Favretto TA surface grinding machine

Favretto TA surface grinding machine 

PRODUCTION RANGE

Surface grinding machines - Tangential grinding wheel on a horizontal spindle - Hydraulic reciprocating worktable. Types TA, TB, TC, and TD.

Surface and slideway grinding machines - One tangential head and two universal wheelheads - Hydraulic reciprocating worktable. Types TC/S and TD/S.

Surface grinding machines suitable for flat, convex, and concave work - Tangential wheel on a swiveling head - Rotary table. Types TR and TD/R.

Surface grinding machines - Frontal grinding wheel on a vertical spindle - Hydraulic reciprocating worktable. Types VA, VA/A, VB, and VB/A.

Surface grinding machines - Frontal grinding wheel on a vertical spindle - Two rotary worktables capable of simultaneous or alternate operation for loading and unloading in production work - Hydraulically controlled rotary tables - Traverse between stations Automatic cycle. Type VB/AR.

Surface and slideway grinding machines - Double housing - Hydraulic reciprocating worktable. FR-TU-TU/P range - equipped with one tangential head; optionally can be equipped with a second head (tangential or universal). FR/S-range - single tangential head, suitable for grinding large-size dies.

Openside planing machines - Hydraulic table drive - Hydraulically controlled feeds and tool lifting. Type P.

GENERAL

The initial section of this manual introduces four types of surface grinding machines featuring advanced design and highly individual operational capabilities. These new machines retain the design features that contributed to the success of their predecessors while incorporating further improvements driven by continuous research and development efforts. Despite being built on proven design principles, they incorporate new solutions to old problems made possible by recent technological advancements.

The four series encompass approximately 22 standard machine types, although this number effectively doubles, as each machine can be supplied upon request with additional grinding height. Furthermore, all surface grinders are available in the AUTOMATIC version, with the option of special-purpose attachments specified for each individual application.

To provide an overview, we offer the following standard machine range: (Please note that TA, TB, TC, and TD denote 30, 40, 50, and 60 cm table widths respectively, while the suffix number represents approximate table stroke in cm.).

Series TA: TA 60 - TA 90 - TA 120.
Series TB: TB 75 - TB 100 - TB 130 - TB 160 - TB 200.
Series TC: TC 70 - TC 90 - TC 120 - TC 160 - TC 200 - TC 250 - TC 300.
Series TD: TD 120 - TD 160 - TD 200 - TD 250 - TD 300 and TD 400.

Extra-length versions of TA and TB machines are often required for special-purpose applications, such as grinding very long components of textile machines, or splined shafts, broaches, shear cutters, slideway inserts, and special-purpose tools.

Standardization of many components within individual machine series, or across multiple series, has led to shorter production times and reduced overall costs, resulting in a corresponding reduction in sales price.

MATERIALS

All castings are manufactured by specialized foundries. Cast components are guaranteed to possess high wear resistance and strength tailored to each specific application. Main castings undergo rough machining to ensure freedom from defects and are then carefully deburred to remove excess metal and casting sand residues. Subsequently, they undergo a stabilizing treatment at 525°C in our shops; after soaking, castings are allowed to cool before removal from the furnace. This treatment aims to relieve internal stresses and soften the metal. Typically, cast components have a hardness of 200 Brinell or more.

Bulkier castings undergo thorough cleaning, priming, and machining. After internal deburring and meticulous cleaning, castings are transferred to the paint shop, where knife stopping, sanding, and spray painting are carried out. Thus, after eliminating all foreign matter that could affect subsequent processing, individual components are assembled. Materials have been selected based solely on performance, with no cost considerations.

DESIGN FEATURES

Our extensive experience in production work over many years has led to the incorporation of proven design features such as:

- MACHINE FRAME comprising bed and column.
- WORK TABLE with reciprocating lengthwise movement.
- WHEELHEAD with vertical and cross traverse motions.
- GRINDING WHEEL SPINDLE of the horizontal type.
- DISC WHEEL in tangential contact with the work.
- Built-in machine RIGIDITY and optimum abrasive wheel power, enabling maximum metal removal in the shortest possible time.

It is noteworthy that grinding is now typically performed under very demanding operating conditions. The increasing precision required for production components of all kinds has mandated very strict tolerances, well below ISO allowances, and surface roughness values approaching superfinish levels on a quantity and quality production basis.

FRAME

The machine frame comprises a bed and column rigidly connected to each other, forming a single structure. The box section components of the frame contribute to its pleasing appearance. Weight distribution and internal ribbing have been meticulously designed to ensure maximum stability of the machine.

BED

The machine bed accommodates the hydraulic power unit and associated controls. The top of the bed features flat-and-V slideways, which are double the length of the table ways, providing complete table support at all times. Both bed slideways undergo precision grinding for optimal performance.

COLUMN

The column of the TB, TC, and TD models features a box-type section that tapers towards the top, providing a wide bearing surface. Internally, the column is reinforced with close-spaced double-wall ribbing to maximize rigidity against deflection and vibration, especially during rough grinding operations. The vertical slideways for the wheelhead bracket are precisely machined along the column's front face and internal walls, ensuring accuracy and stability. Additionally, the column houses the drive mechanism for the vertical traverse of the wheelhead.

WORKTABLE

The worktable is designed with generous ribbing to create a sturdy structure capable of withstanding machining forces. It incorporates two longitudinal slideways for reciprocating motion along the bed. The flat way serves as a bearing surface, while the vee way maintains alignment with the bed. The table casting is composed of a different material than the bed to facilitate smooth sliding and prevent seizing. All working surfaces are meticulously hand-scraped to ensure optimal contact and efficient lubrication.

The table top is equipped with Tee slots that extend beyond the ground surface area, enhancing clamping capacity lengthwise. Both the table top surface and slots undergo precision grinding after final assembly on the machine. Motion reversal of the table at either end of the stroke is controlled by cams retained in a Tee slot on the front of the machine.

Reciprocating motion of the table is achieved through twin single-acting hydraulic cylinders positioned side by side and attached to the bed, with piston rods anchored at each end of the table. Manual control of the table motion is facilitated by a handwheel, while a hydraulically-controlled interlocking device ensures that hydraulic table motion is inhibited when manual control is engaged, and vice versa.

Integral coolant recovery ducts are incorporated into the table casting. On larger machines, protection of the slideways is enhanced by using oil-resistant flexible strips.

WHEELHEAD BRACKET

The wheelhead bracket, also known as the cross-head, is a component with a sophisticated design. Its structure resembles a box with ribs, akin to a tee shape, with external vertical slideways running along the entire length of the casting.

During traverse, the bracket is supported on its largest cross-section to minimize any tendency to deflect, ensuring stability during operations.

On the TA machines, vertical positional accuracy is maintained through easily adjustable gibs. Access to these gibs for adjustment is facilitated from the rear of the column, allowing for convenient fine-tuning.

For the TB, TC, and TD models, adjustment of the wheelhead bracket is achieved through the longitudinal displacement of the taper gibs, which are positioned on the front side of the machine. This adjustment mechanism enables precise control over the vertical positioning of the wheelhead bracket to meet the requirements of various machining tasks.

The vertical movements of the machine can be achieved in the following ways:

1. **Manual Traverse:** This is accomplished by using a handwheel located on the machine frame. It allows the operator to manually control the vertical movement.

2. **Power Traverse:** This method involves utilizing an independent motor controlled by Up and Down pushbuttons. This accessory (Accessory No. 11) provides powered vertical movement for convenience and efficiency.

3. **Fine Automatic In-feed:** For precise adjustments to the final cut depth, fine automatic in-feed synchronized with table or head reversal is available. This feature, designated as Accessory No. 111, ensures accurate machining results.

4. **Incremental In-feed/Semi-Rapid Traverse:** This option involves using an independent motor that can be operated intermittently for incremental in-feed or continuously for semi-rapid movement. It provides flexibility in controlling the vertical movement of the machine. This feature is available as Accessory No. 111A.

The machine's design incorporates integral slideways on both arms of the tee for the horizontal movement of the wheelhead slide. These dovetail ways are precision-machined using specialized milling and grinding machines produced in-house. Additionally, a circular opening in one leg of the tee allows for the cross traverse of the wheelhead. Controls for manual and automatic motion of the wheelhead are housed in the front arm of the tee.

WHEELHEAD
The wheelhead acts as a frame for the dríve motor which is fitted coaxially with the wheel
spindle. The frame is fíxed to the slide runníng horízontally on the dovetaíl ways of the wheelhead bracket. Two taper gíbs fitted end-to-end on the slide permít accurate slidíng motíon and
wear take-up after prolonged machine operation.
The wheelhead is provided with the following cross movements:
1. Manual traverse, by means of a handwheel.
2. Power traverse, hydraulic operation, for wheel dressíng or rapid movement.
3. Hydraulic incremental cross feed.
4. lnching, for settíng-up purposes.
The graduated handwheel on wheelhead bracket front end controls manual wheelhead cross
traverse. The inching device (accessory X1X, optional extra) for setting-up purposes gives
increments of .002 mm.
Adjacent to the handwheel are two graduated rings fitted coaxially with a central zeroing dial
for selecting wheelhead stroke ín either direction, from table mid-positíon. Upon reaching
pre-selected position, wheelhead will automatícally reverse direction of power traverse and cross

The grinding wheel and spindle assembly is a critical component of the machine, designed for optimal performance and stability. Here are the key features:

1. Spindle Housing: The driving spindle is housed within the wheelhead frame. Its front end is supported by a fixed quill housing containing rolling bearings, while the rear end incorporates the motor rotor.

2. Bearing Arrangement: Radial and axial location of the spindle is maintained by two pairs of precision rolling bearings. Each pair is fitted back-to-back with controlled preload to ensure stability and minimize deflection during operation. TD machines are equipped with an additional bearing at the rear end of the spindle for added rigidity.

3. Spindle Rigidity: This bearing arrangement provides maximum spindle rigidity throughout its length, preventing any tendency for the grinding wheel to drop at the end of the working stroke when wheel pressure is suddenly reduced to zero.

4. Frame Design: The wheelhead frame features a double-wall design, allowing for cooling air circulation. It also incorporates the stator to which the electrical harness is connected, ensuring efficient power supply.

5. Compact Drive: The spindle/rotor assembly represents a compact drive system with no intermediate connection between the motor and grinding wheel. This direct transmission of motor power through the spindle ensures minimal power loss and efficient operation.

6. Dynamic Balancing: The entire assembly is dynamically balanced to eliminate any possibility of vibration, ensuring smooth and precise grinding operation.

7. Spindle Nose: The spindle nose carrying the grinding wheel holder undergoes induction hardening for durability. Additionally, the front face of the retaining flange is equipped with counterweights to eliminate any imbalance, further enhancing stability during operation.

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HYDRAULIC POWER UNIT
The hydraulic power unit controls reciprocating table motion and wheelhead cross traverse. Table is slowed automatically on approaching end of stroke to ensure smooth and even reversals. The hydraulic unit is provided with suitable pressure relief valves for protection against overloading. The hydraulic unit control valve is a feature common to all machine types, though it may vary in size for different applications. On assembly, each control valve is extensively tested on a special purpose simulator, and then fitted to the associated machine, adjusted and checked.

The oil reservoir is integral with the machine frame which houses also the drive motor and pump. On TD machines motor/pump and flexible coupling are fitted externally at the rear of the machine, together with a heat exchanger (standard on TD models). The fresh-water heat exchanger prevents the oil from overheating and is particularly useful if the machine is to operate in hot climate countries.
LUBRICATION
Table slideways of the TA-range are lubricated by means of a reduced-pressure oil supply from the hydraulic unit via a cartridge type filter which may be easily dismantled for cleaning and renewing. Lubrication of the TB-TC-TD machines is carried out by oil-bath rollers positioned at preset distance within the machine bed ways. Wheelhead cross slideways, vertical wheelhead bracket ways, cross traverse control leadscrews and vertical leadscrews are covered by a centralized lubrication system controlled by a pressure pump and associated oil distributors conveying an adequate amount of lubricant where necessary

ELECTRICAL EQUIPMENT
Electrical controls are housed in a separate cabinet situated at the back of the machine frame. The cabinet is provided with access door. Door handle is fitted with a mechanical interlock which operates the isolator switch upon opening the door. Thus the cabinet door cannot be opened with isolator switch on. Each machine is shipped with all electrical connections to machine controls and drive motors. Provision has been made in the cabinet for incorporating also any optional accessory. Motors and electrical system are normally supplied for A.C., 3-phase, 50 or 60 Hz operation.

COOLANT SYSTEM
Standard equipment includes a coolant tank situated at the rear of the machine frame, a self-priming electric pump flange-mounted to the tank cover, coolant lines pivoting coolant nozzle, flow control tap, splash guards and coolant return lines to tank. Separators available on request (see accessories V1, V1B and V1C).

CONTROLS
All machine controls are grouped on the front of the machine within easy reach of the operator (see illustration below). A double row of pushbuttons provides for starting and stopping oil pump, wheel drive and coolant motors. This last may be replaced by an exhauster (see accessory 1X). Two selector switches control wheelhead power traverse/ inching as required. Plates are provided which incorporate the symbols associated with the various controls. Thus, all descriptive plates have been eliminated to avoid any misunderstanding possibly caused by translation into the various languages. The two blanks situated adjacent to each handwheel are provided to take any optional extra accessory control that might be required.

12 FAVRETTO To. 1. Worktable manual/power selector lever. 2. Worktable handwheel. 3. Coolant tap. 4. Wheel dresser - Accessory 01 optional extra. 5. Rapid wheelhead vertical traverse controls - Up and Down control pushbuttons. Accessory 11 optional extra. 6. Handwheel, wheelhead manual cross traverse. 7. Adjustable selector knob, wheelhead reversal. 8. Worktable control knob, starting and speed adjustment. 9. Table reversal control lever. 10. Wheelhead control knob, starting and speed adjustment. 11. Vertical movement handwheel. 12. Final cut depth control lever - Accessory 111 optional extra. 13. Selector switches, infeed synchronized with worktable and wheelhead reversal. Accessory 111 optional extra. 14. Control knob, vertical power stroke adjustment - Accessory 111 optional extra. 15. Control lever, fine infeed - Accessory 111 optional extra. 16. Table trip dogs. 17. Automatic lubrication system. 18. Hand-operated micrometric cross-movement. Accessory X1X optional extra. 19. Wheel guard with spark-protection. 20. Hand-knob for engagement and disengagement of automatic downfeed control. 21. Space for additional accessory.

STANDARD EQUIPMENT FOR TA, TB, TC AND TD MACHINES
One wheel suitable for grinding steel components. Size mm. 356 x 50 x 127 (only TA). Appropriate hardness and grit. Wheels for different grinding operations must be ordered specifically with machine. Wheel holder assembly consisting of flanged hub with taper bore, front retaining flange with balancing counterweights and retaining screws. Auxiliary wheel balancing spindle with tapered central portion to suit wheel holder assembly. Wheel holder extractor. Worktable type wheel dresser (diamond excluded). Drive motors: A.C., 3-phase, 220/380 Volt, 50 Hz. Electrical equipment in a separate cabinet with tappings for special purpose accessories (if applicable). Manual worktable traverse control with handwheel
and interlock device. Coolant system, including tank; electric pump, lines, pivoting nozzle, splash guards and recovery ducts. Heat exchanger only for model TA 150. Tool kit, lifting bars, level screws, etc. Instruction book.