Touch-trigger probe

01

Read repeatability and form deviation with their test conditions

Renishaw's TP20 technical data lists, at 10 mm stylus length, unidirectional repeatability (2σ) of 0.35 µm for its low-force (LF), standard-force (SF) and extension modules, 0.5 µm for medium force (MF), 0.65 µm for extended force (EF) and 0.8 µm for the 6-way module, with 2D (XY) form measurement deviation from ±0.6 µm (LF) to ±2 µm (EF). These were measured at a trigger speed of 8 mm/s with a 4 mm test stylus ball on a high-accuracy test rig, and Renishaw notes they may not represent performance achievable on a CMM, referring buyers to the CMM supplier for system accuracy. [1]

The TP20 modules use a kinematic coupling for repeatable stylus positioning, fit a 13.2 mm diameter body, sense in 5 directions (±X, ±Y, +Z) or 6 directions, are sealed to IP30 and are rated for 25,000 module changes; modules with different styli can be changed without re-qualification. [2]

Editorial note: compare probes only at the same stylus length, trigger speed and test method, and ask for the repeatability achieved on your machine, since the machine's own errors add to the probe's.

Give the supplier the machine (CMM or CNC, model and controller), measuring tasks and tolerances, stylus lengths and ball sizes, directions to be probed, required repeatability, signal transmission (cable, optical, radio) and distance, coolant and chip exposure, automatic module or tool changing, and software.

02

Match trigger force, sealing and transmission to the machine

Renishaw gives nominal XY trigger forces at the stylus tip of 0.055 N (LF), 0.08 N (SF), 0.1 N (MF and EF) and 0.14 N (6-way), and Z trigger forces from 0.65 N (LF) to 3.2 N (EF); the modules are specified with stylus lengths of 10 mm (LF, SF, 6-way), 25 mm (MF) and 50 mm (EF). Maximum XY overtravel displacement is ±14°. [2] [1]

For machine tools, Harbin Pioneer's OPS-30 optical probe system lists an OP510 probe with measuring directions ±X, ±Y and +Z, repeatability (2σ) of ≤ 2 µm, trigger force of 600 ± 30 g in Z and 40–80 g in XY, optical transmission over more than 5 m to an OSI-20 receiver with 24 V DC supply, and IP68 sealing for both probe and receiver. [3]

Editorial calculation: 600 g force is about 0.6 × 9.81 ≈ 5.9 N in Z and 40–80 g is about 0.39–0.78 N in XY, about 2.8 to 14 times the 0.055–0.14 N XY forces of the CMM modules above (0.39 ÷ 0.14; 0.78 ÷ 0.055). Force conversions use g = 9.81 m/s²; ask which force suits your parts and styli.

03

One machine-tool probe maker with optical, radio and cable systems

Harbin Pioneer is the company shown below; its OPS-30 data is used in the force and sealing section above. [3]

The listing reviewed covers touch probe systems for CNC machine tools with optical, radio and cable transmission, tool setters and styli. Ask for repeatability test conditions, trigger forces, sealing and the receiver interface for your controller.

04

Ask machine-tool probe makers for accuracy as well as repeatability

HEIDENHAIN lists its TS 460 wireless workpiece touch probe for machine tools with a probing accuracy of ±5 µm with the T404 standard stylus and a probing repeatability of 2σ ≤ 1 µm, radio or infrared signal transmission, HTL or EnDat 2.2 interfaces via a transceiver unit, and IP68 protection. Jets in the probe can clean chips from the workpiece at up to 60 bar if the machine is equipped for it; HEIDENHAIN states that droplets on the workpiece do not affect measurement but chip residues could. An optional collision protection lets the probe give way and thermally decouples it, in addition to a predetermined break point on the styli. [4]

Editorial note: HEIDENHAIN states accuracy and repeatability as separate figures, and the accuracy is tied to one stylus. Ask each supplier for both values, the stylus and probing speed behind them, since the Renishaw module figures above were measured at 8 mm/s on a test rig [1], and for the coolant and chip conditions the sealing is rated for. [4]

05

Body and mount, module, stylus, transmission, receiver and seals

The first three rows follow the Renishaw TP20 pages; transmission, receiver and seals follow the Harbin Pioneer OPS-30 listing.

06

Repeatability, force, overtravel, sealing and receiver data for the quotation

Machine, tasks and tolerances come from your shop. Renishaw module values and the Pioneer receiver figures fill the middle column as examples with their test conditions.

07

Send the machine, task and environment data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Machine: [CMM or CNC; model; controller]
Task: [features; tolerances]
Stylus: [length; ball size]
Performance: [repeatability with test conditions]
Transmission: [cable; optical; radio; distance]
Environment: [coolant; chips; IP]
Changing: [module or tool change]

See manufacturer records Send an enquiry through CNFX