PERFORMANCE AND PRECISION DEGREE

Robbi grinding machines are according to the international precision normes ISO 2433.
The table movement linearity is guaranteed by a max. deviation of 0,002 mm/mt.

Surface finish degree 0,2 Ra m.(**)

The obtainable grinding roundness is :

• Grinding between centers 0,3 m (**)

• Grinding with live spindle 0,4m (**)

(**) for a test workpiece ground in our factory during machine testing

The Grinding Machine is composed of :

BASE

Structure in normalised and stabilised cast iron with large ground guides. The lubrication plant provides oil to the guides by means of a constant oil flow distributed on the complete length. In the middle of the base there is located the hydraulic cylinder for the longitudinal table movement. On the lower part of the perimeter are situated the recesses for machine levelling. Considering the base structure, usually a foundation is not required.

TABLE

The table is manufactured in two parts, both are in normalised and stabilised cast iron. The lower part has large ground guides, accurately hand scrapped to permit a better sliding. Lubrification is assured by a constant oil flow distributed over the complete table length. The upper part, is swivelable in the two directions suitable for grinding tapered workpieces. This part includes a micrometrice device with centesimal dial gauge for taper control. The large machine with center distance of 2030 mm. has an air flow system between the two tables to facilitate precise table swivel movement.

WORKHEAD

The structure in normalised, stabilised and well ribbed cast iron, allows to support the workpiece weight and the force generated by the grinding operation. It is equipped with fixed and turnable spindle. The spindle rotates on high precision ball bearings, guaranteeing restricted tolerance and maximum rigidity in the working. The spindle rotation is by means of a a.c motor and the r.p.m. adjustment is obtained by means of a potentiometer. The spindle rotation may be intermittently manual or automatic.

WHEELHEAD

The structure is composed of two carriages in normalised cast iron.
The upper carriage where the hydrodynamic spindle is located, has a manual stroke positioning of 130 mm. and the air flow facilitates the movement.
The lower carriage slides by means of a re-circulating ball screw with double preloaded nut, on guides covered with anti-friction material. The lubrication of the guides and nut is by means of a timer. The brushless motor which moves the screw, is controlled with a closed ring by the incremental optic rule, which guarantees a positioning precision on the complete stroke of 0,001 mm. The wheelhead may be rotated manually 180°. On request, the wheelhead rotation of 180° may be executed with a HIRTH wheel with index swivel of 2.5°, with manual or automatic positioning.

WHEELHEAD SPINDLE

Hydrodynamic type, rotates on anti-friction metal bushes, which guarantees an high finish degree. The rotation is by means of an a.c. motor. On request, the speed may be regulated by an inverter. The transmission is by means of a pulley and Poly-V belt. On request, the machine may be supplied with a second grinding wheel on the right hand side.

TAILSTOCK

Together with the workhead the tailstock supports the workpiece weight and the force generated by the grinding operation. The structure in normalised and stabilised cast iron, is in two parts, so as to permit the cylindrical manual correction. On request, it may be supplied with an hydraulic treadle drive and safety device against accidental opening. The spindle opening is possible only with the grinding wheel in back position.

MANUAL GRINDING WHEEL FEED HANDWHEEL

Electronic type with encoder. Equipped with double scale, one with division 0.01 mm. and the other with division 0.001 mm. The handwheel is equipped with a selector to assure the stop to measure.

MANUAL TABLE FEED HANDWHEEL

Is automatically disengaged, when the hydraulic table movement is engaged.

DIAMOND DRESSER

The external diamond dressing device is very strong and is position on the tailstock.
The internal diamond dressing device is positioned on the table.

EQUIPMENT AND ELECTRICAL PLANT

The electrical (IP 55) cabinet is separate from the machine. The cabinet houses all the electrical / electronic components PLC control, axis motor controllers etc. Equipped with a forced air ventilation system where the cool air is filtered.

HYDRAULIC PLANT

The hydraulic power pack, is separate from the machine and activates the hydraulic cylinder of the table. It activates also the hydraulic cylinder of the tailstock when this system is requested. It is equipped with an oil-air heat exchanger. Supplied without hydraulic oil.

LUBRICATION PLANT

The lubrication power pack, is separate from the machine and supplies continuous oil to the wheelhead guides and to the re-circulating ball screw nuts, for the working feeds. The recovered oil is filtered and then resent to the power pack.

PNEUMATIC PLANT

Has the function to make lighter the wheelhead over-slide, during the manual movements.

COOLANT PLANT

Large capacity tank for the coolant water. On request, it is possible to equip the coolant plant with a magnetic or paper roll or combined magnetic+paper roll cleaner. The coolant flow is automatic; each time that the grinding wheel approaches the workpiece it starts and each time that the grinding wheel retracts from the workpiece it stops.

PROTECTIONS

For the protection of the operator all movable parts are covered with suitable guards. Precisely: carter for belts, carter for grinding wheel and bellows for guides.
The front protections are sheet sliding doors with poly-carbonate shields.
A movable shield in sheet, controlled by a pneumatic cylinder, protects the operator, when the grinding wheel is in rotation and the front sliding doors are open.
A safety device, does not permit the automatic cycle to start if the front sliding doors are open.