either motor is positioned in a mirrored configuration to the other. In order to have the steppers drive the gantry in the same direction, you must alter the order of the leads. You can reverse the order of either the leftmost pair of leads or you can reverse the pair of rightmost leads or you can swap out the pair on the left for the pair on the right (as pictured below), keeping each pair in their original order.
Instructions for Buildlog Stepper Shield rev.3
With the rev.3 version of the buildlog stepper shield, no modifications are needed. The fourth stepper driver designed for the A-axis can be used to drive the second Y-axis motor. To enable the second y-axis, place two jumpers on the "JMP5" as shown in the picture below (set of jumpers on the farthest left in the image). Note: placing the jumpers during this step incorrectly can damage the stepper drivers. The stepper shield appears to have an error in labeling (for boards labeled "rev 3"), since the two pins directly above the left of the "DY" label have to be left blank in order to work. Instead, the pins above the "A" label need to be connected. Note, rev 3.01: boards that read "rev 3.01" have the silkscreen error corrected. On this board, adding two jumpers over the "DY" label at JMP5 will properly put the fourth axis in Dual Y mode.
This dual y-axis motor setup for the buildlog stepper shield (rev.3) has been tested and works. The stepper motor wires need to be attached in the usual way to the a-axis screw-down connectors.
Instructions for Buildlog Stepper Shield rev.1
Some modifications are required to allow the original stepper shield to drive two motors on the same axis with two separate driver chips.
- Pins 10 and 11 must be disconnected from the Arduino and connected to pins 4 and 5. The easiest way to do this is by using a set of headers between the Arduino and the shield. You have to bend or cut the leg going to pin 10 and solder a wire to pin 4. Repeat with a wire between pins 11 and 5.
- The result should be something like this
- This will allow the usage of one driver for each of the motors of the Y-axis.
It is also possible to connect a second motor to the same driver according to this forum user: http://www.shapeoko.com/forum/viewtopic.php?f=4&t=626
- There are several ways to run the belt but most of them require either buying a couple of smooth idlers and a length of belt or two longer lengths of belt. Here is a way to re-run it that only requires a piece of belt the same length as the ones on the machine.
- One smooth idler should be removed from the current y-axis carriage and installed in the opposite side of the machine.
- The belt must run from the current belt anchor, over the smooth idler, under the pulley, and to the other belt anchor that is flat with the Makerslide railing. That is the trick for making this work.
- In the pictures I am using the belt anchors upgrade proposed by DrRob that's shown here.
Some control systems support doing this automatically, for others it just be done manually.