OPEND CNC Mark 1
A first venture into the world of DIY CNC.
1 Basic Gantry Design
This project aims to build a CNC machine with nothing
more than what is found in a common hardware, timber and electronic
store. The main aim of this design is to explore the
possibilities of building a machine where each plane is set by only 1
surface. This would allow the machine to be built without
needing special alignment tools while minimizing backlash.
The guide rails are made from steel rectangular tubing.
Each rail is acted on from both sides by skateboard bearings. Two bearings locate the
position of next axis, while a spring loaded bearing
on the other side of the guide ensures that the machine is pressed up against the guide surface.
The most common gantry configuration
A map of the machine parts
||The Z Axis
||The Y Axis
||The X Axis
OpenD CNC Mark1
Unlike most gantry type CNC machines, this unit has a
wide rather than
high gantry so a to keep the twisting forces as close
to the rails as
possible. This should reduce the amount of play the machine experiences.
OpendCNC mark1 uses rectangular tubes and (608)
skateboard bearings as opposed to circular tubes and linear
bearings. Also, 3 rectangular tubes are used in each plane. for the X
and Y axis, this means the vertical load is experienced only on the 4
guides highlighted below.
On the X and Y, the sideways forces are handled by one
guide per axis (the light gray ones). Two X axis lead screws are used
as a single lead screw would potentially place tremendous twisting
forces on the x axis guide (light gray).
Here is a close up of the Y and Z axes. The MDF sections
(in red/brown) are placed so that the forces experienced are always
along the sides rather than the thickness of the board. This
increases the designs stiffness.
The Z axis carries the guides with it, as this allows the
bottom bearings, mounted on the Y section, to be as
close to the work face as possible, once again increasing stiffness.
The CAD software used to model the machine is Blender and a good
tutorial on how to use it as a CAD package is available from rab3d.
Forward to part 2...