A case in point

With its Zero Point clamping system, AMF claims set-up times can be reduced by up to 90%
With its Zero Point clamping system, AMF claims set-up times can be reduced by up to 90%

According to clamping technology specialist Andreas Maier Fellbach (AMF), its Zero-Point clamping system can reduce set-up times by as much as 90%.

This has been well-received by machine tool manufacturer Matsuura – on its hybrid machines which combine additive and subtractive methods, the cost-effective AMF Zero-Point system ensures that productivity is maximised.

"The system makes setting-up processes on our Lumex range of machines repeatable, accurate, reliable and efficient,” says Holger Hermann, head of application engineering for additive manufacturing technology at Matsuura Europe GmbH in Wiesbaden, Germany.

Matsuura’s Lumex hybrid additive manufacturing systems effectively unify laser sintering (SLS) and high-speed milling (HSM). Through this combination, components can be fully processed on one machine with additional finishing work only necessary in special circumstances.

In the method developed by Matsuura on two Lumex machines, metal powder is turned into 3D shapes through layered selective laser melting in the powder bed. In this process, a mirror galvanometer precisely directs fibre lasers – 500 or 1,000W in strength, depending on the design of the machine – to the intended point.

After each pass, the scrapers re-distribute the metal powder on the machine table that has been moved downwards and away. On first impressions, this is a conventional 3D printing process, however, after ten powder layers each with a thickness of 50µm, something different happens – the base or substrate plate doesn’t move downwards again to apply the next layer of powder. Instead, it remains in its original position.

Then, the milling head accelerates the cutter to up to 45,000rpm, moves along the outer contours and rough-machines a section with an R2 ball cutter for example. "The milling can’t yet take the part down to finished size because the hot material is still cooling and the geometry is therefore in a state of flux," Mr Hermann explains.

“This process is repeated for all ten layers generated by the laser. A tool changer holds 20 tools at the ready for this purpose, including pre-cutters for rough-machining the layer generated by laser melting. After three times ten layers – or 1.5mm – the final contour is created with the finishing tool at the points where cooling has taken place.

“Comparing to a pure AM process; here we achieve greater precision, especially in places which are subsequently difficult or impossible to access,” he adds. “The process goes down to 0.005mm and Rz 3.5µm compared to 0.05mm and Rz 25 µm.”

So far the attention has been on the visible operations at the top area of the machine table – what has been going on in the substrate remains hidden from the observer – but is no less critical. The zero-point clamping modules specially designed by AMF for additive manufacturing can accelerate the set-up processes involved.

For example, very high temperatures are reached during a 3D printing process: at the melting point of the metal in the powder bed it can be as high as 1,400°C. Even if the clamping modules are underneath a 30mm thick plate, temperatures of up to 150° and higher still can occur.

AMF uses seals and media which can withstand these temperatures. To ensure process reliability and repeat accuracy isn’t compromised due to temperature fluctuations, AMF uses carefully selected materials and processes such as hardened surfaces on its zero-point clamping modules.

On its Lumex machines, Matsuura uses K5.3 built-in clamping modules from AMF in its additive manufacturing processes. They open pneumatically at just 5 bar operating pressure via a single connection. Five modules pick up the clamping bolts, which are housed under the 3D base plate for direct workpiece clamping: "This is because our customers in tool and mould making don’t subsequently cut the base plate off from the finished 3D product at all," stresses Mr Herrmann, who cites warping as the main reason behind this.

The K5.3 built-in clamping modules offer draw-in forces of 1.5kN and holding forces of 13kN. Locking is performed through spring force so that, following the opening and insertion of the clamping bolts, the pressure pipes can be disconnected at any time.

Due to the optimal contour of the clamping bolt, tilt-free retraction and extension, and thus secure locking of the clamping modules, is ensured – even if the plate has been positioned at a slight incline. The optional, integrated blow-out mechanism of the clamping modules and a contact control mechanism for querying as part of automated processes are not installed on the Lumex systems but can be supplied by AMF if required.

Mr Herman is delighted with the speed advantages offered by the AMF zero point system: “By reducing production time by up to 65% such as with injection moulding tools for example with the hybrid method, we are offering our Lumex customers a significant efficiency advantage,” he enthuses. “Here, the zero-point system offers an optimal solution for many applications which contributes to the overall efficiency of the entire process.”

Before AMF’s sales engineer – who has a longstanding relationship with Matsuura – suggested the zero-point solution, clamping was performed manually via conventional technology. Back then, the base plate was bolted down to the machine table with four screws and aligned every time with the dial gauge and calibrated with a zero-point sensor. This cumbersome calibration process had to be performed repeatedly for every component.

"With the AMF Zero-Point system, the set-up time can be reduced by 90%," Mr Hermann concludes.

AMF www.amf.de

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