CNC 3020T T-Slot Touch-Off Plate

thingiverse

These are the parts needed for using a $19 touch probe from Amazon as a $100 touch off plate on a CNC 3020T Router. I've successfully machined aluminum with four tool changes, achieving near perfect accuracy - less than a thousandth surface deviation between tools. This is no small feat for one of the "cheap" Chinese CNC machines! This tool consists of two printed parts and a few other purchased or sourced components. You'll need one of those touch probes from Amazon, preferably with a flat V-groove style mount (you might have to edit the base clamp to fit your probe if you get a different style). Then, print two parts: the first clamps to the top of the probe and provides a flexible shelf to register a larger area of pressure against the probe tip. The second part is the base that slides into the 3020T's slots (check the slot profile in the picture to ensure yours match, of course). A CR2032 battery makes an ideal touch plate; I glued mine on with super glue. Mount and secure it to the side of your work area, clamping mine in place to prevent movement that would completely ruin the calibration after job start. Using your first endmill, clear a consistent level on your workpiece (even if it's just a few thousandths), then jog your tool over to the center of the battery and lower it until it engages slightly. Set the probe to zero by rotating the dial and use your router controls to jog up and down until you're reading zero. Note the coordinates on your CNC machine (you should only have moved the machine via jogs at this point). Now that it reads zero on the dial indicator, lift the Z-axis manually and swap your tool; then lower it manually until the new tool reads zero. Near perfect tool change! Remember to use screws to clamp down the base in front and back - if this moves after initial calibration (after you clear an area and note your coordinates when finding zero), your tool changes will not be accurate.