CNC Z-probe with a (small) microswitch

thingiverse

This is a Z-probe for a CNC router. I had problems with those cheap touchplates because I kept forgetting to connect the wire to the bit. So, this design is based on the microswitch found in endstops for 3D-printers. Check out the picture of the model. If you're looking for a model with a "normal" microswitch, take a look here: https://www.thingiverse.com/thing:3115908. I attached two red LEDs (in series with a 100-ohm resistor - not necessary on a Stepcraft machine; I removed the resistor). The connection is in parallel with the switch. Red LEDs because of their lower forward voltage (~1.6V). If you want another color like blue, use only one LED (blue: ~3.3V). The switch is connected to both C and NC contacts. I used a piece of spare 8mm steel rod between the switch and the bit. To flatten the ends, I used my pillar drilling machine and some sandpaper. I printed it with a 0.4mm nozzle and 0.2mm layers in clear PETG. The height correction is approximately 30mm (depending on the piece of steel rod you use). The repetitivity is excellent; ten probes gave ten identical values. Some videos are available here: https://youtu.be/VvNJ-5EQj_M, https://youtu.be/08NVT6iv0V0, https://youtu.be/A3sQ0L70QQg, and https://youtu.be/MQkDcnywv6I. It can be checked with a macro I wrote for UCCNC: // Purpose: Check probe for repeatability // Author: WHu // Date Version Remarks // 20180825 1.0 Base // double Zmin = -100; // Max.Z depth double Feedrate = 200; // Feedrate for probing double retractheight = 20; // The retract height double MinimumZ = 1000000; // Min measured Z height double MaximumZ = -1000000; // Max measured Z Height double AverageZ = 0; // Average Z height double MaxDev = 0; // Max registered deviation double Deviation = 0; // Intermediate value, actual deviation double MeasuredZ = 0; // Actual measured Z height int i = 0; // Loop counter for (i = 0; i < 10; i++) { exec.Code("G31 Z" + Zmin + "F" + Feedrate); // Start probing while (exec.IsMoving()) {} // Wait until movement stopped exec.Wait(1000); // Safety wait for the UC100 synchronization MeasuredZ = exec.GetZmachpos(); // Read actual Z-height AverageZ = AverageZ + MeasuredZ; // Add to average if (MeasuredZ < MinimumZ) MinimumZ = MeasuredZ; // New minimum value? if (MeasuredZ > MaximumZ) MaximumZ = MeasuredZ; // New maximum value? Deviation = Math.Abs(AverageZ / (i + 1) - MeasuredZ); if (Deviation > MaxDev) MaxDev = Deviation; double Zup = exec.GetZmachpos() + retractheight; // Calculate the new coordinate for the retract of Z axis exec.Code("G00 G53 Z" + Zup); // Retract the Z-axis while (exec.IsMoving()) {} // Wait until movement stopped } if (MaxDev < 0.001) MaxDev = 0; // Absurd to show these values. Even 0.001 is just a gimmick for the Stepcraft ... MessageBox.Show("Average value:" + AverageZ / 10 + "\nMin value:" + MinimumZ + "\nMax value:" + MaximumZ + "\nMax Deviation:" + MaxDev);