WP1: Framework

The aim of this work package is to develop a framework that embodies the scientific and technical backgrounds of in-process dimensional measurements, stakeholder needs and expectations viable to guide this JRP in developing new standards and procedures for assuring traceable in-process measurements. This work package will consider existing in-process material standards, machine performance evaluations, in-process product quality assessments, etc. detailed information on the existing methods, procedures and instrumentation for in-process measurements and the various environmental conditions on the shop floor. These are essential for the success of the JRP. Other areas that will be investigated include: measurement accuracy requirements for different in-process measurement tasks, and for the definition of boundary conditions such as measurement ranges (e.g. machine tools with integrated tactile and optical probes or integrated portable articulated arm CMMs).
This work package will provide technical information about in-process metrology so that the procedures and methods developed align with the needs of end-users as well as with those of machine tool manufacturers.

Leading NMI: CMI

Interim Summary WP1:

This WP is aimed at developing a framework with scientific and technical backgrounds of in-process dimensional measurements. The tasks of this WP is focused on collecting relevant technical information about existing standards, methods, procedures, stakeholders requirements and machine tool manufactures needs in the area of in-process metrology taking into account the variability of different factors (machine tools, workpiece processing, environmental conditions, geometric features etc.).
The work in Task 1 "Review of existing and related in-process measurement standards" was lead by NPL with participation of CEM, PTB, UM, LNE, Metrosert, MIKES and REG(Aalto). This review was concentrated on comprehensive summarization of existing written as well as material measurement standards which are used in in-process quality control procedure. The following reports were produced.

  • Report on relevant written standards for in-process metrology detailing existing standards of dimensional measurements, including those in use and those under development – the main series of written standards applicable to machine tools and machining centres are included in this report (such as those from ISO/TC 39 Machine Tools, ISO/TC 184 Automation systems and integration and ISO/TC 213 Dimensional and geometrical product specifications and verification).
  • Report on existing material measurement standards relevant to dimensional in-process measurements, which gives an overview of existing material measurement standards applicable for the traceability of in-process measurements on machine tools such as gauge blocks, step-gauge, ball-plate, hole plate, hole bar, multi-feature-check, ball-bar, rotary axis analyser, spindle inspector, position inspector, position analyser system, spindle analyser, grid encoders and comparator system.
  • Report on the end-user survey of existing measurement standards for different applications in in-process metrology, which summarises results of a pan European survey of companies from aero industry, car as well as of small independent companies. The aim was to find out the standards which they use and to identify any issues that they have with using these standards.
  • Report on the evaluation of roundness measurement standards with form errors or specific harmonic content, which describes existing material standards for roundness measurements such as hemispheres, flick standards (cylinders with a flat part), ellipse standards (single wave), multi-wave standards and asymmetric multi-wave standards.

Task 2 "Study of in-process metrology" lead by CEM in cooperation with MIKES, Metrosert, REG(KIT), REG(Aalto), MAG IAS, Daimler, IK4-TEKNIKER and UNIZER was focused on investigating the current situation and future requirements of in-process dimensional metrology. Following documents were produced.

  • Review of in-process metrology with an emphasis on the influence and contribution of environmental conditions to the measurement errors of machine tools – the report lists different methods of in-process dimensional and shape measurements of workpieces and environmental influences (temperature gradients) on results of these measurements.
  • Report on the achievable measurement accuracies for in-process measurements with specific examples of a typical machine tool – the current achievable measurement accuracies obtained by applying in–process metrology procedures are discussed in this report and demonstrated on conventional 3-axis high speed machining centre, ultraprecision 3-axis micro-milling machine machining of moulds and dies and CNC milling machine.
  • A report reviewing the economic impact of different applications in in-process metrology – the economic impact of the measurements made directly on the CNC machine in metal rolling, paper industry and low and high volume serial production is analysed in this report.
  • A report on the challenges in roller measurement and machining as currently encountered by roller manufacturers and end-users – the challenges in the measurement of the rolls for steel and paper industry mainly in the area of calibration, measurement accuracy and measurement duration are specified in this report.

Based on the previous tasks, task 3 "Develop a valid definition of traceability and verification requirements for in-process metrology" lead by CMI in cooperation with NPL, PTB, Metrosert, MIKES, REG (Aalto) and REG(KIT) was focused on the formulation of solutions in the field of traceability and verification of in-process metrology on machine tools in dimensional metrology. The obtained results are summarized in:

  • A report describing the methods of in-process measurement verification – which studies methods of in-process measurement verification that are available in mechanical engineering, tool making industry, power generation and transmission relating to wind energy systems, metal cutting industry and automotive industry.
  • A report describing procedures for assessing the “fitness-of-purpose” of machine tools with an integrated on-board metrology system.
  • A report on traceability routes for size, form and position measurements on machine tools focussing on free-form measurements, regular geometric elements and volumetric error mapping of machines.
  • A catalogue describing the general requirements of the material standards of machine tools for ensuring traceability of on-machine measurements even under harsh environmental conditions.
  • Requirements for the measurement standards qualified to ensure the traceability of roundness measurements used in roller machining processes and in in-process run out measurements.  

Task 4 "Developing a unified technical concept for mapping measurement errors" lead by CMI in cooperation with CEM, PTB, UM, IK4-TEKNIKER, UNIZAR, REG(KIT), Daimler, MAG IAS was focused on the development of general technical approaches for mapping in-process measurement errors taking into account the variability of machine tools, workpiece processing, environmental conditions, geometric features, etc. The following documents were produced:

  • A methodology for making traceable surface temperature measurements in in-process conditions - which gives an overview about temperature sensors and their traceability, testing body requirements, calibration of contact thermometers.
  • A report summarising the technical considerations for the mapping of machine errors, in which issues are discussed such as volumetric error mapping and its limitations by thermal stability, clearances and repeatabilites, ambient effects on error characterisation techniques, state-of-the-art of machine verification and application of multi-lateration techniques. Refinements to the VCMM were proposed.
  • A report on practical approaches for the evaluation of machine tool measurement errors which investigates 3 approaches for evaluation machine tool measurement errors regarding the determination of measurement uncertainties and the assessment of maximum permissible deviations of in-process measurements taking into account only machine errors.
  • A guide for evaluating the influence of harsh environmental conditions on measurement results – that investigates methods and procedures for determining task-specific measurements uncertainties taking into account the entire measurement process.


WP2: Robust measurement standards

The aim of this work package is to deliver highly accurate robust material measurement standards, that can be used in the harsh environment of the production floor for verification and mapping of the measurement errors of machine tools. The associated procedural instructions will be developed in WP4. These procedures will be used to enable the mapping of volumetric and task-specific measurement errors and to determine the achievable measurement uncertainty. The latter is a prerequisite for assessing fitness-for-purpose, e.g. to confirm whether or not a machine tool is capable of inspecting various feature elements of the machined parts to the required uncertainty.

Leading NMI: NPL

Interim Summary WP2:

The ‘Robust measurement standards’ work package is aimed at designing and delivering highly accurate robust material measurement standards, that can be used in the harsh environment of the production floor for the verification and mapping of the measurement errors of machine tools. The participants of this work package include: PTB, CMI, MIKES, UM, Metrosert, LNE, Veplas, EMO, IK4-Tekniker, REG(Aalto), REG(KIT), Mag IAS and NPL as the work package leader.

During the running of the work package up to the current midterm period, there have been no discernible delays in its delivery. However, due to the chronology of the individual deliverables, two of the deliverables have been re-assigned new start dates, namely “Report on the comparison of data sets to reverse engineering the CAD model”, having a new start date of April 2015, and “Report on the inter-comparison measurements of the material standards” which will now start during  August 2015.

A report listing the machine tools and their working space has been completed; this report will assist in the design of the material standards that will be manufactured for this project.
The basic design concept of the proposed material standards has been specified in a report. This report is a compilation of the individual material standards, specifying such proposed attributes as: size, construction, assembly. From this report and other proposed designs, a further report was compiled that detailed the final material standards to be manufactured. This report specifies certain attributes for the designed standards,  suitable construction materials, methods of manufacture and techniques suitable and adequate for the intended use. The different standards are designed for a specific application. Following on from the design report, a report describing the individual requirements of the material standard is listed. These requirements include items such as: manufacturing technique, material, surface finish, handling, cleaning, storage, transportation, calibration.

The finding from the investigation of the optical properties of different materials which may be suitable for the manufacture of measurement standards has been documented. The report studied a selection of typical manufacturing materials and designing methods to evaluate properties commensurate to the measurements of material standards using optical techniques, such as fringe projection and line scanners. The report investigated surface properties such as: roughness, colour, reflectance, and measurement angle.

Another report on the subject of mathematical modelling of the behavior of a selection of material standards at different temperatures between 10 °C and 30 °C has been carried out as a complementary analysis for specifying the fundamental attributes for the measurement standards that shall be manufactured. Finite element analysis (FEA) was used to detect potential problems, e.g. non-homogeneous temperature variations in the standard, and to evaluate internal stresses and possibly form deformation. To ensure that a typical temperature fluctuation would be within the chosen limits of the FEA analysis, an in-house study of the variation of the temperature of the cutting fluid on an NPL milling machine over a period of two weeks, was also completed. A presentation of the findings of this report was given in the mid-term meeting. A publication of the findings will be submitted to an external journal.

A listing of the standards that have been selected for manufacture has been compiled. The manufacturing of all the material standards has been completed, however, some remedial on a selection of standards may need to be completed. The individual material standards are given in Table 1 below:

PTB: Hole-plate

UM: Ball bar

LNE: Hole bar

NPL: Rotating squares

NPL:Prismatic geometries

NPL: eccentric cylinders

PTB: Multi feature check

CMI:Hyperbolic paraboloid

MIKE/Aalto: Disc

Table 1 Images of the material standards.

Guidelines containing directives which describe the procedures to be used for the calibration of the all measurement standards have been written. These procedures will be used in the intercomparison of the material standards in conjunction with other project members. It is proposed that this intercomparison shall be completed by August 2015.


WP3: Mobile simulation chamber

The aim of this work package is to develop, manufacture and verify a mobile shop floor chamber suitable for simulating manufacturing and machine tool environmental conditions (e.g. temperature, humidity, air circulation, light, sound, vibration, etc.). The chamber will be used for specifically investigating the thermo-mechanical behaviour of machine tools and for analysing, in general, dimensional measurements on machine tools as they are being influenced by the environmental conditions of the shop floor. The varying environmental conditions on the manufacturing floor account for a huge percentage of dimensional measurement errors on a machine tool, most especially, temperature. With the help of the simulation chamber it will be possible to adjust the environmental conditions as obtained in the production environment within a short time. The goal is to facilitate the investigation and to examine quickly the influence of environmental conditions on the machine geometry, the manufacturing process and the measurement accuracy.

Leading participant: REG(KIT)

Interim Summary WP3:

Work package 3 deals with the design and construction of a mobile climate simulation chamber for machine tools. This kind of mobile simulation chamber is a completely new development which has not been investigated before. Due to the fact that the requirements between a simulation chamber and the mobility aspect are quite diverse the design phase is challenging. It can be said that the chamber will have a high degree of innovation and will offer a variety of possible applications. The design of the mobile simulation chamber is highly influenced by requirements derived from the aim to use it for metrological experiments and investigations. The work package and its deliverables can be transduced in the following steps that are distributed over the work package runtime:
1.    Review of in-process metrology
2.    Design of material standards
3.    Concept for a mobile climate chamber
4.    Fabrication and assembly
5.    Measurements and optimisation
6.    Interface for machine tools and measuring devices
7.    Performance testing
8.    Demonstration

Steps 1 to 3 have been completed successfully with the key achievement in the dimensioning process of two feasible concepts for mobile simulation chambers: one specification with regulation of both temperature and relative humidity in specified operational areas (concept A) and another specification with the regulation of the temperature (concept B). Two concepts were required to be able to achieve a reasonable trade-off between costs and expected fitness of purpose of the climatic cell. Therefore a choice between the concepts was made and resulted in the realization of concept B because of the low expected, additional value that comes with the simulation of relative humidity on systems that are hardly affected by it such as tactile measurement systems.
After the dimensioning process of the climatic components a list of materials was created with all functional components for the ordering process before the assembly of the climate chamber could be initiated. The main components can by separated in four main groups: I) Housing, II) RLT-device, III) Coldwater-/Recooler-/Pump-/Expansion-Module and IV) active subsystems.
The complete system’s arrangement can be seen below.
                                 Figure 1: Schematic system arrangement
The housing is characterized by modular wall elements with low thermal conductivity and a high leakproofness to maintain an acceptable degree of thermal stability.
                                            Figure 2: Modular housing concept
The modified specification of the concept with the regulated temperature was translated into a functional system with a precise description of required parts and their interactions. This list will be published in the search for potential industrial providers that can deliver and assemble the functional simulation chamber. The Coldwater-/Recooler-/Pump-/Expansion-Module is responsible for the handling of the medium between the spots of heat transfer both inside itself and the climate chamber in the process of air conditioning in the RLT-device. The connections of the air pipes to the RLT device are shown in the Figure 3. The blue coloured textile hoses are responsible for the distribution of the conditioned air inside the chamber which is sucked out by the fan that is connected to the red coloured air pipes.                                                                                   
                                                Figure 3: Air pipe arrangement
Additional subsystems that will be installed in order to evaluate the influence of harsh environmental conditions are vibrators that can be attached to surfaces and are able to inflict periodic oscillations.
Other active parts beside the surface vibrator are infrared heating bulbs that will imitate local heat spots inside the working/measurement area of the machine tool.
The next activities according to the presented tasks will be the assembly of the climate chamber and its testing after the ordering process of the main components.


WP4: Procedures for ensuring reliable measurements on machine tools

The aim of this work package is to develop procedures that are qualified and adequate to be used for the implementation of acceptance tests, re-verification, volumetric and task-specific error mapping, correction of the measurement errors of machine tools and for the optimisation of the machining process. In addition, guidelines will be prepared on how the fitness-of-purpose for dimensional measurements on machine tools can be best proved. In developing the procedures, various machine tool conditions that are influential to measurement accuracy and to the traceability of the measurements, such as the heat generated from the machining of the workpiece, environmental factors, dynamic forces and other systematic errors will be considered besides kinematic error contributions.

Leading NMI: PTB

WP5: Demonstration and integration focused on end-user needs

The aim of this work package is to demonstrate to the end-users, machine tool manufacturers and to others that the output of the JRP is suitable for the improvement of measurements on machine tools and the manufacturing quality of machined parts. The robust measurement standards and procedures developed will be applied and tested under industrial conditions. A number of companies have been contacted to accompany the funded JRP-Partners in testing the material standards (WP2), simulation chamber (WP3) and measurement accuracy procedures (WP4). The demonstrations will be performed through real measurements of standards and subsequent workpiece measurements in affiliated industries.

Leading NMI: PTB

WP6: Creating Impact

The goal of this JRP is to ensure a wide dissemination of the standards and procedures developed within the five major technical work packages, to the manufacturing industries, machine tool manufacturers and to various end-users of the machine tools, as well as to in-process metrology at large and beyond.
This WP has three major objectives:

  • Knowledge transfer and dissemination via stakeholder interaction, paper publications, conferences, a workshop, good practice guides, stakeholder group and the JRP website.
  • Training and dissemination of JRP knowledge via standardisation bodies, workshops, direct visits, exchange of staff and video conferences. 
  • Exploitation of JRP results on new procedures, on in-process parts quality assessments, machine performance evaluations, and on the simulation of machine working environments.

Leading NMI: PTB

WP7: JRP Management and Coordination

The project will be managed and coordinated by PTB.

Leading NMI: PTB