"The need to forsake flexible manufacturing for a stand-alone machine was prompted by a number of factors", says managing director Colin Langridge, not least being the continual quest for reduced lead times as well as the requirement for what he describes as a user-friendly manufacturing process.
"When we installed the FMS - a vertical machining centre and vertical turning and boring machine fed by robot automatic guided vehicle from a 12-pallet workpiece 'store', with all operations overseen by a single operator from a control room - every product being produced was effectively a one-off. The result was that we put raw castings in at one end and received finish-machined seals at the other," he says.
"We were focused on supplying the world's navies, producing a wide range of sealing systems that, although based on the same basic castings, featured subtle design differences.
Hence the need for a flexible machining system that could process a variety of parts consecutively. "But the goalposts for the efficient manufacture of these ring-shaped workpieces have moved in recent years as we've reacted to address the impact of environmental issues in terms of sterntube seals (face and lip type) as well as aft, bulkhead and rudderstock seal systems, in particular for commercial shipbuilders the world over.
"While it is still true that every workpiece is, in a sense, a one-off and we still need to be able to produce a wide variety of parts in the quickest possible time, we realised that the benefits of flexible manufacture need to be balanced by the adoption of a relatively 'simple' manufacturing process."
He continues: "The FMS was a very complex system that, to run successfully, needed a lot of programming and technical knowledge. Even then, as the system grew older, we frequently suffered downtimes as we were 'held in jail ' on many occasions through AGV control problems and spares, in particular. "It was time for a re-think," he reflects.
"We wanted similar machining capacity and capability - raw material in, finished components out - but we didn't want a plethora of control interactions nor the cost of FMS (a replacement system was estimated at GBP 2 million). Importantly, we also wanted the successor to be operated by a number of guys, just like all our other CNC machines."
Ron Stevens, manufacturing director, points out that the search for a suitable replacement unearthed 12 candidates meeting the outline specifications for a ram-type machine capable of both vertical and horizontal turning, milling, drilling and tapping of maximum outside diameters of two metres (larger than the FMS) on a range of materials including exotic stainless steels, inconel and ferralium.
The machine also had to have adequate palletisation and auto tool change capability to cope with the varied range of operations - for example, turning and milling followed by drilling, tapping and counterboring a series of holes around the periphery.
Aside from meeting all the selection criteria, another main reason why Deep Sea Seals selected the Toshulin (supplied by Ward CNC of Sheffield) was, he says, because of its user-friendliness.
"It's a big machine - with load/unload station and toolchanger the overall footprint is 10.4 metres by 7.9 metres - but the operator actually feels 'in touch' and in control of every aspect of the machine.
The machining zone, load/unload station and toolchanger are all visible and within easy reach of the operating position.
"We now have huge capabilities in terms of both workpiece capacity and machining operations," continues Ron Stevens, "yet with the Fanuc 16iT CNC the Toshulin isn't complicated to either program or operate and this aligns perfectly with our plan to train up several operators."
At-the-machine programming and editing while the machine is cutting is possible although the plan is to DNC link the Toshulin to the EdgeCAM-based off-line programming system developed by Pathtrace originally for the FMS. "Our customers will enjoy the benefits of the accuracy and improved surface finishes that come with a machine developed for the areospace industry at no extra cost to them."
With a table diameter of 1600mm and capable of accommodating workpieces weighing 12,000kg, the Toshulin Powerturn 1600 C-M 2APC's key characteristics of rigidity and stability are based on a series of high-quality construction features.
The machine frame is a one-piece, heavy-duty, internally-ribbed cast column mounted on the main table base (the main table drive is centrally located relative to the column).
The table base houses the main spindle gearbox, C axis drive mechanism and features pre-loaded precision SKF cross roller table bearing.
Thermal stabilisation is ensured by a refrigerated recirculating oil-cooling system.
The main table can be configured as either: * Faceplate type chuck with four separately-mounted and manually-adjusted clamping jaw units; * Integral base jaw manual chuck with four separate manually-adjusted flush mounted jaw clamping units; * Three- or four-jaw hydraulic chuck with flush mounted jaw clamping units incorporating fine manual adjustment.
The main spindle drive is rated at 60kW as standard (optionally 80kW).
A two-speed planetary gearbox is mounted vertically on the machine base.
A precision hardened and ground helical drive pinion and table rim gear drives the main spindle.
The result is infinitely variable spindle speed up to 500 revs/min with automatic gear changes giving constant power and constant torque.
The C-Axis drive is based on a hydraulic table clamping mechanism that provides partial braking during table positioning and full clamping during machining. Table positional feedback is by Heidenhain encoder. The C-Axis drive mechanism is a separate system to the main spindle, and incorporates a hydraulically operated anti-backlash double split helical drive pinion and separate axis drive motor to ensure a high degree of positioning accuracy.
Accommodating boring, milling, drilling, tapping and leadscrew threading, the live milling spindle boasts infinitely variable speed in two or three gear ranges at constant power and constant torque offering up to 3,000 revs/min and 28kW power.
Clockwise and counter-clockwise spindle rotation is available with spindle orientation (M 19).
The cross-rail assembly elevates to position the ram head to optimise cutting on workpieces of varying size. Vertical adjustment of the cross-rail height is by trapezoidal screw through a worm and wormwheel gearbox, powered by synchronous AC motor.
Cross-rail positioning is to defined heights in fully programmable increments of 100mm with a repeatability of 0.02 mm. Combined guiding is on hardened and ground guideways incorporated in the main column.
Front guideways are heavy-duty sliding type with sideway guiding incorporating pre-loaded rolling elements. Saddle assembly incorporates 16 sets of pre-loaded recirculating linear roller bearing packs fully supporting the ram from all sides and a further 14 sets, pre-loaded with active hydraulics that support the saddle on the crossrail assembly - for exceptional accuracy and long-term performance of the main machine moving elements.
Offering exceptional levels of accuracy and rigidity, the main ram assembly is of hardened and ground forged steel having a 240mm by 240mm cross section.
The Toshulin Powerturn range of high-performance CNC vertical turning machines features the latest development of heavy-duty internal clamping of adapter heads to a unique Toshulin patented design incorporating services for hydraulic tool clamping, milling drive, air purge and three separate coolant delivery systems.
Toshulin's revolutionary design of toolchanger (96-tool maximum capacity) allows the automatic changing of turning or milling adapter heads, which then allows the automatic changing of 50 ISO turning and milling tooling directly into the ram adapter for either axial or radial turning or milling. Mounted on the main column within the machine's work zone is an automatic toolsetting unit.
The machine's twin-pallet load/unload station ("which will probably be expanded as our confidence grows", says Ron Stevens) features a novel design of pallet location based on four pistons that clamp the pallet onto a central spigot location with a radial key.
An air blast under the pallet clears any debris as positioning occurs. The result is that the pallet consistently locates to +/-2 microns.
While it is early days to compare throughput times with the FMS, Ron Stevens says the Toshulin will be quicker and overall output will be higher. "Even though the FMS would be cutting simultaneously on both machines, because of its unreliability we could really only run one shift.
With the Toshulin, we are getting finished parts from just two chuckings (one turnover) and there's no doubt the machine will allow us to make the most of the 168 hours available in a week when required."
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