Production Insight Additively manufactured tools: small and fast
Mapal has been offering additive machining tools since 2014 and has now improved its hydraulic chucks for more precise and faster machining.
Hydraulic expansion chuck: Everybody who isn’t a tool builder will probably read this term twice. The experienced technician knows: It is a tool holder which exerts the same hydraulic force on the clamped tool at every point of the holder and thus keeps it centered and without backlash. At higher temperatures, this effect is intensified by the higher coefficient of expansion of the oil compared to the steel body.
Additively manufactured chucks can withstand higher temperatures (up to 170° C) and strong forces. They also offer additional functions compared to multi-part designs with soldered joints. However, additive manufacturing has higher production times and costs than conventional processes.
The toolmaker has overcome these disadvantages during further development. The guiding principle was miniaturization. Mapal manufactures the chucks according to the motto: "As much conventional base body as possible, as little additive material as necessary". Like with the previous model, the chuck tip is mounted directly on the conventional base body by means of laser sintering (Selective Laser Melting, SLM), but now in as small as possible.
This not only saves production time and costs. Mapal has now also improved the function with very customer-specific clamping chamber systems. "Thanks to the innovative manufacturing process, we have succeeded in manufacturing miniature chucks with HSK-E25 holders, for example for direct clamping of tools with a diameter of only three millimeters," says Jochen Schmidt, Product Manager Clamping Technology at Mapal Präzisionswerkzeuge Dr. Kress KG.
Thanks to miniaturization and the slim contour, the actual clamping area is now closer to the production area. According to Schmidt, this improves the stability and rotation accuracy of the tools and thus the machining tolerances, which are in the range of a few thousandths of a millimeter. Furthermore, the reworked chucks are now equipped with grooves. The micro dirt that is always present can be displaced into these grooves without affecting the rotation accuracy quality in a negative way.
As a result of better rotation accuracy, higher speeds can be achieved, which improves productivity. In addition, tumbling tools are less prone to breaking when they touch the workpiece. The change from a special tool to a standard tool, which is now possible, saves further costs. The more abrasive the machined material is, the higher are the cost savings.
Another functional improvement concerns lubrication. Thanks to the free choice of geometry and depending on parameters such as coolant pressure, setting dimension and speed, Mapal can design the coolant outlets in the chuck in such a way that practically no lubricant is left at the production site after machining. With this "loss lubrication", subsequent cleaning of the components is no longer necessary. Nevertheless, the service life of the tool remains high thanks to a small amount of lubricant required.
In addition to the technical production advantages, miniaturized chucks offer further advantages. "Thanks to the weight reduction, our miniaturized chucks enable us to accelerate and brake the entire tool system consisting of chuck and tool more evenly and with less stress exerted on the spindle," emphasizes Schmidt. Mapal has developed hydraulic expansion chucks with optimized installation space for a customer. Thanks to the extremely length-optimized chuck, the customer was able to use an existing machine for one machining operation and did not have to invest in the next larger machining center.
Simple tool change
The tool change has also been significantly improved. "The smaller the tool and chuck, the easier it must be to handle them. With every reduction in size, handling external peripheral devices becomes more cumbersome and difficult," says Schmidt. Previously, the tool holder always had to be unscrewed and the tool changed externally. In the case of multi-part superstructures, the individual deviations of the components also add up to a not inconsiderable error chain.
With the additively manufactured second generation hydraulic expansion chucks, it is possible to change tools directly on the machining robot. Currently, Mapal manufactures chucks on six 3D printers using additive technology, which already account for about 10 to 15 % of sales of their clamping technology.
This article was first published by Automobil Industrie.