CNC Tool Probe

prusaprinters

This is a normally closed touch probe for your CNC milling machine. Mine is a Stepcraft 420. The contact point is a small (4mm) diameter rod that is spring loaded to keep the contacts closed until the tool presses it down which opens contact.This is not a probe for co-ordinate measurements or probing dimensions of a part, Thingiverse has lots of those too.There is a much easier "Quick and Dirty" sensor made by "kinasmith" as shown in their instructable https://www.instructables.com/Make-a-Tool-Length-sensor-for-Stepcraft-2-CNC/Notice that theirs is normally open and they had to set the probe as active low. This is not needed for my probe which is active high.If you want to mount the tool probe on a pegboard with 1/4" holes spaced 1" apart then you can print the holder too. Sorry Europe and the rest of the world for the inches but maybe the step file will help you design for your pegboard.Print SettingsPrinter Brand:CrealityPrinter: Ender 3Rafts:NoSupports: YesResolution:0.2Infill: 25%Filament: Amz PLA Blue Notes: The top needs supports because I printed it with the narrow edge down. Causes some "Elephants foot" edges which helps it clip togetherThe tool probe holder should be printed with the curled pegs on the bed, with supports to avoid cleanup.Post-PrintingAssemblyClean out the guide hole for the 4mm plunger rod, it needs to be a snug fit so there is no sideways movement.Plunger:The plunger should have a flat top, not domed, dished or uneven. The plunger must not touch the bottom, mine was 19mm long. It needs to have space to travel down when the tool touches it.Brass Washer:-Solder a solid core wire onto the washer edge, I used a a pin from a DIL connector. Both top and bottom of the washer should be flat, no solder blobs on them.The washer should not contact the plunger during operation, I glued mine into the top housing after wrapping some Kapton tape around the plunger section that doesn't go into the guide hole, the tape is a sleeve to align the washer away from the plunger whilst the glue hardens.Place some epoxy or CA glue in the housing then drop the washer over the plunger and tape into its final position, press it flat and let the glue harden.Plunger:Solder a short piece of solid core wire onto the brass nut, mine was a steel nut but brass solders more easily. The brass nut was force fitted onto the plunger, it must be tight. The nut will be one of the contacts, the washer is the other contact. Glue the nut onto the plunger just to be sure.Spring:This should fit around the plunger and should push the nut and plunger up with a reasonable force, mine was about 220g, the force should easily push the plunger back up into position with the nut contacting the washer to close the contact.The OD of the spring should less than 6.4mm to fit into the retainer in the bottom lid.Housing:The two halves should clip together but will only be secure then glued. When you have attached the wires to the short solid core sections soldered onto the washer and nut, assembled the spring and plunger and everything works, glue the 2 halves together applying pressure from a hand clamp ot weights while you wait for the glue to hardenFinal cleanup:Clean up as desired but sand the bottom on some 400 or greater sandpaper so that the bottom is properly flat.Connect:The Stepcraft CNC connection is internal, you'll have to turn the whole CNC on its side and remove the bottom to get to the terminals, there was a jumper next to the terminals on my CNC, this should be removed (put it back on one of the pins only in case you need it again). I ran the wire through a convenient open hole in the back cover.Use a caliper to measure the distance from the bottom to the top of the plunger, your UCCNC tool length sensor macro (M31) will need this distance.For Stepcraft http://www.stepcraftsupport.com/faq-items/install-and-setup-of-the-tool-length-sensor/How I Designed ThisDesignFusion360, files are available.   Category: Machine Tools