1. SP25M The world’s most compact and versatile scanning probe system
The presentation explains how Renishaw designs its scanning systems, as well as providing comparisons of Renishaw’s solutions with those from other metrology suppliers.
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2. SP25M brings exciting new benefits
Two sensors in one!
a SCANNING probe for form measurement and reverse engineering applications, capable of high-accuracy scanning across a stylus length range of 20 mm to 200 mm
a TOUCH TRIGGER probe, using the versatile TP20 range of stylus modules
Unmatched flexibility
highly modular design permits the perfect measurement solution to suit the application
the most flexible change rack system ever!
Cost effectiveness
low priced entry-level scanning kits with easy upgrade to include other system elements
Flexibility through modular design

3. SP25M brings exciting new benefits
Feature access
total reach of nearly 400 mm is possible by using a probe extension bar
five scanning modules each optimised for a specific range of stylus lengths
stiff carbon fibre stylus extensions for excellent effective working length
uses M3 styli up to 200 mm
100 mm extension
In this video, an SP600M is scanning a feature deep inside a cylinder block, using a long stylus. Styli of up to 280 mm (11.0 in) can be used.
The small diameter of the SP600 means that it can itself be inserted into many deep features, further extending the reach of the measurement system.

4. SP25M brings exciting new benefits
Feature access - SP25M
probe can be mounted on an articulating head means that many features can be accessed with fewer styli
lower stylus costs
shorter cycle times
The SP25M’s compact size and low mass makes it ideal for mounting on a PH10M indexing head, enabling flexible access to numerous features around the part, without changing styli. Combined with module and stylus changing, this makes it the most versatile scanning system available.

5. System components - a highly modular concept
SP25M - product naming ...
SH25-1/2/3
SM25-1/2/3
SP25M Probe Body
TM25-20
TP20 module
PA25-20
PA25-SH
FCR25
The SP25M supports three different scanning modules, each with gains and spring rates optimised to carry different length styli. By repositioning the ‘isle of Man’ spring, which provides the pivot point, relative to the readheads, and by adjusting the spring rates, excellent measurement performance can be achieved across a wide range of stylus lengths.
The SM25-1 module carries styli up to 50 mm long
The SM25-2 module carries styli between 50 mm and 100 mm long
The SM25-3 module carries styli between 100 mm and 200 mm long

6. System components - a highly modular concept
SP25M - as a TOUCH TRIGGER PROBE ...
the probe body - would have the SM25-# scanning module replaced by the...
TTP module adaptor (TM25-20) which directly carries any of Renishaw’s TP20 range of stylus modules:
TP20 LF/SF/MF/EF
TP20 EM1/EM2
TP20-6W
The SP25M supports three different scanning modules, each with gains and spring rates optimised to carry different length styli. By repositioning the ‘isle of Man’ spring, which provides the pivot point, relative to the readheads, and by adjusting the spring rates, excellent measurement performance can be achieved across a wide range of stylus lengths.
The SM25-1 module carries styli up to 50 mm long
The SM25-2 module carries styli between 50 mm and 100 mm long
The SM25-3 module carries styli between 100 mm and 200 mm long

7. System components - a highly modular concept
FCR25 - the most flexible change rack ever from Renishaw …
rapidly change between scanning and touch trigger mode to match the ideal solution to the application
FCR25 is a triple-port unit, each port is easily configured to carry any system element of the system:
 SM25-1/2/3  SH25-1/2/3
 TM  TP20 modules
FCR25’s are mounted to the MRS to thus provide 3, 6, 9, 12, 15 etc port systems
provides unmatched versatility !!!
FCR25
PA25-20/SH
SP25M module and stylus changing The SP25M is unique in that it supports both kinematic stylus changing and module changing using a single, modular rack system. Users can switch between a total of four modules - three scanning modules optimised for different stylus lengths, plus a touch-trigger module incorporating the TP20 sensor. Users can then select from a range of scanning styli, or from the full range of TP20 modules and extensions.
The result is a highly flexible measurement system, that can provide the right combination of probe, extension and stylus to suit almost any dimensional measurement task.
MRS

8. Design characteristics, performance and specification
SP25M probe body houses the optical transducer ...
isolated optical transducer uses proven IRED beams and PSD sensor technology (see later slide)
Autojoint provides compatibility with all Renishaw’s multiwired heads and extension bars
The SM25 scanning modules and TM25-20 touch trigger adaptor mount directly to the body via repeatable kinematic joint
ultra-compact mechanism - fits inside Ø25 mm probe
Autojoint
Optical transducer system
Kinematic mount for SM25-# or TM25-20
Compact dimensions - 25 mm diameter
The SP25M is the world’s smallest scanning probe. The SP25M features a patented pivoting mechanism using an 'Isle of Man' spring (see diagram). When in contact with the part, the mechanism is extremely stiff, whilst its light mass requires very low spring rates to suspend it.
When the stylus is in contact with the part, a rigid member connects the stylus tip with the measurement system, resulting in a high natural frequency.
Unlike complex active probes, Renishaw's passive sensors do not require motors, independent dampers or locking mechanisms, all of which add to the mass and inertia of the sensor.
Renishaw's unique design results in a high natural frequency and the capability to handle rapid changes in surface without hitting the bump-stops or losing the surface. A dynamically responsive mechanism, combined with tight machine motion control, allows Renishaw probes to scan at very high speeds.
Another advantage of high speed response is that the maximum stylus travel of the probe can be smaller, thus reducing probe size and probe mass - all to the benefit of high speed scanning performance.

9. Design characteristics, performance and specification
SM25 scanning modules house the motion system ...
patented, pivoting mechanism featuring two diaphragm springs
optimised to give very low inertia, low spring rates of < 0.6 N/mm and high accuracy over dedicated stylus range
high natural frequency (rigid member) when in contact with the component
ultra-compact mechanism - fits inside Ø25 mm probe
0.5 mm spherical radius measuring range
‘Isle of Man’ spring creates XY pivot point
Compact dimensions - 25 mm diameter
The SP25M is the world’s smallest scanning probe. The SP25M features a patented pivoting mechanism using an 'Isle of Man' spring (see diagram). When in contact with the part, the mechanism is extremely stiff, whilst its light mass requires very low spring rates to suspend it.
When the stylus is in contact with the part, a rigid member connects the stylus tip with the measurement system, resulting in a high natural frequency.
Unlike complex active probes, Renishaw's passive sensors do not require motors, independent dampers or locking mechanisms, all of which add to the mass and inertia of the sensor.
Renishaw's unique design results in a high natural frequency and the capability to handle rapid changes in surface without hitting the bump-stops or losing the surface. A dynamically responsive mechanism, combined with tight machine motion control, allows Renishaw probes to scan at very high speeds.
Another advantage of high speed response is that the maximum stylus travel of the probe can be smaller, thus reducing probe size and probe mass - all to the benefit of high speed scanning performance.
Second spring allows translation in all directions

10. Design characteristics, performance and specification
SP25M designed for “isolated optical metrology”
IREDs in probe body reflect light off mirrors in scanning module back onto PSDs
highly integrity performance - motion is faithfully translated to PSD’s
non-linear outputs are compensated by sophisticated 3rd order polynomial algorithms
no moving wires
2 PSDs (in body) detect stylus deflection
2 IRED sources (in body)
IRED beams
2 Mirrors (in scan module) reflect beams back to PSD’s
Body
The SP26M uses a very different mechanism to SP80 and SP60, and a different optical scheme. Like those probes, however, the SP25M features isolated optical metrology, where the light sources (IREDs) and detectors (PSDs) are attached directly to the probe body, and therefore are able to measure the total deflection of the probe mechanism directly.
The IREDs direct light onto two mirrors, mounted to the moving mechanism in the stylus module (the housings and kinematics are not shown for clarity). These mirrors can pivot and translate relative to the probe body and cause the reflected light patches to move on the PSDs. The XY location of both reflected beams are analysed and the resulting data can be used to compute the {x,y,z} deflection of the stylus.
The relationship between the location of the reflected spots on the PSDs and the position of the stylus tip is complex and non-linear. However, Renishaw’s sophisticated compensation algorithms, featuring 3rd order polynomials to linearise the output, enable high accuracy scanning data to be extracted from this compact mechanism.
The ISO test results show excellent performance for such a compact probe.
Note: ISO Tij is the result generally quoted for scanning probes. It is the the total span of readings in the measured data set. Renishaw also quotes ISO Diff values - the maximum radial error from the calibrated perfect sphere to the measured values.
Note that these results are for unknown path scans and are raw data with no filter applied. When a 60Hz harmonic filter is used, the Tij value for SP80 in this test fell to 1.3 microns.
Other details for the ISO test:
Scanning speed = 5 mm/sec
Scanning deflection = 0.3 mm
Total points taken = 2,281
Module
Kinematic joint line between probe body and scanning module

11. Design characteristics, performance and specification
1. Design optimised such that max operating deflection results in highest performance of optical transducer
2. Swept area across PSD is optimised over specified stylus range
3. Reduced performance of sensor if longer stylus is used
Specified stylus range
Module lengths increase as spring gap changes to achieve desired pivot motion
Why are there 5 scan modules to cover the stylus range? - traditionally, increasing stylus length leads to reducing accuracy SP25M addresses this characteristic …
scan modules designed for optimum output from PSD sensors when using shortest stylus at max operating deflection (resulting in largest pivot motion/swept area over PSD’s by IRED beams - so giving best gain, resolution and highest accuracy metrology) whilst restricting loss of performance as longer stylus is used (by ensuring sufficient coverage of sensor is maintained resulting in low degradation of accuracy performance)
if excessive stylus length is used, the pivot motion angle rapidly reduces (resulting in less swept area over PSD’s and non optimised transducer performance giving reduced accuracy)

12. Design characteristics, performance and specification
Why are there 5 scan modules to cover the stylus range? - traditionally, increasing stylus length leads to reducing accuracy SP25M addresses this characteristic …
the dedicated range for each stylus module also means that contact forces at the tip can be closely maintained (if we were to use excessive stylus lengths the force would reduce, reducing stability and accuracy)
the fixed extension design of SH25-2/3 prevents use of illegally short stylus
high accuracy data maintained as stylus length increases
unique design of SP25M can result in times better accuracy than SP600
Module lengths increase as spring gap changes to achieve desired pivot motion
Specified stylus range
4. Design optimised to maintain a nominal deflection force of 60 g/mm across all three modules
5. Possible unsatisfactory contact force if longer stylus is used

13. Design characteristics, performance and specification
Superior scanning performance ...
accurate form measurement, even with long styli
excellent reach capability
ISO Tij m
ISO test data
Test conditions:
CMM spec: L / 1000
Test speed: 5 mm/sec
Controller: UCC1
Filter: None / 60 Hz
Values: Unknown path
3.5
3.0
2.5
2.0
Filtered (60 Hz harmonic)
This chart shows the results of a series of ISO scanning tests using a SP25M probe fitted to a PH10M head, with different stylus configurations. Two ISO Tij values are quoted for each stylus length: raw data and data that has been subject to a 60 Hz harmonic filter, designed to remove high frequency noise from the probe and machine position feedback systems.
Three different scanning modules are used, each of which has been designed to work with a range of stylus lengths, with optimised gains and spring rates to deliver the best scanning accuracy:
Module Stylus
SM mm long, stainless steel stem, 3 mm ball - shortest scanning stylus
SM mm long, ceramic stem, 5 mm ball - typical ‘short’ stylus
SM mm long, graphite fibre stem, 6 mm ball - typical ‘long’ stylus
SM mm long, graphite fibre stem, 6 mm ball - extreme length stylus
Note that SP25M’s small size means that the probe itself can gain access to many deep features, extending the reach of the probe.
1.5
No filter (raw data)
1.0
Module/Stylus used:
21 = SM25-1 with 21 x 3 mm, SS stem
50 = SM25-1 with 50 x 5 mm, Ceramic stem
100 = SM25-2 with 100 x 6 mm, GF stem
200 = SM25-3 with 200 x 6 mm, GF stem
0.5 21 50
100
200
Stylus length (mm)

14. Design characteristics, performance and specification
Noise comparison - SP600M typical plot

15. Design characteristics, performance and specification
Noise comparison - SP25M has lower noise and better gain

16. SP25M The world’s most compact and versatile scanning probe system EMAIL QUESTIONS
The presentation explains how Renishaw designs its scanning systems, as well as providing comparisons of Renishaw’s solutions with those from other metrology suppliers.
technology