Chip Conveyor

Chip Conveyors

•A chip conveyor is used in a metal cutting machine to carry away waste, such

as metal chips during machining and manufacturing operations.

•Most common in machine tool operations, a chip conveyor is an important part

of cleanliness and safety as well as a key item in recycling efforts.

•In a machine shop floor all CNC machine contains a chip conveyor followed by

a waste bin.

Types of Chip conveyors

1.Hinge type chip conveyor

2.Scraper type chip conveyor

3.Magnetic conveyor

4.Screw conveyor

1) Hinge type conveyor

Hinge-belt chip conveyors (or hinge conveyors), the most common format,

offer an effective means of managing heavy chip loads and stringy chips.

Chips that fall from the machine tool land on the conveyor belt and are

conveyed away from the machine tool’s precision surfaces. As shown in

figure...

         2) Scraper type chip conveyor

Scraper-type chip conveyors are most often used for cast iron, bronze or

brass machining, which produces smaller chips that can nest together.

Chips fall directly to the bottom of the conveyor, and scrapers drag debris

to the discharge end of the conveyor.As shown in figure...

         3) Magnetic conveyor

Magnetic chip conveyors are intended for ferrous material applications with

small chips. The chips fall onto the conveyor’s stainless steel surface and

are conveyed by powerful magnets moving underneath. The chips are

released from the magnets at the discharge end, and fall freely into a

collection container.As shown in figure...

       4) Screw conveyor

A screw conveyor is a mechanism that uses a rotating helical screw blade

within a tube, to move granular materials or dry chips.

The screw is fixed with a motor arrangement to rotate the screw in one end

and free in another end.As shown in figure...

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Coolant system

Coolant system

•Coolant is a type of lubricant designed for metal working processes.

•When metal cutting takes place in a machine due to high cutting speed a frictional force is generated in between tool and workpiece.

• The friction generates heat due to which unwanted wear takes place, reduces the tool life, effect machine efficiency also gives poor surface finish to work piece.

•To avoid these a cutting fluid is to be use known as coolant.

    Types of cutting fluid

•Liquid

 Semi-synthetic coolants, also called soluble oil(Water with mineral oil)

•Paste or gels

•Aerosols(Mists)

•CO2 coolant

•Air or other gases

•Solid

       Properties of a good coolant

•keep the work piece at a stable temperature .

•maximize the life of the cutting tip by lubricating the working edge.

•prevent rust on machine parts and cutters.

•Keep the machine and bed clean.

•High thermal capacity and lower viscosity.

Coolant system in CNC machine

•All CNC machines are provided with a coolant tank along with level gauge and sensor.

•In certain cases secondary coolant tank is also provided.

•A feedback signal is generated when the level of coolant goes low from the specified level and an alarm is triggered.

•For every types of coolant there are separate pump and motor arrangement.

•Bag filters are provided in secondary coolant tank to filter the coolant.

Important codes related with coolant system

•M07 : Mist coolant ON

•M08 :  Flood coolant ON

•M26 : Spindle through coolant

•M09 : All coolant OFF

Types of Coolant System in CNC machine

1) Mist Coolant

2) Flood Coolant

3) Through spindle coolant

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Automatic Pallet Changer(APC) in CNC machine

Automatic Pallet Changer

In order to working with CNC machine to reduce the job setting and clamping cycle time on fixture one or more  additional pallet is being provided 

• Machining can be carried out on one pallet, while the others can be used for preparation (seating and clamping of work-pieces etc.)

•The palletizing system consists of two, or more pallets (per customer requirements).

Set of instruction carried out during command of Pallet change(M60)

•Program code : N01 M60;

•All axis return back to reference position(X, Y, Z and B axis).

•Pallet unclamp and air releases from seating cone

•Waiting pallet gets inside for machining  and machined pallet gets out.

•Pallet change takes place either by pallet lifting and rotating or sliding.

Important codes related with pallet change

•M10 : Pallet clamp ON

•M11 : Pallet clamp OFF

•M60 : Automatic pallet change

Clamping Function : Clamping force is ranged from 2.5kN ～ 40kN. It is possible to select clamping force depending on purpose.

Air-Blow and Seat Check :  Foreign substance is removed by air blow. Seating surface is provided with the air hole, seat check is possible if gap sensor is used.

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ATC(Automatic Tool changer) in CNC

Automatic Tool Changer

•An Automatic tool changer or ATC is used in CNC machine to improve the productivity and tool carrying capacity of the machine.

•ATC changes the tool very quickly, reducing the non-productive time.

•Generally, it is used to improve the capacity of the machine to work with a number of tools.

•The code used to change the tool is M06.

•N01 T08 M06;(Program/Block format)

Set of instruction carried out during command of tool change(M06)

•The call tool arrive to waiting pot position.

•All axis goes back to its reference point/position.

•Spindle orientation takes place.

•Tool unclamp command generated, simultaneously ATC arm hold the spindle tool and other side the waiting tool.

•ATC arm get rotated by motorized cam follower mechanism and spindle tool switched by pot tool and vice versa.

•Tool clamp command generate and ATC arm returns to home position. 

Advantages of ATC

• Increase in operator safety by changing tools automatically
• Changes the tools in seconds which reduces machine idle time
• Increases flexibility
• Heavy and large multi-tools can easily be handled
• Decreases total production time

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ATC Magazine in CNC machine

Tool Magazine in CNC machine

•Tool magazine is collection of different types of cutting tools used to complete an operation in CNC machine.

•Eg: Milling tool, Drilling tool, Rimming tool, Taping tool, boring tool etc.

• All tools in magazine is specified with a unique number(T01, T02, T03…..), call tool number.

• A motor and gearbox followed by a chain rotates the magazine.

Types of Magazine

1) Drum type magazine

2) Chain type magazine

3) Matrix/Rack magazine

1) Drum type magazine

                   The Drum or disc type tool magazine rotates to get the desired tool in position with the tool change arm. Larger the diameter of the disc/drum more the number of tools it can hold. It has pockets where tool can be inserted. It carries about 12 to 50 tools. A motor and gearbox is provided to rotate the tool and bring it to the desired position. A pneumatics cylinder is been used for pot position. Figure shows the arrangement of drum magazine.

2) Chain type magazine

                   When the number of tools is more than 50, chain type of magazines are used. The magazine is mounted overhead or as a separate column. In chain magazines the tools are identified either by their location in the tool holder or by means of some coding on the tool holder. In additional with motor gearbox sprocket been provided to rotate the chain, the toolpots are mounted on chain and rotate with the chain, as like drum magazine pneumatic cylinders are provided for pot position.

       3) Matrix/Rack magazine

                   Rack magazines are cost-efficient alternative to usual tool magazine systems. Set-up time can be optimized by utilizing the racks' capacity of up to 50 tools. The high storage capacity of up to 400 tools permits a large production capacity of varying work pieces without tool changes. A AS/RS Automatic storage and retrieval system or robot is been provided for picking and placing the tool.

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Introduction of CNC machine

CNC Machine 

What is  CNC Machine...?

                            CNC machine stands for Computer Numerical Control Machine is a machinery used in production system to convert raw material into a finished product.

CNC machine involves the use of computers and control system to control machine tools.

Tools that can be controlled in this manner include lathes, mills, routers and grinders.

The computer uses a set of numeric codes known as program to control the machine tools.

Block Diagram

Input 

A set of numeric codes call the program uses as input of CNC machine

There are 2 types of codes used to write programm. 

M codes : Miscellaneous codes

G codes : Preparatory codes 

 Commonly input methods are punch tape reader, magnetic tape reader, computer via RS-232-C communication and MDI(MAnually data input).

RS-232 cable

Display unit 

        A monitor is provided in cnc machine to display program, machine behaviors, alarm, maintenance schedule and all related parameters of machine

Machine control unit(MCU)

        It is the heart of the CNC machine. It performs all the controlling action of the CNC machine, the various functions performed by the MCU are

• It reads the coded instructions fed into it.
• It decodes the coded instruction.
• It implements interpolation ( linear, circular and helical ) to generate axis motion commands.
• It feeds the axis motion commands to the amplifier circuits for driving the axis mechanisms.
• It receives the feedback signals of position and speed for each drive axis.
• It implements the auxiliary control functions such as coolant or spindle on/off and tool change.

Feedback System

          This system consists of sensors and transducers. It is also called as measuring system. It contains position and speed transducers that continuously monitor the position and speed of the cutting tool located at any instant. The MCU receives the signals from these transducers and it uses the difference between the reference signals and feedback signals to generate the control signals for correcting the position and speed errors.

Driving System

          The driving system of a CNC machine consists of amplifier circuits, drive motors and ball lead screw. The MCU feeds the signals (i.e. of position and speed) of each axis to the amplifier circuits. The control signals are than augmented (increased) to actuate the drive motors. And the actuated drive motors rotate the ball lead screw to position the machine table.

Machine Tool

       A CNC machine tool always has a slide table and a spindle to control of the position and speed. The machine table is controlled in X and Y axis direction and the spindle is controlled in the Z axis direction.

Features 

•Storage of more than one part program

•Various form of program input

   Eg : Magnetic tape, Floppy disc, RS232, USB, manual data input(MDI)

•Program editing at the machine tool

•Cutter length and size compensation.

•Acceleration and Deceleration calculations.

1) HMC(Horizontal Machining Center) :

The position of spindle is parallel or horizontal with respect to the bed or pallet as shown in figure.

2) VMC(Vertical Machining Center) : 

The position of spindle is perpendicular or vertical with respect to the bed or pallet as shown in figure.

•Advantages

1)High Accuracy and precision 

2)Time saving

3)Continues operation

4)Less manpower requirements

•Disadvantages

1)High initial cost

2)Spare parts are costly and not available at local markets 

2)Required skilled person to operate or maintenance 

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