This Micromachining Center’s Tool Presetter Overcomes Problems with Contact- and Laser-Type Systems
Machining small dies and molds means using small tools, which means accurate presetting is key.
Makino’s iQ300 micromachining center is equipped with a specialized spindle design, thermal control features and 0.005-micron scale feedback for sub-micron accuracy on small dies and molds. To stay precise on such tiny workpieces, the machine usually uses commensurately tiny tools, some with diameters of 0.1 mm or perhaps smaller.
As might be expected, these thin tools can easily break against the workpiece unless they’re accurately preset. But presetting such small tools presents its own challenges, according to Marposs.
Here is an example of the sort of work performed on the iQ300, where accuracy requires precise tool presetting. (Photos courtesy of Marposs.)
The company says that contact-type, on-machine tool setters can’t handle such small tools very well, resulting in unacceptable rates of tool breakage during machining. The traditional solution to this problem is to use non-contact laser tool setters. But lasers can also have difficulty maintaining accuracy with such small tools, because they function by analyzing shading light volume. This process can get fudged if the tool diameter is close to or smaller than the beam diameter. With applications like roughing flat surfaces with flat-tip tools or finishing corner radii with ballnose tools, this weakness can result in inaccurate effective tool length measurements and gaps on the workpiece surface.
While on a larger part such an error could be corrected by hand polishing, Marposs points out that this might not be possible with the tiny die/mold parts machined on the iQ300. A more likely outcome is a scrapped part.
The micromachining center equips Marposs’ Visual Tool Setter (VTS) to counter these problems. As indicated by the name, the VTS is a high-resolution optical system that uses a charge-coupled device (CCD) sensor to elaborate images at different angular phases from the shade projection of the rotating tool. It automatically selects the image containing the maximum diameter projection information for tools with diameters ranging down to 10 microns, the company says. The cutting edges of the tools are visually checked on the display, as shown below.
These images capture the shade projection of the rotating tool’s widest axial part.
The VTS can process a variety of measurements, many of which use a single image acquisition cycle. During such a process, the tool can keep rotating at its highest speed. This eliminates the need to slow down the spindle, improving presetting times while maintaining accuracy.
In addition to checking tool profiles, the VTS can also analyze the tool surface with a continuous frontal light.
The VTS measures a tool on the Makino iQ300 machining center.
The on-machine system has pneumatic shutters that protect the optical lens when not in use and an air barrier to keep chips and coolant away from the optical window.
Learn more about Makino’s iQ300 micromachining center, which equips Marposs’ VTS as standard at its Techspex showroom.
