RETROFITTING OF CNC SYSTEM TO CONVENTIONAL LATHE FOR CONVERTING INTO CNC LATHE

8/10/2019 RETROFITTING OF CNC SYSTEM TO CONVENTIONAL LATHE FOR CONVERTING INTO CNC LATHE

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The Retrofit Advantage FANUC FA America

Document # MWA-018-EN_01_1111 www.fanucfa.com Page 2 of 16

1 I n t r o d u c t i o n 3

2 W h a t i s a C N C r e t r o f i t ? 3

3 W h a t a r e t h e b e n e f i t s o f a C N C r e t r o f i t ? 4

3.1 Lower cost ................................................................................................................................................ 5

3.2

Energy sav ings ......................................................................................................................................... 5

3.3 Performance ............................................................................................................................................. 6

3.4 Improved mean-time-between-failures .................................................................................................. 9

3.5 Improved mean-time-to-repair ................................................................................................................ 9

3.6 Data accessibility and customization .................................................................................................. 10

3.7 Improved suppor t ................................................................................................................................... 11

3.8 Standardization ...................................................................................................................................... 11

3.9 Access to new features ......................................................................................................................... 12

4 H o w t o s e l e c t a r e t r o f i t p a r t n e r 1 2

5 J u s t i f y i n g a r e t r o f i t 1 3

6 S u m m a r y 1 3


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1 IntroductionWithout question, your machine tools are among the most vital and costly pieces of equipmenton your plant floor. For most companies, machine tools represent significant capital investmentsand must therefore maintain their viability for many years. Upgrading to the latest controltechnologies via a CNC retrofit is one way companies are successfully extending the productive lifeof their machine tools. In this whitepaper, well address some of the key considerations you shouldmake before implementing a CNC retrofit project. Well also help you quantify the value of thisimportant decision.

Retrofitting is the process of replacing the CNC, servo and spindle systems on an otherwisemechanically sound machine tool to extend its useful life. Rebuilding and remanufacturing typicallyinclude a CNC retrofit. The anticipated benefits include a lower cost investment than purchasing anew machine and an improvement in uptime and availability. But there are often otherunanticipated benefits to retrofitting including lower energy costs, higher performance and a newlevel of manufacturing data accessibility.

Manufacturing requirements have dramatically changed in the last two decades, and many newfeatures are now available to support Lean Manufacturing. Retrofitting is a competitive business, soretrofitters will often quote a very basic control system configuration unless you specify thefunctionality that is important to your operation.

Selecting the best retrofit partner can sometimes be confusing, and it is important to make sure thatthe company has experience with the specific type of machine tool that is to be upgraded in yourfacility. It is also essential to ensure that the scope of work is clearly defined for an apples-to-apples comparison of competing proposals, and to establish a long term, win-win relationship withthe selected retrofit company.

Justifying the retrofit investment is similar to any other kind of investment. Considering all thefinancial costs and benefits allows you to calculate an ROI for a comparison with other investmentopportunities. By considering all the financial and non-financial benefits associated with the project,you will be able to decide if the retrofit makes sense for your business.

2 What is a CNC retrofit? A CNC retrofit typically upgrades the CNC, the axes servo motors and drives, the spindle motorand drives, and a portion of the associated wiring and related electromechanical components.Unlike rebuilding and remanufacturing, a CNC retrofit does not include any major repairs to themachine mechanics. A CNC retrofit should not be confused with a CNC conversion, where amanual machine is converted into a CNC machine.

Assuming the machine tool is generally in good shape mechanically, CNC retrofitting is typically thelowest cost solution to improve the overall performance of an older machine tool. Though someelectrical subassembly is often performed at the retrofitters business location, most of the work can


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With todays focus on energy conversation, theCNC can display data on real-time energy usage.The data is also accessible via Ethernet to recordthe energy usage information into a database forfurther analysis.

3.3 Performance

When considering a CNC retrofit, it is important torealize that a significant portion of the benefits willactually be delivered by upgrading the servo andspindle system to a high-speed, digital interface. Itdoes not matter how fast the CNC can processblocks of part program data, if the servo andspindle systems cannot keep up.

The CNC, servo and spindle systems integrated inan older machine tool typically communicate usingan analog interface. The CNC commands thedesired velocity of the motor with a 10-volt signal,while low-resolution, analog or digital feedbackdevices tell the CNC where the axes are currentlypositioned. Simple I/O points are used to enableand disable the drive systems, and to report on anydrive or motor failures.

The coarse resolution and the noise susceptibility of the analog drive interface limit the achievablespeed and accuracy of the system. Tuning traditional analog drive systems is more of an art than ascience, requiring experienced engineers using specialized tools for even basic system stability.

The modern CNC and the digital servo and spindle drives are so highly integrated, it is best toconsider them as a single system. The subsystems communicate over high-speed fiber opticcommunication paths to provide the required noise-immune bandwidth for very high-resolution,intelligent feedback devices and inter-process communications. Todays high-performance systemsprovide nanometer resolution from the initial block processing through to the 16-million count, serialencoders delivering the smoothest surface finish on contoured surfaces. A large proportion of theadvanced capabilities of the modern CNC system are at least partially implemented in the digitalservo and spindle systems processors.

The tight integration of todays CNC and digital drive systems provide advanced servo tuningapplications built right into the control that makes standard servo tuning practically automatic. Foradvance tuning, Ethernet communications provide engineers powerful frequency analysis, Bodeplots and Fourier analysis tools to analyze and display the servo system response in real-time andin 3D for 5-axis applications. These tools are also used to tune spindle systems, since they are alsoused as servos for rigid tapping and live-tool applications.


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Diagnostic systems have also advanced, allowing everything from motor temperature to positiondeviation to be displayed on the CNC. Precise error messages are displayed on the CNC for eachspecific potential problem, and common remedies are also provided.

Older machine tool servo systems featured limited exponential acc/dec or perhaps a simple linearacc/dec. Machine structures often reacted violently to exponential acc/dec because of inherentmechanical resonances. Linear acc/dec is more gentle on mechanical structures, but there is still atime when the axis must go from dead stop to accelerating at the start of a move, and then fromdecelerating to a dead stop at the end of a move.

Bell-shaped acc/dec minimizes many of the fundamental problem of machine resonances by usingan S-shaped curve. During the first microseconds of a move, the acceleration of an axis is rampedvery gently until the linear section is reached. When the axis reaches top speed, or when goingfrom top speed to decelerating, or when decelerating to a stop, the same simple. gentle ramping ofacc/dec rate occurs. This typically allows the linear section of the acc/dec curve to be set moreaggressive than is possible with standard linear acc/dec, reducing the overall cycle time.

CNC high-speed machining technology can be applied to any machine tool to speed up processingand reduce cycle time by as much as 50%. Block look ahead, acc/dec before and afterinterpolation, nano-interpolation, nano-smoothing and automatic feedrate control by corner, circularradius, acceleration, cutting load torque, and jerk are just some of the technologies that can beapplied to make the machine more accurate and therefore have the ability to go faster.

The only absolute physical limit to the productivity of a machine tool is typically the spindlehorsepower available to remove material. Practically, machines are not run at maximumhorsepower during finishing cuts because surface finish specifications are more important than


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productivity. However, even during roughing-cuts, a machine rarely takes a full load because ofprocess variation concerns.

The horsepower required to cut a particular material is proportional to its hardness, the depth andwidth of cut, and the sharpness of the cutting tool. The hardness of some materials varies frombatch to batch, from piece to piece, and even within a cut. The depth-of-cut of the initial passes areoften lighter than the subsequent passes because the surface level is unpredictable from part topart. When contouring and facing, the width-of-cut may vary continuously. As tools wear, morehorsepower is required to cut the same material. All of this potential process variation means thatthe programmer ordinarily selects a very conservative feedrate, and the machine capabilities areunder-utilized.

Adaptive control allows a power level to be specified in the part program along with a targetfeedrate. This feature automatically adjusts the actual feedrate to maintain a constant horsepowerthat is suitable for the machine and tooling. As material hardness, depth-of-cut, width-of-cut, andtool condition varies, adaptive control speeds up or slows down the actual feedrate as required,

decreasing the overall cycle time by as much as 40%.High Response Vector (HRV) is an advanced form of field oriented control that uses high-speedDSPs and nano-interpolation to improve surface finish, cycle times and accuracy. Auto-followingfilters dynamically suppresses mechanical resonance even when the frequency changes. Forexample, HRV4 closes the current loop in 31.25 s, the velocity loop at 62.5 s and the positionloop at 250 s.

Since the axes drive systems have to be tuned on the new retrofit system, it is an ideal time to addsome of the performance machining options and get the expert tuning needed to maximize thecapabilities of the machine.


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the 4G storage as a buffer. The Data Server includes an FTP (file transfer protocol) server, so itcan be accessed in Windows Explorer as just another virtual hard disk folder, providing high-speed,drag-and-drop part program downloads.

There are several choices available when implementing custom applications. The FOCAS2 APIcan be used to integrate external PC-based programs. The C-Language Executor option availableon FANUC controls provides a powerful, industry standard tool for creating custom displays andimplementing control algorithms. The FANUC PICTURE tool provides an easy-to-use applicationdevelopment environment that has draw-and-click features similar to many common SCADA tools,and it can be integrated with other C-Language Executor applications.

If the Windows development environment is preferred, Microsoft CE provides the Windowsinterface in an embedded operating system that eliminates virus vulnerability and the unreliablehard disk. FANUC has also introducing Embedded Windows, which supports standard applications,but allows the machine tool retrofitter to select only the operating system components required tosupport an application. This reduces system vulnerability and gives the retrofitter the option to

choose flash storage over a hard disk, thereby increasing reliability.

3.7 Improved support

Technical and training support may be limited on your older CNC. Even if the original manufactureris still in business, they may not have resources available that are experienced with your particularcontrol vintage.

FANUC protects its sizable installed base of CNC users in the Americas with a comprehensivesupport offering. Free technical support is available during normal business hours to assist yourpart programmers, operations staff and maintenance engineers. Support contracts are also

available to provide 24/7 technical support.Seasoned application engineers are available to help you decide what features are most beneficialto your operation, and to assist your chosen retrofit partner to implement the wide range of FANUCsolutions to maximize their effectiveness. In addition, productivity specialists can review youroperations and help identify additional features that may enhance your operational effectiveness,both for the retrofit machine and the other assets in your factories.

3.8 Standardization

Many machining operations use a wide range of machine types for a variety of applications

including turning, machining, grinding, gear cutting, punching, laser cutting and other specializedapplications. There are a few machine tool builders that can offer a comprehensive line of machinetools that cover a significant portion machining applications, but typically the end-user mayconsider that there is a best-in-class manufacturer available for each type of application.

Control standardization is an important factor to simplify operation, part programming andmaintenance, allowing more agility in applying labor resources. The FANUC CNC is available onpractically every type of machine tool, providing commonality for the critical machine function.Manufacturers that might offer an alternative CNC as standard will also offer the worlds leading


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control to meet a specific customers requirements. Therefore, selecting a FANUC CNC for aretrofit is an important element in standardizing manufacturing processes.

3.9 Access to new features

There have been many CNC technology advances in the last twenty years to support the evolution

of machining processes. The CNC is now a relative super-computer when compared with thetechnology that is currently integrated into older machine tools.

With multiple, faster, and distributed microprocessors, and with a magnitude increase in systemmemory, the CNC can now incorporate advanced software algorithms that can model the machinemechanics, and dynamically compensate for inherent, undesirable mechanical characteristics.

Numerous features have been added to the CNC to reduce setup, minimize downtime, increaseprocessing speeds, minimize minor stoppages, and improve setup and production part yields.Many of these new features address issues that are critical success factors for lean manufacturingenvironments, and they typically cost less if implemented with a new CNC purchase, including

during a retrofit.

4 How to select a retrof it partnerNorth America has more than 250 retrofitters, ranging from one-person operations to companieswith 50-employees or more. Many machine tool builders also specialize in retrofitting their ownmachines. There is obviously a cost impact of selecting a partner that is not local, but there couldalso be serious warranty issues if the company is no longer around when you need assistance.

Machine tool builders and retrofitters often specialize in certain kinds of machines. So when

choosing a partner, it is important to make sure that they have competencies related to yourparticular type and model of machine. Ask for references and confirm the quality of the workperformed and determine how long the machine was out of commission during the retrofit.

It pays to get multiple quotes for any significant investment, and compare them for discrepancies touncover any lack of core competencies. Make sure you are comparing apples-to-apples oneverything, including the CNC features, the work to be performed, and the length and terms of thewarranty. Document everything related to the scope of work to ensure a common understanding fora long term, win-win relationship.

Check the availability and quality of the documentation that will be provided with your retrofit,including wiring diagrams, and the machine, CNC, servo and spindle drive manuals. Thedocumentation set needs to cover, operation, programming and maintenance.

Look for pre-engineered kits from machine tool builders, retrofitters and control manufacturers. It isnot uncommon for a company to provide kits for a high-volume machine tool with a good brandname that is common in the industry. These kits typically include everything necessary to completethe retrofit of the machine onsite, amortizing the engineering costs over multiple installations, sothey should cost less than a custom retrofit.


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FANUC FA America1800 Lakewood Boulevard

Hoffm an Estates, IL 60192888-FANUC-US (888-326-8287)Find more info rmation at www.fanucfa.com

Technical data is subject to change without prior notice. No part of this document may be reproduced in any form. All rights reserved. 2011 FANUC FA America Corporation

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RETROFITTING OF CNC SYSTEM TO CONVENTIONAL LATHE FOR CONVERTING INTO CNC LATHE