Integrating laser measuring technology expands the possible applications of process measuring technology in grinding machines, supporting the user in his efforts to increase efficiency in precision machining. Article by STUDER.
Finishing processes on grinding machines often demand exacting tolerances in relation to dimension, form and position accuracies, as well as highly accurate surface qualities. Often, companies have empirical values available to fulfil these requirements.
However, with small lot sizes in particular, process evaluation on the machine is desirable, as intermediate measurement on external measuring machines and the resulting corrections prolong the processing time for part machining. These control measures would significantly increase process reliability and productivity. Solutions that can be flexibly used for a wide variety of workpieces are ideal and preferable.
Measuring Technology in Grinding Processes
Production engineers have diverse measuring functions available for process evaluation, which are based on different principles of production measuring technology. The measurement of process forces such as grinding forces (Ft, Fn) or comparative grinding spindle currents, for example, provide an index for achieving the service life of tools or, equally important, they enable the determination of fluctuating allowances, which can influence process stability and compliance with required tolerances.
In addition, tool costs can be reduced, as excessive dressing is prevented. Familiar acoustic touch sensors assist so-called contact detection in the grinding process to reduce grinding time, or monitor the true-to-profile dressing process with its envelope curve functions. Tactile measuring systems such as measurement and control systems for diameters or workpiece lengths, pneumatic systems or microsensors for longitudinal expansions of spindle systems also support increased process reliability.
Other measuring functions can also be described here, such as the use of camera or laser systems for process monitoring. Laser measuring technology in particular opens up interesting fields of application.
Integrating Laser Measuring Technology into Grinding Machines
STUDER can draw on more than 10 years of experience in the use of machine-integrated laser measuring technology, which have been evaluated for trials in the measurement of grinding wheels or workpieces. Such fundamental studies have a tradition at STUDER, to ensure the company is prepared for future trends in production technology. This knowledge and experience has been used to respond to the current requirements. The systems used in other industries for tool monitoring have been further developed by STUDER, on the basis of the latest laser measuring technology, only recently available, for measuring workpieces on grinding machines.
Users of Renishaw’s XM-60 multi-axis calibrator can now benefit from a new single-axis horizontal stage. This enables precise alignment in applications without an axis perpendicular to the travel. Precision translation of the XM-60 launch unit is easily achieved with the horizontal stage, without disturbing yaw alignment. This feature is particularly useful for applications such as stages and printers.
XM-60 is a laser measurement system capable of measuring errors in six degrees of freedom along a linear axis, simultaneously from a single set-up. It has been designed to measure motion errors directly, by aligning the laser beams with the axis under test. This reduces the inaccuracies which can result from complex mathematics used in alternative measurement techniques. Direct measurement makes comparison, before and after adjustments, a quick and simple task.
A vertical stage that can be used separately or in combination with the horizontal stage will be available later in 2020.
At the upcoming TUBE trade fair, Dango & Dienenthal (D&D) is going to unveil its new laser-supported tool for high-precision sizing of pipes. The Pipe Sizer achieves its extraordinarily high precision level thanks to a laser triangulation sensor which measures the internal contour of the pipe simultaneously with the sizing process. Another benefit of the new tool is that it dramatically cuts the time needed for pipe sizing.
The core element of the system is the expander. This unique component features six axially arranged expandable forming dies that cover the entire internal circumference of the pipe. Each die can be expanded separately by means of a hydraulic cylinder. As each cylinder can be individually actuated, it is possible to size the pipe ends highly precisely and efficiently by actuating only those dies relevant for the sectors of the pipe circumference that need sizing.
Unique about this pipe sizing tool developed by D&D is that it comes with a 360 deg circumference laser which measures the internal contour over the pipe’s complete circumference, generating – in real time – an exact high-resolution image of the internal pipe wall.
High-precision input for high-precision control
The pipe to be sized is fed onto the pipe sizer by means of a roller table. During this process, the 360 deg circumference laser measures all geometry data needed for the subsequent sizing process. From these measurements, the dedicated software calculates the actuation values for each one of the six expandable dies.
During the sizing process, the dies are individually expanded exactly to the point and with the pressure needed to achieve the desired internal contour of the pipe. When the process has been completed, the laser re-measures the contour. In the event that the pipe wall has sprung back, the control software re-calculates the actuation values for a second sizing cycle and the sizing process starts anew.
Each one of the six dies covers a sector of 60 deg. It may happen that the contour measurements show that the pipe wall needs to be expanded at a point located between two adjacent dies. In this case, the pipe can be rotated on the roller table.
The first pipe sizing machine of this type designed by D&D will be used for sizing the ends of pipes with diameters ranging between 400 and 1,000 mm and wall thicknesses between 20 and 60 mm.
Denis Albayrak, Sales Manager at Dango & Dienenthal Umformtechnik, describes the benefits for producers and processors of tubes and pipes: “The inline laser measurement makes it possible, for the first time ever, not only to obtain information about the internal geometry of a pipe “live”, during the sizing process, but to actually use this information inline for the control of the sizing operation in process. This shortens the entire procedure while achieving ultra-high precision.“
Best Fit and full body expansion
With the contour measurement by a laser it is now possible to introduce 100 percent pipe inspection without having to set up a time-consuming procedure. Gapless documentation of the geometry – inside diameter and ovality, for example – no longer poses a challenge. This data can even be used to apply the Best Fit process, a highly efficient process to optimise line pipe welding assembly operations.
Moreover, the new laser-based sizing technology also enables the sizing of pipes along their full body. The demands on the quality of pipes – especially, in terms of perfect roundness – have become increasingly exacting during the last few years, presenting pipe manufacturers constantly with new challenges. Here the new laser-supported tool has the potential to accelerate the pipe sizing process perceptibly and reduce the number of out-of-spec pipes shipped.
For years, the trend for many companies has been in the direction of combination turning/milling machines. In order to respond to this development, Blum has already marketed a hybrid measuring system. Article by Blum-Novotest.
The LC52-DIGILOG by Blum-Novotest is a hybrid laser measuring system for tool measurement and monitoring in combination turning and milling. The company is also introducing the intuitive ‘measureXpert’ app for the rapid generation of cycle calls for Blum measuring systems.
Winfried Weiland, Head of Marketing for Blum-Novotest GmbH, explained, “For years, the trend for many companies has been in the direction of combination turning/milling machines. In order to respond to this development, Blum has already successfully marketed the LaserControl NT-H 3D measuring system since 2007.”
The introduction of the LC50-DIGILOG at EMO 2017 then made it possible to develop a system with future-oriented digital-analogue technology for these machines as well. The new LC52-DIGILOG combines the advantages of non-contact, digilog measurement with those of tactile measurement via touch probe in one compact device. Another highlight is the ‘measureXpert’ app as it makes the use of measuring systems simpler.
Rotating Tools
Machine concepts combining several manufacturing processes require a different configuration for tool setting and monitoring than standard milling centres. While rotating tools are always measured quickly and reliably by the laser, it is recommended that non-rotating tools be monitored tactilely. The reason for this is that stationary tools, such as turning tools, require a time-consuming high point search on the tool cutting edge for high-precision measurement. In this instance, coolant also has a greater influence on process capability than is the case when measuring rotating tools. Rapid contact measurement of turning tools is therefore an advantage.
The tactile measurement is carried out by the adapted Blum probe with shark360 measuring mechanism with face gearing. The TC76 has all the characteristics typical of Blum probes, such as precise, non-lobing touch characteristics and wear-free, optoelectronic signal generation. Unique worldwide, the shark360 technology complements the multi-directional measuring mechanism with a face gear comprising 72 teeth, guaranteeing the greatest accuracy even with off-centre probing, which can occur with the measurement of turning tools. When the stylus is deflected, a precision pin moves into a light barrier, which generates the trigger signal for recording the measuring value.
DIGILOG Technology In Measurement
The company also relies on the recently launched DIGILOG technology for the measurement of rotating tools on the new hybrid system. The innovative technology offers surprising advantages: including even greater process reliability under the influence of coolant as wells the up to 60 percent faster measurement of rotating tools. This is made possible by generating thousands of measurements per second while dynamically adjusting the measuring speed according to the nominal speed of the tool. Each cutting edge is also individually measured, rather than just determining the value for the highest cutting edge, meaning it is possible to make a comparison between the shortest and the longest cutting edge.
As a result, run-out errors, caused by contamination on the taper of the tool holder for example, are automatically detected. Furthermore, the LC52-DIGILOG detects any contaminants and cooling lubricants adhering to the tool – due to the large number of measurements per cutting edge – and deducts them from the result to make measurement results even more reliable.
Using the ‘measureXpert’ app makes it very quick and easy to generate cycle calls for different controllers and measuring systems. The intuitive operation is to be emphasised here: The user is guided step-by-step to the appropriate cycle call for their measuring task.
Renishaw’s Void Scanner is a cavity monitoring system that is used in mining and civil engineering industries to produce accurate 3D laser scans of voids where access is limited, dangerous or prohibited.
Handling responsibility for quality control means closing the loop on coordinate measuring machine operations. By Daniel Brown, B Eng, senior product manager at Creaform.
Quality control managers in the automotive and aerospace industries are responsible for ensuring that manufactured parts meet customers’ requirements, specifications, and tolerances. To do so, they rely on coordinate measuring machines (CMMs), which are the most precise metrology equipment available for quality inspection.
Getting this level of precision, however, comes at a price (often in the form of inconvenience). The CMM may not be available to practice first article inspection (FAI), or, worse, it may be totally loaded because a fault has been found at the end of the production of a part. Then, lots of back and forth between the CMM and the shop floor is necessary to locate where the issue has occurred.
Handcuffed
In those situations, quality managers are handcuffed by the technology and limited in the execution of their work. What if they had a secret weapon to deploy when the CMM is loaded? What if they could have access to a portfolio of alternative solutions that they could rely on to improve the quality inspection?
In order to make sure that you are never restricted in the exercise of your duties, we’ve compiled the following list of different metrology tools available to QC managers, with the pros and cons of each.
A Look At Options
The pros of hand measuring tools are: simplicity of use; a basic level of technical expertise needed; high precision; quick use for simple measurement and features.Hand measuring tools are among the ways to approach the issue of monitoring. The most common hand measuring tools include micrometres, slide callipers, indicators, and gages. These tools are mainly used for simple inspections and basic measurements such as measuring a diameter or a thickness or any other dimensions that do not justify or require a report.
But there are reasons as well not to rely exclusively on such tools, including repetition: because the measurement depends on the operator’s manipulations and difficulty selecting the most suitable tool, because each measurement requires a different tool. As well, they can be hard to use for complex parts.
Fixed CMMs
The next option is to rely on fixed CMMs, which are definitely a better choice than hand measuring tools for complex parts. Indeed, they can measure any type of feature with a high level of precision. Because of that, they are the no.1 metrology equipment choice for quality control managers. They are so popular that they are often loaded by different operations.
Fixed CMMs are also flexible, allow access to automated reports and show ability to measure and inspect any types of feature as well as provide unbeatable precision.
However, they also have some drawbacks, including that the shape of measured parts is limited due to the size of the measuring table, high cost of utilisation and a high level of technical expertise needed for equipment fixed to the ground and that requires a rigid setup.
Laser Trackers
There is also a subcategory in laser trackers that are often used to measure parts of large dimensions. While fixed CMMs are limited by the table surface and portable CMMs are limited by their measuring volume, laser trackers can measure parts like aircraft wings or auto frames, as well as large toolings. Their disadvantages are that they require a rigid setup and are sensitive to instabilities in the environment.
Portable CMMs
That brings us to portable CMMs, an alternative solution when a part cannot be moved from the production floor to the measurement lab. These include the advantages of fixed CMMs, as well as portability, which enable one to move the CMM to the shop-floor, another building, or a supplier’s facility.
On the plus side, they show portability: the measurement tool goes to the measured part (rather than the opposite, simplicity of use and the ability to measure directly on the production floor.
However, they may be sensitive to vibrations and not adapted to unstable shop-floor measurements as well as requiring a rigid setup, and noting that operator experience and skills can affect the measurement accuracy.
Optical
There is also a subcategory here in optical portable CMMs.
This subcategory offers the same advantages of portable CMMs, with an extra: a rigid setup is no longer required. This means that everything (i.e., the tracker, the measuring tool, and the measured part) can move during the measurement.
Therefore, it reduces the pressure placed on operators. In addition, their level of expertise does not need to be so high because fewer errors will be caused by extra manipulations and alignments. In short, optical portable CMMs are perfectly adapted to shop-floor measurements.
3D Scanners
Finally, there are metrology-grade 3D scanners complete our portfolio of alternative solutions to rely on to improve quality inspection.
Like portable CMMs, most 3D scanners can be moved around on the production floor, but they also have the capability to measure in a complex production environment—just like optical portable CMMs—that is often influenced by temperature variations, vibrations and inexperienced operators.
However, it is through the information density they can acquire and analyse that 3D scanners distinguish themselves from other measuring equipment. Because of that, they are the preferred solution for FAI, where each dimension measurement is critical. The complete part (dimensions and aesthetics) must be inspected and approved during the FAI. Therefore, it is risky to omit defaults with a probing unit that only measures a restricted number of points (or samples of points).
This occurs through speed of acquisition and density of information analysed, the short time required to characterise a complete part and via efficiently digitising complex shapes with a very large number of points and without contact.
However, there are some drawbacks too such as the need for the measured part to be in the line of sight of the scanner and as an overkill solution to inspect simple geometrical features like pins and holes.
The Answer
So the secret weapon for quality control teams, therefore, is to have different measurement options to inspect parts. Because each solution has its pros and cons, being able to rely on different tools according to the type of inspection being performed or the shape of the piece being measured is the key to performing excellent quality controls.
The Contour GT-X by Bruker has a self-calibrating, metrology optimising laser reference, automated measurement capabilities (focus, intensity, tip/tilt head, staging, FOV) and nanometer-scale resolution on high-contour surfaces.
The system can accommodate sample height of up to 100 mm, with a maximum weight of 23 kg. It has a maximum scan range of up to 10 mm, a scan range rate of 114 µm per sec with standard camera.
The system’s configuration includes an air table stabiliser kit for enhanced X, Y, Z wafer placement accuracy, to optimisation of PDU, EMO and vacuum systems for integration and modified vacuum chucks for autoloader end-effector compatibility.
The In-Sight Laser Profiler by Cognex is a measurement system that verifies part dimensions. Applications include the automotive and electronics industry.
It generates an accurate 2D profile of an object along a laser line, providing geometric information. The profiler uses In-Sight VC200 vision controller which has camera ports that support up to two laser displacement sensor heads.
Additionally, access to the mobile, platform-independent visualisation allows the monitoring of production line activity using a web-enabled laptop, tablet or smartphone.
The SmartScope Zip Advance 250 is has a 1.0 x adapter tube and a 2.0 x replacement lens combination which yields a 38 mm working distance.
The system uses the Vu-Light LED illuminator to provide optimal lighting conditions and also through-the-lens laser support. Its field-of-view size, when measured diagonally, is 5.4 mm (low magnification) to 0.95 mm (high magnification).
The system has a travel range of 300, 150 and 200 mm in the X, Y and Z axis respectively. It has an area accuracy of (1.0 + 6L/1,000) µm, and z accuracy of up to (1.4 + 5L/1,000) µm.
