Schaeffler offers new mounting and dismounting
service for large sized bearings and components

When it comes to the mounting or dismounting of large rolling element bearings, flexible induction heaters can save significant time and resources. Ian Pledger of Schaeffler (UK) Ltd explains why this new heating method is the preferred option compared with other more traditional approaches.
 
The correct mounting and dismounting of rolling element bearings can save companies valuable time and increase the life of the bearings, as well as maximise the availability of critical plant and machinery by avoiding costly breakdowns.

But in order to correctly mount or dismount bearings, it is usually necessary to heat the bearing first. There are a variety of heating methods available to do this, each with its own advantages and disadvantages.
 
Heating methods include thermal mounting and dismounting tools (i.e. heating plates), induction heating devices, mounting paste and heating rings. Selecting the most appropriate heating method will ensure that the bearings (or similar circular steel components) are mounted and removed easily and quickly, in a safe, reliable manner, without causing any damage to the bearings or surrounding equipment.
 
When it comes to heating large-sized bearings (1500mm outside diameter and above), there are several options available: using an oil bath, a gas flame burner, or a medium frequency induction heater.
 
Heating in an Oil Bath
Using an oil bath requires the customer to have a large enough bath for the bearings to be heated in. If such a bath does not exist, one will need to be constructed, which will require welding work, large quantities of steel and 1-2 days of manpower. Hundreds of litres of oil are also required, which must then be disposed of in the appropriate way and which can be expensive.
 
Heating using Gas Flame Burners
Compared to oil bath heating, using gas flame burners is a much easier method in terms of preparation, as it requires nothing more than a couple of gas cylinders and a burner. However, heating the rolling bearing and the housing may tie up 3-4 people for up to four hours per component.
 
With gas burners, there is also a risk of local overheating, which can cause changes to the structure of the component being heated. In addition, after heating is completed, the bearing itself may need to be cleaned or the housing painted, as these parts often become discoloured with black soot from the flames.
 
Induction heating
Induction heating is superior to traditional heating methods, as it is faster, cleaner and more suitable for batch heating. Heat is transferred directly to the workpiece and unlike alternative heating methods, does not need to be transmitted via convection, radiation or thermal conduction. Fixed and mobile induction heaters are available for this.
 
As induction heating is uniform across the bearings, local overheating is prevented. During the heating process, rolling bearing steels are automatically de-magnetised.
 
Due to their increased energy efficiency, induction heaters can reduce heating times by up to 50 per cent, keeping maintenance costs to a minimum. Also, as the systems do not require oil, they have the added advantage of being both clean and environmentally friendly.
 
Flexible Induction Heating
Whilst induction heaters are suitable for many types of rolling element bearings, they are not always effective with large-sized bearings and housings. The availability of an induction heater that is large enough to cope with the job in hand, not only causes problems because of its physical size, but is also likely to cost tens of thousands of pounds - making it uneconomical for a one-off mounting or dismounting task.
 
In addition, the housings (e.g. plummer blocks) for large-sized bearings usually have an unusual shape, which makes it difficult to fit the component in the heater, or again means that the heater itself has to be very large.
 
However, using flexible induction heaters solves these types of issues. Here, medium frequency induction heaters are fitted with flexible inductors, which offer complete flexibility when it comes to the size and geometry of the workpiece or bearings.
 
The heating cable is flexible, enabling it to be placed in and around the workpiece, or in areas of a component that would normally be inaccessible. This method is also ideally suited to mountings that do not take place at regular intervals.
 
The workpiece itself does not necessarily have to be a bearing; it could be any large circular, ring-shaped steel structure that requires heating. Examples here include the heating of bearing seats in a machine carrier such as a wind turbine. Other applications include the preheating of welds in pipeline construction, as well as the dismantling of bearing inner rings and other shrink connections.
 
Preparation time with flexible induction heaters is relatively fast and heating time is only 1-2 hours, depending on the size and mass of the bearings. The heating process itself is automatic, which means resources are not tied up, and the bearings do not require cleaning post-heating. A sensor is mounted to the bearing in order to monitor the temperature during heating. Once the bearings have been heated to the required temperature, the heater is stopped automatically.
 
For further information, e-mail: info.uk@schaeffler.com  or view website: www.schaeffler.co.uk   Refer to page 153

Kocurex excavators unearth ideal workholding solutions

Everything about the equipment manufactured by Ipswich-based Kocurek Excavators Ltd is tough - from its arduous operating environments to the aggressive machining strategies used to produce the company's custom-engineered excavator products.

With roots in the earthmoving and plant hire sector, Kocurek Excavators has amassed more than 25 years experience in developing long reach arms and multi-purpose units that extends the versatility of standard hydraulic diggers - to the point that the company's products can be fitted to many manufacturers' standard vehicles without invalidating their warranty. Kocurek equipment covers applications across industries as diverse as mining, rail, marine, materials handling, mineral extraction, demolition, shaft sinking and tunnelling. In addition, the company offers a wide range of additional fitments to enhance the safety and operation of their modified excavators, including a variety of cab options, seats,  additional counterweights, auxiliary fuel tanks and modified vehicle undercarriages.

Kocurek prides itself on a policy of designing and manufacturing virtually all items in  house, on the basis that it not only creates work for its own employees, but also provides full control of product quality. Furthermore, modifications and updated designs can be transferred to the shop floor very quickly in order to provide a highly flexible response to users' requirements.

With customised excavators costing several hundred thousand pounds and civil engineering projects invariably run against short deadlines, the pressure is always on to maximise equipment utilisation on site. That, in turn, necessitates heavy duty components that are made available quickly and accurately, right-first-time.

According to Kocurek's machine shop supervisor, Ben Woollard, it typically involves the machining of prismatic parts from 30 to 350 mm diameter in mild steel, aluminium bronze and Weldox, a high strength weldable steel.

"The ability to maintain consistent manufacturing quality and throughput has to be based on good workholding - used in conjunction with high capability machine tools," he says. "At the heart of our machining capabilities are six Haas CNC machines; three lathes and three vertical machining centres. Until recently, we employed traditional knee mill vices to locate components during machining operations, but these proved to be less than ideal."

"In order to generate the necessary grip to hold parts securely, operators would regularly use a hammer to tighten the vices' crank handles," Woollard explains. "That not only tended to deflect the units' fixed jaws, leading to machining accuracy and repeatability issues, but the leadscrew would also become stretched, making the units increasingly difficult to use. Even so, components could still occasionally work loose under heavy cuts. What's more, the high loads exerted on the vices have been known to simply fracture their castings." 

Woollard adds that due to the bespoke nature of Kocurek's work, component batches rarely exceed 15 units. Accordingly, each operator undertakes several set ups a day. Using traditional vices, they would often find themselves winding the crank handle in and out 'forever' to accommodate differently sized components - further compromising set up times and throughput.

"We would typically wear out our old milling vices in around six months," Woollard adds. "So when we heard about the new Chick One-Lok system from 1^st Machine Tool Accessories (1^st MTA), we were keen to get our hands on one, just to see if it really could live up to its claimed performance.

Pictures show the the new Chick One-Lok system and an engineer demonstrating the system. 

"Our first impressions were very good. The unit's modular design incorporates a precision ground solid base, which not only enhances its rigidity, but also eliminates swarf traps, reducing the need for cleaning between machine cycles. It also offers a number of other novel features that lift it 'head and shoulders' above traditional milling vices."

A key factor is One-Lok's rugged construction, which enables more than 4.5 tonnes of gripping force to be generated - along with a pull down action - using only hand pressure on the operating handle.

"Since using One-Lok, we've never had a component work loose," Woollard adds. "This has given us the confidence to push up cutting speeds and feeds on several jobs, and trim cycle times as a result."

The adoption of more aggressive machining strategies can frequently lead to machining quality and repeatability issues. However, One-Lok's novel 'squeeze' clamping action applies an equal and opposite internal force to the fixed jaw as the moving jaw closes, providing virtually deflection free component clamping - even under extreme load.

For further information, contact Catherine Kelly at 1^st MTA, e-mail: enquiries@1mta.com