FEATURE CNC Machines
The lower-cost motion control assembly that Thomson customised for Bend- Tech integrated a stepper-motor driven motorised lead screw into previously ball-screw driven linear slide. The Thomson slides bolt together in a cross-like formation to move the plasma cutting torch and marking tools attached to the other side of the red plate on the right.
This meant it could specify a motorised lead screw (MLS) that does not need to be supported on both ends because the bearings within the motor support the load. And because the lead screw and the MLS rotor are one, there is no longer a need for external coupling of the screw to the rotor. “The way that Thomson has designed the components on this is really slick,” added Mr Merry. “They get the cost down by keeping components to a minimum. Using a motor with an integrated lead screw instead of a ball screw cuts the cost of coupling screw and motor together and all the support hardware that goes along with that.” The new motion control assembly is smaller than the system used on the A400 but it looks very similar with round rails, bearing, blocks and a carriage. Mr Merry said the fact that the new system looked exactly like a smaller version of the previous system was also a selling point for him because it provided continuity.
REDUCING THE COST OF REPEATABILITY In operation, the actuation system connects to a Windows PC that hosts the CAD/CAM software that stores design parameters such as lengths, bend angles, rotations, and material characteristics for each customer. The motion control system receives that information and follows the pre- programmed sequence, enabling the tool to switch from plasma cutting or part marking automatically. For both the A400 and the A250, all cuts and markings must be within a +/- 0.010-inch (0.25mm) tolerance. Enforcing such high precision are position sensors that establish a zero point and record
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The Dragon A250’s CAD/CAM software is pre-programmed with design parameters, which guide the Thomson linear motion assembly, controlling the system’s movement and achieving high repeatability.
With creative, cost-cutting engineering expertise from Thomson, Bend-Tech was able to develop the Dragon A250 to help meet increasing market demand.
any variation from it. In the A400, the sensors extended out to the side of the actuator assembly. All wiring was housed in an extruded, aluminium handle-like structure that ran from one end of the assembly to the other. In the A250 design, Thomson condensed all limit switching into systems electronics, machined a pocket into the end block and tapped in a hole into which the sensor could screw. Supporting the accuracy demands in this way without external fi xtures reduced the cost of the system further. Also contributing to what Mr Merry called “spot-on” reliability was pre-loading an ACME- threaded nut. Factory aligning the ball screw and the composite polymer nut resulted in much less play than the original ball screw assembly, which used a standard moulded nut.
BENT ON SUCCESS On the day Bend-Tech announced availability of the Dragon A250, the company sold four systems, and demand has been steady since. Some middle- market customers who had been using manual methods are anticipating more than a 500 per cent increase in productivity. And with interest in outdoor activities accelerated by pandemic- related quarantines and prospects of a building boom ge nerated by economic recovery, Bend- Tech is well-positioned for continued success.
Thomson
www.thomsonlinear.com
Irish Manufacturing September 2021 31
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