CNC routers are wonderful machines for cutting and shaping wood and other materials. However, sometimes there's no choice but to use a router without computer control. For example, when trimming the edges of wood to size, or for using the router as a finisher with sanding drums. When that kind of work is needed I don't want another machine: rather I want to use the CNC router for occasional manual feeding. To do that a fence is very useful, as it allows pieces of feedstock to be pushed past the tool/sander in a straight line. Not only can that help ensure edges are kept parallel, but it also allows creation of small mouldings with edge-shaping bits.
The models (and OpenSCAD files for them) here are my attempt at creating a very simple fence system for my cheap Chinese CNC. The fence part simply slides into the groove along the top of the CNC bed, after light sanding to get a good fit that doesn't wobble but will slide along the bed. That also means you can use it for computer-controlled routing to keep the edges of materials parallel to the Y-axis. However, for manual feeding we don't want the fence to be able to move from the edge of the bed, so a model is included for a simple stop that can be used to prevent the fence sliding along the groove. The stop connects to the side of the bed using a winged hold-down nut as shown in the photo.
Hopefully you won't mind if I finish with a word of caution. But, using a CNC router for manual feeding of materials brings risks you may not be experienced with. Probably two of the main ones are the dangers of having hands near your tool/cutter (which can be avoided using a proper push/feed stick) and extra dangers of pieces of tools and feedstock breaking and flying away (which can be largely avoided by feeding slowly and wearing sensible clothes and eye protection).
Another rookie error is to feed material with the rotation of the tool, which means it could unexpectedly get pulled through and shoot out like a javelin (I did that on a router table years ago and it's amazing how fast the expelled material can be). Not only is that dangerous: it can even ruin your work. You may also want to wear ear protection as the sound level will be higher working close to the motor and tool. Basically, please be very careful and don't take chances using the models here :-)
And if you're interested you can also read my blog-post about this project at the link below.
I used 30% infill, slow speed, 0.3mm layer height and thick shells. Support material is only needed for the fence part. For the fence part I also used a brim to ensure it didn't warp along the length, as that would make it very difficult to insert into the CNC-bed groove. The base of the fence will need a little light sanding or filing, as it's sized for a snug fit so it doesn't wobble in use.