Linea Spindle: one single CNC multi spindle for all working phases

The machine must integrate all the phases: turning, diamond dressing, milling, boring, deburring and any other additional machining. All these different processes must be easily programmable according to the variable work cycles for each type of ball or piece to produce.
The machine must be more compact, accessible and ergonomic than other possible alternatives.
Furthermore, the machine must be suitable to work various types of materials: brass, lead-free bronze, aluminium, steel.
Set-up time was important for the customer, since the machine must also competitively manufacture small batches of pieces.

Therefore, to ensure the set-up time does not affect production costs also for small quantities of pieces, the set-up time must be as short as possible.

The market offers the following solutions:

1. MULTI SPINDLE: the classic, bar multi spindle was not suitable, because it can’t cover the dimensional range required, from 20 to 80 mm, nor can it meet the requirement to manufacture different types of blanks, such as bars, moulded and cast pieces.
2. TRANSFER: The transfer solution coupled with an external turning machine proved inadequate, since it is not possible to integrate in a single machine the roughing, diamond dressing and additional machining phases.
   An optimal ball machining cycle actually requires a trimming phase to create a fixed piece, followed by turning and diamond dressing with a rotating piece and then the additional machining phases again on the fixed piece.
   With a TRANSFER type solution, three machines would therefore be necessary (transfer-turning-transfer machine) which would make the plant very large, complex to manage and difficult to set up and not ergonomic.
   Furthermore, the wide range of balls and pieces to manufacture, with the minimum production batches including even a few thousand pieces was NOT suitable for TRANSFER machines that have high costs, tools for each piece model to produce and very long tooling times, therefore NOT suitable for the manufacture of small series pieces.
3. THE TRADITIONAL “SALA” MACHINE: this also cannot meet all the customer's requirements since the “SALA FLEXIBALL” solution, used for years in the production of brass balls, presents the following limitations:

1. Flexiball has an excessive production capacity compared to customer needs, especially in the manufacture of very limited batches.
2. The dimensional range must be extended of the workable pieces.
3. Flexiball is not suitable for machining materials such as aluminium or steel with the need for an emulsified coolant plant.
4. The request for multiple, additional processes, which were numerous and different (boring, milling, chamfering, unloading) would have generated an excessive number of work stations, greatly increasing the size of the FLEXIBALL type machine and resulting in an increase in set-up time.

THE DESIGN
Sala therefore developed a particular design to resolve this customer's problem, benefiting from its know-how and experience, even in sectors different to that of ball valves.
Meeting the set of requirements was based on the primary need of obtaining flexible production of pieces, even differing greatly from one another.
Setting the SALA LINEA SPINDLE type machine with piece holding spindles equipped with CNC controlled movement axes and the possibility of direct exchange of pieces from spindle to spindle proved to be the most suitable solution.
By doing so, two spindles and a series of tool holders and standard tools would suffice to perform all the required machining, using simple and flexible CNC programming.
There are however numerous, hard additional processes. We therefore thought about adding a third line type spindle unit to perform the additional machining on the fixed piece parallel to the internal and external turning and diamond dressing phases, with considerable benefit and reduced cycle time.
INTERFACE: a specific study was also developed to prepare a highly developed and intuitive interface to enable rapid programming of the cycles based on ball type and different dimensional range.
Use of the tool holder with rapid change, presettable outside the machine, completed the result of a flexible system that in less than 30 minutes allows passage from one type of piece produced to another.
FINAL SOLUTION
A linear turning centre, with CNC controlled work cycles programmable using an interface.

• Total number of CNC controlled axes: 15 axes, to manage 3 spindle units + 4 independent operating units.
• Rapid and intuitive user interface.

RESULTS OBTAINED
All customer requirements were met:

1. Dimensional range of workable balls:
   with an external diameter of 20 mm to 80 mm
2. Type of balls: 2-way, 3-way, with through milling, transversal boring off centre with programmable positions, deburring of the milling and transversal boring, internal turning with additional removal, possibility of internal and external threading.
3. Possibility of manufacturing balls starting from the cast or moulded raw piece or solid or bored bar piece.
4. Possibility of also manufacturing turned pieces with different spherical shapes.
5. Possibility of activating the tool coolant system with emulsion.
6. Possibility of machining different materials: brass, aluminium, bronze, steel.
7. Compact machine, with 50% in the occupied area, compared to alternative, traditional solutions (Transfer multiple turning and diamond dressing machines for balls)
8. Maximum ergonomics, thanks to the vertical spindles setting, arranged in a line, a setting that equally guarantees easy accessibility for set-up and tool adjustment.
9. Completely integrated automation, with automatic change of raw pieces and accumulation of the finished balls on a belt or palletisation of the individual balls on storage balls.
10. Extremely reduced set-up time, thanks to development of an intuitive user interface and use of tools preset outside the machine.
    The set-up time for passage from production of a spherical model to another is 25 minutes, thereby guaranteeing cost-effective production even for very small batches.
    It is therefore possible to produce the minimum batch of pieces necessary when required, reducing the weight of the warehouse.
11. Quality: Sala also guaranteed the T2S LINEA machine, the result of high quality standards on the finished product, obtaining dimensional tolerances and a significantly better surface finish compared to the limits required.
    An advanced system for constant control of tool wear and breakage during the automatic cycle contributes to guaranteeing the quality of the end product, even with unmanned production.
12. Manufacturing efficiency: setting the machine with mobile spindles on 3 axes enables loading and unloading automation to be obtained simply by moving the spindles on controlled CNC axes. By doing so, the automation system is simplified, with positive effects also on the efficiency of the machine, resulting as extremely high and allowing unmanned production.