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How To Increase Energy Efficiency With Machine Tools

How To Increase Energy Efficiency With Machine Tools

Machine tools include numerous motors and auxiliary components. Energy consumption varies significantly during operations. From the process itself to individual component power consumption, savings potential can be evaluated and measures defined for more efficient energy use. Article by Grainger.

One area of potential savings comes from the machine tool base load, which consumes energy even in nonproductive phases. The base load is determined substantially by the machine’s auxiliary components. Besides use of energy-efficient motors in these components, many opportunities for reducing the base load can be found. Some energy consumers, for example, can be switched off by the machine control during non-productive phases.

Scrap inevitably increases energy consumption per good part. Manufacturing with accuracy from the very first part can therefore be decisive for energy efficiency. Machine designs with balanced thermal behaviour and precise position measuring technology have a distinct advantage here.

Energy Demand During Milling

Power requirements of a milling process fall into the following consumer groups:

  • Cooling lubricant processing
  • Compressed air generation
  • Electrically powered milling-machine auxiliary components
  • CNC control package with main spindle and feed-axis motors

Proportionally calculated energy for lighting, ventilation, and air conditioning must be added to these groups. Milling process energy demand depends primarily on the size of the milling machine and the machining task.

Dry machining has great potential for improved energy and resource efficiency. In many milling applications, however, doing without cooling lubricant increases scrap rate and, therefore, raises mean energy consumption as well.

Compressed air is required for minimum spindle lubrication, tool changing, and work piece cleaning. Small quantities are required as sealing air. Mean compressed air power changes only slightly across production readiness, roughing, and finishing.

Machine electricity consumers include the CNC control with main spindle and feed-axis motors, as well as numerous auxiliary components, including the pallet changer and cooling, hydraulics and automation systems.

Drive Component Efficiency

Spindle and feed-axis motors are among the central components of a machine tool. Drive-component energy efficiency depends on the ratio of delivered power to consumed power. The network of drives converts consumed electrical energy to delivered mechanical power. Drive network components include a power supply module, drive modules, motors and mechanical components. Data on efficiency typically refer to the rated power. For other rated values, individual component efficiency can vary significantly. Supply modules and drive modules can attain efficiency values of more than 95 percent.

Comparing power consumption during rough-face and circular-pocket milling reveals that feed drives consume only a small share of the CNC’s total power usage. On the other hand, spindle selection can significantly affect energy consumption. If a spindle drive operates far below its rated power, the drive’s intrinsic losses increase in proportion, with negative effects on the energy balance. If the spindle limits the maximum possible metal removal rate, the milling process inevitably takes longer. The result: energy efficiency decreases due to the base load generated by the auxiliary components. Potential also exists for more efficient design of milling processes through consideration of spindle-motor efficiency, for example by using synchronous instead of asynchronous motors.

Regenerative Supply Modules

Every drive’s acceleration requires a braking process in return. Energy from the drives’ moving masses is largely reconverted to electrical energy. In a non-regenerative supply module, kinetic energy released by braking is converted to heat by the braking resistors. A regenerative supply module returns this energy to the power grid. However, the path required for returning the energy and the necessary components for smoothing the grid power generate losses even when the drives have no power requirement. Power loss increases slightly even when power is not being regenerated. Thus, a regenerative supply module operates more efficiently than a non-regenerative module when the regenerated energy more than compensates the higher power loss. Machine operation therefore determines what type supply module to employ.

Tool change frequency also impacts this decision. In one example, a milling operation at 15 kW is interrupted cyclically by a tool change. Starting the spindle requires peak power of approximately 60 kW. A regenerative supply module returns 48 kW to grid power. High metal-cutting power requirements mean that the mean-input power sinks the more frequently the milling process is interrupted by tool changes.

A regenerative supply module works more efficiently as soon as the time interval between two tool changes is less than 100 seconds (equals 0.6 tool changes per minute). In processes with many tool changes per minute, a regenerative supply module often proves to be the better choice. During contour milling with infrequent tool changes, the advantages are on the side of the non-regenerative system.

Deactivation Of Auxiliary Components

In the ready condition, energy use of several consumer groups is only slightly reduced. Therefore, these nonproductive phases must be kept as brief as possible. With machining centres for smaller production batches, energy consumption can be significantly reduced by the selective deactivation of auxiliary components. Beyond this, potential savings result from the use of energy efficient pumps in the coolant and lubricant circuit.

However, consistent switch-off of auxiliary components – such as hydraulics and spindle cooling – or of the compressed-air supply can also have a deleterious effect. If sudden removal of waste heat from auxiliary components, or of temperature-stabilising media, leads to thermal displacement in the machine frame, scrap can result. Selective auxiliary component switch-off therefore functions best on machines with little inclination to thermal displacement.

CNCs can be the central control unit for machine tool energy management, taking advantage of special PLC functions for linking events in the production process (such as NC stop) with outputs for controlling auxiliary components. Delay times can be assigned to events so that, for example, motors can be locked and disconnected from current after standstill. Functions for deactivating various auxiliary devices, axes, light in the working space, etc., can be generated on this basis. These basic functions are the responsibility of the machine tool builder. For users, it is helpful to adapt energy management to specific usage habits.

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Case Study: Collaboration Between Hartford And Renishaw In The Implementation Of Smart Factory Solutions

Case Study: Collaboration Between Hartford And Renishaw In The Implementation Of Smart Factory Solutions

In the face of global skills shortages and rapidly emerging Industry 4.0 trends, Taiwanese CNC machine manufacturer, Hartford, sought to develop an innovative, easier-to-use human machine interface (HMI) for its CNC machines. At the same time the company strived to ensure process measurement and inspection at its CNC machine manufacturing operations could keep pace with the company’s ever-improving product quality goals.

Achieving The Goal Of “Intelligent Manufacturing”

At Hartford’s manufacturing facility in Taiwan, the company produces a complete range of medium to large-sized three-axis and five-axis CNC machines for use in major industry sectors including the aerospace, automotive, electronics and energy industries. And with more than 95 percent of the company’s cast components being manufactured and machined in-house, a continuous and progressive approach towards quality inspection is essential for achieving the precision required for a wide range of machine components, including machine heads, spindles and automatic tool changers.

However, a widespread shortage of skilled labour has presented Hartford with a further vital challenge to address, as Mr. Bruce Lin, Manager of Hartford’s R&D Intelligent Technology Department explained:

“Our customers [need] to process work pieces of increasing complexity, however a lack of skilled labour means they are having to insist on machining centres that are even simpler to use.”

Intelligent HMI Through Renishaw’s App

Hartford has invested significant resources into the research and development of intelligent CNC controllers in recent years and developed the Hartrol Plus, which is an intelligent controller that is as simple to use as a smartphone.

The HMI provided by the Hartrol Plus CNC controller follows key design principles promoted by Industry 4.0 ideals and helps address skills shortages. It provides machine operators with all the information they need to make the right decisions.  The way in which it visualises data also helps operators to make more informed decisions and solve problems rapidly.

Furthermore, by integrating Renishaw’s Set and Inspect on-machine app with Hartford’s new controller, users can now exploit advances in automated measurement and data collection, making machine tool operation and human-machine interactions simpler and more intuitive. This is because, Set and Inspect is a highly visual graphical user interface (GUI) which leads the operator through every step of on-machine probing processes including workpiece set-up, tool setting and other measurement tasks.

Hence, operators no longer need to commit machine code instructions to memory. This reduces data entry errors and programming times and facilitates processing efficiency by as much as 20 percent.

Precision Measurement For High Quality CNC Manufacturing

Hartford began using Renishaw products more than 20 years ago. In order to meet its stringent high-quality objectives, the company has introduced a variety of Renishaw high-precision measurement systems.

The precision of all CNC machined components it manufactures is verified using Renishaw PH20 5-axis probes on co-ordinate measuring machines (CMMs). This happens before components enter the assembly line, to ensure that they are ready to be assembled.

Precise assembly and positioning of machine tools is also critically important, with five-axis machine tools needing to be positioned with a deviation of less than ±6 µm. A Renishaw XL-80 laser interferometer is used to measure machine position and both linear and angular errors. The XL-80 generates an extremely stable laser beam with a wavelength that conforms to international standards.  Linear measurement accuracy of ±0.5 ppm can be guaranteed, thanks to a precision stabilised laser source and accurate environmental compensation. Hartford uses the Renishaw QC20-W ballbar measurement system to perform cross-validation at different operating speeds to ensure that X- and Y-axes of the machine tool are correctly matched, and errors are kept down to less than 5 µm.

Every Hartford CNC machine not only undergoes 100 percent laser verification and ballbar testing before dispatch, it can also use the customer’s own workpiece for processing verification, with Renishaw OMP40, OMP60 and RMP60 machine tool measurement probes used to measure the precision of the processed work piece.

Axiset Check-Up For Rotation Centre Compensation

Hartford also uses Renishaw AxiSet Check-Up to analyse the performance of machine rotary axes. Compatible with common 5-axis and multi-axis machines, it provides CNC machine users with a fast and accurate way to check the location of rotary axis pivot points and automatically compensate if necessary.

Most importantly, AxiSet Check-Up does not need to rely on operator experience, as the operator can simply call up the relevant program and press “Cycle Start” to complete the test process in just a few minutes. Data is automatically recorded into parameters for use in analysis, further guaranteeing the standardisation of every machine tool produced.

Regarding this, Mr. Lin has said, “We also recommend that users use AxiSet Check-Up to test the machines’ rotary axes after they are installed, as factory conditions may differ significantly from Hartford’s manufacturing conditions, in terms of foundations and how level surfaces are.  Shipping and installation can also cause precision errors, so AxiSet Check-Up’s automatic compensation allows machine tools to maintain high levels of precision and quality.”

He continued that, “All machine tools can suffer from wear and drift after a certain period of usage, with the level of precision of their positioning declining over time and causing a correspondingly poor level of machining precision. We therefore recommend that users perform scheduled checks on machine tools using AxiSet Check-Up every 6 to 12 months, in order to ensure that the level of machining precision remains consistent and productivity remains high.”

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Launch Of Taiwan International Machine Tool Show 2018

Launch Of Taiwan International Machine Tool Show 2018

TAIWAN: Taiwan International Machine Tool Show (TMTS), a machine tools and accessory procurement platform organised jointly by Taichung City Government and the Taiwan Machine Tool and Accessory Builders’ Association (TMBA) has been launched!

Boosting wp to 720 exhibitors in a five-day exhibition, TMTS is estimated to have attracted more than 80,000 visitors from Taiwan and abroad. The exhibitors will endeavor to secure orders amounted to as much as NT$10 billion.

Mr. Jui-Hsiung Yan, chairman of the Taiwan Machine Tool and Accessory Builders’ Association (TMBA), said that the theme of the 2018 TMTS is “Manufacture Linking • Activate the Future”. TMTS called on the stars of the machine tool and accessory industry to showcase Taiwan’s complete and diversified industrial supply chain. Major manufacturers such as TONGTAI, YCM, Victor Taichung, GOODWAY, AWEA, and HARTFORD, etc. will take a lead to demonstrate Taiwan’s most competitive machine models and main products, such as vertical and horizontal machining centres, lathes, milling machines or turning and milling centers, etc. Moreover, products that emphasise smart manufacturing elements such as COSEN’s smart Bandsaw CPC System for Industry 4.0, FEMCO’s Wheel Machining Automation, the intelligent lathes of SUNFIRM, and the Intelligent Linear Motor Drive Wire Cut EDM of CHMER are also expected to be highlighted in this exhibition.

In addition to the momentum of the whole machine factories, component manufacturers that have had a place in the global machine tool supply chain are equally invigorated. For example, besides the well-known linear guideway components, this year HIWIN will also present its successfully mass-produced Harmonic Drive. POSA is also geared to show visitors a complete spindle product line. TANSHING will display the 5-Axis CNC Rotary Table which is in line with intelligent automation requirements. HABOR will showcase energy-saving and environmentally-friendly industrial coolers. Products from other partners including index tables, tool magazines, cutting tools, toolholding & workholding devices, tools, measuring instruments will also be on display. It is also believed that TMTS can meet the needs of visitors and offer high-quality and customised services.

Besides diverse and innovative exhibition items, the Taiwan Machine Tool and Accessory Builders’ Association (TMBA) will organise purchasing conferences during the 2018 TMTS to help Taiwanese companies expand their overseas markets and seek business opportunities with foreign companies. TMBA will invite international buyers and exhibitors to conduct one-on-one negotiations, effectively matching international buyers and exhibitors, and thus making TMTS the best platform for the industry and customers to communicate with each other and grasp the market pulse.

Furthermore, during the show, not only enthusiastic exhibitors are fully committed to providing buyers from all over the world with complete and diversified manufacturing services, but TMBA will also cooperate with machine tool manufacturers to extend business opportunities from the exhibition venue to the factory. From November 7 to November 9, there will be eleven factories open to foreign buyers to visit, allowing customers to break the limit of the exhibition venue, and witness the production status and working attitude of Taiwan’s machine tools and accessory manufacturers. Customers will also be able to see the most authentic aspect of Taiwan’s machine tool industry.

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Hydrostatics—The Solution For High Precision In XXL Machine Tools

Hydrostatics—The Solution For High Precision In XXL Machine Tools

Does your customer have high requirements with regards to workpiece accuracy? One adjusting screw to guarantee a high accuracy is hydrostatic. Especially if you produce lot size 1 or large and complex workpieces, you have to avoid inaccuracy has to be avoided in the finished part, because if these parts are wasted, so is a lot of time and money. By Schiess GmbH

But what are the functions, advantages and disadvantages? References are also important for customers. Here you’ll find some answers to these questions.

Function/Explanation

Hydrostatic: An explanation | Image Source: Schiess

The contact surfaces of a guide or bearing are separated through a permanent oil film during the usage. The oil quantity is delivered from outside the machine. It is needed to generate and sustain the oil film. Therefore the height of the oil film is independent from the sliding velocity (one difference to hydrodynamic guides and bearings). How does it work? One side is equipped with pockets inside, e .g. the moveable gantry at our VertiMaster VMG. The oil is pushed into the pockets through supply lines. The distance between the pocket surface and the guide surface is named as the gap height h. The starting height h0 is about 10 µm to 60 µm (depends on the design and calculation of the pockets and the oil quantity). The pressure distribution is shown in the figure.

The pressure in the pocket pT is constant over the pocket and falls down to zero at the end of the pocket surface. If the oil aggregates are working, there will be a permanent oil film between the pocket surface and guide surface.

Advantages and disadvantages

The usage of hydrostatic guides and bearings has a lot of advantages:

  • Wear-free, therefore lower maintenance costs, higher machine availability and life cycle time
  • No change of the parameters of guides and bearings during the life cycle
  • High positioning accuracy
  • No start-up friction (pure fluid friction)
  • No stick-slip-effect
  • Excellent damping

The challenge—you have no advantages without disadvantages:

  • High manufacturing costs and challenging tasks to manufacture
  • High costs in case of additional aggregates

High Accuracy

In the opinion of Schiess GmbH, a German machine tool builder with over 160 years of experience, the usage of hydrostatic is a very important feature and advantages of our machines. They build up XL machines, aerospace machines and XXL machines (faceplate diameter till 12,000 mm, table length till 60,000 mm and longer, passage height till 8,000 mm). They offer a high product quality thanks to high manufacturing depth and quality (e.g. complete assembly in-house, air conditioned measuring laboratory, 100 percent measurement of the finished components) and high process quality thanks to extensive studies and support (e.g. preparation of stability maps as the basis for technology proposals (production optimisation).

Furthermore, there are some solutions to guarantee high precision manufacture without hydrostatics. Here you will see two of them.

Solution 1: Accuracy through process design

A machine tool manufacturer supports its customers during the selection of the right tools and process strategies. The reason: they don’t believe that they know everything better. But if they know the ideas and requirments of their customers from the beginning, they are better equipped to help at a later stage. Our application technology provide the complete process from the first ideas till the successful implementation in our instance.

Solution 2: Accuracy through design and usage of hydrostatic guides and bearings

Schiess XXL machines are equipped with hydrostatic guides in all linear axes. They are wear-free and keep the accuracy over the complete lifetime. The most important advantage is the huge damping. The faceplate is also equipped with a hydrostatic bearing.

Hydrostatic face plate | Image Source: Schiess

The combination of the guides and the bearing take care that the process forces are not transferred to the rest of the machine. No external vibrations disturb the process, thus the process is decoupled. This is extremely important for high precision finishing or the “last cut“ of a workpiece. Additionally, we perform static and dynamic finite element method for all cast parts and modal analysis for the complete machine. The aim is to find resonance vibrations and to shift them in uncritical areas.

These both solutions are parts of the modules to build a machine with high accuracy for years.

But if you want to use hydrostatic you have to solve two challenges:

  • The design:

The design of hydrostatic guides and bearings is a litte bit more difficult than „normal“ ones. But if you master the design it isn’t a problem anymore.

  • The manufacture:

Schiess uses finest milling by machine and scraping by hand. The scraping is an art that requires a great deal of experience and the workers have to fullfil these requirements.

These solutions should be offered only if these two challenges can be mastered. Otherwise, costumers will have a problem a few years down the road.

However, the hydrostatic is not the best solution for every machine‘s requirements. Therefore, Schiess manufacturers also do machining with “normal“ guides and bearings. For the XL machines, the ground machine comprises the components and the customer has the option to change to the hydrostatic version in (almost) all machines.

Arno Werkzeuge Holder With Targeted Coolant

Arno Werkzeuge Holder With Targeted Coolant

Arno Werkzeuge is expanding its product range with through tool coolant holders integrated with precise coolants straight to the cutting edge.

The holder is available in shank sizes 12 x 12 and 16 x 16. The coolant inlet is individually placed, it can be inserted from the rear of the holder or the side. Various threaded connectors are also available. Efficient cooling of the insert cutting edge protects coatings which can be deteriorate due temperature changes. Swarf control is improved even on problematic materials, owing to secure and reliable machining.

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Metal Forming Sector Positive In India

Metal Forming Sector Positive In India

India: The Indian Machine Tool Manufacturers’ Association’s (IMTMA) president P Ramadas said that the country’s machine tool industry is expected to grow around 20 per cent in 2017-18, and the metal forming industry is expected to grow at a compound annual growth rate of around 15 per cent in the next three years.

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