Product category:
CNC automatic lathes
News Release from: Star Micronics GB | Subject: Star SV-32 CNC sliding-head mill-turn automatic
Edited by the Manufacturingtalk Editorial
Team on 20 April 2005
One CNC sliding head auto replaces four
cam types
Every multi-axis automatic lathe with sub spindle and driven tooling replaces three or four cam machines; freeing space and providing faster metalcutting cycles and eliminating second operations.
Merseyside turned parts subcontractor, Wealdpark, installed its fifth Star sliding-headstock CNC lathe in November 2004, continuing its systematic replacement of 50 single-spindle cam automatics that the company has used since it was established in 1965 Each multi-axis Star machine with sub spindle and driven tooling replaces three or four cam machines, freeing space and cutting production times through faster metalcutting cycles and elimination of second operations
This article was originally published on Manufacturingtalk on 14 Jul 2000 at 8.00am (UK)
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The latest lathe, a turret- and platen-type Star SV-32, has resulted in dramatic savings when producing a truck transmission part from 25mm diameter, SAE8620 bar.
In a 47 second cycle, the part comes off without burrs and with all pre-hardening operations completed, thanks in part to Star GB's suggestion to retrofit one of its angle drilling/milling heads in one of the live crossworking positions.
For 20 years, the same alloy steel part was produced by the subcontractor on three separate machines - a cam auto, a microprocessor-controlled lathe and a milling machine - in a combined metalcutting cycle time that was nearly four times longer at 178 seconds.
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Further time had to be added for handling the work-in-progress and reclamping each part twice; plus it took two hours to deburr batches of 400 components in a rumbler.
The final grinding operation remains, as although the Star is capable of turning the part to the required accuracy, there is a risk of dimensions altering during the penultimate, case-hardening operation.
Batches of 3,000-off are produced per month, which previously required constant working of the three-machine cell and entailed a significant amount of overtime labour at time-and-a-half.
Now the month's production takes less than a week of largely unmanned running on the Star SV-32, so the machine is able to produce a variety of other jobs as well, like parts for fuel injector test systems.
Said Wealdpark director, Phil Smith, "The production cost of the transmission component has come down enormously, which will help to amortise our investment in the SV-32 in less than a year".
"We will then offer the customer a price reduction - not bad considering that we have not increased our prices since my father, Jim, took over the business in 1995." The previous Star installation was only two months prior to the SV-32's arrival.
It was an SR-20RII with live cross-, front- and rear-working capabilities.
One job put on the machine involved producing 5,000-off batches of connectors requiring an off-centre hole drilled into one end.
Compared with the Star SV-20 on which the part was previously produced, cycle time has been nearly halved from 45 to 23 seconds, as it is relatively simple and benefits from the speed of the all-platen configuration on the SR-type machine.
The SV-20 was bought at the end of 2002 to manufacture parts for after-market seat belts, when that business took off in the wake of legislation requiring them to be installed in coaches.
The subcontractor started making the EN8 components in batches of 100,000-off on three machines - a cam auto, a slotting machine and a mill - a process that took three months.
Running 24/7, the Star turn/mill lathe produced the parts in a single hit and the 100,000 were finished in five weeks.
The annual order for six times that quantity was sufficient to pay for the machine, leaving spare capacity for other work.
It was towards the end of 2001 that Wealdpark acquired its first CNC sliding-headstock lathe, a Star SV-32J, not for a particular job but to improve the efficiency with which it fulfilled existing contracts.
At that time, the company operated 53 cam autos and employed 55 staff.
The most that had ever been spent on a machine tool was GBP 3,000 and suddenly the company was looking at investing GBP 120,000 and ousting four cam autos.
So it was a big step for Jim, Phil, and his brother and co-director, Steve, especially as they had no experience of sliding-head work.
Continued Smith, "We could kick ourselves for not having started down the CNC slider route as soon as our family took over the company in the mid 90s".
"It would have put us in a stronger position earlier and we would now be upgrading our plant with new Stars, like so many turned parts subcontractors around the country, rather than growing our installed base"".
"" We are putting in Stars at the rate of at least one per year and expect to have 10 by the end of the decade".
"By then, our 53 cam autos, which today number 37, will be reduced to three or four cam autos of 50mm capacity and our second-op section will be very small." He went on to comment that cam auto shops in the UK will go out of business unless they start to embrace CNC turn/mill soon, as cam equipment is only competitive on long runs and it is precisely this work which is being lost to India, China and other low-wage countries.
It was the prime motivation for Wealdpark embarking on the programme of Star acquisitions.
He suggests it is no coincidence that three auction notices fall on his desk every week offering the contents of cam auto shops that have gone into liquidation, or where the owner has decided to retire, whereas it is unusual to see a CNC turning shop going out of business and very rare indeed if a CNC sliding-headstock specialist goes under.
Steve Totty, engineering manager at Star GB, says that there is little financial reason for cam shops not to upgrade to CNC sliding-headstock turn/mill of components in one hit, as entry-level models like the Star SB-16 are relatively inexpensive, costing around GBP 60,000 including bar magazine.
Moreover, skilled operators needed for setting cam machines are no longer necessary, resulting in significant labour cost savings when modern CNC plant is installed.
An SB-16 is also in operation at Wealdpark.
With overseas competition producing a majority of big runs these days, 500-off is an average batch at the Merseyside firm, sometimes rising to around 3,000-off and only occasionally into six figures.
CNC turning is ideal for economic production of shorter runs as the machines are quick to set up and changing a tip takes a few minutes.
These times contrast favourably with operation of a cam auto, which takes at least a day to set up and whose form tools have to be reground every four hours, which takes half an hour, resulting in a lot of non-productive time.
Tolerances of 0.02mm are routinely held on the Stars while some are substantially tighter.
When interviewed, Smith had on his desk a component drawing defining one datum diameter as 4.300mm exactly".
""Customers like the repeatability and good surface finish of parts that come off the Stars," he commented.
Although a general provider of turned parts to diverse industries, Wealdpark supplies around half of its output to the standby power sector.
Other applications include standby batteries for ejector seats and telecoms exchanges.
Asked why he continues to opt for Star lathes to the exclusion of all others, Smith said that one factor is the superior installed weight of the machines.
For example, the 3.8 tonne Star SV-32 is 22.5 per cent heavier than the equivalent lathe from a major competitor and in his opinion, the higher rigidity translates into less vibration, better accuracy and longer tool life.
He also likes the quiet operation, an important health and safety issue these days, and the good access to the working area of the Star machines.
Now that the association with Star GB has been established for over three years, Smith feels he is in a position to comment that after-sales service from this supplier has been "faultless", from the telephone help line to the prompt visits by an engineer on the few occasions that they have been necessary.
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