Transcript Renishaw touch-trigger probing

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Renishaw
touch-trigger
probing
technology
Rugged and flexible solutions
for discrete point measurement
on CMMs
Issue 2
Slide 1
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Questions to ask your metrology system supplier
• Are my measurement applications best inspected with
discrete points?
– if so, should I use a scanning probe or a touch-trigger probe?
• 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
Slide 2
– what are the likely failure modes and what protection is
provided?
– repair / replacement costs and speed of service
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Renishaw touch-trigger probing - our objectives
• robustness
– compact and rugged
– crash protection
– extended operating life
• flexibility
– probe changing
– stylus changing
– articulation
• cost effectiveness
Slide 3
– innovative hardware
– simple programming for lower running
costs
– robust designs and responsive service
for lower lifetime costs
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Renishaw touch-trigger probing systems
Touch-trigger probe applications
Metrology of trigger probes
Trigger probe design
Articulating heads
Slide 4
Probe and stylus changing
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Probing applications - factors
Manufacturers need a range of
measurement solutions.
Why?

machining processes have different
levels of stability:
 stable form :
 therefore control size and position
 discrete point measurement
 form variation significant :
 therefore form must be measured and
controlled
 scanning
Slide 5
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Probing applications - factors
Manufacturers need a range of
measurement solutions.
Why?

Features have different functions:
 for clearance or location
form is not important
 Discrete point measurement
 for functional fits
form is critical and must be controlled
 Scanning
Measured values
Best fit circle
Slide 6
Maximum inscribed
(functional fit) circle
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Discrete point measurement
Ideal for controlling the position or size of
clearance and location features
• Data capture rates of 1 or 2 points per
second
• Avoids stylus wear
• Touch-trigger probes are ideal
– lower cost, small size and great versatility
• Scanning probes can also be used
– passive probes can probe quickly
Slide 7
– active probes are slower because the
probe must settle at a target force to take
the reading
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Discrete point measurement
Speed comparison
Slide 8
Touch-trigger probes are ideal
for high speed discrete point
measurement
Scanning probes can also
measure discrete points
quickly, and provide higher
data capture rates when
scanning
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Touch-trigger probing operation
Trigger probes measure discrete points...
• a trigger probe is in one of two states:
– seated when the stylus is not in contact
with the part
– unseated when the stylus is touching the
part
• a trigger signal is generated when the
probe changes from seated to unseated
• the trigger signal latches the machine
position to record the location of the
surface
Slide 9
• feature geometry is computed from a
best fit of discrete surface points
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Touch-trigger probing characteristics
Versatile
• wide range of probes
– sensors that range in size from the
small, industry-standard TP20, to
larger, high accuracy sensors like
the TP7M
– probes suitable for use on manual
and motorised heads and for quill
mounting
High accuracy
TP7M
Slide 10
Ultra-compact
TP20
Quill mounted
TP800
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Touch-trigger probing characteristics
Versatile
• stylus changing
– fast and automated stylus changing
without re-qualification
• sensor changing
– allows for a range of probes on your CMM,
each suited to a specific measurement task
Slide 11
Sensor
changing
Stylus
changing
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Touch-trigger probing characteristics
Flexible part access
• articulating heads
– flexible reorientation of inspection
sensors for better part access
• extensions
– compact sensors can be
mounted on long extension bars
for access to deep features
Slide 12
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Touch-trigger probing characteristics
Robust and crash resistant
• rugged design
– simple and robust mechanism
• crash protection
– magnetic kinematic mount allows
stylus module to detach when
over travelled
Robust kinematic
mechanism
Slide 13
Magnetic mount
for stylus module
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Touch-trigger probing characteristics
Cost effective
• simple and affordable
• low lifetime costs
– advance replacement
service at discounted price
Slide 14
Service Centre
Renishaw Inc
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Renishaw touch-trigger probing systems
Touch-trigger probe applications
Metrology of trigger probes
Trigger probe design
Articulating heads
Slide 15
Probe and stylus changing
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Touch-trigger probe technologies
Slide 16
Resistive
• simple
• compact
• rugged
Strain-gauge
• solid-state switching
• high accuracy and
repeatability
• long operating life
Piezo
• three sensing methods
in one probe
• ultra-high accuracy
• quill mounted
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Kinematic resistive probe operation
Slide 17
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Kinematic resistive probe operation
All kinematics
Pivots
about
Contacts
in
contact
these
Reactive
separate
contacts
force
• probe in seated position
• stylus makes contact with
component
• contact force resisted by reactive
force in probe mechanism
resulting in bending of the stylus
• stylus assembly pivots about
kinematic contacts, resulting in
one or two contacts moving apart
• trigger generated before
contacts separate
Motion of
machine
Slide 18
Contact
force
• machine backs off surface and
probe reseats
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Kinematic resistive probe operation
Electrical switching
• electrical circuit through
contacts
• resistance measured
• contact patches reduce in
size as stylus forces build
Close-up view of
kinematics:
Section through
kinematics:
Current flows
through
kinematics
Kinematics bonded to (and
insulated from) probe body
Resistance rises as area
reduces (R = /A)
Elastic deformation
Slide 19
Contact patch shrinks as
stylus force balances
spring force
Kinematic
attached to
stylus
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Kinematic resistive probe operation
Electrical switching
• resistance breaches
threshold and probe
triggers
Resistance
Force on kinematics
when stylus is in
free space
• kinematics are still in
contact when probe
triggers
– stylus in defined
position
• current cut before
kinematics separate to
avoid arcing
Slide 20
Trigger
threshold
Trigger
signal
generated
Force on
kinematics
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Factors in measurement performance
Pre-travel
• stylus bending under contact
loads before trigger threshold is
reached
• pre-travel depends on FC and L
• trigger is generated a short
distance after the stylus first
touches the component
Slide 21
FC x L = FS x R
L and FS are constant
FC is proportional to R
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Factors in measurement performance
Top view
Pre-travel variation - ‘lobing’
• trigger force depends on probing
direction, since pivot point varies
– FC is proportional to R
• therefore, pre-travel varies around
the XY plane
High force
direction:
Low force
direction:
R1 > R2
FC1 > FC2
Slide 22
Pivot
point
Pivot
point
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Factors in measurement performance
Pre-travel variation - ‘lobing’
• trigger force in Z direction is higher than
in XY plane
– no mechanical advantage over spring
– F C = FS
• kinematic resistive probes exhibit 3D
(XYZ) pre-travel variation
– combination of Z and XY trigger effects
– low XYZ PTV useful for contoured part
inspection
Test data:
Slide 23
ISO 10360-2 3D form
TP20 with 50 mm stylus: 4.0 m (0.00016 in)
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Factors in measurement performance
Probe calibration
• pre-travel can be compensated by probe
calibration
• a datum feature (of known size and position) is
measured to establish the average pre-travel
• key performance factor is repeatability
Limitations
• on complex parts, many probing directions may
be needed
• low PTV means simple calibration can be used
for complex measurements
Slide 24
• if PTV is significant compared to allowable
measurement error, may need to qualify the
probe / stylus in each probing direction
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Factors in measurement performance
Typical pre-travel variation
• XY plane
Slide 25
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Factors in measurement performance
Repeatability
Hysteresis
• the ability of a probe to trigger
at the same point each time
• error arising from the direction
of the preceding probing move
– a random error with a Normal
distribution
– for a given probe and probing
condition, repeatability is equal
to twice the standard deviation
(2) of the Normal distribution
– 95% confidence level that all
readings taken in this mode
will repeat within +/- 2  from a
mean value
Slide 26
– maximum hysteresis occurs
when a measurement follows
a probing moves in opposite
directions to each other in the
probe’s XY plane
– hysteresis errors increases
linearly with trigger force and
stylus length
– kinematic mechanism
minimises hysteresis
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Factors in measurement performance
Ranked in terms of importance
• repeatability
– key requirement of any trigger probe
– fundamental limit on system measurement performance
– hysteresis contributes to measurement repeatability
• pre-travel variation
– can be calibrated, provided all probing directions are known
– measurement accuracy will be reduced if probe used in un-qualified
direction and PTV is high
– increases rapidly with stylus length
• hysteresis
Slide 27
– small error factor for probes with kinematic mechanisms
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Renishaw touch-trigger probing systems
Touch-trigger probe applications
Metrology of trigger probes
Trigger probe design
Articulating heads
Slide 28
Probe and stylus changing
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Kinematic resistive probe technology
Simple electro-mechanical
switching
• resistive probes use the probe
kinematics as an electrical trigger
circuit
• pre-travel variation is significant due
to the arrangement of the kinematics
Slide 29
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Kinematic resistive probe characteristics
• Extremely robust
• Compact
– good part access
– suitable for long extensions
• Good repeatability
– excellent performance with shorter styli
– low contact and overtravel forces minimise
stylus bending and part deflection
• Universal fitment
– simple interfacing
Slide 30
• Cost-effective
• Finite operating life
– electro-mechanical switching
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TP20 stylus changing probe
Concept
• direct replacement for TP2
– ultra-compact probe at just Ø13.2 mm
• TP20 features fast and highly repeatable
stylus changing
– manual or automatic
– enhanced functionality through extended
force and extension modules
Slide 31
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TP20 stylus changing probe
Benefits
• reduced cycle times achieved by fast
stylus changing without re-qualification
• optimised probe and stylus
performance with seven specialised
probe modules
• easily retrofitted to all Renishaw
standard probe heads (M8 or Autojoint
coupling)
• compatible with existing touch-trigger
probe interfaces
Slide 32
• metrology performance equivalent to
industry proven TP2 system but with
greater flexibility of operation
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TP20 stylus modules
Optimal measuring performance
• seven specialised probe
modules allow optimisation of
stylus arrangement for best
accuracy and feature access in
all user applications
• module attaches to probe body
via a quick release, highly
repeatable kinematic coupling
• module range covers all forces
supported by TP2
• 6-way module replaces TP2-6W
Slide 33
TP20 probe
body
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Comparative module and stylus lengths
Soft materials
General use
Longer or
heavier styli
Grooves and
undercuts
Reach up to
125 mm (5 in)
Slide 34
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Strain-gauge probe technology
• Solid state switching
– silicon strain gauges measure contact forces transmitted through
the stylus
– trigger signal generated once a threshold force is reached
– consistent, low trigger force in all directions
– kinematics retain the stylus / not used for triggering
Slide 35
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Strain-gauge probe operation
Force sensing
• four strain gauges are mounted
on webs inside the probe body
– X, Y and Z directions, plus one
control gauge to counter
thermal drift
• low contact forces from the
stylus tip is transmitted via the
kinematics, which remain
seated at these low forces
Slide 36
• gauges measure force in each
direction and trigger once force
threshold is breached (before
kinematics are unseated)
Silicon strain
gauges
mounted on
webs
(1 out of 4
shown)
Kinematics
remain seated at
low FC
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Strain-gauge probe operation
Low lobing measurement
• trigger force is uniform in
all directions
– very low pre-travel
variation
Slide 37
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Strain-gauge probe operation
Lobing comparison
• plots at same scale
Slide 38
Strain-gauge
XY PTV = 0.34 m
Kinematic resistive
XY PTV = 3.28 m
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Strain-gauge probe characteristics
• High accuracy and repeatability
– probe accuracy even better than standard
kinematic probes
– minimal lobing (very low pre-travel variation)
• Reliable operation
– no reseat failures
– suitable for intensive "peck" or "stitch” scanning
– life greater than 10 Million triggers
• Flexibility
– long stylus reach
– suitable for mounting on articulating heads and
extension bars
Slide 39
– stylus changing available on some models
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TP7M strain-gauge probe
• Concept
– 25 mm (1 in) diameter probe
– Autojoint mounted for use with PH10M
• multi-wire probe output
• Benefits
– highest accuracy, even when used with long
styli - up to 180mm long ("GF" range)
– compatible with full range of multi-wired
probe heads and extension bars for flexible
part access
– plus general strain-gauge benefits:
Slide 40
• non-lobing
• no reseat failures
• extended operating life
• 6-way measuring capability
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TP7M performance
Uni - directional repeatability
0.3
Specification
Microns
0.25
0.2
Test
results
from 5
probes
0.15
0.1
0.05
0
20
18
No. of triggers (*1,000,000)
16
14
12
10
8
6
4
2
0
Slide 41
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TP7M performance
XY (2D) form measurement deviation
0.6
Specification
Microns
0.5
0.4
0.3
Test
results
from 5
probes
0.2
0.1
0
20
18
No. of triggers (*1,000,000)
16
14
12
10
8
6
4
2
0
Slide 42
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TP200 stylus changing probe
• Concept
– TP2-sized probe, with strain gauge accuracy
– stylus changing for greater flexibility and
measurement automation
– 2-wire probe output (like TP2)
• Benefits
– long stylus reach - up to 100mm long ("GF"
range)
– match stylus to the workpiece using high
speed stylus changing
• improve accuracy for each feature
• no re-qualification
• manual or automatic changing with SCR200
Slide 43
– compatible with full range of heads and
extension bars
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TP200 stylus modules
Optimal sensor performance
• 6-way operation ±X, ±Y and ±Z
• two types of module:
– SF (standard force)
– LF (low force) provides lower overtravel
force option for use with small ball styli
and for probing soft materials
• detachable from probe sensor via a
highly repeatable magnetic coupling
– provides overtravel capability
• suitable for both automatic and manual
stylus changing
Slide 44
• module life of >10 million triggers
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Piezo shock sensing
Shock sensing
• piezo sensors generate a voltage
when subjected to pressure
Piezo ceramic
• piezos can detect the
mechanical shock signal
generated when the stylus ball
impacts the workpiece
sensor detects
shock of
impact
– they can respond to frequencies Stylus
changing
higher than those detected by
kinematics
many other sensors
– the result is that piezo probes
"hear" the stylus ball touch the
surface
Slide 45
Shock wave
travels up
stylus and is
transmitted
through
kinematics
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Piezo shock sensing
Ultra-sensitivity
• shock travels at speed of sound
through the stylus and probe
Piezo ceramic
sensor detects
– 800 m per second (2,600 ft/sec) shock of
– response time is 1.25 sec / mm impact
High performance
• pre-travel depends on stylus
length and probing speed
– pre-travel is the same in all
directions since mechanical
signal path is constant
Slide 46
– lobing effect limited to ball
sphericity!
Stylus
changing
kinematics
Shock wave
travels up
stylus and is
transmitted
through
kinematics
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Multi-sensor operation
Kinematic and strain sensing
• shock sensing is not 100%
reliable
– speed sensitive
– surface contamination
– workpiece hardness
– small stylus ball diameters are
not reliable
• shock can be backed by
kinematic and strain sensing to
confirm triggers generated by
shock sensor
Slide 47
– life of piezo probes are limited by
electro-mechanical elements
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TP800 piezo probe
Unprecedented performance
• quill mounted probe featuring unique
multi-sensor design
• ultra-high accuracy
– repeatability specification:
0.25 m with 50 mm stylus
1 m with 250 mm stylus
– low trigger force < 1 gf
– pre-travel variation << 0.5 m
– typical values for 150 mm stylus:
0.15 m repeatability
0.25 m PTV
• support for very large stylus clusters
Slide 48
– 350 mm straight
– 200 mm star
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TP800 piezo probe
Application limitations
• cannot measure small bores
– probe works best with larger stylus balls
(e.g. 6 mm)
– machine may not reach calibrated probing
speed without sufficient clearance
• surface condition is critical
– dirt on the surface can reduce shock and
prevent a clean trigger
– soft surfaces such as plastics do not
generate sufficient shock
• probing speed must be controlled to
within 1 mms-1
Slide 49
• large probe size prevents use with
articulating heads or extension bars
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Trigger probe measurement performance comparison
Slide 50
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Renishaw touch-trigger probing systems
Touch-trigger probe applications
Metrology of trigger probes
Trigger probe design
Articulating heads
Slide 51
Probe and stylus changing
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Articulation or fixed sensors?
Articulating heads are a standard
feature of most computercontrolled CMMs
– heads are the most cost-effective
way to measure complex parts
Fixed probes are best suited to
small machines on which simple
parts are to be measured
– ideal for flat parts where a single
stylus can access all features
Slide 52
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Renishaw articulating heads
Increased flexibility…

easy access to all features on the part

repeatable re-orientation of the probe

reduced need for stylus changing

optimise stylus stiffness for better
metrology
Reduced costs…
Slide 53

indexing is faster than stylus changing

less expensive than active scanning
systems

reduced stylus costs

simpler programming
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Renishaw articulating heads for trigger probing
Slide 54
PH10T
PH10M / MQ
PHS1
• indexing head
• 2-wire probes
• TP20
• TP200
• indexing head
• Autojoint connector
(multi-wire)
• TP7M & 2-wire probes
with PAA adaptors
• servo positioning head
• infinite range of
orientations
• longer extension bars
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Articulating head applications
Flexible probe orientation
• PH10M offers 7.5°
increments in 2 axes - is
this enough?
• prismatic parts
– generally few features at
irregular angles
– use a custom stylus to suit
the angle required
Slide 55
– fixed scanning probes also
need customer styli for
such features
Knuckle joint
needed to
access
features at
irregular
angles
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Articulating head applications
Flexible probe orientation
• PH10M offers 7.5° increments in 2
axes - is this enough?
• sheet metal / contoured parts
– many features at different irregular
angles
– stylus must be perfectly aligned with
surface in each case
– no indexing head is suitable
Slide 56
– fixed probes also unsuitable due to need
for many stylus orientations
– need continuously variable head (PHS1)
Cylindrical
stylus must be
perfectly
aligned with
hole
Sheet
metal
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PH10M indexing head - design characteristics
Head repeatability test results:
• Method:
– 50 measurements of calibration sphere at {A45,B45}, then 50 with
an index of the PH10M head to {A0,B0} between each reading
• TP200 trigger probe with 10mm stylus
• Results:
Result
X
Y
Z
Span fixed
0.00063
0.00039
0.00045
Span index
0.00119
0.00161
0.00081
 [Span]
0.00056
0.00122
0.00036
 [Repeatability]
± 0.00034
± 0.00036
± 0.00014
• Comment:
Slide 57
– indexing head repeatability has a similar effect on measurement
accuracy to stylus changing repeatability
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PH10M indexing head - design characteristics
Indexing repeatability affects the
measured position of features
– Size and form are unaffected
Most features relationships are
measured ‘in a plane’
– Feature positions are defined relative
to datum features in the same plane
(i.e. the same index position)
• Datum feature used to establish a part
co-ordinate system
Slide 58
– Therefore indexing typically has no
negative impact on measurement
results, but many benefits
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PH10 series indexing head - design characteristics
Light weight
• 650 g (1.4 lbs)
• lightest indexing head available
• total weight of < 1 kg including scanning
probe
Fast indexing
• typical indexing time is 2 to 3 seconds
• indexes can occur during positioning
moves
– no impact on measurement cycle time
Slide 59
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PH10M indexing head - design characteristics
Flexible part access
Slide 60
Rapid indexing during CMM positioning moves
give flexible access with no impact on cycle times
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PH10M indexing head - design characteristics
Autojoint
• programmable sensor changing with no
manual intervention required
• use scanning and touch-trigger probes in
the same measurement cycle
Slide 61
Autojoint features
kinematic connection
for high repeatability
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PHS1 servo head - design characteristics
Servo positioning for total flexibility
• full 360° rotation in two axes for total
flexibility of part access
– resolution of 0.2 arc sec
– equivalent to 0.1µm at 100mm radius
• servo control of both axes for infinitely
variable positioning and full velocity
control
– speeds of up to 150° per second
– 5-axis control required
Slide 62
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PHS1 servo head - design characteristics
High torque for long reach
• extension bars of up to 750 mm
(30 in)
– ideal for auto body inspection
– touch-trigger probes only
• Autojoint for use with SP600M
and TP7M
• Powerful motors generate 2 Nm
torque
– 4 times more than a PH10
Slide 63
– carry probes and extension bars of
up to 1 kg (2.2 lbs)
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PHS1 servo head - design characteristics
Infinitely variable positioning
Slide 64
PHS1’s motion can be combined with the CMM
motion to generate blended 5 axis moves
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Renishaw touch-trigger probing systems
Touch-trigger probe applications
Metrology of trigger probes
Trigger probe design
Articulating heads
Slide 65
Probe and stylus changing
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ACR3 probe changer for use with PH10M
• 4 or 8 changer ports
– store a range of sensors,
extensions and stylus
configurations
• Passive mechanism
Slide 66
– CMM motion used to lock and
unlock the Autojoint for secure and
fully automatic sensor changes
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New ACR3 probe changer for use with PH10M
Probe changing
Video commentary
• new ACR3 sensor
changer
• no motors or
separate control
• change is controlled
by motion of the
CMM
Slide 67
Quick and repeatable sensor changing for
maximum flexibility
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ACR2 probe changer for use with PHS1
Probe module changing
• flexible storage of probes and extension bars
Slide 68
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TP20 stylus changing
MCR20 - passive rack
• simple design for rapid stylus changes
under program control
• storage for up to 6 stylus modules
• kinematic stylus changing mechanism
– highly repeatable connection between stylus
and probe
MCR20 rack for
DCC CMMs
– styli can be stored and re-used without the
need for qualification
• collision protection
MSR1 manual rack
Slide 69
• stores and protects up to 6 modules on
manual CMMs
MSR1
manual rack
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TP200 stylus changing
SCR200 - active rack
• automated changing for up to 6
stylus modules
• active rack, but no communications
are needed with the CMM controller
– operation handled by the PI200
interface
• 2 operating modes:
– TAMPER PROOF ON - protects
against accidentally inhibiting probe
operation
Slide 70
– TAMPER PROOF OFF - for automatic
loading or high speed operation
• full collision protection
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TP800 stylus changing
SCR800 - passive rack
• automated changing for up to
3 or 4 stylus modules
• passive rack, operated by
motion of the CMM
• adjustable to suit long styli
and large star configurations
Slide 71
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Renishaw touch-trigger probing - our offering
• Robust solutions
– compact and rugged sensors
– crash protection to avoid damage
– extended operating life with solid-state
switching
• The most flexible and productive
solution
– probe changing
– stylus changing
– articulation
• The lowest ownership costs
– innovative and affordable hardware
Slide 72
– responsive service for lower lifetime costs
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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 www.renishaw.com/support
Service facility
at Renishaw
Inc, USA
Slide 73
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Questions?
Slide 74