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After every tool change, the laser automatically measures the length and radius of the tool prior to machining, and after machining, checks for breakage and wear

Image: Blum Novotest

Die & Mould Reliability for automated mould making

Mar 29, 2018

The article talks on laser measurement systems for CNC machine tools that are used for non-contact tool measurement and tool monitoring, while highlighting how it helped Playmobil to set-up automated production lines at its in-house mould shop

As the company approaches its 40th anniversary, some 2.6 billion Playmobil figures currently populate the earth. Many new figures are released every year, placing high demands on the in-house mould shop. To achieve maximum efficiency in unmanned, automated operation, Playmobil’s numerous machining centres have been using LaserControl measuring systems of Blum-Novotest already for 15 years.

“For Playmobil figures, hundredths of a millimetre count,” says Attila Britting, Head of Playmobil’s in-house mould shop in Zirndorf near Nuremberg. “The aim in building the injection moulds is to produce finished plastic items that require virtually no rework – which is vital in view of a daily production of approximately 10 million individual parts and over 100 million figures a year. Consequently, the mould separation must also be a high-precision operation, so that there are not any burrs on the individual parts or the finished figure.”

Need for automated production

The moulds are specified for extremely high volumes, and production runs of 200,000 to 300,000 pieces from one mould are no rarity. The required productivity can only be achieved by partially automated production alongside the normal two-shift operation. So, an array of machines work overnight on prepared jobs. To execute these jobs, several of the machining centres are equipped with pallet changers and tool magazines with the capacity to hold as many as 120 tools. The machines even keep running unmanned over the weekend. The Blum-Novotest systems are installed in the machining area of the automated DMG five-axis machining centres.

After every tool change, the laser automatically measures the length and radius of the tool prior to machining, and after machining, checks for breakage and wear. Thus, our skilled workers no longer have to pre-set the tool in the pre-setting device. A new tool is simply shrink-fitted into the holder and measured at machining speed after fitting. This ensures that the tool data in the machine is correct, numerical errors or data reading mistakes can no longer occur. Further features include high-speed automatic compensation for the thermal expansion of the entire machine and for spindle displacement. Incorrect tool data can have costly consequences such as defective tools, rejects, or machine stoppage. A spindle damaged by a crash will cost at least 18,000 Euros to replace.

Laser measurement systems

Without a monitoring system to detect worn or broken tools, automated production is hardly possible. The LaserControl system’s breakage monitor ensures that broken tool detection runs immediately after every machining step. Depending on the programming, the machining centre can then either exchange the tool for a twin or notify the on-call service staff, who can log in to the machine over the internet and monitor the workshop through a webcam. At Playmobil, as many as four of the key tools are held in the tool changer, which means that the automated overnight jobs run very reliably.

We mostly use steel with high chromium content because it shows the least wear during the large volume production. It does cause considerable tool wear during cutting, however. That is why it is very important to keep an eye on the running times of the individual tools. The BLUM laser measuring systems do this very well.

High-precision measurement in a dirty environment poses a major challenge, and cooling is essential to the production process. To protect the optical system from being soiled, the measuring system is mechanically sealed off from the coolant by a pneumatically operated shutter piston during machining. The rotating tool is also cleaned with compressed air prior to measuring in order to ensure that the measurement is not impaired by swarf, dirt or cooling lubricants. During measurement, a stream of barrier air provides protection against soiling.

Accuracy and repeatability

The LaserControl systems have truly been their money’s worth at Playmobil. The systems are practically maintenance free; and, after more than 10 years in continuous operation, the seals look like new. Above all, however, the experts have never been let down by the laser systems and have experienced nothing but good things in terms of service, too. “We have had only good experience with BLUM lasers – and we save working time because there is no need for pre-setting,” Marco Mendl, Team leader-CAD/CAM/NC, summarises. “The accuracy of the LaserControl systems is astounding, as well. Based on our experience, its repeatability is within less than two thousandths of a millimetre. And for us, one thing is for certain: Without the BLUM laser systems, this degree of automation would not be possible.”

Source: Blum Novotest

Image Gallery

  • In the manufacture of highly complex injection-moulded tools, hundredths of a millimetre count: All single parts are precisely matched to each other

    Image: Blum Novotest

  • Playmobil is a line of toys produced by the Brandstätter Group, headquartered in Zirndorf, Germany

    Image: Blum Novotest

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