Introduction

1.1 Generation introduction

What exactly is a coordinate measuring machine ?

A coordinate measuring machine (CMM) is a device for measuring the physical geometrical characteristics of an object. This machine may be manually controlled by an operator or it may be computer controlled. Measurements are defined by a probe attached to the third moving axis of this machine. Probes may be mechanical, optical, laser, or white light, among others.

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Fig 1.1 Coordinate Measuring Machine

1.2 Description

The typical "bridge" CMM is composed of three axes, an X, Y and Z. These axes are orthogonal to each other in a typical three dimensional coordinate system. Each axis has a scale system that indicates the location of that axis. The machine will read the input from the touch probe, as directed by the operator or programmer. The machine then uses the X,Y,Z coordinates of each of these points to determine size and position. Typical precision of a coordinate measuring machine is measured in Microns, or Micrometres, which is 1/1,000,000 of a metre.

A coordinate measuring machine (CMM) is also a device used in manufacturing and assembly processes to test a part or assembly against the design intent. By precisely recording the X, Y, and Z coordinates of the target, points are generated which can then be analyzed via regression algorithms for the construction of features. These points are collected by using a probe that is positioned manually by an operator or automatically via Direct Computer Control (DCC). DCC CMMs can be programmed to repeatedly measure identical parts, thus a CMM is a specialized form of industrial robot.

1.3 Specific parts

Machine body:

In modern machines, the gantry type superstructure has two legs and is often called a bridge. This moves freely along the granite table with one leg (often referred to as the inside leg) following a guide rail attached to one side of the granite table. The opposite leg (often outside leg) simply rests on the granite table following the vertical surface contour. Air bearings are the chosen method for ensuring friction free travel. In these, compressed air is forced through a series of very small holes in a flat bearing surface to provide a smooth but controlled air cushion on which the CMM can move in a frictionless manner. The movement of the bridge or gantry along the granite table forms one axis of the XY plane. The bridge of the gantry contains a carriage which traverses between the inside and outside legs and forms the other X or Y horizontal axis. The third axis of movement (Z axis) is provided by the addition of a vertical quill or spindle which moves up and down through the center of the carriage. The touch probe forms the sensing device on the end of the quill. The movement of the X, Y and Z axes fully describes the measuring envelope. Optional rotary tables can be used to enhance the approachability of the measuring probe to complicated workpieces. The rotary table as a fourth drive axis does not enhance the measuring dimensions, which remain 3D, but it does provide a degree of flexibility. Some touch probes are themselves powered rotary devices with the probe tip able to swivel vertically through 90 degrees and through a full 360 degree rotation.

1.4 New Probing Systems

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There are newer models that have probes that drag along the surface of the part taking points at specified intervals, known as scanning probes. This method of CMM inspection is often more accurate than the conventional touch-probe method and most times faster as well.

The next generation of scanning, known as non-contact scanning includes high speed laser single point triangulation, laser line scanning, and white light scanning, is advancing very quickly. This method uses either laser beams or white light that are projected against the surface of the part. Many thousands of points can then be taken and used to not only check size and position, but to create a 3D image of the part as well. This "point-cloud data" can then be transferred to CAD software to create a working 3D model of the part. These optical scanners often used on soft or delicate parts or to facilitate reverse engineering

Micrometrology Probes:

Probing systems for microscale metrology applications are another emerging area . There are several commercially available coordinate measuring machines (CMM) that have a microprobe integrated into the system, several specialty systems at government laboratories, and any number of university built metrology platforms for microscale metrology. Although these machines are good and in many cases excellent metrology platforms with nanometric scales their primary limitation is a reliable, robust, capable micro/nano probe. Challenges for microscale probing technologies include the need for a high aspect ratio probe giving the ability to access deep, narrow features with low contact forces so as to not damage the surface and high precision (nanometer level). Additionally microscale probes are susceptible to environmental conditions such as humidity and surface interactions such as stiction (caused by adhesion, meniscus, and/or Van der Waals forces among others).

Technologies to achieve microscale probing include scaled down version of classical CMM probes, optical probes, and a standing wave probe among others. However, current optical technologies cannot be scaled small enough to measure deep, narrow feature, and optical resolution is limited by the wavelength of light. X-ray imaging provides a picture of the feature but no traceable metrology information.

Physical Principles:

Optical probes and/or laser probes can be used (if possible in combination), which change CMMs to measuring microscopes or multi sensor measuring machines. Fringe projection systems, theodolite triangulation systems or laser distant and triangulation systems are not called measuring machines, but the measuring result is the same: a space point. Laser probes are used to detect the distance between the surface and the reference point on the end of the kinematic chain (i.e.: end of the Z-drive component). This can use an interferometrical, focus variation, a light deflection or half beam shadowing principle

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Chapter2

Technical details

2.1 Parts:

Coordinate-measuring machines include three main components:

The main structure which include three axes of motion Probing system

Data collection and Reduction system - typically includes a machine controller, desktop computer and application software

2.2 Features:

They are offered with features like: Crash protection Offline programming

Reverse engineering

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Shop floor suitability

SPC software and temperature compensation.

CAD Model import capability

Compliance with the DMIS standard

I++ controller compatibility

The machines are available in a wide range of sizes and designs with a variety of different probe technologies. They can be operated manually or automatically through Direct Computer Control (DCC). They are offered in various configurations such as benchtop, free-standing, handheld and portable

Chapter 3

Discription

3.1 Specifying Coordinate Measuring Machine

The type, shape, size and dimensional tolerance of the part to be inspected determine the kind of equipment to be considered. Flat parts (sheet metal stampings, plastic, rubber, etc.) can be inspected faster with a video system. An optical comparator is likewise a 2-D device, best for checking profiles or small flat parts by hand. They are not suited for production.

Height Gages, as the name implies, are good for checking heights on a surface plate. Inspecting a hole pattern with this 1-D device by flipping the part, still practiced by some, is cumbersome, time consuming and unreliable. In this day and age, when a small CMM does not cost more than some height gages, this is a truly wasteful approach.

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For 3-D measurements the CMM should be the equipment of choice. A motorized CMM with a powerful computer and software does cost just a few thousand dollars more today than did a manual CMM of the same size twenty five years ago. They were equipped with a digital readout only. The variety and configuration of sensors available today give the user the possibility to inspect just about any type of part, be it a complex aircraft valve body, a plastic or rubber part, a glass lens or polished mold. Line lasers, capable of taking thousands of points per second can digitize an odd shaped part in minutes.

In short, CMMs cover the whole gamut from simple to use manual units with a basic touch probe and software to fully automatic machines in a production environment pre-programmed to inspect the most sophisticated of parts to a fair accuracy. You can have anything in between. Like the survival of the fittest, time has removed inferior designs from the market.

Of the many styles out there the traveling bridge, the gantry and the horizontal arm design are most common with the traveling bridge being the most popular. Horizontal arm units, capable of measuring large envelopes at acceptable accuracies are used mainly for large auto body parts, large weldments, etc.

When selecting a CMM the following issues should be addressed first before looking at accessories: a) size, b) manual or DCC (CNC), c) Inspection room or shop floor application.

(a) The size is obviously determined by your largest part.

Then again if this particular part shows up only 2 times a year, you should reconsider. The smaller the unit the better. On the other hand you also have to look at the configuration of the parts. If you have a part that is 12” wide, for instance, with 3” deep bores on either side that you wish to access with an articulating head, you need an additional 5” of travel on each side. This brings the total travel to 22” with no safety clearance added. Pre-qualifying these positions on the reference sphere further adds to the necessary envelope.

(b) Manual or DCC.

Financial issues aside, this is largely a function of part quantity or a combination of quantity and complexity. A prototype shop should have a manual unit and a production environment requires a DCC unit. Aside from the fact that CNC units have dramatically come down in price, medium part quantities e.g. 10-30 can be efficiently checked manually with a pre-written program. An unskilled operator then simply touches the points on the part as commanded by the screen. The in and out of tolerance condition may be printed out.

A ROI calculations sheet is available for cross-over quantities making a decision as to manual or DCC easy.

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If a part is complex and small, with fine features, a DCC unit is recommended even for small quantities. It is hard to negotiate a .5mm stylus into a 1.5mm hole without breaking it.

(c) Shop floor or inspection room application.

Since an inspection room has to cover all eventualities it should be equipped with a fair size unit, the top of the line software offered by the OEM, an indexable probe head (manual or motorized) and a good selection of styli and extensions. This requires a well trained and/or experienced operator. Any new operator should be well trained by the OEM.

When selecting a shop floor CMM robustness of the equipment has to be considered. Mechanical bearing units are inherently more reliable, since they do not require a constant supply of dry and clean air which can create a maintenance headache. Air bearing CMMs are a poor choice for applications in a dirty environment, requiring an expensive enclosure that a mechanical bearing unit with covers and bellows can do without. The potential user should educate himself on this issue.

Production CMMs are usually dedicated to one or just a few specific parts. Parts should be fixtured. Fixtures can be supplied by the user or the OEM. The same goes for the part programs. Probing systems should be as simple as possible. Motorized probe heads should be avoided in high production situations if the part is not too complex. Probes with detachable stylus modules and a stylus rack may accomplish the same task at half the price if no more than 6-8 orientations are required. Angled styli orientations can be created with stylus knuckles.

Fast start menus make the operation and program selection easy for shop floor personnel.

If the temperature in the shop varies substantially from 68°F (20°C), the standard OEM calibration temperature, you may want to look at a temperature compensation package or purchase a unit with metal scales on metal structures if you inspect metal parts. It is always a good practice to let the part “soak” to reach the same temperature as the CMM.

3.2 Sensors:

The electronic touch trigger probe, the scanning probe, the single point laser, the line laser and the video camera are the sensors offered on CMMs today.

Touch Trigger Probes, being the least expensive yet capable of measuring just about everything on a machined part, are used in the majority of applications. They usually consist of a probe head, fixed or indexable, the touch probe itself and the styli. DCC machines may be outfitted

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with a motorized indexable head (7 ½°), but add substantially to the overall cost. For a few thousand dollars more you can purchase a small DCC CMM.

Probes with detachable stylus modules are a good investment, especially for DCC units. They allow the use of a stylus rack (6 stalls) akin to a tool changer on a machining center. Modules are held in place magnetically and detach in the event of a collision without damaging the probe itself. A multitude of styli (measuring tips) are available from several sources that cover just about any measuring task, from a .3mm ball tip to a 1” diameter disc to a cylinder for thin sheet metal.

Mechanical Scanning Probes are used to gather a high number of points in bores and surfaces of prismatic parts and for digitizing non-linear unknown surfaces. Higher density points give you a more accurate picture of the feature as required by ANSI 14.5 e.g. roundness, cylindricity and flatness. These probes are obviously more expensive than trigger probes and require a high end controller.

The Single Point Laser is also used for digitizing. It is an excellent tool to check the profile of delicate surfaces e.g. coated optics and soft parts since it does not physically touch the part.

The Line Laser is the fastest way to digitize or inspect non-linear surfaces and contours like cell phone housings or car body parts. The lines are up to 2” wide taking 4000 or more points per second. The accuracies range from + .001” to + .00025”. It is a powerful tool in conjunction with CAD software having a 3-D best fit option. The line laser is popular for reverse engineering.

Video attachments for CMMs require additional software and back-lighting and are therefore not widely used.

3.3 Software:

Measuring software is the most important part of a CMM next to the physical structure. It may be your main purchasing criteria. Most OEM’s have their own brand, some do not. You should inquire as to how long the software has been on the market. It is very hard to evaluate CMM software in just a couple of hours unless you are an experienced CMM operator. The big names in the industry do not necessarily have the easiest to use systems, which is what the buyer should be looking for. Whichever software takes the least number of keystrokes or mouse clicks to measure a feature or a complete part is the better one. Fancy graphics and many windows do not measure a part. If time permits take a somewhat complex part to the vendors and compare inspection and DCC programming time as well as the ease to do so.

Beyond user friendliness you may need other features like real time SPC, export to CAD or a 4th axis.

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You should be cautious with the much talked about CMM program writing from CAD. It’s O.K. for simple parts, but a DCC motion program with a motorized head and widely varying styli is fraught with pitfalls. If and when it has progressed to a point where it’s close to being seamless, it would require quite a knowledgeable operator. Most people do not recognize the fact that a CMM is not a simple single point system like a machine tool with only one fixed and defined coordinate system where the part to be machined is always aligned to the axis travels. Therefore a CMM programmer, not necessarily the operator has to have a good grasp of 3-D points in space and coordinate system transformations. Good and thorough training of the programmer is imperative. Once a program is written a lesser trained person may push the buttons. There is many a CMM that sits in a corner because nobody knows how to use it.

When evaluating software you also may inquire about the platform (Windows and C++) and whether there are service contracts with future upgrades available. Proper support is important.

3.4 Accuracy:

The potential user should understand the difference between resolution, repeatability, and accuracy. In brief; resolution is the least count of the measuring system. Repeatability is how well the CMM repeats a given dimension or feature; this is always some multiple of the resolution and includes the non-repeatability of the probe, which in some instances exceeds that of the CMM itself. Linear accuracy, taken along each axis travel, is how much any linear dimension deviates from the absolute NIST standard. The volumetric accuracy is usually determined with a ball bar according to B89.4.1a or another artifact and includes the non-linearity of the ways, out of sureness condition, length variation of all axes to one another as well as the non-repeatability of the probe. Consequently this number is substantially higher than the linear accuracy. If you have a collision, lose the compensation table or upgrade to a better software system down the line, re-mapping the CMM will be expensive. CMMs with intrinsic accuracy have the lowest maintenance cost over their life span.

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Chapter 4

CMM PRODUCTS

4.1 Check master:

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Fig4.1 Checkmaster Benchtop CMMs

Checkmaster Reliability:

The compact Checkmaster is a bench top CMM ideal for lab or production floor. Hardened stainless steel ways and steel scales on steel structures offer uniform linear expansion minimizing thermal errors. The low cost means you can put competent inspection capability in multiple locations throughout your plant.

Intrinsic Accuracy Manual CMM:

We test every CMM before it leaves the factory for repeatability and accuracy, that meets or exceeds the industry standards as defined in ANSI B89.4.1a-1998. Our testing includes a repeatability test that exceed a minimum of 150 cycles, often recording a total range of 2.0 µm (0.00008") or better! These stringent targets are maintained without the need for expensive software compensation maps. Our goal is to build the CMM mechanically correct that will deliver the results you expect, year-after-year.

Every Checkmaster is designed and packaged for fast and secure installation by the customer. All key components are protected during shipping by specially designed brackets, that when removed, ensures the CMM is ready for your first inspection.

4.2 Phoenix:

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Fig4.2 Phoenix

The Phoenix line of CMMs offers two popular sizes to fit your quality inspection needs.

Building on decades of experience with shop floor Coordinate Measuring Machines, Helmel now offers the Phoenix... a heavy-duty, DCC version of its popular Checkmaster benchtop manual CMMs.  The Phoenix is made for harsh environments, with well-placed covers that prevent temperature shock. Its steel measuring scales on metal structures assure uniform expansion.

The Phoenix CMM incorporates all the time-proven features of its "big brother", the Microstar: hardened precision-ground ways, dual beam bridge with reliable V-and-Flat bearing arrangement and intrinsic accuracy. The latter is very important to reliably retain accuracy over time and reduce calibration cost. The Phoenix comes equipped with a full granite base and ergonomic stand.

The motorized system is outfitted with the powerful PMAC controller, the latest computer system and our proprietary GEOMET software, the best CMM package on the market.

4.3 Microstar:

Fig4.3 Microstar “L” Bridge

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Microstar "L" Bridge Type CMMs Series

The "L" Series is Helmel's product line designed for your larger applications.

Large capacity range-of-moving bridge type CMMs built on a massive granite base including a raised granite beam for the Y axis guideway. This design improves the bridge geometry, providing dimensional and thermal stability, while positioning the Y axis drive closer to the center of moving mass Dual beam steel bridge structure. Designed for stiffness, low mass and balance for swift, accurate movements. Suited for lab or plant floor use.

Non-contact optical steel encoder scales, mounted on steel members assure uniform thermal behavior. Solid design emphasizes powerful bearing ratios in its use of hardened and ground ways and precision pre-loaded, mechanical linear bearings, insuring dynamic accuracy. Straight and square construction guarantees intrinsic mechanical accuracy without relying on volumetric error correcting software tricks so you save money on every calibration .

CNC MICROSTAR "L" SERIES CMMs feature a state-of-the-art layout with joysticks, motion controller, PC and the GEOMET Measuring System for Windows. Helmel features the ultimate drive system: brushless non-contact linear motors consisting of a coil between parallel rows of magnets running the full length of travel. There are no other moving parts. Conventional drives must convert rotary motion to linear motion, inducing torque into the machine structure while requiring gear reduction and friction. Our linear motors eliminate the heat, vibration, wear, backlash and cogging of rotary motor systems. Even better, when the motors are off, you are free to use your MICROSTAR for manual measurement.

We use the American made PMAC programmable multi-axis motion controller from Delta Tau , considered to be the most powerful on the market. The open architecture allows it to be easily upgraded in the field as motion features are enhanced.

Our joystick control is enclosed in a durable die-cast aluminum housing with all needed function keys so you won't have to go to the PC every time you want to perform an operation at the machine during the self-teach programming cycle.

4.4Axium:

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Fig4.4 High Precision - 4-Axis Shaft Measuring Machine.

Automatic Shaft Analysisin the Factory Environment:

The Helmel Axium Shaft Measuring Machine has been developed to provide precise, automatic dimensional measurement of cylindrical and shaft-like or manufactured parts. The Axium is well suited to crankshaft inspections. The SMM is hardened for use in production and on the factory floor, and requires minimal training for non-metrology employees.

Designed as a 4-Axis System:

Although the Axium has been designed as a 4-axis measuring system, it can be configured as a 3-axis system to fit your manufacturing needs. The Geomet metrology software is designed for measurement, verification and GD&T applications. The Geomet software is resides on a  powerful Windows based system which contains the motion controller with proprietary motion control software.

The Helmel Axium shaft measuring machine presents a horizontal format, with a major cylindrical axis oriented left to right, duplicating the way most shafts are manufactured and ground. Parts are typically staged between centers, or on solid or rotating Vees. The system employs the Renishaw Touch Trigger or scanning probes for part sensing and can incorporate an automatic stylus changing system for totally automatic operation.

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Chapter 5

CMM Probe System

Electronic Touch Trigger Probes are without any question used in the majority of the measuring tasks. Touching the part physically assures reliable and repeatable measurements.

Renishaw, as the main supplier, has a great variety of Heads and Probes available. We have standardized on a particular selection that has been proven popular and relatively complete. Programmable motorized probe heads for automatic indexing are offered for DCC machines.

We have put together an Probe System Summary Page for your review. This information illustrates the main components of your system and highlights certain applications.

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5. 1 Probe System Configuration Summary:

This page is designed to provide an overview of a complete probe system. Additional information can be obtained from the product links below, and in the left menu.

The mechanical part of the probing system is available in four different arrangements to suit particular applications, CMM sizes and budgets. The styli or measuring tips are common to all systems.

Two Piece System:

The 5-way mechanical switching probe is built into the probe head. The compact design extends the Z-capacity of the CMM. Probe extensions, such as the M8 - PEL family can not be used. Standard extensions between the probe head and styli can be used. The lower cost makes it attractive for small machines or for simple parts on larger machines.

Fixed Head Manual Indexing Heads Motorized Indexing Heads

TP-ES, TP1S/TP1SM    

Three Piece System - M8 Thread Mount:

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The separate touch probe screws into the probe head via a M8 thread. This style allows the use of M8 - 13mm diameter probe extensions (PEL family) between the probe and the head to reach into deep parts, see example below. Touch probes can be exchanged if damaged or worn.

The M8 thread mount is compatible with the standard TP2 and TP6 touch probes.

 

Fixed Head Manual Indexing Heads Motorized Indexing Heads

PH1, PH5, PH6, MP100 PH1(1), MH8 PH10T

Note 1 - PH1 provides non-repeatable indexing.

Three Piece System - TP20, Integral Kinematic Mount:

The separate touch module attaches to the probe head via the integral kinematic stylus mount. The use of this style allows changing of the stylus module, either manually or in conjunction with a stylus change rack, without the need to re-qualify.

This style allows the use of extended length modules to reach into deep parts, see example at right. Stylus modules mount to the probe head using a magnetic mount and can break away from the probe head which provides extended crash protect. The modules can be exchanged if damaged or worn.

Fixed Head Manual Indexing Heads Motorized Indexing Heads

  MH20(1), MH20i RTP20(2)

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Note 1 - MH20 provides non-repeatable indexing.Note 2 - The RTP20 is powered by the motors on the CMM.

Four Piece System-M8 Thread Mount,Stylus Change Module:

The touch probe is a two piece design with a detachable stylus module. Facilitates the use of several pre-qualified styli. Modules can be changed manually or automatically using an optional stylus module change rack with DCC machines. Applies to TP-20 and TP-200 touch probes.

This style allows the use of M8 - 13mm diameter probe extensions (PEL family) between the probe and the head to reach into deep parts.

Fixed Head Manual Indexing Heads Motorized Indexing Heads

PH1, PH6, MP100 PH1(1), MH8 PH10T

Note 1 - PH1 provides non-repeatable indexing.

 

SP25 Compact Scanning Probe System:

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The SP25 scanning system is attached to the probe head through the use of an autojoint. Supports both scanning and touch-trigger operations through the use of the TP20 stylus modules.

The scanning system can utilize a variety of SM25 modules to extend the reach between 20 mm (0.78 in) to 400 mm (15.75 in). The probe system can be mounted on the PH10M/MQ motorized probe head. For a complete description of the SP25 probe system, click here.

Requires the use of the Renishaw UCC scanning controller.

Fixed Head Manual Indexing Heads Motorized Indexing Heads

PH6M   PH10M

 

 

5.2 CMM Probe Heads :

Your probe system starts with the Probe Head. The selection of the probe head will determine the touch probe type, extension capabilities, articulation and even scanning.

 

TP-ES:

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CMM Style: Manual and DCC

Two piece system, one body mounted in a fixed vertical axis. Most economical touch probe. Includes the Standard Probe Kit listed here, plus a M3/M2 adapter.

TP1S/TP1SM:

CMM Style: Manual and DCC

Two piece system, one body mounted in a fixed vertical axis. The TPs/TPSM is a 1 inch diameter, shank mounted probe that is ideally suited for manual CMM operations due to its robust design and extended over travel range. It has an M3 stylus mount that carries a wide range of styli.

 

PH6:

CMM Style: Manual and DCC

The compact vertical and fixed head accepts all M8 mounting probes (TP2, TP6, TP20, TP200). Economical approach if indexing is not required. Recommended for production applications in conjunction with the stylus rack with up to 6 stylus configurations.

Compatible with the MCR20 and SCR200 stylus change racks.

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PH6M:

CMM Style: Manual and DCC

The PH6M is a fixed head with an autojoint connection that is compatible with multiwired probes SP25M, SP600M and TP7M. TP20 touch probes can be used with the use of the PAA1 adapter.

PH1:

CMM Style: Manual and DCC

A manual probe head that offers non-repeatable, articulation in the A and B axes. The A axis swivels 0° to 115° with a cap head lock screw. The B axis rotates 360° in 15° spring tensioned indexable increments. Offers limited over travel for crash protections. Accepts all M8 mounted touch probes (TP2, TP6, TP20, TP200).

 

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PH5:

CMM Style: Manual and DCC

A manual probe head that offers support for up to 5 M8 style probes heads. Accepts all M8 mounted touch probes (TP2, TP6, TP20, TP200).

CMM Style: Manual and DCC

Manually indexable probe head with 720° repeatable positions eliminating the need to re-qualify. Provides indexing 360° in the horizontal plane and 105° of elevation in 7,5° steps. Accepts all Autojoint mounted touch probes (TP7M, TP6A) or M8 style touch probes when using the PAA1 adapter (TP2, TP6, TP20, TP200).

MH8:

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CMM Style: Manual and DCC

Manually indexable probe head with repeatable positioning eliminating the need to re-qualify. Provides indexing 360° in the horizontal plane and 90° of elevation in 15° steps. Accepts all M8 mounted touch probes (TP2, TP6, TP20, TP200).

Compatible with the MCR20 and SCR200 stylus change racks.

MH20i:

CMM Style: Manual and DCC

Manually indexable probe head with a built in TP20 probe and kinematic mount for TP20 modules. The exchangeable modules allow the use of multiple styli configurations eliminating the need for re-qualifications. Provides indexing 360° in the horizontal plane and 90° of elevation in 15° steps.

Note: The MH20i is not compatible with the MCR20 module change rack.

RTP20:

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CMM Style: DCC

A low cost / low profile solution to index the probe head automatically. This compact probe head is designed for use on DCC style CMMs only. Indexes in the A and B direction in 15° increments utilizing the powered axes of the CMM  to articulate and lock the probe head. Based on the MH20i probe head and compatible with the TP20 touch probe.

Compatible with the MCR20 stylus change rack.

 

PH10:

CMM Style: DCC

The new PH10T motorized probe head allows complete, rapid, and repeatable inspection of most complex components with minimum human intervention. Full orientation of your TP2, TP6, TP20 or TP200 probe between any of 720 positions, under manual or program control, turns your 3 axis CMM into a 5 axis machine. Index steps are 7,5°.

Compatible with the MCR20 and SCR200 stylus change racks.

PH10M:

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CMM Style: DCC

The PH10M probe head is designed with the Autojoint to accommodate longer extensions (300 mm) as well as the heavier scanning probes, SP25M, SP600M and TP7M. The autojoint is compatible with the ACR1, probe and extension change system.

With the use of the PAA1, standard M8 mounting touch probes can be used (TP2, TP6, TP20, TP200). When using the PAA1 adapter, the system is compatible with the MCR20 and SCR200 stylus change racks.

 

MP100:

CMM Style: Manual

The MP100 MultiProbe is designed to extend your manual CMM capabilities by including a video, non-contact probe system to compliment your existing touch probe capabilities.

The MultiProbe includes a high-resolution color CCD camera with a video crosshair generator and LED ring illumination. The unti incorporates a M8

 

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5.3 CMM Touch Trigger Probes:

A key member of your probe system selection is the touch trigger probe. The touch trigger probe provides the connection between your probe head and the stylus and contains the necessary trigger capability to record a data point, or scan data when in contact with the artifact.

Some touch trigger probe models provide stylus separation extending the range of functionality for your CMM.

TP2 Touch Probe:

This is the traditional slimline switching probe for most applications. The small diameter, 13mm or 0.51", allows access into restricted areas. Its adjustable stylus force enables the probe to support a wide range of styli and extensions. Can be attached to the ends of the same diameter extension bars (PEL family) for longer reach. For manual or DCC applications.

Available in the 6-way configuration for minus-Z measurements.

Fixed Head Manual Indexing Heads Motorized Indexing Heads

PH1, PH5, PH6, MP100 PH1, MH8 PH10T

TP6 Touch Probe:

A larger, more robust probe than the TP2. The body diameter is 25mm or 0.98". Recommended for shop and production applications. The extended stylus force range of 10g-30g allows the use of longer styli without the problem of false triggers.

The TP6A model connects directly to the Autojoint mounting on compatible probe heads.

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Fixed Head Manual Indexing Heads Motorized Indexing Heads

PH1, PH5, PH6 PH1, MH8 PH10T

TP20 Modular Probe System:

  Mounting M8

    

Mounting Magnetic, Indexed

Stylus Mounting M2

Repeatability±0.35 µm (±0.000014") to±0.65 µm (±0.000026")

Lobe Variation±0.6 µm (0.000023") to±2.0 µm (0.000079")

Trigger Force XY: 0.06 N to 0.10 N

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.

Available in the 6-way configuration for minus-Z measurements.

*NOTE: The RTP20 utilizes the motorized axes of the CMM for articulation.

Fixed Head Manual Indexing Heads Motorized Indexing Heads

PH1, PH5, PH6, MP100 PH1, MH8 PH10T, RTP20*

TP20 Stylus Modules:

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CMM Style: Manual and DCC

The MCR20 system has 5 standard length modules, plus two extended length modules to fit your inspection needs.

These modules also mount directly to the MH20 and MH20i indexing probe head without the use of the TP20 touch probe body.

  Force TriggerBody

Length Max Stylus Len.

LF Low 0.06 N 13 mm 10 mm

SF Standard 0.08 N 13 mm 10 mm

MF Medium 0.10 N 13 mm 25 mm

EF Extended 0.10 M 13 mm 50 mm

6W 6-way 0.14 N 24 mm 10 mm

EM1 Standard 0.08 N 88 mm 10 mm

EM2 Standard 0.08 N 113 mm 10 mm

 

TP200 Modular Probe System:

Probe Body

Mounting M8

Probe Interface - PI200

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The TP-200 is a highly sensitive and accurate probe based on micro strain gauge technology. It favors a detachable module like the TP20; the outside appearance is quite similar. The body diameter again is 13mm (.51"). 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 CMMs.

Fixed Head Manual Indexing Heads Motorized Indexing Heads

PH1, PH5, PH6 PH1, MH8 PH10T

 

SCR200 Stylus Modules:

CMM Style: DCC

The SCR200 system has 3 stylus modules to fit your inspection needs. The EO module is designed to provide extended Z-Axis over travel of 12.5 mm to higher speed applications where the CMM may require extended over-shoot distances.

 

  Force TriggerBody

Length Max Stylus Len.

LF Low 0.06 N 13 mm20 mm

50 mm (1)

SF Standard 0.08 N 13 mm 50 mm

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100 mm (1)

EO Standard 0.10 N 24 mm50 mm

100 mm (1)

Note 1 - Carbon Fiber Styli

TP7M Strain Gauge Probe:

Mounting Autojoint, Multiwire

Stylus Mounting M4

Repeatability 0.25 µm (0.000009")

Trigger Force XY2.0 g

Trigger Force Z 15.0 g

The TP7M is based on strain gauge technology which provides a higher accuracy than standard touch probes. This technology should only be used on DCC style CMMs where the contact speeds can be controlled and constant. Requires the use of the PI7-2 probe interface.

Fixed Head Manual Indexing Heads Motorized Indexing Heads

PH6M   PH10M

SP25M Scanning Probe System:

Mounting Autojoint

Mounting Magnetic/Optical

Resolution <0.10 µm (<0.00004")

Stylus Length 20mm - 200mm

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The SP25M scanning probe system has a compact 25mm diameter body that supports scanning and touch trigger probe configurations. There are 4 scanning modules to support various length styli and one TP20 touch probe adapter to data point capturing.

The SP25M system works with the UCC2 CMM Controller which provides full scanning and touch point operations. This system can be mounted on any Probe Head that supports the Autojoint with multiwire.

Additional accessories include various changing racks to fit your needs.

Fixed Head Manual Indexing Heads Motorized Indexing Heads

PH6M   PH10M

 

SP25M Scanning and Touch Probe Modules:

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CMM Style: DCC

The SP25M system has 4 scanning  modules that provide a variety of stylus length, plus one TP20 touch probe adapter module to perform standard data point capturing.

 Body

Length Max Stylus Len.

SM25-1 26.25 mm 20 mm - 50 mm

SM25-2 33.85 mm 20 mm - 75 mm

SM25-3 48.05 mm 20 mm - 100 mm

SM25-4 63.05 mm 20 mm - 200 mm

TM25-20 16.95 mm Module Dependent

MP100 MultiProbe, Video and Touch Probe:

Mounting Direct, Helmel Mount

Auto Zoom 44x - 288x

Digital Crosshair Generator

Color Video

LED Ring Illumination

The MP-100 Video Probe is intended for use with manual CMMs, and provides an accurate means of measuring 2D features, such as printed or etched images like circuit boards, where tactile probes are not effective. It is normally used to measure features in the XY plane, and is positioned manually by means of the locks and fine adjustment knobs. Positions are entered via the keyboard or footswitch.

The system includes a high resolution color camera, flat panel monitor, 6:1 motorized zoom lens, variable intensity LED ring light, a multifunctional crosshair generator, a control console, mounting shank, and cables.

As an added benefit, the MP-100 includes support for the standard Renishaw PH6 probe head and includes support for touch probes such as the TP2, TP200 and TP20. This

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will save having to remove one to use the other.

 

5.4 To select a stylus that will enhance your inspection, we recommend:

Stylus ball size and length:

A ball stylus, when used during the inspection process produces a single point of contact with your artifact. Variations in surface condition affect repeatability. To counter this, it is recommended to use as large a ball stylus as possible.

Furthermore, identify the shortest possible combination of stylus and extension that will still allow you access to all features being inspected. The longer the probe system, the greater the pre-travel length before the trigger occurs. In some cases, the relationship between the ball size and shank size can impede the depth the stylus can go into smaller features. Care must be taken to prevent the shank from contacting your part during the inspection process. This condition is exaggerated when using small ball size and long extensions.

Some inspection processes require long reaches to make contact on a feature, otherwise most features have short access distances. To counter this, it is recommended to utilize stylus change racks where the touch probe can switch stylus configurations to optimize the inspection results.

Chapter 6

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Intrinsic CMM Accuracy

6.1 Intrinsic Accuracy means that the CMM accuracy specifications are met by virtue of the physical and mechanical precision and repeatability of the machine structure, geometry and scales. You can measure accurately with just the Digital Readout and hard probes, or with dial or electronic indicators. The machine is constructed and assembled to be straight, square, stable and has accurate measuring scales.

a CMM can be constructed and assembled less conscientiously, and may be physically straight and square to only a few or even many thousandths of an inch. This would be a terrible CMM, but it can be fixed. By use of a laser or other instruments the specific inaccuracies of the machine can be measured and detected throughout the machine volume. The volume can be gridded or "mapped" by software, and corrections can be made for any position in the volume. Thus, measurement results can be compensated for, and accuracy can be produced. There is nothing inherently wrong with this electronic error compensation provided it is not used as a quick fix to cover up machine deficiencies.

If a CMM measures accurately with error comp, and meets specification, then why worry whether the machine is intrinsically accurate? Here are some points to consider :

• The uncompensated accuracy of a CMM is an indication of the quality of the underlying product. It is much more difficult to produce a CMM with uncompensated volumetric accuracy of .0005" than .005", obviously. To achieve it, each component must be made to exacting standards, and checked closely. Extreme care must be taken in assembly so that axes are set perfectly straight and square to each other. Every bearing must be tested and hand selected, and the same applies to the measuring scales. Mounting surfaces, guide ways, or both may have to be hand lapped to produce the necessary precision. With every element subjected to severe scrutiny, and the ultimate assembly tested throughout every position along the length of travel repeatedly, only a product of the highest quality can make it to the shipping dock.

• A lesser machine can be assembled with less precise, even lower quality components, by far less skilled people. It can be assembled without great concern for its raw performance or precision, because everyone involved in the process understands that at the end of the line, any flaws or inaccuracies, even poor component or assembly quality, can be "fixed" with a laser, computer and software. therefore, must be a "better" machine than the equivalent CMM claiming only .0005" accuracy, even though the later machine offers intrinsic mechanical accuracy.

CMM Maintenance

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The necessity of a clean air supply for air bearing machines has already been covered. This problem is nonexistent with mechanical bearing units.

Some people are concerned about chips. Our latest designs enclose all ways under covers or bellows to protect them against dirt, dust, oil and chips. The economical Checkmaster is equipped with wipers. Should a chip find its way in and cling to the bearing or way, it will make itself known immediately and can be removed quickly. That same chip can find its way just as well between the air pad and way of an air bearing machine, and is much more likely to do serious and costly damage there than to our machine.

As traditional QC decentralizes, CMMs are migrating to the shop floor where some regular preventive maintenance is important. The simplicity and reliability of mechanical bearings becomes even more advantageous here. Mechanical bearings are extremely accessible and can easily be cleaned or oiled when necessary. Air pads are less accessible, require more caution and skill and take longer to perform preventive maintenance.

The Helmel CMM construction is an elegantly simple and uncluttered concept designed for ease of assembly and therefore ease of service.

 

Fig6.1 Flat Bearing Design

An example is the gravity loaded V-and-Flat design, see figure 1, employed in the X-axis of all models and certain Y-axes. This approach has been used successfully in machine tools for over 100 years. It never needs adjusting. Again: improved reliability and less service!

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Fig6.2

Please compare this to a typical air bearing system as shown in figure 2. Imagine adjusting all those pads by means of a threaded stem and a jam nut, keeping an eye on the delicate air gap and squareness at the same time.

Operating costs should also be considered. An air bearing CMM will consume $500.00 to $2,000.00 worth of compressed air each and every year, over and above the installation cost of the air supply line and filter system. This cost is non-existent with Helmel machines.

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Uses

They are often used for:

(1) Dimensional measurement

(2) Profile measurement

(3) Angularity or orientation measurement

(4) Depth mapping

(5) Digitizing or imaging

CONCLUSION

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Extended research and practical application have shown that CMMs can be very powerfultool for calibrating measuring standards and instruments. They shall be, however, alwaysused together with calibrated standards of measurement. The most universal traceable highprecision standard for such use is laser interferometer. Application possibilities have beentested but not yet fully applied in our laboratory. Some uncertainty estimation models havealready been developed and environmental conditions put fully under control. However,many research possibilities, especially those related to the uncertainty of measurement, arestill open. Further work will be focused into development of measuring setups for laserapplication including special flat mirror optics. Additional probing systems with betterrepeatability will be tested, too. It is also planned to develop measuring software forcalibrating lots of measuring standards - especially setting rings. One of the most importantstandards to be calibrated on the CMM is step gauge, which is widely used in industry andcalibration laboratories.

Reference

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Wikipedia, the free encyclopedia.

http://brownandsharpe.com/vision-metrology-solutions. www.helmel.com.

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