Automation of a shaft measuring machine
03. September 2019
Whether it is rotating parts with a safety-relevant function in the automotive industry or bone screws in medical technology, many industrial products must satisfy strict standards and are subject to precise and reproducible measurements for quality control. Since these measurements must be conducted in fast sequence, various optical measurement procedures were tried and tested, especially for high throughput rates or applications with a high inspection depth.
Such a measuring system is now available from Mahr GmbH, specialist in industrial production measurement technology covering a broad application spectrum in the field of quality control, in the form of the MarShaft Scope 750 plus shaft measuring station. The solution is specially designed for the automated inspection of rotationally symmetrical workpieces, e.g. shafts and other rotating parts, in the harsh workshop environment. It has an optical measuring system, i.e. contactless, that instantly analyses the workpiece contours. Depending on the task or model, measurement can be accurate to 0.0001 mm or 0.0001°. The system offers a high degree of flexibility. Many different geometries can be measured, and also large workpieces of up to 600 mm in length and 120 mm in diameter. In addition to the hardware, the MarWin EasyShaft software provides significant benefits due to its specialization in the measurement of rotationally symmetrical workpieces.
Fully automatic optical shaft measuring system
In particular due to the high rate of throughput that the MarShaft Scope 750 plus permits, the measuring station is predestined for automation, e.g. for loading and unloading by a robot. Mahr and YASKAWA presented a fully automatic optical shaft measuring system of this type at the Hanover Fair 2019. The measuring station is loaded by a YASKAWA MOTOMAN HC10 industrial robot. With a flexible gripper, it satisfies the special requirements for handling a wide range of possible workpieces. The robot and machine controller communicate via a MotoLogix Profinet interface that permits the programming of the robot in the IEC61131 environment and thus directly via the PLC.
In practice, the measuring station and robot are positioned directly next to the production machine or production line, where the freshly manufactured workpieces are inspected in a fully automatic procedure. The robot independently inserts the parts to be inspected into the machine and removes them following the – likewise fully automatic – measuring process. There are many advantages compared to conventional, manual loading: the entire quality assurance process is faster and more reliable. Since operating errors are virtually impossible, constantly high measurement accuracy and exactly reproducible measurement results are guaranteed. Furthermore, around-the-clock operation is possible without additional personnel deployment.
MOTOMAN-HC10 HRC-capable hybrid robot
In this specific application YASKAWA and Mahr opted to use a MOTOMAN HC10 with control unit YRC1000, a hybrid robot with a range of 1.2 m and a handling weight of 10 kg. It offers a special advantage: as an HRC-capable hybrid robot, the model permits direct contact with the operator for the purposes of human-machine-collaboration (HRC). If this is not necessary, the MOTOMAN HC10 can also be employed as a high-grade industrial robot and operated at full speed.
As a collaborative robot, the MOTOMAN HC10 not only satisfies the requirements of European Machine Directive 2006/42/EC. Its YRC1000 controller with FSU and PFL circuit board also meets the performance level (PL) “d” Category 3 in accordance with DIN EN ISO 13849-1 and thus exceeds standard specifications. The EC Type Examination Certificate meanwhile issued by TÜV Rhineland as a notified body (NB) confirms conformity with these specific requirements. As far as German and European safety standards are concerned, the MOTOMAN HC10 can be employed as a robot with power and force limitation of the 4th collaboration type pursuant to technical specification ISO TS15066. The required safety in direct contact with the operator is guaranteed by unique sixfold force and torque monitoring that enables flexible interaction between the robot and its surroundings.
Due to its sophisticated design, the MOTOMAN HC10 – first introduced as a prototype in 2016 – is a powerful example of an HRC-capable robot. Tuned to the respective application, it requires no additional protective measures such as a safety enclosure, thus saving space and costs. Installation is extremely flexible, and it is thus viable at different workplaces and in a variety of concepts.
Besides the safety aspects, in the development of the HC10 concept particular emphasis was placed on user-friendly operation. Programming can optionally be performed with the “Easy Teaching HUB” on the robot itself. If the robot stops at a specific set contact, movement can be reactivated directly on the robot arm (manipulator). The robot arm was carefully designed, taking into account ergonomic and collaborative aspects. There are no sharp edges or other protruding contours; potential crushing zones were reliably eliminated.
Potential and perspectives
Besides the technical aspects and resulting customer benefits, the cooperation with YASKAWA is in line with Mahr’s aim to be a world leader in the field of automated measuring technology. The company is currently observing increased demand in this area and envisages great potential for other measuring stations. Where robots are to be used, connectivity to other models is possible at all times – such as the latest MOTOMAN GP series of handling robots with payloads of 7 to 225 kg. The optimum automation solution must always be tailored to the specific task. The right concept – and thus the choice of robot model – will take into account parameters such as testing depth, weight and shape of the specimen, production speed and measuring time. This considered, there are no limits to system design. It is also conceivable that a central robot attends to a number of different measuring systems.
Authors: Dr. Andreas Kelling, Product Manager Marketing Engineered Solution Systems – Mahr GmbH, 37073 Göttingen, Germany
Dirk Drehsen, Project Manager Rental & Fairs – YASKAWA Europe GmbH Robotics Division, 85391 Allershausen, Germany