Efficiency & Sustainability in Sheet Metalworking Machinery: Getting All Green About It

The global sheet metalworking industry is a major user of energy and the cost of electricity is becoming more expensive every year. Paul Hillam, area export manager, SafanDarley tells us more about energy reduction trends in the sheet metalworking arena.

These days, major manufacturers are developing systems to be more efficient with lower operating costs, higher productivity and lower maintenance.

A modern company can be defined not only by its products but also by its attitude to energy conservation, sustainability and social responsibility. Customers and perhaps the local community expect that manufacturers have a positive and proactive approach which will help define themselves as better than the rest. With this, it is expected that manufacturers will also produce better components at a competitive cost.

Reducing one’s energy consumption, the use of environmentally harmful oil and noise, all contribute to better world. For too long now people have assumed that all press brakes and guillotines have the same energy requirements, productivity and maintenance costs. This is a mind-set that needs some adjustments.

When buying a laser or punching system, purchasers look carefully at all of these areas before making an informed choice. The purchase price is only one part of the equation because the performance and productivity of the systems can have a greater effect on the return on investment. So it is time to employ this same decision making process when choosing other machinery.

Press Brakes

When you are programming, setting up tools, collecting material,
rest breaks – all this time is wasted energy on a hydraulic machine
and energy saved with the servo electric machines.

The era of the electric press brake is well and truly here. Leading the way in in the mid- 1990s was sheet metal working company, SafanDarley and others are beginning to follow their lead in this area. Many versions are available including ball screw drives and hybrid systems but the most successful is without doubt the servo driven belt and pulley machines.

The problems with the old technology of hydraulic systems are many fold. They are very inefficient with high energy costs, high maintenance costs and low productivity amongst other reasons. So how is the servo driven belt and pulley system better?

Firstly, in these systems, the energy requirement is drastically reduced. Once hydraulic machines are switched on, the pump is running and using energy, this oil is heated up and so is the workshop even though one is not actually engaged in bending.

With servo electric machines the machine only really uses power when making a bend and even then they will typically use less energy than a hydraulic machine. When not bending, the only energy being used is that required to run a PC & PLC (pipe bending machine).

How Much Bending Daily?

When you are programming, setting up tools, collecting material, rest breaks – all this time is wasted energy on a hydraulic machine and energy saved with the servo electric machines. For most companies the wasted energy is in excess of 50 percent. In job shops up to 90 percent of the operating time of a press brake is not bending it is handling the product, programming, setting up tools and general preparation.

Switching off the drive of a hydraulic machine might seem to be a suitable alternative but each time you start the pump requires a large power surge often 20 times the normal flow and many power companies charge heavily for such loads.

The graph below gives a comparison for when the press brake is actually in operation. During the stand-by periods – which, due to breaks, sheet handling and change-over times, can be up to 90 percent – the electronic press brake can save an extra 3,000 kWh per year.

New Press-Brakes Operating In Identical Environmental Conditions

The higher the tonnage of the hydraulic machine, the bigger the pump and so, the greater the energy consumption. This means that the savings are even greater on the larger Servo Electric systems which are available up to 300 tons. There is much talk also about the actual CO2 emissions. Calculating from the energy consumption of machines (kWh) to CO2 emission (kg) is not that simple as it depends on the local energy supplier how much their CO2 emission is.

For instance, in many countries the CO2 emission can vary between 0 to 500+ gr/kWh. The wind or water hydrogen energy generators can have an emission value of 0 and the coke or gas energy suppliers can have an emission value of more than 500 gr/kWh.

If we take a typical value (422 gr/kWh) and the average of the energy consumption of an 80-150 tons electric press-brake in single shift operation you could make the following assumption:

– The CO2 emission for an electric-press brake at 80 tons is 2.200 (kWh) x 422 = 928 kg per year.

– The CO2 emission for a hydraulic-press brake at 80 tons is 5.000 (kWh) x 422 = 2.110 kg per year.

– The CO2 emission for an electric-brake press at 150/200 tons is 3.960 (kWh) x 422 = 1.671 kg per year.

So the CO2 reduction for the electric-press brake with an 80 ton capacity compared with a hydraulic press brake of 80 tons is = 1.182 kg per year. That makes it more than 55 percent.

What To Maintain On A Press Brake?

Most of the focus would be on the hydraulic system which means changing oil, seals, filters, valves – the servo electric machine has none of these, so the benefits are obvious. In addition, the time normally set aside for maintenance can be used for production and there is only environmentally harmful oil to dispose of now.

More Productivity Using The Servo Electric System

Let’s use the analogy of an F1 racing car. Some cars have a higher top speed than others so are great in a straight line race over a long distance. However, most races are around tracks with many corners and short straights so often they never reach the top speed. Therefore the speed at which they can accelerate out of a corner and the later they can break into the corner becomes more important.

This is where the servo electric systems are at an advantage because they have much better acceleration and deceleration times than a hydraulic machine. So the bigger the machine, the slower the hydraulics. The servo electric system can typically increase productivity by up to 30 percent.

It is now possible to purchase a servo electric belt and pulley machine with up to a 300 ton capacity.

So the key features of an electric press brake include a servo-electric drive system, increased productivity, high accuracy because the belt and pulley system distributes the bending force over the whole bending length, lower power consumption, hardly any maintenance needed and no harmful oil.

From an energy perspective guillotine shears have similar problems as the press brakes in that they are powered on all of the day and even in a high production environment are not actually cutting most of the time.

Making The Cut: Guillotine Shears

Some might find this surprising but guillotines usually use even more energy than press brakes. Even though many companies laser cut or punch from full sheets there is still no more efficient and low cost way of cutting regular shaped blanks than shearing.

From an energy perspective guillotine shears have similar problems as the press brakes in that they are powered on all of the day and even in a high production environment are not actually cutting most of the time. In normal use with an average use of 80 percent of the duty time the guillotine is not actually cutting. Much time is used in loading and unloading, making adjustments and programming.

One way of addressing this is with a hybrid system for the cutting movement. In the hybrid systems the pump only runs when the cutting beam is in motion with the result being that the energy consumption is minimised when not cutting. In this standby mode the only power consumed is for running the control.

An added benefit is that these systems typically have only around 22 litres of oil compared with the 150 -200 litres on conventional machines. This results in reduced and simpler maintenance and less use of environmentally harmful oil.

Fibre Lasers

Compared to CO2 lasers the fibre lasers with high laser conversion efficiency consume less electricity. The electricity costs during standby can typically be reduced by around 70 percent in addition the relative costs of assist gas is also reduced.

These systems also require significantly less maintenance. With the CO2 Laser systems the optical system comprises a system of mirrors that require period cleaning and replacement.

The fibre lasers use optical fibre thus no maintenance or replacement mirrors necessary. Its key features include:

– Greater efficiency

– Low maintenance

– Fewer consumables

Servo Electric Punching Systems

The early steps towards the introduction of the servo-electric punch presses happened in the late 1990s. The servo electric punching systems combine energy savings with productivity.

Purchasing an electric punching system is a win-win situation for the user and for sustainable development combining manufacturing efficiency with productivity.

In summary it is evident that energy efficiency and sustainability will be at the forefront of product development for the more innovative manufacturers.

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