Product category:
Sawing and cutting-off machines and automation systems
News Release from: Kasto | Subject: Kasto high-speed, automatic circular saws
Edited by the Manufacturingtalk Editorial
Team on 26 June 2003
High speed saws deliver forging billets
JIT
Investment in two high-speed, automatic circular sawing machines has enabled Imatra Steel to introduce a new service, namely the delivery of swarf-free billets on a just-in-time (JIT) basis.
Investment in two Kasto high-speed, automatic circular sawing machines from Rivers Machinery has enabled the Wolverhampton works of Imatra Steel to introduce a new service, namely the delivery of swarf-free billets on a just-in-time (JIT) basis to forges throughout the UK Previously the steel was supplied as long stock for customers to cut into the required billet sizes
This article was originally published on Manufacturingtalk on 23 May 2001 at 8.00am (UK)
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Imatra is a Finnish mill producing 250,000 tonnes of steel annually.
The English subsidiary is a major supplier of engineering grades to the UK forging market, a sector which accounts for two thirds of its business.
A majority of the steel finds its way into cars, trucks, lorries and off-road vehicles.
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The automotive industry was a pioneer of outsourcing and now subcontracts much of its production, minimising stocks by asking supplier companies to make JIT deliveries.
Tiers of firms below the OEMs followed suit and by the end of the 1990s, the forging industry was putting pressure on steel suppliers to supply cut-to-weight billets ready to go straight into the forging presses.
Imatra's UK managing director, Keith Wall, was quick to spot the trend and responded by installing the two Kasto saws.
From a standing start, within nine months the company was cutting over one thousand tonnes of steel per month.
Said Wall, "Sawing billets is a low added value operation, so we had to be careful to choose the most cost effective and productive method.
Ours is a high-volume business, where we typically supply 5,000 identical billets a week to a customer and the saw will be working two shifts for two or three days continuously cutting the same material.
"We compared bandsaws with circular saws and found that for our type of work, we would have needed six bandsaws instead of the two circular saws.
This would have meant not only extra capital investment but also higher labour costs." It is perhaps surprising that an evaluation of single-bar circular sawing versus bundle cutting on a bandsaw should show such superior performance for the former.
Speed of operation is one factor - nine metre lengths of some smaller diameters are sawn into billets in under eight seconds, depending on cut length, using the disposable, tungsten carbide tipped (TCT) saw blade.
Often the larger saw processes five tonnes of steel per hour, making as many as 400 cuts also with a TCT blade.
The fact that the stock is nine metres long rather than six metres as handled by other automatic circular saws on the market is helpful, as feeding through a new bar takes place 50 per cent less frequently, minimising non-productive time.
Another factor to be taken into account, according to Wall, is the tendency for bandsaw blades to wander when cutting alloy steel grades up to 290 Brinnell hardness.
He continued, "Some people are overly concerned about the larger kerf of circular saws, but I think this is of secondary importance.
We use 3.2mm circular blades, and although they produce more swarf than a 1.6 mm bandsaw blade, the difference in metal loss over a tonne of steel might be, say, two per cent.
The extra cost due to increased yield loss is far outweighed by the higher productivity." "Once these saws are set up, our statistical process control procedures show that they are very consistent," continued Wall.
Prior to installing the two Kasto circular saws, a process capability study was carried out for one of Imatra's customers.
A sample run of 30 gudgeon pin forging blanks were cut from 35 mm diameter 16MnCr5 peeled steel bar.
Upper and lower tolerance limits in grams were 526.3 and 519.3 respectively, giving a mean of 522.8 grams.
Maximum and minimum weights in the sample were 522.0 and 520.6 grams and the mean was 521.02, which translates into +3 standard deviations of 521.92 and -3 standard deviations of 520.13.
Process capability criteria of Pp = Ppk = 1.66 were thus easily met, as the value of Pp was an impressive 3.92 while Ppk was calculated to be 1.93.
The Kastospeed C14 is the larger of the two saws, capable of cutting 140mm diameter / square stock.
Cut piece length at Imatra falls within the range 110 to 1000mm.
The C70's maximum cutting capacity is 70mm, with lengths generally in the 85 to 300mm range.
Mr Wall advised that the bulk of cut billets Imatra delivers is from 55 to 90mm diameter, and also pointed out that the company supplies uncut steel up to 150mm diameter.
One operator per shift looks after both saws from 6.00 am until 10.00 pm.
A five tonne bundle loader is fitted to the larger saw, supplemented by a chain drive transfer system which itself holds a further five tonnes of material.
The saws come as standard with a swarf management system whereby chips are carried on a conveyor away from the cutting area into a separate bin while cut pieces are discharged into another.
This is a stipulation of the forgers, as swarf can damage the coils of their induction hardening furnaces.
Additionally, oil mist blade lubrication of the saw blades contributes further to the cleanliness of billets, eliminating the need for degreasing.
Such is the speed of the C14 that the two tonne capacity bin for cut pieces is full in under half an hour and currently has to be exchanged manually.
Imatra is in talks with Rivers and Kasto about installing a conveyor or carousel system to automate and speed this function, with a view to increasing productivity still further through shorter bin changeover time and the introduction of ghost shift working.
With an eye to even higher production output, another area of discussion is modification to the bar pusher system to effect continuous nose-to-tail infeed.
Concluded Wall, "The saws have proved to be ideal for our high volume production environment, and the supplier has been very supportive in our requests for ongoing enhancements to the C14 so that we can maximise the return on our investment.".
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