Powered tooling and two Y-axis cross feeds scored
March 18th 2009
In a subcontrator’s view, its latest mill/turn centre stands out for its powered tooling ability to mill and drill and in particular, through the added flexibility from its two Y-axis cross feeds.
With seven Citizen CNC sliding head automatic lathes already fully occupied and capacity filling fast on the most recent pair of Citizen L32 mill/turn centres installed at HPC (Services) of Ilkeston in Derbyshire, managing director Paul Cobb decided a detailed review had to be made of the type of components and in particular, the amount of milling required in the future.
Only then he maintains, would he make the decision to look for extra machines.
As a very timely result he explains: “We decided to go along to the NC Engineering open house and see first-hand what Citizen could provide.
Our review had already highlighted how milling was becoming more and more important on ‘one-hit’ cycles so high levels of milling and turning flexibility had to be at the top of our agenda.” In Cobb’s view, the new Series 3 version of the M32-V stood out for its powered tooling capability to mill and drill and in particular, through the added flexibility from its two Y-axis cross feeds, one to the turret and second to the gang tool slide.
“So we bought one,” he says “as well as a Citizen L20-VIII.” Cobb describes how his setters cannot believe how the metalcutting efficiency has improved with the new M32.
He says: “We are getting parts from the machine at least 25 per cent and, in some cases almost a third, faster which is proving very beneficial in helping to meet cost-down targets of certain of our customers.” The new M32 machine has not only freed up capacity on the existing Citizen L32s at HPC by enabling more complex work to be transferred resulting in shorter cycle times, there is more.
As he outlines: “With the additional Y-axis we can very quickly electronically adjust tool centre height bringing it exactly on centre line which speeds up our setting.
In-cycle tool change is now much quicker with the new Citizen tool holders you just program a Y-axis move of the turret sideways to the next tool and save an index.” However when it comes to milling - the prime motivator for the purchase, “We can get a lot of very complex milling and drilling performed on a component in the subspindle for free, in terms of cycle time, while still machining away at the main spindle.” The fact that setters no longer have to contend with polar interpolation to produce a flat on a part, for instance, is another bonus.
“We just come in from the side with the tool and mill across the job with the added advantage of using the bottom of the cutter and not the edges.” Maintains Cobb: “We reckon the latest Citizen M32 is the most highly developed machine of its type for producing the class of parts we make up to 32mm diameter.
More and more we are exploiting the machine’s configuration of tooling and axes to machine not only brass and stainless steel components but also aluminium and plastics.” Very effective cutting cycles that could never have been considered before include taking large cuts, up to 10mm deep, by simultaneous twin turning the same diameter from 25mm down to 15mm in stainless steel at 0.12 mm/rev.
Previously, multiple single cuts at 0.03mm/rev would have been taken so the new method has saved over one minute floor to floor time on one component alone.
Then there is the added bonus of reduced idle times from the faster processing of the new control which reduce cycles further.
“When you have a batch of several thousand to run - these are savings really worth making,” he says.
Cobb then adds comments on the latest specification LNS Express 332 barfeed fitted to the sliding head machine.
“Changeover is much quicker and the split block arrangement is far superior to other barfeed designs giving better support to the bar and enabling higher, up to 8,000 revs/min spindle speeds, to be used without any vibration.” HPC employs 50 people and has seen order books swelling month on month from customers in the luxury goods, printing and domestic appliance sectors.
By setting the business to provide a prototyping service, this now accounts for about 10 per cent of the business.
Production and sub-assembly services, as well as a strong design for manufacture consultancy and component development capability, has meant a build-up of a very loyal partnership with a relatively small band of regular customers.
But central to the philosophy of the business is Cobb’s contract machining component superstore theory.
Although it means risk because completed parts are held in the finish parts store for customers to simply call-off when required, it has created three major advantages.
Firstly, customers can enjoy a next day delivery service which pretty well eliminates panic jobs, the scourge of production schedules, but most important, allows Cobb and his team to plan for maximum machine utilisation and efficiency of changeover.
In short, HPC’s machines are producing through three shifts a day over a six days a week with changeovers performed when it is convenient to them! “The spin-off,” maintains Cobb, “is that we are generating profits from sales of over GBP 5 million a year that are ploughed back in the business and we are steadily installing new equipment.” In the first half of 2003, GBP 500,000 was spent, the end of the year a further GBP 550,000 was committed which included both the new Citizens.
For 2004, similar investment plans have been laid and funded in order to maintain ‘The edge’ over competitors in the UK and especially those from overseas that are trying to attract supply contracts against lower pricing.
“If we can maintain a competitive edge through technology and help customers with ‘cost down’ programmes we have found they would rather buy from a known UK source they can work very closely with and one that fully understands the requirements.
It is not all price wars - the benefits of trust in a supplier still holds water providing the supplier does not get complacent and begins to let customers down.”.