Manufacturers wishing to progress from manual metrology to using a CNC coordinate measuring machine (CMM) have a new option to consider — the new ALTO 6.5.5 from CMM manufacturer LK Metrology. Appealing to the entry point of the CMM market, the machine has guideways made from aluminum, lowering the capital cost compared with making those components from ceramic, as is the case with most LK CMMs. Several innovative design features have resulted in a surprisingly compact measuring machine with the high accuracy and rapid throughput normally associated with more expensive systems.
The CMM is of half-gantry design, which improves accuracy by shortening the leg supporting the bridge. Additionally, the fixed aperture created beneath the short leg facilitates easier loading and unloading of components from that side of the machine. Micro-machining of the aluminum elements by fly-cutting them in an unclamped condition eliminates distortion that might occur on releasing conventional work-holding fixtures after milling. All aluminum parts are hard anodized before the assembly of the CMM, creating a 50-µm thick layer that imparts extreme durability and prevents corrosion.
Rapid 5-axis touch-trigger measurement
Designed for touch-trigger probing only, the CMM can rapidly capture precise measurements, as it can deploy a motorized PH20 5-axis probe head from Renishaw for a three-fold increase in inspection speed. Continuous angular rotation and infinite positioning (similar to the company’s REVO2 probing system) avoid moving the machine’s X, Y, and Z axes at high speed, minimizing dynamic errors. For some measurements in a cycle, it is not necessary to move the linear axes at all. The results are better accuracy and repeatability.
Furthermore, 5-axis motion allows larger parts to be measured on the CMM by minimizing the space required around the part for head rotation. Unsurprisingly the PH20 is the most expensive probe head on offer. Mindful that price will likely constrain many potential ALTO purchasers, LK offers lower-cost motorized and manual head options. Available also is a range of surface roughness probing solutions and stylus change racks with self-calibration and automatic tip correction on changeover.
Advanced CMM construction
The design of the ALTO is optimized around the need for a compact CMM with linear travels of 600 x 500 x 500 mm. All electronics, including the PC system, are integrated within the base for a small footprint, and guideways do not extend beyond the table as in other designs.
Apart from using aluminum in place of ceramic for the guideways, no compromises have been made in constructing the new machine, which integrates all top-end features of LK’s other CMMs. They include a 100-mm thick granite table, low-maintenance pre-loaded air bearings, and zero-hysteresis friction drives in all axes for smooth motion and exact positioning. Standard equipment is a sub-micron optical measuring scale system with dynamic signal processing for stability, pneumatic counterbalance in the Z-axis, and multi-sensor thermal compensation. The machine minimizes inspection cycle times due to rapid acceleration at 1,500 mm/s2 up to axis speeds of 500 mm/s.
The machine can measure a length L to an accuracy of 2.5 + 3.0L/1000 μm to a high degree of repeatability in an environment temperature between 16 and 26° C. An optional shop-floor pack with a pneumatic anti-vibration system and extended operating temperature range of between 15 and 35° C is available if the CMM is to be deployed in harsher or uncontrolled production environments outside a quality control room.
Simple one-touch software
The world’s first all-touch CMM software, TouchDMIS, is supplied with the machine. Requiring just a few hours of training for an operator to become proficient, it deskills CMM programming and measuring through its minimalistic user interface. It offers native import of STEP and IGES files and full CAD capability.
Ergonomically developed to provide maximum productivity for novice and expert CMM users, the touchscreen graphical user interface incorporates floating toolbars to maximize the area available for graphics, with all principal software actions accessed via eight large buttons. TouchDMIS has no drop-down menus or stacked toolbars — all functionality is accessed with a single touch. A choice of reporting options is provided.