MT-284 MANUFACTURING PROCESSES INSTRUCTOR: SHAMRAIZ AHMAD MS-Design and Manufacturing Engineering Shamraiz_88@yahoo.com Topic: Broaching and Press Working

Today’s Lecture Broaching Process Broaching machines Press work operations Press machine Types of Press machines,

BROACHING Movement through or along the part Broaching is a machining operation that involves the use of a multiple-tooth cutting tool moved linearly relative to the work-piece in the direction of the tool axis. Movement through or along the part

BROACHING The cutting tool is called a broach, and the machine used is called a broaching machine. The shape of the machined surface is determined by the contour of the cutting edges on the broach, particularly the shape of final cutting teeth. It is very fast material removal process and productivity may increase up to ten times.

Broaching advantages Broaching is used when precision machining is required, especially for odd shapes. It produces; Good surface finish Close tolerances Variety of possible machined surface shapes, some of them can be produced only by broaching. Owing to the complicated geometry of the broach, tooling is expensive but suitable for mass production. Commonly machined surfaces include circular and non-circular holes,  keyways, gears and flat surfaces

Broaching tool Most broaches are made of high-speed steel, although broaches with carbide inserts are also available.  The cut is performed in one pass of the broach, which makes it very efficient.

External broaching tool

Broaching Operation Broaching is an unusual machining process because it has the feed built into the tool. The profile of the machined surface is always the inverse of the profile of the broach. The rise per tooth (RPT), also known as the step or feed per tooth, determines the amount of material removed and the size of the chip. The broach can be moved relative to the work-piece or vice-versa. Because all of the features are built into the broach no complex motion or skilled labor is required to use it

Broaching works best on softer materials, such as brass, bronze, copperalloys, aluminium, graphite, hard rubbers, wood, composites, and plastic. However, it still has a good machinability rating on mild steels. Broaching is more difficult on harder materials like stainless steel and titanium, but is still possible.

Broaching machines Broaching machines are relatively simple as they only have to move the broach in a linear motion at a predetermined speed and provide a means for handling the broach automatically. Most machines are hydraulic but a few specialty machines are mechanically driven. The machines are distinguished by whether their motion is horizontal or vertical. The choice of machine is primarily dictated by the stroke required. Vertical broaching machines rarely have a stroke longer than 1.5 m.

Broaching machines vertical ► horizontal ▼

Broaching machines The Horizontal are suitable for broaching of relatively long and small diameter holes, while the Vertical are used for short lengths and large diameters.

PRESS and PRESS WORK Press is a metal forming machine tool designed to shape or cut metal by applying some mechanical force or pressure, It is almost chip less operation. . Metal work pieces are deformed into desired shape through pressure. Presses and press tools facilitate mass production work. These are considered fastest and most efficient way to form a sheet metal. The main tools used on press are punch and die.

PRESS The Press Work is also called cold stamping because product of this operation is called ‘pressing’ or ‘stamping’. In press work a large force is applied for short interval of time which results in cutting or deformation. The raw material is generally soft metals which is called as stock. These process are generally carried out at room temperature. And a Press is a machine tool that changes the shape of a workpiece.

Press Work Operations/Terms 1. Punching: Punching is a cutting process in which material is removed from a piece of sheet metal by applying a great enough shearing force. Punching is very similar to blanking except that the removed material, called the slug, is scrap. The punching process requires a punch press, sheet metal stock, punch, and die.

Press Work Operations/Terms 2. Blanking: Operation of cutting flat sheet into desire shape. Here the metal punched out is the required product and the plate left with hole is a waste. In this process, the piece removed, called the blank.

PRESS TYPES Open Back Inclinable Press Screw Press Hydraulic Press

1. OPEN BACK INCLINABLE (OBI) PRESS The OBI press has C-type frame which can be inclined at an angle to the base, allowing for disposal of finished parts by gravity. Major components of OBI press are: Rectangular Bed Bolster Plate Ram Knock outs Cushion

Main Parts of a OBI-Press

Main Parts of OBI-Press Bed It is usually rectangular in shape and in vertical direction. It supports the bolter plate. Ram (Slide) This is main operating part of the press which works directly during processing of a workpiece. Ram reciprocates to and fro within its guide ways with prescribed stroke length and power. The stroke length and power transferred can be adjusted as per the requirements. Ram at its bottom end carries punch to process the workpiece.

Main Parts of OBI-Press Bolster Plate It is a thick plate attached to the bed or base of the press. It is used to clamp the die assembly rigidly to support the work piece. The die used in press working may have more than one part that is why the phrase die assembly is being used at the place of die. Knockouts Knockout is also a type of stripper which is used generally in case of inverted dies. After the completion of cutting action, the blank is ejected by the knockout plate out of cutting edge. Cushion It is a press accessory, located beneath or within bolster for producing an upward motion and force which actuated by air, oil, rubber or spring.

2. SCREW PRESS A screw press also known as fly press or ball press and is operated by hand, therefore it is also called hand driven or manual press. In this press the power is transmitted through a screw. Screw press are low capacity press machines. The energy is supplied through human efforts at the Ram through power screw.

Main Parts of a Screw Press Die Frame Ram Screw Arm Balls Handle Guide Punch

Main Parts of a Screw Press Die It is a part of press tool which has opening or cavity and it receives the punch. Frame Frame constitute main body of the press located at one edge of its base. It houses support for ram, driving mechanism and control mechanisms. Some of the press have column shaped frame.

Main Parts of a Screw Press Ram This is main operating part of the press which works directly during processing of a work piece. Ram reciprocates to and fro within its guide ways with prescribed stroke length and power. The stroke length and power transferred can be adjusted as per the requirements. Ram at its bottom end carries punch to process the work piece. Screw A long screw which runs through the body or frame of the press and transmit the manual power to the Ram and Punch for producing pressure on work piece.

Main Parts of a Press Arm It helps to turn the power screw up and down and mounted on the end and top of the screw. Balls Heavy metal Balls are fixed at the two ends of the arm which due to their heavy weights act as fly wheel to store energy for the ease of operation . Handle It helps in turning the arm.

Main Parts of a Screw Press Guide It supports the lower end of the power press and Ram so that it is correctly guided towards the work piece for the Die and Punch operation. Punch It is attached to the Ram of the press and is forced into the Die cavity. The punch is known as male part of the press.

3. HYDRAULIC PRESS The press having large piston and cylinder to drive the ram. These presses provide longer stroke than mechanical presses with adjustable intensity of blow.

Main Parts of Hydraulic Press Cylinder Piston Hydraulic Pump Slide for Ram Motor Punch Die Ram Guide Base for Frame

Main Parts of Hydraulic Press Cylinder: A chamber in which a piston movers up and down, under the pressure of highly pressurized fluid. Piston: A cylindrical part which moves up and down inside a cylinder under the pressure of fluid. Hydraulic Pump: A device used to raise, transfer or pressurise liquid.

Main Parts of Hydraulic Press Motor: Electric motor is device which converts electrical power to mechanical power. Punch and Die: Ram Guide: It supports and guides the Ram in the press work. Base/ Frame: The structure of frame is called as frame and the lower structure is called as base on which the parts are mounted.

Hydraulic press Hydraulic press has longer ram stroke than mechanical presses. The speed and pressure are constant through out the entire stroke in hydraulic press. However its process is slower to mechanical press.

Uses of hydraulic press Hydraulic press is used in many die cutting operations like blanking, cutting off, shaving and trimming etc. It is used as mass production tool in large industrial units. It is mainly used for forming and drawing .

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