Automatic tool length probing avoids manual measurements and touch offs and helps verify lengths already in the tool table. Probing tool-length offsets is done into LinuxCNC with an automatic tool length sensor. The sensor has two electrical connections to a Mesa 7i76e board for detecting the tool and for protecting against over travel, and an air solenoid controls an air blast to clear chips between the probe and tool. Reproducibility on a CNC retrofitted mill is high but accuracy is so-so. A good amount of the video is the analysis of sources of error.
The analysis code (Python) and raw data are available. I don’t plan to clean them up or post them to GitHub, but will send them to anyone who asks.
00:00 – Introduction
03:08 – Initial testing
04:27 – Backlash and homing error
07:07 – Spindle nose error
08:28 – Modeling tilt error
10:06 – Tramming
12:05 – Probe elevation
13:07 – Following-error
15:14 – Error modeling
18:21– Closing thoughts
GitHub repository of LinuxCNC config and routines.
Full project notes on Notion.
Parts from McMaster:
51835K232 D.O.T. Brass Compression Tube Fitting for Air, Straight Adapter, for 1/4″ Tube OD x 1/4 NPTF Male
62005K133 Air Flow Control Valve, Elbow, 1/4″ Push-Connect Female Inlet x 1/4 NPT Outlet
5097T41 D. O. T. Hard Nylon Plastic Tubing for Air Opaque Black, 11/64″ ID, 1/4″ OD, 25 ft.
4429K412 Low-Pressure Brass Threaded Pipe Fitting, Bushing Adapter with Hex Body, 3/8 Male x 1/4 Female NPT
4464K562 Low-Pressure 302 Stainless Steel Plug with Hex Drive, 1/4 NPTF
5975K12 Aluminum Right-Angle Flow Rectangular Manifold, Anodized, 4 Outlets on 1 Side, 3/8 NPT, 6-1/4″ Long
4450K3 Muffler, 3/8 NPT Male, Steel, 23 scfm @ 100 PSI Maximum Flow Rate
47865K22 Brass On/Off Valve with Lever Handle, 3/8 NPT Female
44615K463 Standard-Wall Steel Pipe Nipple, Threaded on Both Ends, 3/8 NPT, 4″ Long
Parts from Northern Tools:
Milton M-Style Safety Coupler — Push Button, 1/4in. MNPT, Model# S99706