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  • Writer's picturePaxton Shantz

TwinCAT CNC Helps Custom Robots Handle Precision Part Machining

Drawing on experience with underwater robotics, toolcraft’s solutions stand up to ultra-fine dust particles that damage traditional systems while optimizing performance with control and drive technology from Beckhoff


As robots become ubiquitous, they’re taking on tasks that seemed unlikely, if not impossible, a short time ago. The experts at toolcraft AG, for example, have deployed articulated robot arms for precise machining blocks of solid silicon carbide, gray cast iron and other ultra-hard materials. To ensure it stands up to tough environmental conditions, the engineering team draws on its experience with underwater robotics.


Based in Georgensgmünd, Germany, toolcraft understands exactly what the digital manufacturing industry needs. They also know which processes work, which technologies are worth the investment and which are not. That’s because toolcraft not only manufactures on behalf of customers using its 60 CNC machines, but also designs, plans and builds turnkey production systems for companies in many industries.


A toolcraft robot machining cell
For its next-generation of machining robots, toolcraft leverages PC-based control and drive technology from Beckhoff to enhance kinematics and overall precision.

Founded in 1989 as a contract manufacturer, the company gradually added greater capabilities in different manufacturing technologies, including injection molding and mold making in 2005 and additive manufacturing in 2011. In 2015, robotics became the newest technology division at toolcraft. “No matter what technology we operate in, we always want to have the expertise needed to offer complete solutions,” says Daniel Distler, division manager for robotics with a focus on sales and human resources.


The range extends from simple devices to complex systems with integration into existing systems at the customer site. “Connecting machines with new technology to existing controllers at the end customer’s site is not always the easiest method, but it works when you use flexible control technology,” says Andreas Bauer, division manager for robotics with a focus on engineering at toolcraft.

 

One automation platform for every application


The requirements for robust CNC and robotics tech with open, flexible communication led Bauer and Distler to PC-based control from Beckhoff. In complex applications, such as the production cells with 7-axis milling robots for machining components, the comprehensive portfolio of EtherCAT networking, TwinCAT 3 automation software and Industrial PC (IPC) technologies delivered a strong solution.


A Beckhoff HMI for operating the robotic fabrication system
Operation and path planning are carried out in G-code, just as the 5-axis CNC, and visualized on a customer-specific CP3921 multi-touch Control Panel.

“TwinCAT CNC was the first controller with an integrated interface to the Stäubli robot controller (TwinCAT Robotics uniVAL PLC, TF5130). This technology package made a lot of things easier for us when implementing the project,” Bauer says.


Using the machining cell designed by toolcraft, one user now mills base frames for wafer production from large blocks of silicon carbide and gray cast iron. “In this case, toolcraft was already using our TwinCAT CNC,” adds Alexander Klos, Sales at the Beckhoff office in Nuremberg.


Initially, the customer was still machining the blocks with conventional 5-axis CNC machines. But milling the hard material produces ultra-fine dust that would penetrate every joint, linear guide and bearing, causing huge problems in a short time. The CNC machines quickly became worn out and required major repairs.


However, the toolcraft team had experience with projects that required completely dismantling and sealing robots for use underwater. Protected effectively, the robots functioned reliably even when submerged in water up to 20 meters, so why couldn’t they use the same approach with ultra-fine dust?


“We knew that with the TwinCAT CNC we could achieve the required accuracy of 2/10 of a millimeter within a machining area of up to 1 meter squared, as well as seal the Stäubli robots and apply overpressure,” Distler explains.

 

Next-generation CNC robot


The potential of robots in parts processing is enormous, so toolcraft needed to focus its developments. “We thought long and hard about where we wanted to go with robotic milling and, of course, how to get there,” Distler says.


Beckhoff I/O and IPC technologies
Complete control and monitoring of the prototype runs on a CX2040 Embedded PC (bottom left) with a quad-core Intel® Core™ i7 processor.

The aim was not only to raise machining quality to a new level, but also to ensure that there were no changes for users when creating the machining programs. At the start of the project in 2018, all components of a machining cell were examined in a “best of breed approach”: robot, rotary table, tool changer, milling spindle and, of course, the control technology.


“Based on our expertise over the last eight years, we know the exact strengths and weaknesses of the various kinematics and designs,” Bauer says.



This expertise was applied in collaboration with a robot supplier to develop kinematics that increase stiffness, dust/water resistance, payload and reach. The result is the current configuration of a machining cell with a high-end CNC robot based on new kinematics.


The robot was equipped with double-bearing gears on all axes, encoders on the drive and output sides, and a modified spindle mount. Other positive side effects of the new design include the internal hose assemblies, which simplify handling.


Beckhoff AX8000 and AX5000 servo drives
The AX8000 multi-axis servo system, in combination with the AX5000 Servo Drive (bottom left), controls the high-performance spindle and the servomotors installed in the axes of the CNC robot.

The overarching control technology of the milling robot relies on a CX2040 Embedded PC from Beckhoff. The powerful, multi-core controller eliminates the need for a separate robot controller, freeing up space in the control cabinet and reducing the complexity of the project. For the operator interface, a CP3921-1502-0010 CNC multi-touch Control Panel connects to the embedded PC via CP-Link 4 with only one Ethernet cable.


Precision drive technology from Beckhoff rounds out the solution, Klos explains: “In the newest generation, toolcraft also uses AM8000 servomotors and the AX8000 multi-axis servo system from Beckhoff in addition to TwinCAT CNC.”

 

Straightforward drive technology conversion


Here, the openness and flexibility of PC-based control were two critical advantages. “Although toolcraft started with TwinCAT CNC and TwinCAT Robotics uniVAL PLC, it was possible to quickly switch to another robot type with different mechanics, kinematics and our servo drive technology,” adds Klos.


Precision milling robot from toolcraft with Beckhoff servomotor
In the robot, Beckhoff AM8000 servomotors together with the encoders on the drive and output sides ensure highly precise movements.

Now, the drive-side and output-side encoders of the robot axes are easily integrated into the software function blocks of the axis controllers without any problems. And with the fully integrated Beckhoff portfolio, ranging from CNC to servo drives and motors, toolcraft benefits from completely different optimization options.


“Direct access to all parameters and process settings has played a large part in the further improvement of the accuracy,” Bauer says.


For example, the low but still detectable hysteresis of the gearing was further compensated via the output-side encoders and appropriate control algorithms. Even when high forces are applied, e.g., during solid milling or depending on the position of the tool center point (TCP) in the working area, the axes are tracked with speed and precision. “And the integration of measurement and calibration cycles ensures consistent properties,” Distler says.


On top of this, toolcraft retains flexibility in its choice of feedback systems and use of other technologies. The servo drives support many encoder interfaces and additional options are available via EtherCAT. “We are always thinking ahead and are considering integrating camera systems to detect and automatically load components,” Bauer says.

 

Post-processors and coordinate transformation do the heavy lifting


Beckhoff and toolcraft industrial automation and robotics engineers
The two robotics division managers at toolcraft, Andreas Bauer (Engineering) and Daniel Distler (Sales and Human Resources), together with Alexander Klos from the Beckhoff branch office in Nuremberg (from left to right).

From the CAD drawing to the machining program, an efficient process chain is crucial for manufacturers. Here, toolcraft works to empower customers as they add more advanced technologies.


PC-based control offers key benefits in this area. The post-processors and coordinate transformation run on the same Beckhoff embedded PC in parallel with the path control of the CNC robot. The machining programs can therefore be programmed in standard G-code and generated from the usual CAD/CAM programs.


“We want the robot to work perfectly with the user’s CAM software,” Distler says. “Our approach is to take away users’ fear of operating and programming the robots, while at the same time providing more freedom in machining.”


Ready to get your time back with powerful, efficient and precise CNC and industrial automation tech? Contact your local Beckhoff sales engineer today.


 

Paxton Shantz of Beckhoff Automation USA

Paxton Shantz is the Digital Manufacturing Industry Manager at Beckhoff Automation LLC.


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