Modern manufacturing techniques, coupled with advanced and lightweight airframe designs, place immense amounts of stress on the materials and structures being used in the latest generation of passenger aircraft. With this issue in mind, aircraft manufacturers have to be confident that the materials being delivered to them are capable of undergoing hours of vibration, thermal cycling and multiple load conditions.
Goods-in inspection is the first line of defence in this battle to ensure optimum material suitability. So, when a leading aerospace company needed to ensure the stress state of the aluminium arriving at its production facility it turned to Henlow-based Ansell Motion Control for a test rig. In turn, Ansell Motion Control turned to Hampshire-based Oriental Motor to deliver the precision needed for this demanding task.
Oriental Motor's EZLimo linear actuator range combines advanced stepping motor functionality and sophisticated motion control features and houses them in an easy-to-use linear motion solution. The range uses an Oriental Motor stepping motor with built-in feedback system and closed-loop control to ensure stable operation. The motor, ball screw and feedback system are all housed in a compact and stylish body.
In this particular application, the EZLimo units and drivers are used to control the position of aluminium test billets – representative of material destined to become wing spars – throughout a milling operation that is used to determine the residual stress in the material. The Wide Slot Stress Analysis rig machines a slot, to a depth of up to 60% of the depth of the test billet, at a variety of increments between 0.1 and 1mm. The aluminium is supposed to be delivered de-stressed from the supplier – but the airframe manufacturer cannot take chances. And, by measuring the deflection of the far end of the 12-inch long aluminium billet after each pass of the cutting tool, the stress levels within the material can be determined.
The calculations, performed by software developed by a leading UK university, use figures supplied by Ansell's test rig, such as depth of cut, step number and the amount of deflection – measured by LVDTs. These figure are used to generate at a stress value for the particular batch being tested. According to Andrew Sell, of Ansell Motion control: "The deflection is not always uniform, a bar could bend downwards during the first cuts and then bend upwards towards the end of the procedure. It is the LVDT figures we are interested in, in relation to the cutting schedule.
"I chose Oriental Motor's EZ Limo unit because it cuts a huge chunk out of my design and development time. Because the actuator is all self contained it is simply a case of mounting the device and marrying the end of the rod with the component that needs to be moved – I do not have to worry about the alignment because it is already there.”