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Major machine tool builder offers their customer an entry-level, compact machine that works a 440-pound steel workpiece into a rock bit with better tool life, higher degree of accuracy and overall production efficiencies through partnership with Siemens
DMG MORI manufactures a wide variety of conventional chip-cutting machining centers for OEMs and production job shops serving the demanding oil-and-gas industry. Inherent in this market are several factors that lobby for great care and planning in the machining process. Typically, components produced for the oil-and-gas field are very large, very heavy and often have complex contours, making the machining time long and the tool life short. The DMU 50, although an entry-level 5-axis machining center from DMG MORI, is a compact unit that features considerable strength, as the following example will detail. “It is a David handles Goliath type of story,” says Matthias Leinberger, the business development director for Siemens PLM (Product Lifecycle Management).
On one recent application, DMG MORI was challenged with a 440-pound, 8” diameter x 8” high workpiece made from 1045 grade steel and being machined into a rock bit for oil field exploration. The customer further presented the builder with the need for fast changeover to produce the part from various metal materials, with all the attendant tool changes and workpiece setup variances present. The customer, a major upstream oil industry supplier, was trying to decide if the better path for this product was a single block of steel or a near net casting being machined. Both high-speed roughing and then very precise 5-axis machining were required in this small footprint machine, which had been selected by the customer due to specific plant capacity utilization concerns, plus their desire for a flexible, reasonably priced and highly cost-effective machine tool.
The machine builder turned to its longtime business partner, Siemens, for assistance. By offering a total package of CAD-CAM-CNC hardware, software and engineering services, Siemens was able to help the machine builder substantially improve every aspect of part production, including reduction of design-to-part protocols, machining time, tool life, surface finish, dimensional accuracies and overall production efficiencies. This scenario was particularly applicable in this case, as the production runs were anticipated to be low with short lead times.
Starting from the CAD file, the Siemens PLM team ran the program through its NX CAM process, eliminating the set-ups through full 5-axis operation. The User Defined Events (UDEs) feature inside the NX program allows simple check boxes for triggering post-processors references for coolant pressure, spindle speed settings and more. This avoids manual programming and, as a result, reduced the program transition time from as long as two days to approximately 30 minutes.
Once the program was ready for the CNC, the features of that control allowed a more streamlined simulation of the actual cutting path. The 3D quick set compressor feature provides a parametric itemized data file for all path motions, thereby eliminating collision and ensuring the optimum tool path, in conjunction with the NC kernel and PLC on the machine tool. As Siemens technical applications center manager Randy Pearson observes, “This feature is a huge time saver for our customer, as the test ball and probe in the spindle mechanism can be run at any point in the cycle, testing the actual machine kinematics at any time. The procedure can also be automated to run on the table at prescribed time intervals.”
The high-speed machining feature is highlighted here by Cycle 800, which is a static plane transformation that allows a 5-axis machine to define a rotated working plane in space. It is commonly known in the trade as 3+2 programming. The cycle converts the actual workpiece zero and tool offsets to refer to the rotated surface. Of note here, the cycle accommodates particular machine kinematics and positions the physical axes normal to the working plane. This is referenced as TRAORI or transformation orientation.
Meanwhile, Sinumerik Operate, the CNC’s easy-to-use, graphical user interface on the machine allows the operator to perform a variety of integrated tool management and information management functions, all transportable on a USB or network connection.
In the simulation, the loading and fixturing of the workpiece is performed virtually in the NX CAM program, which also calculates a consistent chip load, critical in these large material removal applications. The simulation further verifies the tool length at all cutting sections and the program is finalized for the machine to begin.
In production, this process also yielded a substantial improvement in tool life on this very heavy part over the 3-¾hour cycle time, according to DMG National Product Manager, Luke Ivaska. “With the combination of the NX CAM software, plus the CNC on the machine and all it could do, we had some initial challenges, as most software programs are purpose-built CAM packages that allow quick and easy use by anyone. They have significant limitations; however, as the software drives the tool path and the operator has very little control. With NX and Sinumerik CNC, we have a lot more input on the creation of the tool path. I have yet to find a problem I could not solve with NX.”
In the CNC, the Sinumerik Operate affords the end user’s operator and manufacturing engineering personnel full access to a variety of conditions in production, including all roughing and finishing data in plain text, plus all 5-axis transformation orientation data logged for restart after any interruption and manual restart.
Easy-to-use probing for work offsets is another advantage the builder and their customer enjoy with the CNC used on this machine. The operator is guided graphically for setting the workpiece zero, for example, while the tool length is automatically included in the calculation. With the Operate system, the difference between the position value in the machine coordinate system and workpiece coordinate system is saved in the active zero offset.
The variable streamline operation of the machine tool combines here with an interpolated vector to produce a smoother finish in the machining of the intricate rock bit surfaces in a single tool path. The machine seamlessly transitions from square-to-round machining and then the extreme angle paths needed to accurately machine the internal surfaces. A single bit portion of the program is automatically captured, so a step-and-repeat program can be built-up. The simulation of each bit cutting path was done on both the NX CAM and the CNC programs. It is literally like working with a “Digital Twin” of the machine.
This vectored program, it should be noted, is transportable to any machine with comparable results, according to Randy Pearson and PLM director of business development Matthias Leinberger, who comments, “Precisely because the machine kinematics are knowable, this program, once created, can be transferred onto multiple machines within the same facility or run by shops around the world, all tied together by the control, so there is total continuity between the operations, the data capture protocol and feedback received for production analysis.” Randy Pearson further noted that, in this application, the customer’s desire to change the materials used on successive runs could be easily accommodated by the control, owing to its ability for on-the-fly adjustments, based on the orientation of the tool tip to the workpiece.
This project was accomplished, using CELOS® onboard the DMG MORI machine. CELOS facilitates the total interaction between operator and machine, in this application, as it has numerous apps to enable instant call-up of actual conditions, full data comparison through a link to CAD and CAM products, plus full interface to the customer company’s ERP system for logging and analysis, with in-process remote adjustments achievable. In the case of this oil-and-gas customer, interactive communication to a global production network is also provided, which allow the customer to run parallel production of different rock bits at locations around the world, with seamless data tracking and full production analysis.
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Today’s machine shops, whether in the medical technology or tool and moldmaking sectors, can take advantage of an integrated Siemens CNC solution for everything from the design concept to the finished product.
The production of today’s medical implants involves an entire process chain, starting with the doctor and ending with the finished device. Doctors use the imaging data of a complex fracture, acquired with a computed tomography (CT) scan, to select an appropriate implant and then position it in the fracture area of the patient on the computer. Of course, this is only possible if the implant geometries are stored in a database, and the doctor has implants in stock or can access them immediately from a manufacturer.
Simulation of machining sequences
In plastic surgery, however, where implants specifically manufactured for each individual patient are needed, a different process is employed. Instead of pre-machined parts, implants are custom-made with the help of 3D imaging. In this case, the machine tools are controlled using the implant geometries. Calculated contours and shapes are acquired by the CT scan to produce implants that are literally a perfect fit. However, the feasibility of the planned production process can first be determined on a monitor using, for example, an NX graphic simulation from Siemens to avoid potential collisions or damage to the workpiece contours.
Technology package for milling
High-speed cutting (HSC) is a machining process with high material processing speeds. HSC machine tools achieve high spindle speeds, combined with feed rates that are much higher than those of conventional machine tools. Consequently, they require control systems and part programs that perform equally fast. The Siemens Sinumerik® 840D solution line CNC is specifically designed for the requirements of medical technology and this precision part HSC work. Integrated functions onboard the CNC assist users with set-up and programming, thus allowing faster and more precise production sequences.
Together, the Sinumerik CNC system and ShopMill® software from Siemens form a milling technology package that allows machine operators rapid access to the functions they need. Thanks to graphic function display and plain language input dialogs, cycles can be used quickly and effectively, after a brief training period. Even the smallest errors can be corrected during operation, using multi-axis kinematic analysis. The Siemens Safety Integrated® solution further provides protection for personnel and machinery. This software can be used to interlink emergency stop buttons and light barriers. In the event of an operating error, dangerous movements are immediately brought to a standstill and the power supply to the motor is quickly cut.
The use of measuring probes
The production of artificial knee joints on an HSC 20 linear milling center manufactured by DMG, for example, can be fully controlled and monitored by a Siemens Sinumerik CNC system. With its broad range of functions, this milling center is particularly well suited for use in the medical technology sector. It is equipped with linear drives on all axes and achieves acceleration rates over 2g. The machine can also generate a surface finish down to 0.2 micrometers Ra. The liquid-cooled machining spindle operates at speeds up to 42,000 rpm, thereby covering an extensive range of potential applications in the medical sector, where materials such as titanium, chromium-molybdenum, tantalum and niobium are typically milled.
In order to achieve maximum precision during implant production, while also maintaining a consistently high level of product quality, parametric measurements must taken continuously from both the machine and the workpiece. probes, for example, on HSC production machines measure tool dimensions in-process, detect broken tools and are used for the set-up and measurement of workpieces. In medical machine shops currently, the targeted use of such measuring probes can reduce set-up times by up to 90%, while substantially improving process control.
Metal parts used in medical technology are often extremely complex. Therefore, choosing the right tooling can have a great impact on the quality of the finished products. After all, proper cutting tools ensure that the parts leaving the machining center are absolutely precise and require no further finishing work. Although the materials used for many medical and orthopedic parts are often quite difficult to machine, the tools must fulfill high performance requirements with respect to the precision and surface quality of these implants. Iscar, one supplier of such tools, offers a program for monitoring the use of precision tools on turning, drilling, milling and finishing jobs. They also help users assess the performance qualities of non-vibrating carbide milling cutters, which are well-suited for machining implant materials, plus they can offer information on more cost-effective and efficient machining processes.
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Siemens Industry Sector is the world’s leading supplier of innovative and environmentally friendly products, solutions and services for industrial customers. With end-to-end automation technology and industrial software, solid vertical-market expertise, and technology-based services, the sector enhances its customers’ productivity, efficiency and flexibility. With a global workforce of more than 100,000 employees, the Industry Sector comprises the Industry Automation, Drive Technologies and Customer Services Divisions as well as the Metals Technologies Business Unit. For more information, visit http://www.usa.siemens.com/industry.
The Siemens Drive Technologies Division is the world’s leading supplier of products, systems, applications, solutions and services for the entire drive train, with electrical and mechanical components. Drive Technologies serves all vertical markets in the production and process industries as well as the infrastructure/energy segment. With its products and solutions, the division enables its customers to achieve productivity, energy efficiency and reliability. For more information, visit http://www.usa.siemens.com/drivetechnologies.Continue reading