5-axis machining cell is ideal for high mix, low-to medium batch production.
A new, 5-axis machining cell has dramatically increased the efficiency and flexibility with which prismatic components are manufactured around the clock at the Crediton works of subcontractor, Adaero Precision Components.
The turnkey cell, costing one-third less than similar equipment shortlisted, was supplied in February 2014 by Whitehouse Machine Tools, sole UK agent for the Japanese machining centre manufacturer, Brother.
The installation is fundamentally different from Adaero’s larger capacity, 40-taper, 4-axis machining cell installed in 2009, in which each of 15 pallets has fixturing dedicated to the production of a specific part. In contrast, the Brother 32BN-FT 30-taper, 5-axis machining centre is equipped with a System 3R WorkPartner 1+ automated, multi-level storage and retrieval system for 84 pallets, each of which carries a vice for securing any component.
Gary Raymont, Adaero’s Engineering Director, said, “Ours is a high precision, high mix production environment involving machining of a few hundred different prismatic parts in batches of between 6 and 300 off.
“Customers are constantly demanding that prices be held or reduced while quality is maintained or increased, which means that we have to be a part of their design teams to engineer out cost and improve methods of manufacture.
“We have to pay particular attention to the number of times we set up a job to complete it and to the amount of time it takes for each set-up, in addition to minimising cycle times.
“It was clear that 5-axis machining was key to reducing the number of operations to typically one or two, while offline set-up would minimise changeover time.
“In addition, we recognised that workpiece storage with automated load / unload would have the added advantage of allowing unmanned running for raised output and lower cost per part, bearing in mind that adding a second manned shift is expensive.”
Mr Raymont also pointed out that they have experienced a big increase in enquiries for 5-axis work in the past couple of years and it is relatively easy to sell the capacity.
Adaero has also reengineered numerous existing jobs to put on two stand-alone Brother 5-axis machines, based on a 2-axis trunnion arrangement, that were installed several years ago in order to make better margins and take workload off the 3- and 4-axis machines.
Further advantages of 5-axis machining are shorter floor to- floor times and reduced work-in-progress. Accuracy is also improved, as it is easier to control tolerances and there is less risk of operator error.
So Mr Raymont and his colleague, Production Engineer Mark Hutchings, who between them have over 40 years’ experience working at Adaero, set about finding a 5-axis, automated production cell to machine components falling within a nominal half metre cube.
Bearing in mind that 50 per cent of production at Crediton involves aluminium, the other half being in plastic, brass and some stainless steel, it was felt that a 30-taper machine would meet the purpose.
Most components at Crediton are produced for the medical, ophthalmic, industrial laser and pneumatics / hydraulics sectors.
Electronic housings for race and road car engines are also machined for parent company, Cosworth, which has owned the subcontracting firm since 2012.
The company shortlisted five automated machining centre options but decided on the Brother solution from Whitehouse Machine Tools, as it offered best value for money at around two-thirds of the price of the other options.
Adaero had been impressed with the performance of the other Brother machining centres on site, which have operated with very few problems over the years, and there was the added advantage of being able to swap programs easily between the automated cell and the stand-alone machines.
Mr Raymont continued, “The Whitehouse engineer that came here was very helpful. Rather than telling us how we should use the new cell, he listened to what we thought we wanted from it and guided us as to how we could utilise it better to extract maximum benefit across our range of applications.
“The week after installation, the Brother cell was operating around the clock, manned up to 6.00 pm and ghost shift running through the night until the pallet magazine was reloaded at 6.30 am the next day.
“The whole package including service and support provided by Whitehouse and 2 by System 3R have been really good, which is not the case with many suppliers.”
The Brother 32BN-FT machining centre is equipped with a 5 -axis compound table from Nikken to provide the rotary axes. The latter are used almost exclusively to position workpieces for 3 -axis machining, although occasionally some components require simultaneous 5 -axis profiling of small features.
Adaero’s view is that fully interpolative machining is time consuming, as it is limited by the slowest axis, so it engineers out such features wherever possible.
The 84-position pallet store from System 3R, positioned to the left of the machine, is populated by Lang vices, currently of sizes 120 and 200, supplied through Thame Workholding. Each vice with its fixtured workpiece is picked up from a pallet and loaded into a similar table-mounted chuck on the Nikken table by a linear transfer arm carrying a pneumatically operated gripping device. The entire cell has a compact footprint and large doors facilitate loading of workpieces into the pallet magazine.
The subcontractor uses the cell either to complete Op 10 on components ready for Op 20 to be carried out on other machines, or alternatively to carry out both operations so that parts leave the cell completely finished. Many jobs involve kits, so families of components are often produced. Typical accuracies achieved are ± 0.1 mm on dimensions down to ± 6 microns on some bores. These are held with ease, which is just as well, as many parts are anodised and that process consumes much of the drawing tolerance.
During unattended operation, tool breakage detection integrated as standard by Brother within the 40 -station magazine provides security against producing scrap.
So too does Adaero’s policy of machining each type of component from a different size of billet. It allows a spindle-mounted probe to be programmed at the start of each cycle to identify the billet type and cross check it against the program to be run. A check is also made to ensure that all tools are available for the job.
The 1.5 minutes that all this takes, and its attendant cost, is recouped through reduced wastage and security of production, bearing in mind that many customers are on Kanban supply and any interruption in deliveries can potentially be disastrous.
Scheduling software written in-house by Mr Raymont drives shop floor production, based on customers’ changing demands, their stock levels and those held on consignment at Crediton. The production planning system flags up if more or fewer parts are being used and triggers increased batch quantities and perhaps the use of larger bin sizes for delivery, which also saves the user money.
Use of the latest production cell is still being fine-tuned to suit customer requirements, raise productivity and moderate operating costs.
The way forward will either be unmanned operation overnight, or a minimally manned shop floor over a second shift, which will also allow the automated cells to be supervised. Either way, Mr Raymont said that the future is definitely 5 -axis machining.
About the Brother TC32B FT
The attributes of Brother’s TC-32B FT (fixed table) vertical machining centre set it apart from most models on the market designed for highspeed production of prismatic components.
The nimble yet robust, 30-taper, moving-column machine supports fixtured workpieces up to 600 kg and has a spindle speed of 12,000 rpm (optionally 16,000 rpm), offering high torque above 5,000 rpm.
Rapid traverse of 70 m/min in all axes, axis acceleration of up to 1.5g and cutting feed rate of 20 m/min all contribute to very high productivity.
This is assisted by automatic tool change in 2.1 seconds, including not only the physical exchange of the cutter but also spindle deceleration and acceleration. 70 bar through tool coolant maximises machining accuracy, metal removal rate and tool life.
High resolution servo drives and encoders from Yaskawa result in high machining accuracy and surface finish, especially where the axes change direction while in cut. As the encoders are absolute, there is no need for limit switches or return to machine zero. Positioning accuracy is 5 microns per 300 mm with repeatability of ± 3 microns, assisted by thermal expansion compensation in X, Y and Z.
The Brother control is Fanuc-based with a proprietary front end, which means that programs from other Fanuccontrolled machining centres can be run with very little modification.