Listed below is a detailed description of the most common types and current of Renishaw probing as used with CMM's. Contact us for detailed information. Special Upgrade promotion
Electronic Touch Trigger Probes are used for most measuring tasks. Touching the part physically assures reliable and repeatable measurements.
There are a great variety of probing and it can be a complicated choice at first, therefore we are always available to advise the correct type for you - not the most expensive. E.G. Programmable motorized probe heads for automatic indexing are offered for DCC machines and manual Indexable or fixed probing is generally offered for manual machines.
Upgrades are available for obsolete probes such as the TP2 and TP6 & MIP heads. Special trade in allowances make upgrading very economical but these are life limited offers therefore it is recommended advantage is takes of these if they exist.
Touch Probe Description
TP-20, 5-Way
The TP20 is basically a two-piece TP2. The switching mechanism is in the module, which attaches magnetically to the probe body via a repeatable kinematic mount. Since the modules are less expensive than a TP2, multiple stylus configurations for repetitive parts become less costly. Add to this the MCR20 Stylus Rack and you approach the versatility of a costly motorized probe head. The detachable module also prevents costly damage in the event of a collision. Accepts M2 styli.
TP20 Probe Module
The probe module houses the switching mechanism and provides over-travel in 3 axes. The module is held onto the probe body magnetically with a highly repeatable kinematic coupling.
Three trigger force options are available: standard, medium and extended force, for handling styli of various mass and length.
TP-200, 6-Way
The TP-200 is a highly sensitive and accurate probe based on strain gauge technology. It favours a detachable module like the TP20; the outside appearance is quite similar. The body diameter again is .51" (13mm). Triggering takes place in the probe body, the modules are therefore less expensive. The lobing error, associated with the other mechanical probes is absent. It is, therefore, recommended for accurate roundness measurements in bearing bores and the like. To achieve the higher accuracy it is imperative that the qualification speed and the speed while taking points are the same and constant. Consequently this Probe should NOT be used on manual CMM's.
The SCR 200 Stylus Rack with 6 stalls allows for automatic and efficient module exchange.
TP200 Stylus Module
Similar repeatable mount as the TP20 Module. Two force options are available: the standard force module is recommended for general applications. The low force is used for small ball styli or delicate materials.
Probe TP-ES Manual or DCC CMM's
Two Piece System One Body, fixed vertical construction. Most economical touch probe. Includes Adapter for M2 Styli.
Probe MH8 used with TP2, TP6, TP20 or TP200
Manual or DCC CMM's
Three-piece system. Manually indexable probe Head accepting all probes and extensions. Allows 360° rotation and 90° elevation of probe in 15° increments providing 168 repeatable positions. Locks in position via rotating lever.
Probe PH6 use with TP2, TP6, TP20 or TP200
Manual or DCC CMM's
Three piece system. The compact vertical and fixed head accepts all probes. Economical approach if indexing not required. Recommended for production applications in conjunction with the stylus rack with up to 6 stylus configurations.
Probe Kit MH20i with TP20
Manual or DCC CMM's
Compact three piece system. Manually indexable probe head with a built in TP20 kinematic mount. Same index mechanism as the MH8. The exchangeable modules allow the use of multiple styli configurations in any of the 168 indexable and repeatable positions eliminating the need for re-qualifications.
Has special probe extensions and cannot be used with the MCR20 Stylus Rack.
The motorised probes below are suitable only for CNC machines
Probe Kit PH10T with TP2,TP6,TP20 or TP200
DCC
Motorized indexing probe head for more demanding applications. Accepts longer probe extensions than the PH50. Has 720 index positions in 7.5° increments with 360° rotation and 105° elevation. Self locking. 90° cycle time is 3.5 seconds.
Probe Kit PH10M or PH10MQ
DCC N.B. PH10MQ fits the square body internal to the CMM quill, suitable CMM's only
High Torque version of the PH10T allows probe extensions up to 300mm long. This head has an auto-joint mounting to accept the TP7 high accuracy touch probe, the SP600 Scanning Probe and the OTP6M optical trigger probe. Requires the PAA1 adapter to accept the TP2, TP6, TP20 and the TP200 touch probes.
MCR20 Stylus Rack for TP20
SCR200 Stylus Rack for TP200
These module changing racks provide rapid automatic change of modules without the need to re-qualify. Rack functions completely passive not requiring electrical connections. Installation and set up is simple. Properly locating the rack within the machine coordinates. Hinged over travel serves as crash protection.
The MCR20 comes with two modules, the SCR200 with three. Each rack has 6 ports which are covered with protective docking plates to shield the modules from dirt and debris.
The following information is designed to help you choose the correct stylus for your application
Accuracy at the point of contact
As industry has developed its requirement for increasingly diverse and complex manufactured parts, inspection systems have had to work hard to keep up. The use of co-ordinate measuring machines (CMMs) with probing systems and in-process inspection on machine tools are two of the solutions offered by Renishaw to help you maximise your productivity and maintain the highest quality. Successful gauging depends very much on the ability of the probe’s stylus to access a feature and then maintain accuracy at the point of contact. At Renishaw, we have used our expertise in probe and stylus design to develop a comprehensive range of CMM and machine tool styli to offer you the greatest possible precision. These notes explain the critical features of every stylus type, helping you to choose the right design for each inspection need.
What is a stylus?
A stylus is that part of the measuring system which makes contact with the component, causing the probe's mechanism to displace. The generated signal enables a measurement to be taken. The feature to be inspected dictates the type and size of stylus used. In all cases, however, maximum rigidity of the stylus and perfect sphericity of the tip are vital. To achieve this, Renishaw's stylus stems are produced on CNC machine tools to exacting standards. Great care is taken to ensure that location faces give maximum stiffness whilst stylus mass is optimised to suit Renishaw’s range of probes. Genuine Renishaw stylus balls are produced to the highest standards and are bonded to the stems in such a way as to ensure maximum joint integrity. The performance of your gauging can easily be degraded if you use a stylus with poor ball roundness, poor ball location, bad thread fit or a compromised design that allows excessive bending during measurement. To ensure the integrity of the data you gather, make certain that you specify and use a stylus from the comprehensive range of genuine Renishaw styli.
Terminology
Overall length Renishaw uses a standard description of overall length, measuring from the rear mounting face of the stylus to the centre of the ball.
Effective working length (EWL)
This is measured from the centre of the ball to the point at which the stem will foul against the feature when measuring 'normal' to the part.
Choosing a stylus
To maintain accuracy at the point of contact we recommend that you:-
Keep styli short
The more that a stylus bends or deflects, the lower the accuracy. Probing with the minimum stylus length for your application is the best option.
Minimise joints
Every time you join styli and extensions, you introduce potential bending and deflection points. Try, wherever possible, to keep to the minimum number of pieces for your application.
Keep the ball as large as possible
There are two reasons for this,
• firstly, it maximises your ball/stem clearance thereby reducing the chances for false triggers caused by 'shanking out' on the stylus stem;
• secondly, the larger ball reduces the effect of the surface finish of the component being inspected.
Material selection - ball and stem
Ball material
Ruby
The industry standard and the optimum stylus ball material for a vast majority of measurement applications, ruby is one of the hardest known materials. Synthetic ruby is 99% pure aluminium oxide which is grown into crystals (or “boules”) at 2000 °C using the Verneuil process.
The boules are then cut and gradually machined into a highly spherical form. Ruby balls are exceptionally smooth on the surface, have great compressive strength and a high resistance to mechanical corrosion.
Very few applications exists where ruby is not the preferred ball material, however there are two applications where balls manufactured from other materials are recommended.
The first is for heavy duty scanning applications on aluminium. Because the materials attract, a phenomenon known as ‘adhesive wear’ can occur which involves build up of aluminium from the surface onto the ball. A better ball material for such applications is silicon nitride.
The second is in heavy duty scanning applications on cast iron. Interaction between the two materials can result in ‘abrasive wear’ of the ruby ball surface. For such applications, Zirconia balls are recommended.
Silicon nitride
Silicon nitride possesses many similar properties to ruby. It is a very hard and wear-resistant ceramic which can be machined into very high precision spheres. It can also be polished to an extremely smooth surface finish. Silicon nitride does not have the attraction to aluminium and so does not exhibit the adhesive wear seen with ruby in similar applications. However, silicon nitride does show significant abrasive wear characteristics when scanning on steel surfaces and so its applications are best confined to aluminium.
Zirconia
Zirconia is a particularly tough ceramic material with hardness and wear characteristics approaching those of ruby. Its surface properties make it an ideal material for aggressive scanning applications on cast iron components.
Stem material
Steel
Stylus stems manufactured from non-magnetic stainless steel are used widely for styli with ball/tip diameters of 2 mm or greater and with lengths up to 30 mm. Within this range, one-piece steel stems offer the optimum stiffness to weight ratio, giving adequate ball/stem clearance without compromising stiffness with a joint between the stem and threaded body.
Tungsten carbide
Tungsten carbide stems are best used for maximising stiffness with either small stem diameters required for ball diameters of 1 mm and below, or lengths up to 50 mm. Beyond this, weight can become a problem and stiffness is lost due to deflection at the stem to body joint.
Ceramic
For ball diameters greater than 3 mm, and lengths over 30 mm, ceramic stems offer stiffness comparable to steel but are significantly lighter than tungsten carbide. Ceramic stemmed styli can also offer additional crash protection to your probe as the stem will shatter in a collision.
Carbon fibre (Renishaw GF)
There are many grades of carbon fibre materials. However, Renishaw GF combines optimum stiffness characteristics, both longitudinally and in torsion (important in star constructions), with extremely low weight. Carbon fibre is inert and this, combined with a special resin matrix, provides excellent protection in the most hostile of machine tool environments.
Renishaw GF is ideal for maximising stiffness while giving very low mass for styli above 50 mm in length. It is the optimum stem material for high accuracy strain gauge technology probes with excellent vibration damping characteristics and negligible co-efficient of thermal expansion.
These are the simplest form of stylus, incorporating highly spherical industrial ruby balls and a choice of stem material.
Ruby is an extremely hard material and hence stylus wear is minimised. It is also of low density, keeping tip mass to a minimum, which avoids unwanted probe triggers caused by machine motion or vibration.
Mounted on stems made from a range of materials – stainless steel, tungsten carbide, ceramic and a specialised carbon fibre material, “Renishaw GF” – these simple ruby ball styli are suitable for most inspection applications.
Each stylus has an effective working length (EWL) which is the penetration that can be achieved by the ball before the stem fouls against the feature.
The size of the ball and the EWL of the stylus chosen are dictated by the size of the feature to be inspected. However, keeping the stylus ball as large as possible and the stem as short as possible will ensure maximum ball/stem clearance, whilst providing a greater yet still rigid EWL. Using larger ruby balls also reduces the effect of the surface finish of the component being inspected.
Probing with very long stylus/extension combinations is not recommended with standard kinematic touch trigger probes as the rigidity is reduced and accuracy lost due to stylus bending. This is not the case with other types of probe such as those with strain gauge technology, as their very low trigger forces permit the use of long stylus/extension combinations without a significant loss of accuracy.
These stylus clusters provide you with multiple-tip probing of complex features and bores. Four or five ruby ball systems are mounted rigidly on a stainless steel centre. Three standard sizes are offered – alternatively, you can create custom-made star styli using a 5-way stylus centre and any of the genuine Renishaw stylus range.
Star styli can be used to inspect a variety of different features. Their use can reduce inspection cycle times by allowing multi-tip probing, minimising the need to move the probe to extreme points of internal features such as the sides or grooves in a bore. Using star styli also allows effective probing in the –Z (upwards) direction when using a 5- way probe, provided that the stylus tips extend beyond the diameter of the probe body. Each tip on a star stylus requires datuming (sometimes referred to as ‘qualifying’ or ‘calibrating’) in the same manner as a single-ball stylus. The 'span' of star styli is taken from ball centre to ball centre.
These styli are used to probe undercuts and grooves within bores which may be inaccessible to star styli. They are ‘sections’ of highly spherical balls and are available in various diameters and thicknesses. Full rotational adjustment and the ability to add a centre stylus are features of the Renishaw range of disc styli that make them particularly flexible and easy to use.
Probing with the ‘spherical edge’ of a simple disc is effectively the same as probing on or about the equator of a large stylus ball. However, only a small area of this ball surface is available for contact and hence thinner discs require careful angular alignment in order to ensure correct contact with the feature being probed.
A simple disc requires datuming for only one diameter (usually in a ring gauge), but limits effective probing to only X and Y directions.
Adding a ‘radius end roller’ allows you to datum and hence probe in the Z direction, provided that the centre of the ‘radius end roller’ extends beyond the diameter of the probe. The ‘radius end roller’ can be datumed on a sphere or a slip gauge. Rotating and locking the disc about its centre axis allows the ‘radius end roller’ to be positioned to suit the application.
Discs may also have a threaded centre to allow the fixing of a centre stylus, giving the additional flexibility of probing the bottom of deep bores (where access for the disc may be limited).
These are used for probing holes in thin sheet material. In addition, various threaded features can be probed and the centres of tapped holes located. Ball-ended cylinder styli allow full datuming and probing in X, Y and
Pointer and ceramic hollow ball styli
Pointer styli are designed for the inspection of thread forms, specific points and scribed lines (to lower accuracy). The use of a radius end pointer stylus allows more accurate datuming and probing of features as detailed above and can also be used to inspect the location of very small holes.
Ceramic hollow ball styli are ideal for probing deep features and bores in X, Y and Z directions, with the need to datum only one ball. There are two versions in the range, 18 and 30 mm diameter, specially designed for the TP2 / TP20 / TP200 and TP6 probes respectively. Probing with such a large diameter ball can average out the effects of very rough surfaces.
These are typically fitted with a square tip and can have threaded or plain shaft attachments. The tip faces are ground to ensure high squareness and parallelism. The TS27R tool setting probe for machining centres can also be fitted with a tungsten carbide disc stylus.
Renishaw’s stylus crash protection devices are designed to break in the event of impact and protect the probe from damage.
These provide maximum probing flexibility with a single probe. Taking up to five styli of the same mounting thread, this accessory allows you to build stylus configurations to your own specification.
Stylus knuckles
These give full adjustment about two axes, allowing the stylus to be orientated to probe angled features. This adjustment is especially useful when the probe cannot be correctly orientated by the probe head, or when access for the head is limited.
These provide additional probing penetration by extending the stylus away from the probe. However, using stylus extensions can reduce probe accuracy due to loss of rigidity. This is not the case with electronic probes, whose extremely low trigger forces render them less sensitive to this type of inaccuracy.
These allow M2, M3, M4 and M5 threaded styli to be interchanged on the majority of touch trigger probes. They are particularly useful for adapting the extensive range of specialised application M2 styli for use on larger probes.
Special Upgrade promotion - Limited time offer and subject to change from the manufacturer.
Transform the productivity of your CMM with TP20 stylus changing and the extra capabilities of a PH10
TP20 Probe Upgrade (with 3 Modules) - FROM £900 Trade in your old TP2 or TP6 for a TP20 with 3 stylus changing modules
PH10 Motorised head upgrade -
Exchange your obsolete PH9 for PH10T or PH10M* or PH10MQ*Option 3
Take advantage of both offers simultaneously and receive an extra £400 discountN.B. Some CMM's may also require new controllers and this may be an additional cost