R15 cartesian system is built up from linear modules, fully assembled and tested by ST.

The first step is to decide which format you need. Usually the first axis will be the X-axis. If you need simple X-Y motion then the next axis will be the Y-axis as in diagrams A and B. This would be X-Y format. You might instead need the second axis to be vertical; this is X-Z format.
If you need three axes of motion this could be X-Y-Z format where the vertical (Z) motion is the third axis as in diagrams C and D or X-Z-Y format where the vertical motion is the second axis as in diagrams E and F.
For the second and/or third axes you can choose whether the axis is fixed with a carriage that moves carrying the payload as in diagram A or carrying the next axis as in diagrams C and E, or you can have the carriage fixed so that the whole axis moves as in diagrams B, D and F. To clarify: in the case of a Y axis a moving carriage has the axis fixed and always occupying the workspace. The Y-axis is cantilevered and the carriage moves along it as in diagrams A and C. A moving axis has its carriage fixed to and carried by the X-axis and it moves in and out such that when fully retracted it extends backwards behind the robot as in diagrams B and D.
When a very long Y axis is required you need two X-axes, one at each end of the Y-axis to support it as in diagram G. The limit for a cantilevered axis is about 500mm depending on payload and expected acceleration.

The first axis, which is always called the X-axis (even though it may be mounted vertically) has to be fairly strong to support the weight of the other axes. Usual choice is the L-type which has dual crossed roller bearings. A K-type may optionally be used; it is fast and smooth but is harder to mount. The L-type is only ever used as the first axis.
The second axis is usually a strong axis and may be a K-type or an Ultraglide as used on R19.
The third axis may be another K-type or an Ultraglide.

Finally up to 3 rotary axes may fitted, pitch, yaw and/or roll.

Common formats

Possible configurations