Belt run over the periphery the job give drive the job

INTERNSHIP IN: Ashok Manufacturing Corporation Pvt. Ltd.

2003ME10516

Dynamic Balancing

Causes

The International Standards Organization defines unbalance as:

Fig 1

Different types of unbalance can be defined by the relationship between the two centerlines. These include:

Many causes are listed as contributing to an unbalance condition, including material problems such as density, porosity, voids and blowholes. Fabrication problems such as misshapen castings, eccentric machining and poor assembly. Distortion problems such as rotational stresses, aerodynamics and temperature changes. Even inherent rotor design criteria that cannot be avoided. Many of these occur during manufacture, others during the operational life of the machine. Whilst some corrections for eccentricity can be counteracted by balancing, it is a compromise. Dynamic balancing should not be a substitute for poor machining or other compromise manufacturing practices.

In the manufacturing process, if proper care is taken to ensure that castings are sound and machining is concentric, then it follows that the two axes will coincide and the assembled rotor will be in a state of balance.

Installed Machines - Causes

When a rotor has been in service for some time, various other factors can contribute to the balance condition. These include corrosion; wear, distortion, and deposit build up. Deposits can also break off unevenly, which can lead to severe unbalance. This particularly applies to fans, blowers, compressors and other rotating devices handling process variables. Routine inspection and cleaning can minimize the effect, but eventually the machines will have to be removed from service for balancing. Large unbalances will of course require large weight corrections and unless care is taken, this can have a detrimental effect on the integrity of the rotor. Concentrating a weight adjustment (whether adding or taking away) at a given point can weaken the rotor. For example paper rolls are fabricated from tubing and large additions or removal of weight can affect the strength of the walls of the roll. This may cause it to deflect when spinning at operating speed and thus induce harmful vibrations on the bearings and paper machine frame.

Field Balancing

Many rotors can often be balanced in place, running at their own operating speed, with minimum disassembly. To balance in place, of course, a basic requirement is that the rotor has to be accessible to make corrections. Machines such as fans and blowers are good candidates. Totally enclosed motor armatures and pump impellers are not.

· The resultant vibration can be the tolerance applied to the rotor, rather than the published balance tolerances normally used in a balancing machine. This is particularly advantageous if the supporting structure is close to a resonance. The unbalance in the rotor may have to be adjusted to abnormally fine levels to minimize the resultant resonant structural vibration. Modern instruments such as vibration analyzers, data collectors and portable balancers provide accurate information to assist in the balancing process. The vibration level measured at the rotating speed frequency is used as an indicator of the amount of unbalance. The location is determined by measuring the phase. Phase, (the relative motion of one part of a machine to another) is measured by means of a stroboscopic light or by an indicator in the instrument, triggered by a photocell.

It is imperative that the vibration measured is a result of the unbalance and not some other exiting force. Only a detailed, thorough, analysis can identify where the vibration measured is coming from. Many sources of vibration can occur at the rotating speed frequency. (1) When field balancing, trial weights for balance computation and permanent weights for final correction are normally added to the rotor. Care should be taken when attaching weights. They should be attached securely so that they cannot ‘fly off’ when the machine is operating. They not only constitute a personnel safety hazard but also can cause damage.

Balancing machines can be divided into two different types:

Production Machines

a balance check as the last task before re-assembly.

Consequences

Airborne noise is often directly attributable to mechanical vibration.

• Minimize structural stress

The time between outages can be extended if the machine is running smoothly.

• Increase bearing life

Dangers associated with machine failure are minimized.

• Increase productivity

Everything that rotates needs to be in a state of balance to ensure smooth running when in operation. Precision balancing is essential to the manufacture of rotating equipment and to the repair and renovation of installed machines. As machine speeds increase, the effects of unbalance become more detrimental. Modern technology allows for accurate balancing to be performed both in the field and in the workshop.

Increased time between outages and availability for production is the prime benefit.

ABRO also has a range of soft bearing dynamic balancing machines which are given when any such type of enquiry is received.

ABRO DYNAMIC BALANCING MACHINES COMES WITH PRECISION ELECTRONICS

Digital electronics type DS12C for dynamic balancing of 6-throw crankshaft.

Digital electronics type SSAP (D)/9C/EREC. Single plane electronic unit with component and polar indication and electronic remount error compensation to eliminate tje effect of adaptor unbalance and run out.

Recently, the above manufacturers have purchased ABRO designs and are shifting to ABRO designs for the machines they make in their plants in London, Rochester, Torino and Barcelona.

WORLD-FIRST DEVELOPMENTS

Large, high-speed balancing and over-speed testing machines which can also do accurate low speed balancing of rotors upto 90 tons. While these machines have high dynamic load capacities, they also have a good sensitivity at low speeds.

Precision vertical two-plane balancing machines of ‘hard bearing’ design for balancing small rotors in their own bearings (textile flyers and spindles).

‘ABRO’ also undertakes modification/ augmentation of machines maked by other manufacturers. ABRO has modified various dynamic balancing machines madeby Hoffman, Schenck Avery, Reutlinger, ,etc.

RANGE OF ‘ABRO’ DYNAMIC BALANCING MACHINES.

PRODUCTION MACHINES: - Modular design of ABRO machines makes it possible to produce machines for low, medium or high level of automation suitable for different production requirements.

SPECIAL MACHINES: - Special requirements require special machines. ‘ABRO’ manufactures special purpose machines. A very few examples are given below:

Dynamic Balancing Machine used for balancing vertical textile spindle in their own bearings.

Maximum work piece weight for symmetrical rotor : 450 kg

Hence per pedestal : 225 kg

Minimum diameter under belt : 30

Maximum work piece length : 2000 mm

Speed of 1500 rpm

1.4 BALANCING ACCURACY

SPEED : 1500 RPM

2. SWITCH GEAR

Maximum dial setting : 1047

3. MACHINE DESCRIPTION

In case of surface belt drive machine, a belt is run over the periphery of the job to give drive to the job, surface belt drive to the job. Surface belt drive system consists of:

• Drive motor with pulleys & supporting arrangement.

ii)IDLER BRACKET

Idler bracket consists of a bracket with slots, idler pulleys tension adjusting screw and wheel .The whole bracket is either permanently bolted on the bed or clamped to the bed with the help of T- nuts and bolts. Two of the idler pulleys which are flat (not crowned) are fixed in slots in the idler bracket .The third pulley is the tensioner pulleys. The RPM of the job depend upon the diameter of the job under belt and diameter of motor pulleys.

The speed may vary due to slip variation as the belt tension may vary .the belt tension is adjustable from the wheel provided on the front side .The belt should not be too tight or too loose and it should run in the centre of pulleys without touching the pulley collars.

3.2.2 END STOPPER ARRANGEMENT

ii) A square /round rod

iii) A bearing /a hard sleeve mounted on far end of the rod.

The A.C drive is housed in a separate cabinet The push buttons ,speed control potentiometer and speed/voltage /current meters are either located on panel machine headstock.

In case of end drive machines, the motor may be connected to machine directly or through a gearbox. In this case it is connected directly, the machine flange itself is mounted on the motor shaft.othewise the machine is given drive through a gear box. The motor is connected to gear box .The motor is connected to gear box input shaft through a flexible coupling or V belt or pulleys .suitable interclockwises are provided with U-shaft safety limit switch and the hand brake limit switch if provided.

There are two pick ups, one for left plane in left pedestal and the other for right plane in right pedestal.

Phase generator generates a reference signal with respect to job. This reference signal along with the unbalance signals from the pedestals is fed to the electronic unit which processes this signal and gives final unbalance in grams.

CNC TURRET PUNCH PRESS

When finished with one punch and die combination, the programmer can command that another be placed in punching position. It is common for turret of this kind of machine to be able to hold from punch and die combinations. This makes the machine extremely flexible, allowing a wide variety of shapes to be punched in a work piece with tool available in the turret. Turret punch presses are commonly found in metal fabrication shops.

PROGRAMING THE CNC MACHINE

It is likely that order by which the holes are prepared will have no correctness of program. Still it is recommended that the programmer prepare a process plan .In this case ,the process plan will only serve to help the programmer keep track of holes to be machined ,assure that all the holes are pierced ,and provide documentation that can be used by others in future. Developing machining process before the program is written will serve several purposes. First, it will allow the programmer to check th process for errors in basic machining practices. The programmer will be forced to think through the entire process before the first CNC command is written. AS we have seen many times while developing a process up front,” the programmer will spot the problem a problem with the process that would have difficult to repair if the process had been developed while writing the program.

Developing the machine process prior to writing the program also allows one concentrate on machining practice skills and your programming skills separately. while developing a machining process one concentrate on machining practice in order to develop a workable process. Our mind is occupied only with work at hand.

Higher hit rates on a mechanical ram system are a direct result of the faster axis speeds and quicker acceleration and deceleration supplied by servo systems. A mechanical ram has a fixed stroke length, which starts at the fully retracted position and finishes with the ram at the exact bottom position. This type of system is simple to program and operate, but it does not have all the capabilities of servo-controlled hydraulic ram systems.

Most advances in punch press versatility are associated with hydraulic ram systems. Hydraulic ram systems were introduced to allow the punch stroke to start and stop at any point along the ram path. Starting the ram at a point close to the material to be punched shortens considerably the overall distance the ram travels, providing increased hit rates.

A scribe tool is another example. A diamond-stylus punch is positioned into the material by the ram and remains rigid while the sheet is moved under the tool to create alphanumeric characters, company names, or logos. Character size is unlimited. The width and depth of the scribe can be controlled so secondary operations such as sheet finishing or painting will not hide the scribed marks.

Control and Software Integration

Straight-line wheel cutting requires less sophisticated control than does radius cutting. In many instances, the programmer must control the depth of the upper cutting wheel and input the proper feed rate during radius cutting. The feed rate will change depending on the size of the radius and the characteristics of the material.

The feed rate is especially important with thin material, because if the feed rate is too fast, the material may buckle. Some machine controls automatically calculate the proper changing feed rates as the wheel tool enters a radius and then accelerates out of the radius.

MACHINE SPECIFICATION – HYDRAULIC RAM

1. MODEL TAN 256 H Spl.

2. MACHINE CAPACITY

3. MACHINE ACCURACY

`X’ Axis ± 0.10 mm

AMADA / AMC Tooling

7. PUNCHING HEAD

9. SERVO SYSTEM

SERVO VOLTAGE STABILIZER 10 KVA

Height 2170 mm

Width 2720 mm

Power consumption 25 KVA

Supply cable 3 phase and earth / 6mm²

Flow 15 Liters per minute

SITE PREPRATION

1. Generator and mains supply earth resistance: kindly ensure that this should be less than 1 Ohm.

3. PNEUMATICS & AIR CONDITIONING

2. RS-232 Cable of suitable length would be required to transfer programs from the PC to the CNC control.

5. OTHER ACCESSORIES

Spanner set, allen key set, screw drivers, nylon hammer.

Feeler gauge, dial gauge with stand, tape, scale, vernier callipers.

INSTALLATION AND SAFETY ZONES

It is assumed that the machine has been correctly installed and that the owner has seen to it that passive safety barriers have been erected. In addition to these barriers, the entry points into safety exclusion zones must be protected.

1. When the machine covers are opened punching is inhibited.

2. While the machine is running it must not be left unattended.

2. Make sure that the safety exclusion zone is not occupied by other personnel when the machine is being run.

6. MACHINE

5. Never operate the machine unless there’s a sheet in the Sheet clamps

6. Always test run a new program with a sheet in the sheet clamps and the ‘Punch Inhibit’ in the ‘ON’ state.

2. Never wear loose clothing

3. Never remove or by-pass safety devices

1. The axes drives will be disabled and the ‘X’ and ‘Y’ axes will stop.

2. The Contactor enable relay will de-energies, the turret and hydraulic motors will stop.

1. 6 Axis Kawasaki robot with it control panel

The two robots are hanging from the roof of the cutting cabin and hold the cutting nozzle in its wrist. It moves in 3 dimensional spaces over the entire palette which is placed under the robot. On the palette a mould for the job to be cut is fixed permanently so that mould and palette becomes one piece. The palette can be placed on and removed from the table very easily. Each time the palette is placed on the table, it takes exactly the same position with high degree of repeatability. The robot moves along the desired 3 dimensional paths over the job loaded on mould for pure water jet cutting. The pressure water jet (3000 bar) coming out of the cutting nozzles cuts the job as desired at high speed.

4. Water proof & sound proof cutting cabin with stainless steel floor and safety door .

When robot is cutting the jobs with high –pressure pure water jet, there is great noise and water is splashing around every where .So the cutting has to be done in a room or cabin ,which does not allow the loud noise or the water mist to come out. So a water proof and sound proof cabin is provided which has stainless steel floor and safety walls for corrosion resistence.for entry in this room door is provided. The door has safety feature that if the door is opened .the entire system comes into state of emergency .Further the person entering the room can take one one of safety plugs with him so that no body can operate the system till he is inside the room.

4.1 Introduction

As a supplier in the highly competitive and rapidly changing CNC machines

4.2 Method of Observation

For observation a data sheet is prepared in which time study of workers is done. the observation was taken at an intervals of 5 min.

These are further sub divided.

We want to maximize the productive work by reducing the waste time and by managing the manageable time. . So first work after observation is to produce the efficiency of the worker and the next task is to prepare an effective way or model to reduce the wastage in time and to increase productivity.

4. A mean of assessing the amount of rest and other allowances which should be associated with job.

Standard time: -

• At a standard pace.

Basic time is the time required to perform a task by a normal operator working at a standard pace with no allowance or personal delay unavoidable delays or fatigue.

Pie chart of the time average is shown below:

From the above graph we observe that Manageable time is varying fast initially but in the later part of days it’s decreasing sharply.

-series3 = manageable time

-series5 = waste time

-series1 = productive time in finishing work

-series2 = productive time in sub assembly work

-series2 = Manageable time in sub assembly work

-series 3 = Manageable time in main assembly work

Suggestions for reducing store time:

This can be improved if material required is made available to the worker directly. This can be done by:

We get for manageable time:

Pie chart after implementation

Conclusion

• Efficiency before, = 329 x 100/450

Waste time reduction

1. 30 min are daily wasted in tea time which cant be reduced

Thus the overall increase in the efficiency=14.62% can be achieved

Few suggestions apart from above:

People working are dedicated to their work and they make sure that product deliver

by them are free from any error.

VRS scheme

There doesn’t exist any vrs policy. It was introduced some time back but later it was withdrawn due to less number of employees and employees are specific to their work.

1. Sort: Eliminate what is not needed

2. Straighten: Organize what remains

Value Stream Management: VSM aims to achieve process effectiveness, efficiency and agility through waste elimination and standardization.

Red Tag: For proper management of the unused goods and quality improvement of the existing ones.

3. Guarantee that no product or program goes to market before its ready

4. Ensure that current field problems are not designed into new products and services

3. ISO Standard 8821:1989 “Mechanical Vibration-Balancing-Shaft and

Fitment Key Conventions.”