VERICUT probes aero engine machining efficiency

Tusas Engine Industries (TEI) was founded to create a permanent aircraft engine industry in Turkey, providing products and services that will technologically develop the aviation and space industry. Its vision to be a worldwide, high quality and competitive main aircraft engine manufacturer is supported by strategic investment in advanced manufacturing CNC equipment and technologies. The latter includes on-machine component probing for closed-loop machining (CLM). Here, CGTech’s simulation and verification software, VERICUT, is not only providing protection for the company’s machine tools, but is also supporting the company’s technology drive.

From the technical knowledge gained in the Turkish defence industries through the Lockheed Martin (formerly General Dynamics) F-16 Fighting Falcon aircraft and the F110 engine which powered it; Tusas Engine Industries (TEI) was established in 1985 as a joint venture with General Electric and the Turkish Aircraft Industries (TUSAS), Turkish Armed Forces Foundation and Turkish Aeronautical Association.

Component manufacturing activities started in 1987, with the machining of 12 different engine parts. Today, over 700 different engine parts for 38 different fixed and rotary wing military and commercial engine programmes are produced. The engine parts manufactured by TEI are all flight safety assured for the latest generation aircraft from world leading aircraft producers, such as the Boeing B787 Dreamliner and Airbus A380.

Aero engine programmes for both civil and defence aircraft are supported by TEI

Aero engine programmes for both civil and defence aircraft are supported by TEI

The company is also gaining new technological abilities on its way to becoming a complete engine manufacturer with improved part manufacturing activities. These include Blisk-Spool production that requires completely different and critical manufacturing technology. A blisk agreement with GE to machine parts for the new LEAP (Leading Edge Aviation Propulsion) engine to replace less efficient engines for Boeing and Airbus single-aisle aircraft requires parts machined from forged blanks and friction welded at TEI’s facility.

With a constantly expanding range of rotating and non-rotating engine components, around 35 new parts come into the business each year for both civil and military aero engine programmes. Data for these come from various customers as solid models into TEI’s engineering department where the staff will decide how to produce the parts, which machine tools and cutting tools will be used and so on.

Complex CNC program files checked with VERICUT

Once the production method has been established it is passed to the CNC programmers. Siemens NX is used to produce the CAM manufacturing program with the NC code created by post processors written in-house for each machine tool type. TEI has a variety of Mazak and DMG machine tools and the post processors are very specialised, built using knowledge of the NC software and are optimised for high efficiency machining.

At TEI, the 10 CAD/CAM seats are supported by three seats of VERICUT, with the Siemens NX interface to make the transfer of files as efficient as possible. Once the NC program is complete the CAM programmers run VERICUT for every component. Component raw material can be cast, forged or billet with batches ranging from 1 off up to 200 parts, so change overs are frequent and the raw material is difficult or even impossible to replace if any errors occur during programming.

Engine programmes are supported with components for both hot and cold engine sections, produced in a wide range of nickel-based superalloys such as Inconel, Hastelloy and Waspaloy, as well as titanium and aluminium alloys. Machining cycle times can be up to 200 hours for complex components cut from these hard to machine materials, so there is no time in the delivery schedule to produce a replacement part, making VERICUT even more important.

With over 1,200 employees and 200 CNC milling and turning machines and only six CNC programmers providing CAM support, the department is always under pressure to improve cycle times and increase efficiency. This drive to improve machining time calls for the use of VERICUT simulation to protect the machines and the components and optimisation to improve efficiency.

Probing advantages

Creating a closed-loop production system, the company has already been using the custom made on-machine probing cycles to check the accuracy of the machined component. However, TEI is the first company in Turkey to set up such an advanced measurement and inspection routing within VERICUT. Checking collision of probe is normal within VERICUT, but TEI is starting to use full simulation during set-up and at predetermined points during the machining cycle using the VERICUT stage models.

Once the operator has placed the raw material in the machine, a preliminary measurement is made using the custom part probing cycles ­developed by TEI. Datum points are set by the design model and the (G54) work co-ordinate system, and the tooling offsets are calculated from these key points.

Rough machining is followed by probing and a gage cut before the component is probed for an accurate finishing cut. If there is still material on the part the offset is calculated by probing macros and applied to the tool and it is re-cut as a final operation. A final measurement probing will confirm the part is correct to the design model and then the next component is loaded ready to be machined. Probing only takes a few minutes for gage and finish cut, although the set-up probing can take a bit longer.

Finished parts will still have a full CMM check and report for the customer. The VERICUT supported probing provides internal assurance the process is controlled and closed-loop machining allows 24 hour operation on some machine tools with minimal staff. TEI plan to have the most advanced machine tools fitted with this probing capability.

DMG 5-axis milling machines

TEI’s most advanced multi-axis machine tools are protected by VERICUT

Before VERICUT was installed in March 2012, the NC programs were evaluated on the machine tools, using dummy raw material with the speeds and feeds turned right down in case of any collisions. This was time consuming given the variety of parts and the low batch volumes required. Although dummy parts are still used today, they are only to prove the cutting conditions are correct to achieve the specified surface finish.

Scrap rate has been reduced thanks to VERICUT, before the software was installed there was always some doubt with the NC program in case some mistakes may have been made, but since the verification software has been used the operators are confident that the program is correct and ready to use.

New machine tools are also introduced regularly and this presents another risk to the business. Although high level technical information from the machine tool supplier is requested to allow the post processor to be created as efficiently as possible, the options available on each machine and the parameters that can be specified makes each one unique. Again, VERICUT is needed with the machine tool accurately configured and simulated in the software to provide maximum protection.

Article published in Machinery, October 2014 [PDF]
Machinery Aerospace Supplement, March 2015 [PDF]