03.11.2022

Efficient deburring with robots

KADIA system processes battery trays

If a milling cutter is guided by a robot, the machining is fundamentally more unstable than on a machining centre. To reliably ensure the shortest cycle times in industrial production in this instance, KADIA is using MAPAL’s FlyCutter with three cutting edges in a newly developed system with three robots for deburring battery trays for electric vehicles.

The PCD milling cutter FlyCutter from MAPAL clamped in the robot from KADIA in front of the battery tray.
  • The PCD milling cutter FlyCutter from MAPAL clamped in the robot from KADIA in front of the battery tray.
  • Jannik Weiss from KADIA and Norbert Meier from MAPAL in discussion.
  • A battery tray made of aluminium profiles.
  • The KADIA special machine for deburring in layout with three robots.
  • The PCD-tipped FlyCutter with three cutting edges from MAPAL.
  • The component shows chatter marks.

The story of Nürtingen-based KADIA Produktion GmbH + Co began back in 1959 with the production of honing tools. The first honing machines were developed ten years later. The company tapped into another branch of business in 1981 with the manufacture of deburring machines. Today, KADIA is a leading specialist in honing and deburring technology and currently employs 200 people.

Its main customers are car manufacturers and suppliers, construction and agricultural machinery manufacturers, wind power plant producers and the aerospace industry. While the manufacturer offers standard machinery in different sizes for honing, in principle, custom machines are built for deburring. Customers include major machine manufacturers that bring KADIA on board as a deburring expert.

Jannik Weiss from KADIA and Norbert Meier from MAPAL in discussion.
Jannik Weiss, Sales Specialist Deburring & Robotics at KADIA (left), and Norbert Meier, Technical Consultant at MAPAL, are very happy with the results of this joint project.  ©MAPAL

Pencil test for burrs

In mechanical machining, a distinction is made between loose and fixed burrs. After deburring, depending on what’s required, the part should have sharp edges, edge rounding or a chamfer, which is why this is also known as edge design. To assess a burr, KADIA uses a simple but meaningful test using the lead of a mechanical pencil extended by five millimetres. If it can be used to remove the burr, then the burr is loose. If the lead breaks, it’s a fixed burr, which needs to either be milled off or can be left in place, as it won’t come off later.

The size of the workpiece is also crucial to machining processes that make use of robots. Guiding the workpiece is favoured for smaller parts. The robot guides the workpiece along fixed processing units. In a tool-guided strategy, the robot arm processes a workpiece firmly clamped in place. “For bigger workpieces, I’m much more skilful with the milling cutter in hand than if I have to move the bulky part,” explains Jannik Weiss, Sales Specialist Deburring & Robotics at KADIA.

A battery tray made of aluminium profiles.
The aluminium profile tray design is roughly the same size as a double bed frame and is used to hold batteries in an electric vehicle. Deburring ensures the lid fits cleanly and remains tightly sealed after “closing”.  ©KADIA Produktion GmbH + Co.
When a major car manufacturer requested a deburring machine for battery trays in electric vehicles, it soon became clear that the robot would have to guide the tools in this instance. The aluminium frame, welded together from extruded profiles, measures 1,900 x 1,400 x 100 mm. The requirements for KADIA involved milling the separating surfaces and then brushing the burrs created by the milling cutter so that the frames can later be bolted and sealed with a lid. Tasks of this nature are performed more efficiently and flexibly by a robot cell than a machining centre, especially as the surface finish requirements are moderate.

Machining in the test cell

The centrepiece of development at KADIA is a five-by-six-metre test cell with a six-axle industrial robot and a quick-release unit. This enables testing of what is set to go on to become the system. Preliminary tests determine the optimum cutting data and assess stability. The cell is home to 15 changeable units. The robot has automated access with an action radius of 2.70 m to nine of these. Each unit represents a specific function that is used for machining a part. Typically, it consists of a motor spindle with a connection and a cutting tool.

A rotary table as the seventh axle is also part of the equipment of the test cell, which also has enough space to accommodate other systems, such as coolant supply or additional process units. At KADIA, several parts are equipped for various tests in the cell at the same time.

The KADIA special machine for deburring in layout with three robots.
The custom machine layout requires the use of three robots. Two deburr the front, while the third machines the back. This achieves the optimum cycle rate in industrial production.  ©KADIA Produktion GmbH + Co.

For initial preliminary tests on a dummy part for the battery tray, KADIA used a round-insert milling cutter already in stock in. The tool proved wholly unsuitable for the task. The vibrations that occurred were so severe that even the processing spindle was damaged. Even with low cutting values, the background noise during milling was still noticeable in the adjacent building.

With the task to deliver a suitable milling cutter for the aluminium housing, MAPAL was chosen as the partner of choice. “We evaluate in advance in which tool manufacturer we see the potential for cooperation,” says Jannik Weiss. Although KADIA initially focuses on standard tools, it was a major plus for MAPAL that the tool manufacturer produces custom tools where necessary.

Two milling cutters to choose from

KADIA already used this service in a previous project for which MAPAL developed a special hydraulic chuck. The services of the Aalen-based manufacturer came to be appreciated here. When Norbert Meier, Technical Consultant at MAPAL, was on site to deal with this chuck, the battery tray project was explained to him. Meier had solutions ready right away and brought two milling cutters from MAPAL’s standard range with him on his next visit: the seven-blade face milling cutter IFM751 and the FlyCutter D63 with three cutting edges. Both milling cutters demonstrated they were up to the task in the tests, but to Jannik Weiss’s amazement, the little three-blade milling cutter gave much better results: “What the FlyCutter did there was really great.”
The PCD-tipped FlyCutter with three cutting edges from MAPAL.
The FlyCutter with PCD-tipped milling inserts was developed specifically for unstable machining processes and small connections.  ©KADIA Produktion GmbH + Co.

But Norbert Meier, who wanted to show the customer an alternative with the second milling cutter, had reckoned with this outcome. “We specially developed our FlyCutter for requirements like these,” he explains. MAPAL developed the lightweight tool specifically for unstable machining requirements that occur in robot applications. It is optimised for small connections such as BT30. The innovative design and use of aluminium ensure the milling head is particularly lightweight. With the diameter of 63 millimetres used at KADIA, the PCD milling head, including milling inserts, weighs just 220 grams.

The sensitive wedge adjustment make µ-precise adjustment of the milling inserts possible. The dovetail guide and an additional worm screw ensure perfect seating and high accuracy of repetition for the assembly of the milling inserts. The special, ultra-positive cutting edge geometry means only weak forces are applied to the part and the tool spindle guided by the robot.

When machining the battery tray, accuracy down to the µm is not required. In fact, to ensure the sealant applied by the automotive manufacturer holds better, a certain rawness of the surface is needed. Only the waviness must not be too high. In the tests, the milling cutter was moved beyond the limit to determine up to which point chatter marks on the relatively thin part still lay within the required tolerance.

The component shows chatter marks.
  ロボットアームが伸びれば伸びるほど、振動やビビリが発生する危険性が高まりますMAPALのフライスカッターで良好な加工面を確実に得るための、切削速度、送り、切削深さに関する結果がテストシリーズから得られます。 ©KADIA Produktion GmbH + Co.

切削データと位置決めが鍵

「ロボット加工の核心は、工具、治具、ロボットの相互作用です」とノルベルト・マイヤー氏は説明します。剛性は加工における基本的な問題です。ロボットアームが伸びれば伸びるほど、加工は不安定になります。そのためKADIAは様々な切削データをテストするだけでなく、ワークの前や横などのロボットの様々な位置もテストします。

このケースでは、主軸回転数11,000 rpmでの最適な切削データは、送り0.16 m/s、材料除去率0.5 mmであるとパートナーは判断しました。Fly Cutterは非常に優れた表面品質を確実に実現しました。KADIA社はこのテストデータをカスタムマシンのコンセプトに組み込みました。このためメーカーは、1つのセルに3台のロボットを使用することが、連続生産において最もコスト効率の良いソリューションになると判断しました。2台が前面加工を分担し、3台目が背面加工を行います。切削データに加え、KADIA社 は加工ステップの所要時間と達成可能なサイクルタイムを顧客に提供します。従って大型バッテリートレイのバリ取りには約80秒かかります。「ロボット加工では、このような切削データのプロセス情報はCNCマシンのように標準的なものではありません。ロボットの位置によって、同じデータでも異なる結果が得られます。」とヤニック・ヴァイス氏は話します。

KADIAとMAPALは、この好結果を受け、さらに協力関係を深めたいと考えています。様々な加工プロセスに対する更なるテストが既に計画されています。


Kathrin Rehor, PR Project Manager at MAPAL

Contact

Kathrin Rehor Public Relations Kathrin.Rehor@mapal.com Phone: +49 7361 585 3342


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