Stiffening the X-axis is a bit harder. I'd done some calculations before hand that showed there would be some flex with the maker slide given the rather large size I'm building out to. For 1800mm, with an 44 newton load, a single maker slide would deflect over a millimeter. Makerslide just isn't that stiff, and midpoint deflection goes as the cube of the length.
I've been looking at a couple of alternatives for stiffening things.
There are a couple of really cool projects that stiffen things up with steel. Unfortunately, when I did the math, 1/8" of steel will not add much to the stiffness, and even a 25mm by 50mm extrusion doesn't add a lot of stiffness. Stiffness goes as the cube of the height.
Another possibility would be to sandwich the maker slide around a custom cut steel piece. It looks like there are places that will custom cut steel for you, but, again, after doing the math, it doesn't look like it would add that much stiffness --- steel's modulus of elasticity is about three times that of aluminum, but a solid square steel bar that would fit inside the maker slide (4cm by 2 cm) would have a moment of inertia of about (( (4 cm)3 * 2 cm) /12) or 10 cm4
To get really stiff you need to move up to a taller extrusion, something like the 25-5010, with a moment of inertia of 132. Of course, the motor mount plates won't fit anymore. I'll have to design some custom ones. From looking over the shapeoko forums, it looks like 6061 is the alloy of choice.
So, that makes the plan:
- Design taller motor mount plates that can also fit nema-23 motors
- Order 1/4" aluminum plates
- Order longer screws for the motor mount
- Order longer screws for the X axis carriage
- Order more spacers for the X axis carriage
