Economics and Maintenance

8/11/2019 Economics and Maintenance

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ECONOMICS AND MAINTENANCE

Factors influencing selection of CNC Machines – Cost

of operation of CNC Machines –

Practical aspects of

introducing CNC machines in industries – Maintenance

features of CNC Machines – Preventive Maintenance,

Other maintenance requirements



SELECTING A CNC MACHINE

• Working envelope

• Types of workpiece material

• Positional accuracy

• Control system

• Spindle speed & power

• Tooling / cutters

• Table type

• Technical support




• What is the maximum job size that to bemanufactured ?

• The larger the cutting area or bed size themore expensive the machine.

• Cutting soft materials such as wood, plastic isnormally fine for most machines, but cuttingsteel usually requires a heavy duty machine.




• For a very fine engraving the resolution of the

motors that position the cutter is crucial to

the final product quality, and a precision on

(0.005mm) might be required.

• Typically the more precise the more costly the

machine will be.




• Most of the new CNC machines have PC basedcontrol systems that run from industrystandard file formats such as ISO G-code.

• If the control system is proprietary (unique tomanufacture) then make sure that it will workwith third party software solutions.

•

Check whether the controller can benetworked to PC – for easy & fast file transferdirectly from the design software




• Check there is need to a DNC (Direct

Numerical Control) link from the PC to the

controller?

• Data processing speed is also a factor, notably

for high speed/ volume product or complex

3D work, where large toolpath files are

commonly used.




• G-code

• Stepper

• Servo

• Speed

• Accuracy

• Quality

• PC based

• DNC Link




• When cutting finely detailed products, high

spindle speeds, typically over 20,000 rpm and

up to 60,000 rpm depending upon the

material being machined.

• The power rating for the spindle is also crucial.

For high volume material removal rates the

spindle needs to be powerful, but not to very

fast (rpm)




• How many different tools will be needed to

produce your typical jobs ?

• Automatic

• ATC

• Carousel

•

Rack• Manual




• How will jobs to be held on the table ?

• Will you require a vacuum table, vice or

special fixturing?

• What kind of Technical Assistant needed for

the machine ?

• Checking for – service availability



Maintenance of CNC Machines

• Breakdown Maintenance

– Starting a maintenance work until failure occurs.

– This type of maintenance will be useful, when the

machine does not affect the operation or

production or generate any significant loss other

than repair cost.

–

This type of maintenance lead to loss ofproduction.




• Preventive maintenance

– It is a daily maintenance (cleaning, inspection,oiling and re-tightening), design to retain the

healthy condition of equipment and preventfailure through the prevention of deterioration,periodic inspection or equipment conditiondiagnosis, to measure deterioration.

–

Periodic maintenance ( Time based maintenance –TBM)

– Predictive maintenance




• Time based maintenance consists of

periodically inspecting, servicing and cleaning

equipment and replacing parts to prevent

sudden failure and process problems.

• Periodic maintenance is a method in which

the service life of important part is predicted

based on inspection or diagnosis, in order touse the parts to the limit of their service life






• Maintenance Prevention :

– It indicates the design of a new equipment.

– Design failures/weakness of current machines are

sufficiently studied (Onsite information leading to

failure prevention, easier maintenance and

prevents of defects, safety and ease of

manufacturing ) and are incorporated before

commissioning a new equipment.




• Backlog Maintenance

– Maintenance that is necessary to prevent the

deterioration in the performance or functioning of

the machine but which has not been carried out.

– Accordingly, backlog maintenance has a higher

priority than deferred maintenance. The

maintenance practices to be deferred and which

comes under backlog list will have to be reviewed

annually and documented.



Systems and Sub-Systems of CNC

Machines

• Mechanical system

• Electronic systems (CNC and drives)

• Work holding systems

• Tool clamping systems.

• Lubrication systems.

• Coolant systems

• Hydraulic systems

• Pneumatic systems

• Chip Conveying Systems



Functions of Mechanical Systems

• Primary functions of the mechanical systems

in CNC machines are similar to conventional

machines.

• CNC Lathe Machine sub-systems

– Headstock, Axis assembly, Tool post & Tailstock

– Axis assembly, Tool magazine, Bed



DC Motor – Troubleshooting



ATC Troubleshooting



Hydraulics and Pneumatic

Troubleshooting

Documents

Economics and Maintenance