I think my cheap Chinese 1610 CNC machine is excellent, and for routing the bed size is fine for all the work I do. However, for LASER cutting a little bigger than 160x100mm would be very useful. Enlarging the cutting area isn't difficult on these machines as the side frames, guide rods and lead-screw are easily replaced. However, if all that's needed is an increase to 160x140mm then these bed risers will do the job for a fraction of the cost.
Basically, raising the bed up by a few millimetres, and moving the four guide rod slider blocks to the next slot, allows the bed to run over the guide rod mounts. That can add up to an extra 40mm of travel along the Y-axis, and for the cost of just a small amount of filament and ten new bolts (I used 16mm length to suit the riser height here). The change doesn't seem to have any impact on bed movement or rigidity.
Fitting them is simple too, and I've included photos so you can see how I did it. Also, in case you need to make adjustments I've included the OpenSCAD file here. Finally, if you're interested, you can also read my blog post about this project at the link below.
I printed these at slow speed, thick shells and 0.2mm layer height.