Milling Curved Objects With A G-Code Ripper

HaD Mouse

Milling and routing flat surfaces is pretty much the point of a CNC router, but how about curved surfaces? Auto leveling of hobby CNC machines and 3D printers is becoming commonplace, but Scorch Works is doing just the opposite: using a probe touch probe on a CNC machine to transform a G-Code file into something that can be milled on a curved surface.

The technique is pretty much the complete opposite of Autoleveller, the tool of choice for milling and routing objects that aren’t completely flat or perpendicular to the bed with a MACH3 or LinuxCNC machine. In this case, a touch probe attached to the router scans a curved part, applies bilinear interpolation to a G-Code file, and then starts machining.

The probe can be used on just about anything – in the videos below, you can see a perfect engraving in a block of plastic that’s about 30 degrees off perpendicular to the bed, letters carved in a baseball bat, and a guaranteed way to get your project featured on Hackaday.

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Wooden CNC touch probe

diy-touch-probe

[Gary] sent a few pictures of his latest project our way via Flickr, which we thought a few of you CNC owners might be interested in. He has been working with his CNC machine a lot lately and decided it was about time he built a touch probe for his rig.

His initial goal was to use the touch probe to ensure his CNC table was perfectly level, but we’re thinking it will be helpful for a lot of different projects in the future. [Gary] says he was really looking to put together a proof of concept device, but that things worked out so well he had to share.

His probe seems to work very well, even without the fit and finish of others we’ve seen in the past. The body of the probe itself was built using several layers of quarter inch plywood, housing three sets of two screws. The screws are wired together in order to form a closed circuit when the brass probe is inserted. When the probe makes contact with a solid object, the circuit is broken, and the coordinates of the probe’s head are recorded.

Though [Gary] admits that he was not super careful when it came to building the probe, we think the results speak for themselves. For a first iteration its scanning abilities are pretty impressive – we can’t wait to see version 2.

DIY CNC touch probe

diy_cnc_touchprobe

[Dennis] recently invested some money in the Tormach Tooling System for his CNC’d Sieg SX3 mill in order to make his tool changes easier. While the kit allows him to easily account for height offsets while changing tools, he has no quick, reliable means of locating the spindle in relation to his workpiece. Tired of manually finding the edges of his workpiece for each axis, he built himself a DIY touch probe to automate the process.

The theory behind the probe’s operation is pretty simple. In the probe’s housing, three conductive rods are mounted perpendicular to the probe tip. Each rod rests between two metal balls forming a complete circuit. When the probe touches the edge of his milling material, the circuit is broken, sending a signal to his CNC control box.

The probe is comprised of several different parts, milled from either aluminum or black delrin. [Dennis] says that after everything was assembled, the runout on the probe was unacceptable, so he made a few tweaks, and now the runout has been reduced to about 0.00025” – well within acceptable tolerance limits for any work he will be doing.

Be sure to check out his site, as there are plenty more pictures of the probe’s construction, as well as additional video.

In the meantime, continue reading to see a quick video of the finished probe in action.

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