SP600 family of analogue scanning probes

SP600 family of analogue scanning probes
This presentation outlines the key choices facing a CMM user who needs to specify a probing system. Key questions: Do my measurement applications require a scanning solution? If so, what is the scanning performance of the system? Scanning accuracy at high speeds Total measurement cycle time, including stylus changes If I also need to measure discrete points, how fast can I do this? Will I benefit from the flexibility of an articulating head Access to the component Sensor and stylus changing What are the lifetime costs? Purchase price What are the likely failure modes and what protection is provided? Repair / replacement costs and speed of service Compact scanning probe with rapid dynamic response for high speed measurement technology

Q. What should an ideal scanning system offer? Q. What are the SP600 family of probes? Q. Where can these probes be used? Q. What comprises the SP600 system? Q. What’s the specification and performance? Q. How do I compare SP600 with competitor offerings? This presentation outlines the key choices facing a CMM user who needs to specify a probing system. Key questions: Do my measurement applications require a scanning solution? If so, what is the scanning performance of the system? Scanning accuracy at high speeds Total measurement cycle time, including stylus changes If I also need to measure discrete points, how fast can I do this? Will I benefit from the flexibility of an articulating head Access to the component Sensor and stylus changing What are the lifetime costs? Purchase price What are the likely failure modes and what protection is provided? Repair / replacement costs and speed of service

What should an ideal scanning system offer?
High speed, accurate scanning of the form of known and unknown parts Rapid discrete point measurement when measuring feature position Flexible access to the component to allow rapid measurement of all critical features Easy interchange between stylus arrangements and also between other types of sensor, including touch-trigger probes and non-contact sensors. This allows optimised choice of stylus/sensor to each measurement application Minimum stylus wear Reliability, productivity and low cost of ownership The typical manufacturer will require a combination of high speed, accurate scanning for critical features where form measurement is essential, plus discrete point measurement for features that require just size or position control Scanning systems can do both of these things, although they are not the optimum solution for fast measurement of discrete points. The ideal scanning system therefore has the following characteristics. For more information on how Renishaw scanning systems are designed to meet these criteria, explore the Renishaw scanning topic in the Quick links below. Ideal scanning system characteristics High speed, accurate scanning of the form of known and unknown parts Rapid point measurement to capture discrete data points when measuring feature position Flexible access to the component to allow rapid measurement of all critical features on the part Easy interchange with other types of sensor, including touch-trigger probes and non-contact sensors. This allows users to optimise their sensor choice for each measurement application. Renishaw’s SP600 scanning probe family gives you all this functionality

What are the SP600 family of probes?
Renishaw’s SP600 product family are analogue scanning probes providing high-performance inspection, digitising and profile scanning, and are suited to a wide range of CMMs 3 models are available, designed to suit varying CMM mounting arrangements and diverse application requirements: SP600 Shank Mounted Uses a shank adaptor to suit the CMM SP600M Autojoint Mounted for use with articulating heads SP600Q In-Quill Mounted The typical manufacturer will require a combination of high speed, accurate scanning for critical features where form measurement is essential, plus discrete point measurement for features that require just size or position control Scanning systems can do both of these things, although they are not the optimum solution for fast measurement of discrete points. The ideal scanning system therefore has the following characteristics. For more information on how Renishaw scanning systems are designed to meet these criteria, explore the Renishaw scanning topic in the Quick links below. Ideal scanning system characteristics High speed, accurate scanning of the form of known and unknown parts Rapid point measurement to capture discrete data points when measuring feature position Flexible access to the component to allow rapid measurement of all critical features on the part Easy interchange with other types of sensor, including touch-trigger probes and non-contact sensors. This allows users to optimise their sensor choice for each measurement application. All 3 models have identical sensor mechanisms and specifications

What are the SP600 family of probes?
What is an ANALOGUE scanning probe anyway? a probe that gives a continuous reading at any time while in contact with the part an integral part of the CMMs motion control system - giving real time response X, Y and Z outputs a probe whose output is proportional to its deflection The SP600 probe family are PASSIVE sensors (as opposed to ACTIVE sensor type) - so SP600 gives: simple, compact, accurate and high-performance design robust with high resistance to most collision damage use of short, light, simple and rapidly interchangeable styli long service life, reliability and low cost of ownership 

Where can these probes be used?
SCANNING applications controlling the form or profile of complex surfaces or features that form functional fits with other parts determining the feature position, accurately measuring the feature size and identifying errors in the feature’s form or shape data capture speeds of up to 500 points per second (with UCC1) giving significantly improved productivity over other sensing methods Scanning allows you to gather a lot of data very quickly. This data can be used to determine not just the size and position of features on your components, but their form as well With a scanning inspection system you can acquire several hundred points per second, rapidly gaining an accurate understanding of the surface of your components. This is ideally suited to features where the tolerance of form is a significant proportion of the total tolerance Features which must form a functional fit with another component benefit most from scanning. Where form is not important (on clearance features, for instance), discrete point measurement is generally preferred.

Scanning a cylinder block Typical scanning routine, measuring precision features where form is critical to performance Scanning should be used where measurement of form is required. This example shows inspection of an F1 cylinder block, in which precision surfaces are critical to the performance of the race engine. Scanning provides much more information about the form of a feature than discrete point measurement

DISCRETE POINT MEASUREMENT applications not quite as fast as using a dedicated touch trigger probe but still very viable where requirement is secondary to scanning work extrapolate to zero routines have no need to pause and give averaging for best measurement results most features on most parts are best measured with discrete point measurement so ability to do this effectively with a scanning probe is of great benefit Scanning allows you to gather a lot of data very quickly. This data can be used to determine not just the size and position of features on your components, but their form as well With a scanning inspection system you can acquire several hundred points per second, rapidly gaining an accurate understanding of the surface of your components. This is ideally suited to features where the tolerance of form is a significant proportion of the total tolerance Features which must form a functional fit with another component benefit most from scanning. Where form is not important (on clearance features, for instance), discrete point measurement is generally preferred.

Discrete point measurement Video commentary Scanning probe taking discrete points at high speed ‘Extrapolate to zero’ routines High speed scanning Discrete point measurement With SP600 and extrapolate to zero measurement routines, cycle times for discrete point measurement approach those achievable with tough-trigger probes. The video shows a scanning probe taking discrete points on a bore, and then shows a scanning cycle on the same feature for comparison. It is important for a scanning probe to be able to measure discrete points quickly, as well as to scan at high speed, since many features are best controlled with discrete points. Discrete point measurement also minimises stylus wear. Active scanning sensors measure discrete points more slowly since they need to adjust the contact force once the stylus has been positioned on the surface of the component. Scanning probes must be able to measure discrete points quickly

DIGITISING applications capturing large amounts of data about an unknown surface creation of CAD models uses many of the same techniques as scanning REVERSE ENGINEERING applications digitised data can be exported to CAD for reverse engineering purposes used to generate a machining program for re-manufacture Like scanning, digitising is best performed using a scanning probe since the amount of data required is very high. Whilst discrete point measurement techniques can be used, these are very much slower Digitising uses many of the techniques needed for scanning, except that the motion of the CMM is controlled in a different manner On described parts, the probe can move in a pre-defined path, accommodating any surface deviations. By contrast, on an unknown part the probe is moved within a pre-defined area and the probe deflection vector is used to determine which way to move the CMM to keep the probe stylus in constant contact with the surface Digitising is used for re-manufacture and reverse engineering where a master part must either be replicated or converted into digital form.

Re-manufacture and reverse engineering Digitising a master part to acquire an accurate description of the surface Scanning cycle and data analysis handled by Tracecut software Digitising can be performed on CMMs, machine tools or dedicated platforms like Cyclone This digitising routine shows a typical master component being measured as a series of scan lines across the surface, with a small step-over between each line. The motion of the machine is driven by the deflection of the scanning probe as it responds to the shape of the surface. Using Renishaw’s Tracecut software, a series of grids can be set-up to cover the component. As data is captured it is filtered and a picture of the surface is built up. Tracecut can export surface data to CAD, plus it can produce a machining program to produce a mould or stamping tool to reproduce the master part. Digitising provides large amounts of data to define unknown contoured surfaces

What comprises the SP600 system?
SCANNING PROBE - 3 variants to meet your need: SP600 simple shank mount via adaptors and with external cabling SP600M patented Autojoint mount for fitment to Renishaw’s PH10M & PH10MQ indexing heads, the PHS1 servo positioning head and also the PH6M fixed probe head - note that the ability to articulate the probe brings maximum application flexibility to the majority of CMMs SP600Q fixed in-quill mounting ideally suited to smaller CMMs where ‘Z’ space is limited and probe articulation is not required Like scanning, digitising is best performed using a scanning probe since the amount of data required is very high. Whilst discrete point measurement techniques can be used, these are very much slower Digitising uses many of the techniques needed for scanning, except that the motion of the CMM is controlled in a different manner On described parts, the probe can move in a pre-defined path, accommodating any surface deviations. By contrast, on an unknown part the probe is moved within a pre-defined area and the probe deflection vector is used to determine which way to move the CMM to keep the probe stylus in constant contact with the surface Digitising is used for re-manufacture and reverse engineering where a master part must either be replicated or converted into digital form.

STYLUS MODULES - to give you more flexibility: allow rapid and repeatable interchange between optimised styli arrangements without the need for re-qualification of the styli tips save you time and ensure you can easily use the best styli configuration for the application SCR600 STYLUS CHANGE RACK simple passive operation and ability to carry up to stylus modules - use multiple racks if required rapid module changing with excellent repeatability so eliminating need to re-qualify the styli tips increases your productivity significantly through shorter inspection cycles crash protection in-built into the design Like scanning, digitising is best performed using a scanning probe since the amount of data required is very high. Whilst discrete point measurement techniques can be used, these are very much slower Digitising uses many of the techniques needed for scanning, except that the motion of the CMM is controlled in a different manner On described parts, the probe can move in a pre-defined path, accommodating any surface deviations. By contrast, on an unknown part the probe is moved within a pre-defined area and the probe deflection vector is used to determine which way to move the CMM to keep the probe stylus in constant contact with the surface Digitising is used for re-manufacture and reverse engineering where a master part must either be replicated or converted into digital form.

MODULAR STYLUS CHANGER SYSTEM MRS - modular rack system offering choice of rail lengths to carry individual SCP600 ports modular legs to provide variable height adjustment SCP600 - individual stylus change ports for SP600 stylus modules choose the number you need for your applications and simply mount them onto the MRS - easy programming of change cycle Like scanning, digitising is best performed using a scanning probe since the amount of data required is very high. Whilst discrete point measurement techniques can be used, these are very much slower Digitising uses many of the techniques needed for scanning, except that the motion of the CMM is controlled in a different manner On described parts, the probe can move in a pre-defined path, accommodating any surface deviations. By contrast, on an unknown part the probe is moved within a pre-defined area and the probe deflection vector is used to determine which way to move the CMM to keep the probe stylus in constant contact with the surface Digitising is used for re-manufacture and reverse engineering where a master part must either be replicated or converted into digital form.

INTERFACE CARD - choice of two... - analogue counter card performs probe management functions - connects directly to a standard Renishaw multiwire probe signal cable AC1 - 8 bit ISA bus adaptor card - gives 1.0 µm resolution - compatible with 8 bit PC expansion slot AC bit ISA bus adaptor card - gives better than 0.1 µm resolution - compatible with 16 bit PC expansion slot Like scanning, digitising is best performed using a scanning probe since the amount of data required is very high. Whilst discrete point measurement techniques can be used, these are very much slower Digitising uses many of the techniques needed for scanning, except that the motion of the CMM is controlled in a different manner On described parts, the probe can move in a pre-defined path, accommodating any surface deviations. By contrast, on an unknown part the probe is moved within a pre-defined area and the probe deflection vector is used to determine which way to move the CMM to keep the probe stylus in constant contact with the surface Digitising is used for re-manufacture and reverse engineering where a master part must either be replicated or converted into digital form.

What’s the specification and performance?
Measurement range ±1mm in all axes and orientations (50mm stylus) Linear and Parallel motion in all axes Resolution AC1 gives 1.0µm whilst AC2 gives <0.1µm Spring rate N/mm nominal in all directions Damping 20% (X, Y, Z) typical at 23°C Operating temp 10°C to 40°C Physical mass SP g / SP600M 216g / SP600Q 299g Physical size SP600: 50mm max x 89mm (excl shank) SP600M: 50mm max x 107.5mm SP600Q: 60mm ‘’ flange x 99mm Max stylus lgth/mass 280 mm/20 g Data collection rate Up to 500 points per second (with UCC1) Service life Renishaw’s service records indicate an operational life in excess of 50,000 hours

Discrete point measurement results (3D tests) PROBE TP7 TP200 SP600M Styli (lgth x ball diam) 50 x  x  x 3 ISO µm µm µm B µm µm µm PROBE SP600M with extended styli operation Styli (lgth x ball diam) 50 x  x  x 6 ISO µm µm µm B µm µm µm Test conditions CMM spec’n: U3 =0.9+L(mm)/500mm Ring Gauge: 50mm Grade AA, Form error 0.35µm Probe: SP600M Controller / Head: UCC1 / PH10MQ Datum Ball: 25mm Grade 5, roundness 0.08µm Styli: Ball stylus - lgth & diam as above

Scanning results (2D tests) VDI / VDE 2617 V2 = 0.88µm ADAPTIVE PATH Filtered data Radius Test conditions CMM spec’n: U3 =0.9+L(mm)/500mm Ring Gauge: 50mm Grade AA, Form error 0.35µm Probe: SP600M Controller / Head: UCC1 / PH10MQ Datum Ball: 25mm Grade 5, roundness 0.08µm Styli: 50mm long x 6mm ball diameter

Scanning results (3D tests) ISO THN = 2.6 µm Time = 70 secs A Circle B Circle Test conditions CMM spec’n: U3 =0.9+L(mm)/500mm Ring Gauge: 50mm Grade AA, Form error 0.35µm Probe: SP600M Controller / Head: UCC1 / PH10MQ Datum Ball: 25mm Grade 5, roundness 0.08µm Styli: 50mm long x 6mm ball diameter

Scanning Results (3D tests) ISO THN = 2.6 µm Time = 70 secs C ½ Circle D ½ Circle Test conditions CMM spec’n: U3 =0.9+L(mm)/500mm Ring Gauge: 50mm Grade AA, Form error 0.35µm Probe: SP600M Controller / Head: UCC1 / PH10MQ Datum Ball: 25mm Grade 5, roundness 0.08µm Styli: 50mm long x 6mm ball diameter

Renishaw scanning - our offering
The fastest and most accurate scanning passive scanning probes with dynamically superior mechanisms sophisticated probe calibration The most flexible and productive solution probe changing stylus changing articulation The lowest ownership costs innovative hardware and scanning techniques reduce complexity robust designs and responsive service for lower lifetime costs Renishaw’s approach to scanning system design delivers the best performing and most cost-effective solution available.

Responsive service and expert support
Application and product support wherever you are Renishaw has offices in over 20 countries responsive service to keep you running optional advance RBE (repair by exchange) service on many products we ship a replacement on the day you call trouble-shooting and FAQs on Service facility at Renishaw Inc, USA

This presentation outlines the key choices facing a CMM user who needs to specify a probing system. Key questions: Do my measurement applications require a scanning solution? If so, what is the scanning performance of the system? Scanning accuracy at high speeds Total measurement cycle time, including stylus changes If I also need to measure discrete points, how fast can I do this? Will I benefit from the flexibility of an articulating head Access to the component Sensor and stylus changing What are the lifetime costs? Purchase price What are the likely failure modes and what protection is provided? Repair / replacement costs and speed of service Compact scanning probe with rapid dynamic response for high speed measurement technology

Q. How do I compare SP600 against competitor scanning offerings? A. The following slides will help explain the justification for choosing a SP600 probe... This presentation outlines the key choices facing a CMM user who needs to specify a probing system. Key questions: Do my measurement applications require a scanning solution? If so, what is the scanning performance of the system? Scanning accuracy at high speeds Total measurement cycle time, including stylus changes If I also need to measure discrete points, how fast can I do this? Will I benefit from the flexibility of an articulating head Access to the component Sensor and stylus changing What are the lifetime costs? Purchase price What are the likely failure modes and what protection is provided? Repair / replacement costs and speed of service

Active or passive sensors?
Active sensors Complexity Drive motors 3 Dampers LVDTs mounted on stacked axes Simplicity no motor drives no locking mechanism no tare system no electromagnet s no electronic damping Design Active sensors are large, heavy and complex Passive sensors are small and relatively simple

Compact passive sensor
Method of control Passive sensors Active sensors simple device senses deflection no powered motion measurements taken using machine to control stylus deflection 3 axes under servo control effectively a miniature CMM motors control the deflection to minimise the force on the stylus 6 axes under servo control Compact passive sensor Complex active sensor

Sensor design and calibration
Passive sensors Active sensors smaller axis travels required at 300 mm/sec, deflections can be held within a 100 µm range* stylus bending compensated by sophisticated calibration routine large probe travel needed to keep the contact force steady during scanning direction- dependent stylus bending variations minimised by controlling the contact force Compact passive sensor Complex active sensor * using adaptive scanning

Dynamic response Passive sensors Active sensors Light weight
high natural frequency suspension system Motorised stylus carrier driven on internal servo loop Modern CMMs are able to move very quickly - often faster than 500 mm/sec - and can generate high accelerations - sometimes more than 0.5g. Yet scanning on conventional scanning systems is typically performed at a tiny fraction (less than 5%) of this potential. These slow scanning moves offset most of the gains in cycle time made by having a fast measuring machine. Clearly there is scope for significant cycle time improvements if some of this untapped potential can be released. Renishaw has met this challenge with its innovative Renscan DCTM technology. This is explained in the Renishaw CMM motion control presentation. Probe suspension must respond whilst scan vector is adjusted Motors adjust stylus position to keep contact force within set limits

Measurement performance
Passive sensors Active sensors low inertia probe holds surface at high speeds fast discrete point measurement cycles with 'extrapolate to zero' routines no heat sources for improved stability 500 mW power consumption < 1ºC temperature change inside probe motorised probe mechanism enables high speed scanning slow discrete point measurement cycles due to the need to servo and static average probe data heat sources: motors and control circuits generate heat Probe inertia A high natural frequency can be achieved, even with low spring rates, due to the low suspended mass of Renishaw’s compact scanning probes. In active sensors, masses are much higher but not suspended on springs, so motorised control is used to allow the stylus to track the surface quickly. Discrete point measurement Active sensors measure discrete points by driving the stylus against the surface, holding machine position steady and then using the probe’s motors to modulate the contact force. With six axes under simultaneous servo control, there are oscillations that must be accounted for by averaging the probe output for a period of time. Only then can the probe be moved off the surface. This whole process can take several seconds. Passive sensors do not need to go through such a complex or time-consuming process. The probe is simply moved so that the stylus meets the surface and reaches a specified deflection. The probe’s deflection is monitored throughout. As the probe moves off the surface, the probe’s readings during the period of contact can be examined to find the true surface position by ‘extrapolating back to zero’ - effectively the same as static averaging except that it is done on the move. This process typically takes less than one second per point. Heat soak Renishaw scanning probes consume little electrical power since there is no requirement to drive the stylus carrier, or lock the axes. With a peak power consumption of less than 1W, the SP600 family do not have significant internal heat sources. Experiments show that temperature variations inside the probe are less then 1 ºC.

Minimum inspection cycle times
High speed measurement High speed scanning A dynamically responsive sensor, combined with adaptive scanning algorithms, allows high speed scanning whilst coping with unexpected obstacles. The first video shows very high speed scanning on a regular feature. The second video shows high speed measurement on a contoured surface in which the probe must adapt rapidly to changing contours. High speed scanning on a large component Scanning a complex surface at high speed

Minimum inspection cycle times
High speed measurement Video commentary scanning probe taking discrete points at high speed ‘extrapolate to zero’ routines high speed scanning Discrete point measurement With SP600 and extrapolate to zero measurement routines, cycle times for discrete point measurement approach those achievable with tough-trigger probes. The video shows a scanning probe taking discrete points on a bore, and then shows a scanning cycle on the same feature for comparison. It is important for a scanning probe to be able to measure discrete points quickly, as well as to scan at high speed, since many features are best controlled with discrete points. Discrete point measurement also minimises stylus wear. Active scanning sensors measure discrete points more slowly since they need to adjust the contact force once the stylus has been positioned on the surface of the component. Rapid discrete point measurement and scanning combined

Robustness Passive sensors Active sensors no motors
position feedback system is only electro-mechanical element kinematic stylus changing and Z over-travel bump stop provides robust crash protection probe will survive most accidents simpler motion control more things to go wrong motor drives locking mechanism tare system electromagnets electronic damping control hardware for the above limited crash protection if the stylus is deflected beyond its limits more complex motion control Kinematic stylus changing provides a low force ‘break joint’ which causes the stylus to detach in XY collisions. In the Z direction, a patented ‘bump stop’ prevents damage to the probe mechanism. The chances are, a Renishaw scanning probe will survive most crashes and still work to spec. In more than 8 years of sales, no SP600 field failures returned the Renishaw can be attributed to crash damage. The same cannot be said for active sensors that do not provide robust crash protection features. Plus, crash damage to active sensors tends to be more costly due to their complexity and high repair charges.

Robustness Crash protection Video commentary overtravel in XY plane
causes stylus module to unseat stop signal generated stylus reseats as machine backs off surface probe still operational Renishaw scanning sensors are equipped with a unique kinematic stylus changing system, allowing for rapid swapping between styli and crash protection for the scanning probe. Accidents do happen, and you will want to minimise their impact on your scanning system. Renishaw's patented stylus changing systems use a magnetically retained kinematic joint, giving excellent repeatability and a high speed stylus changing mechanism A key benefit is crash protection - in the event of a collision the stylus detaches from the probe, without inducing forces in the sensor that could damage the sensing mechanism. You may have to pick up your stylus, but at least the probe should be OK. Video commentary In the video, the scanning probe is first overtravelled in the Z direction, causing the kinematic stylus to unseat from its magnetic coupling. An alarm signal causes the machine to stop, and the stylus module reseats as the machine backs off. The probe is still operation and measures normally without any need to re-qualify the stylus. The same process is repeated in the XY plan - once again the probe is OK to continue measuring. Scanning probes with high attachment forces do not offer the same level of crash protection, either for the stylus or for the component. Detachable styli allow stylus overtravel without damage to the probe or component

Lifetime costs Passive sensors Active sensors lower purchase costs
simple and cost-effective to purchase lower running costs crash protection for greater reliability 50,000+ hours MTBF advance replacement service at discounted price customer-replacement on site due to simple fittings less downtime cost-effective repair higher purchase costs complex and high cost sensor higher running costs complex sensor limited crash protection vendor technician needed to remove damaged sensor more downtime high repair charges Renishaw service Renishaw’s RBE facility enables customers to quickly replace faulty product with one that is rebuilt to factory specification, at a heavily discounted price. Renishaw’s objective is to make the cost of ownership affordable, both in terms of service charges and in terms of costly downtime. Robustness SP600 probes have exceeded 50,000 hours of service with no failures. This is more than twice the MTBF claimed for active sensors.

SP600 family - key design characteristics
Passive sensor - no motors minimal heat source for greater stability no electro-mechanical wear reduced vibration during discrete point measurement Box spring mechanism unique design compact mechanism - fits inside Ø50 mm probe body low inertia rapid dynamic response low spring rates single 3D ferro-fluid damper Compact dimensions - 50 mm diameter, 89 mm length Compact dimensions are valuable since they allow the probe itself to enter deep features, thus reducing the length of stylus needed to access the surface. It is always sensible to minimise stylus length to reduce stylus bending and to minimise suspended mass, thus maximising the dynamic response of the probe. The SP600 is much smaller than probes fitted to conventional scanning systems. Light weight - SP600M weighs just 216g (7.6 oz) The light overall weight of Renishaw scanning probes means that versions can be mounted on articulating heads for flexible part access. Renishaw's SP600M is the only scanning probe that can be mounted on an articulating head. When mounted on a PH10 indexing head, the combined weight is less than 1 kg (2.2 lbs). Even on fixed probes, a light mass reduces the dynamic loads on the CMM quill during scanning. Here, the compact size of the SP600Q makes it ideal for use on small CMMs where the measurement volume is limited. The SP600Q weighs 299g (10.5 oz). By contrast, 'active' probes are heavy - some weigh more than 5 kg (11 lbs). This can increase the inertial loads on the machine quill, limiting scanning accuracy at higher speeds. Parallel acting springs

Z pos Isolated optical metrology readheads attached to probe housing measures deflection of whole mechanism, not just one axis eliminates inter-axis errors picks up thermal and dynamic effects competitor probes with stacked axes cannot measure inter-axis errors directly Y pos Readheads attached to probe body X pos A scanning probe has three axes of deflection - X, Y and Z. The probes use parallel-acting springs to allow each axis to move relative to one another. Each axis moves in an arc, resulting in a small amount of motion in a direction perpendicular to the axis that is moving. This small deflection - or inter-axis error - must be accounted for to ensure that the position of the stylus is accurately known. In a Renishaw scanning probe, the three axes are arranged to form a unique 'box spring', making for a very compact design. The transduction (position sensing) system is located behind the spring assembly. By contrast, a tower probe features stacked axes, making the probe much longer. A position sensing device is mounted on each axis. Renishaw's SP600 probe mechanism features a transduction system with readheads fixed to the body of the probe, measuring the deflection in each direction on a target mounted to the moving mechanism. This arrangement means that any inter-axis errors caused by the arc motion of each pair of parallel-acting springs are directly measured by the readheads - the deflection in each direction is measured 'back to earth'. The motion of the stylus is measured directly by the readheads, meaning that the system is not reliant on the mechanical design of the structure for its accuracy. By contrast, probes that feature position sensing devices mounted to each axis can only measure linear deflections relative to the axis above. They cannot detect inter-axis errors, nor errors of squareness of the probe axes. Whilst these errors can be compensated, this is not necessary for a Renishaw scanning probe. 'Back to earth' measurement systems can detect sources of variable error such as thermal and dynamic effects. Stacked axis probes cannot detect these and so perform less well in real world conditions, or when scanning quickly. Inter-axis error

Kinematic stylus changing optimise stylus and hence repeatability for each feature: minimum length Longer styli degrade repeatability maximum stiffness minimum joints maximum ball size Maximum effective working length repeatable re-location no need for re-qualification passive no signal cables easy installation Renishaw scanning sensors are equipped with a unique kinematic stylus changing system, allowing for rapid swapping between styli and crash protection for the scanning probe. Using Renishaw’s new modular rack system, any number of stylus changing ports can be fitted to a CMM, allowing great flexibility in your choice of styli. This allows you to select the best stylus for each measurement task, resulting in more repeatable measurements. Video commentary The video shows how quick and simple an automatic stylus change is. In just 10 seconds, the stylus is switched and the probe is ready to measure again. The repeatable kinematics mean that the stylus can be changed many times and will always be in the same position relative to the probe, so there is no need to re-qualify after each change. Kinematic stylus changing in around 10 seconds means that you can pick the best stylus for each feature

Long styli Video commentary 200 mm (8 in) stylus scanning deep features in a cylinder block compact probe dimensions further extend the reach of the probe styli up to 280 mm (11.0 in) can be used with SP600 probes 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. SP600 scanning with a 200 mm (8 in) stylus for access to deep features

Crash protection stylus change joint has low release force over-travel in XY causes stylus to detach patented Z crash protection outer housing provides a ‘bump stop’ to prevent probe mechanism and readhead damage Renishaw's kinematic stylus changing system provides crash protections when the stylus travel is exceeded in a lateral direction (X or Y). However, this does not provide full protection for crashes in the Z direction A feature of Renishaw scanning probes is a Z 'bump stop' that transfers any compression forces into the probe body before the Z travel of the scanning mechanism is exceeded. This means that in the event of an uncontrolled Z movement of the machine, the probe stylus and the probe body take the load whilst protecting the box spring and readheads from damage. Stylus deforms in a severe Z crash, whilst probe mechanism is protected

Crash protection Video commentary steel stylus crushed against SP600 more severe than any Z crash since E Stop would prevent continued force bump-stop protection system saves probe mechanism probe was still functional after test completed This video shows a Renishaw scanning probe being deliberately ‘crashed’ and still measuring accurately afterwards. The stylus is crushed against the probe, causing it to buckle. In a real Z crash, the emergency stop facility on the CMM would cut in to limit the force applied to the quill, meaning that the forces applied to the probe would be lower and less sustained than in this test.. The patented bump stop takes the force of the impact and protects the probe mechanism and electronics. The probe still functioned normally and was found to meet specification following a recalibration cycle. Renishaw scanning probes are robust - even after bending or breaking the stylus, they still work!

Compression test data Circle C Circle B Stylus ball shatters Circle A Force (N) Circle D ISO Part 4 Scan deflection = 0.5 mm (All data in m) Circle Before After A B C D Result The chart shows the force / deflection profile during the compression test. The peak force applied to the probe was over 1,630 N (365 lb), which occurs at the point where the ball shattered. The force then builds up again as the stylus starts to buckle. An ISO Part 4 scanning test was performed on the probe before and after the compression test. There is no degradation in performance as a result of the compression test. Deflection (mm)

Renishaw scanning - our offering
The fastest and most accurate scanning passive scanning probes with dynamically superior mechanisms sophisticated probe calibration The most flexible and productive solution probe changing stylus changing articulation The lowest ownership costs innovative hardware and scanning techniques reduce complexity robust designs and responsive service for lower lifetime costs Renishaw’s approach to scanning system design delivers the best performing and most cost-effective solution available.

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