economics and maintenance
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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
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SELECTING A CNC MACHINE
• Working envelope
• Types of workpiece material
• Positional accuracy
• Control system
• Spindle speed & power
• Tooling / cutters
• Table type
• Technical support
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SELECTING A CNC MACHINE
• 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.
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SELECTING A CNC 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.
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SELECTING A CNC MACHINE
• 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
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SELECTING A CNC MACHINE
• 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.
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SELECTING A CNC MACHINE
• G-code
• Stepper
• Servo
• Speed
• Accuracy
• Quality
• PC based
• DNC Link
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SELECTING A CNC MACHINE
• 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)
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SELECTING A CNC MACHINE
• How many different tools will be needed to
produce your typical jobs ?
• Automatic
• ATC
• Carousel
•
Rack• Manual
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SELECTING A CNC MACHINE
• 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
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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.
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Maintenance of CNC Machines
• 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
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Maintenance of CNC Machines
• 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
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Maintenance of CNC Machines
• 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.
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Maintenance of CNC Machines
• 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.
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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
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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
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DC Motor – Troubleshooting
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ATC Troubleshooting