Oct 19, 2012
A strategic overview of the production turning industry in SABack
DURBAN|Africa|Components|Paper|Africa|South Africa|Automotive|Electronics|Metal Removal Rate|Product|Product Manufacturer|Products
© Reuse this
A vast number of industries, including the automotive, appliance, electronics, bathroom fittings and other industries, and products make use of turned components, says machine tools manufacturer FAS Machine Tools CEO Peter Frow.
In a research paper written by Frow, he points out that some of these components are made in-house by the product manufacturer, while others are subcontracted to specialist repetition turning ‘job shops.’ The component type and size vary enormously, as do batch sizes – anything from ten to hundreds of thousands.
“Where batch sizes increase above 100 and particularly above 1 000, the components will typically be made on one or other type of production lathe,” he states.
A production lathe is any lathe where the tool movements are achieved by some automatic means. Thus, once set, they can produce components without any direct operator action, except for loading the raw material.
“In the production turning stakes, it is important to select the best machine for the job.
“The best machine is the one that yields the lowest cost for a particular component and a particular batch size,” says Frow.
Generally speaking, the production turning industry uses two distinct types of production lathes – Cam automatic lathes and computer-numerically controlled (CNC) lathes.
The paper highlights that the design of the cam automatic lathe was pioneered over a hundred years ago and it uses cams for achieving tool movements. The lathes are characterised by fast cycle times and long set-up times.
Further, the paper states that CNC lathes were developed in the seventies, initially as hard-wired numerically controlled machines. They soon incorporated microprocessors, hence the term CNC. These lathes have relatively long cycle times, compared with cam-operated lathes, especially for smaller components, but are far more user-friendly and have relatively short set-up times.
“Within these two broad categories, production lathes can be further broken down into various subtypes (see Figure 1).
“The diagram illustrates that there is usually something of a trade-off between cycle time and set-up time.
“Cycle time is a function of the metal removal rate (MRR) of the different tools, the number of tools that can be made to work simultaneously on the work piece, and the time taken for nonproductive or idle operations, such as the feeding of material and indexing of tools.
“Thus, to optimise the cycle time, one must maximise the MRR, maximise the number of tools working simultaneously and minimise the duration of idle operations,” says Frow.
He points out that the cam-operated multi-spindle lathe (Type A, Figure 1) works on six components in various stages of completion at any one time. Thus, it has as many as 12 tools cutting simultaneously.
“Amazingly, this type of machine was developed in the late nineteenth century and still produces the quickest cycle times of any production lathe.
“However, South Africa has less than 150 of this type of machine in regular operation.
“The greatest number (estimated at 2 500+) of cam automatics in the country, are of the single spindle type (Types B, C, & D),” he says.
Frow notes that these machines can typically have four tools working simultaneously. They make extensive use of the ‘plunge forming’ technique, where tools having a particular shape are advanced into the work piece along an axis perpendicular to the spindle axis.
“By contrast, CNC lathes use single point tools and generate the required shapes with a digitally programmed tool path. Form tools can generally be applied at the same time that end working is taking place. This technique is known as ‘overlapping’.
“In order to select the best machine for a particular application, one should plot the cost-effectiveness curve for each machine being considered. Figure 2 would be a typical set of curves for a component of less than 40 mm in diameter made from bar stock.
“Other things being equal, the batch size represented by X would be the point at which it would be more cost effective to make the component on a cam automatic than a CNC lathe. Batch size Y would be the point at which a multi-spindle would become the better choice,” says Frow.
He points out, however, that other things are not equal: In particular, there is a dwindling pool of tool setters with the skills necessary to set cam automatic lathes. Each job requires a set of job-specific cams. The number of persons capable of designing optimum cams has also shrunk.
“There is thus a tendency to run jobs on CNC lathes despite their longer cycle times where the cost effectiveness curves would suggest otherwise.
“The great majority of CNC lathes in the country are of types J and K, although there are a fair number of type H lathes.
“Viewed at a macro level, the net effect of this is a tendency to drive component prices upward, making South Africa less competitive in a global market,” says Frow.
He notes that imported type E CNC lathes have cycle times comparable with cam automatics, but unfortunately are priced such that one can purchase about three type J machines for the same figure.
Further, he says that, despite fierce competition from the East, South Africa has CNC lathe manufacturers. “Efamatic in Gauteng produces a range of type J machines, while FAS Machine Tools in Durban manufactures a type E multi-slide machine with cycle times that more than match those of equivalent cam automatics.”
Edited by: Chanel de Bruyn© Reuse this Comment Guidelines (150 word limit)
Other Machine Tools News
Industrial products supplier Dowson & Dobson (D&D) Industrial expects its distribution agreement with industrial products supplier Pneumatic & General Supplies for Richards Bay, in KwaZulu-Natal (KZN) to expand its reach to industries that include the coal,...
A modern computer numerically controlled (CNC) turning machine must be productive, flexible and easy to operate, says local machine tools distributor Retecon MD Hans-Peter Neth. He tells Engineering News that the new monoBlock and CTX ecoline series of machine tools...
Professional sawing and drilling contractors have shown significant interest in the new Titan high-frequency wall saw, which is apparent in the several orders pending final financial clearance by companies, diamond tools and equipment manufacturer and supplier...
Recent Research Reports
Real Economy Year Book 2014 (PDF Report)
This edition drills down into the performance and outlook for a variety of sectors, including automotive, construction, electricity, transport, steel, water, coal, gold, iron-ore and platinum.
Real Economy Insight: Automotive 2014 (PDF Report)
This four-page brief covers key developments in the automotive industry over the past 12 months, including an overview of South Africa’s automotive market, trade figures, production and the policies influencing the sector.
Real Economy Insight: Construction 2014 (PDF Report)
This five-page brief covers key developments in the construction industry over the past 12 months. It provides an overview of the sector and includes details of employment in the sector, infrastructure and municipal spending, as well as insight into companies’...
Real Economy Insight: Electricity 2014 (PDF Report)
This five-page brief covers key developments in the electricity industry over the past 12 months, including details of State-owned power utility Eskom’s generation activities, funding and tariffs, independent power producers and prospects for the sector.
Real Economy Insight: Road and Rail 2014 (PDF Report)
This six-page brief covers key developments in the road and rail industries over the past 12 months, including details of South Africa’s road and rail network and prospects for both sectors.
Real Economy Insight: Steel 2014 (PDF Report)
This four-page brief covers key developments in the steel industry over the past 12 months. It provides an overview of the global and South African steel and stainless steel markets, South Africa’s major steel producers and events that have shaped these markets.
This Week's Magazine
Updated 1 hour 35 minutes ago South African construction company Group Five says work on the rehabilitation of the 800 km stretch of the Plumtree–Mutare highway, in Zimbabwe, should be completed by the end of this year. Giving evidence before the Parliamentary Porfolio Committee on Transport...
Updated 1 hour 38 minutes ago The Space Operations division of the South African National Space Agency (Sansa) revealed on July 17 that it had supported the successful launch of the US National Aeronautics and Space Administration’s Orbiting Carbon Observatory-2 (OCO-2) satellite on July 2. The...
Updated 1 hour 38 minutes ago Phase 1A of Johannesburg’s Rea Vaya bus rapid transit (BRT) system should carry around 42 000 people a day, while it was been expected that Phase 1B, rolled out last year, would add another 60 000 daily passengers. However, the entire system is currently carrying...
Updated 1 hour 38 minutes ago A stormwater project in Bedforview, east of Johannesburg, has stalled for eight months after project managers in the Ekurhuleni municipality resigned and municipal managers were placed on special leave without designating replacements. Construction to reinforce the...
Updated 1 hour 38 minutes ago The design of the Beit Bridge border post is the biggest impediment to efficient freight movement between Zimbabwe and South Africa, says Cross-border Road Transport Agency CEO Sipho Khumalo. Beit Bridge is the busiest border post in Africa. A research study on the...