Group 4 11/16/05 David Reis Jeremy Huckins Alberto Barraza Nick Mellady.
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Transcript of Group 4 11/16/05 David Reis Jeremy Huckins Alberto Barraza Nick Mellady.
Group 411/16/05
David ReisJeremy HuckinsAlberto Barraza
Nick Mellady
The Process of grinding Grinding – a chip
removal process that uses an individual abrasive grain as the cutting tool.
Work pieces
Cylindrical, conical, fillets, helical, concave, slotting, internal grinding
Naturally Occurring Abrasives
Emery, corundum, quartz, garnet, diamond
Grinding Wheels
Structure, wear, and fracture patterns
Grinding Wheels
•The surface of grinding wheels are made up of these grains.
•Grains have random irregular shapes that are located at the edge of the grinding wheels.
Common Grinding Wheels
Colored surfaces indicate grinding faces
Superabrasive wheels
Colored surfaces indicate grinding faces
Types of Bonds Vitrified (ceramic bond) – most common
type of bond. Resistant to water, oil, and acids. Sometimes made with steel backing plates to improve physical strength.
Resinold (thermosetting resins) – Also known as organic wheels. Resistant to extremely high temperatures
Reinforced Wheels – Made with layers of fiberglass. If it did break it would not disintegrate, it would just crack.
Types of Bonds
Thermoplastic – sol-gel abrasives bonded with thermo plastics
Rubber – the most flexible bond. Metal – lowest cost. Used mainly
in small quantity production
Grinding FormulaL = (Dd)
Undeformed length = (Diameter)(depth)
Chip Formation
•When a chip forms ridges are formed where the chip left the material. This is known as plowing.
Considerations while grinding
Temperature If it gets too high it can:
Affect surface properties, including metallurgical change
Cause residual stress on the work piece Cause distortions in the work piece,
therefore accuracy goes down
Wheel wear
Once a wheel starts wearing it becomes less accurate
Grain wear – grains become flat and dull
Bond fracture – the bond breaks and the grains come off the wheel
Grinding Ratio
G = Volume of material removed
These vary widely, ranging from 2 to 200+ Using grinding fluids can increase the life
of a grinding wheel 10 fold.
Volume of wheel wear
Shaping grinding wheels
•The edges of grinding wheels are shaped with diamond dressing tools controlled by computers.
•Shaping the wheel sharpens it and restores its accuracy.
Grinding
Almost any material can be ground - aluminum, steel, ceramics, even diamond or glass.
Grinding is used whenever something needs to be smoothed or shaped.
Grinding is used to form countless types of products such as automobile engines, sharp edges on knives, ball bearings and drills. The smooth, accurate surface of the Hubble Telescope lens was formed by a process of grinding and polishing.
How Grinding Is Used
Types of grinding Machines Surface grinder
Cylindrical grinder
Universal Tool and Cutter Grinder
Lapping and Polishing
• Cylindrical grinding
center
cylindrical grinding centerless.
The bench grinder
Chemical Milling
• chemical milling/blanking is a chemical process that dissolves material from unmasked (unprotected) areas of metallic parts immersed in a tank of heated and agitated chemical reagents. The term "blanking" denotes small, thin workpieces, and "milling" indicates relatively large workpieces.
(a) Schematic illustration of the chemical machining process. Note that no forces or machine tools are involved in this process.
(b) Stages in producing a profiled cavity by chemical machining; note the undercut.
• considerable advantages compared to punching, laser-cutting and wire-erosion
(left) Missile skin-panel section contoured by chemical milling to improve the stiffness to-weight ratio of the part.
(top) Weight reduction of space launch vehicles by chemical milling
aluminum-alloy plates. These panels are chemically milled after the plates have first been formed
into shape by processes such as roll forming or stretch forming.
Chemical milling is used to reduce the overall weight and other non desirable factors of a workpiece
Process of Chem. Milling1. Artwork and Negative Preparation
An image is printed by a program with a laser plotter directly to the film at any size needed
2. Photoresist Application / Exposure / Develop
Apply Photoresist coating to make the metal sensitive to light.Expose coated metal to UV light source which applies the image from the art work to the metal part.Treat exposed metal part with a developing solution which removes the soft portion of the Photoresist.
3. Etching / Resist Removal
Process the metal through chemical etcher which dissolves all metal not protected by the hardened photoresist coating.
Electrochemical Machining (ECM)
uses an electrolyte at a high rate from the tool piece to wash away the metal ions from the workpiece
the tool is usually solid or tubular form
Material removal rate is 1.5 – 4mm³
ECM was developed in 1929 Not as widely used as other processes Generally used to make complex
cavities and shapes Finishes parts burr-free and bright
surfaces Never has any thermal damage to
part or wear on the tools
Parts From Electrochemical Mill
Replacement Knees
Design Considerations for ECM
ECM is not suitable for producing sharp edges or flat sufaces
Flow of electrolyte can become difficult
Designs should make provision for a small taper for holes to be machined
Electrochemical Grinding (ECG)
• Process that combines electrochemical machining with conventional grinding
• Grinder wheel is embeded with abrasive particles of dimond or aluminum oxide
Abrassives on the spindle have two functions
To act as insulators between the wheel and workpiece
To remove electrolytic products from the work area
• Majority of material is removed by the electrolytic action, less than 5% is removed by the wheel
The ECG process is similar to that of milling, and grinding
Much better than traditional grinding where wheel wear is high
Electrical discharge machining Erosion of metals
by spark discharge Capacitor
discharge is between 50 and 380 V
EDM can be used on any material that is an electrical conductor
• Uses an electrode that sends out the sparks which erodes the metal
• Uses dielectric fluids for cooling and flushing of the material
• EDM wire • Wire is brass,
copper or tungsten• With wire edm you
can basically cut out any design
Laser-Beam Machining
Focuses optical energy on the work piece The high focus high density energy melts
the material Rough surface and has heat affected
areas Oxygen maybe added to the laser for increase
of energy, doing this leave a oxide free edge which improves welding
Lasers are also used for etching
Design consideration with LBM
Sharp corners should be avoided Deep holes will have tapered walls Don’t use highly reflective material
Electron-Beam Machining
The energy source in EBM is high-velocity electrons that move from 50% to 80% the speed of light!
It is a lot like Laser beam Machining but needs a vacuum because it puts of harmful x-rays, so is only used by trained personnel
Electron Beam Machine
• Plasma arc cutting is a type of EBM its temp. gets from 9400 C to 17,000 C
Which makes the process much faster the LBM and EDM with better products
• EBM have limited machining because of the vacuum capacity
Water Jet Machining• Cut a variety of metal and nonmetal
material up to 6-ft. x 12-ft. x 12-in. thick • Reduce machining time by as much as
70% • Provide a burr-free finished edge • Leave no heat-affected zone (HAZ) • Reduce waste material • Eliminate costly set-up time
Water jet cutters have no start holes
The jets have an extremely high velocity
No heat during cutting
Very intricate designs
The water jet is the most versatile machine on the market today
The water leaving the nozzle is from 400 MPa to 1400 MPa
The diameter of the spray is .05mm - 1mm
It is used in lots of industries from wood, to food processing, metal working
The material is wet very little It is environmentally safe process
Abrasive water jet machining
The same thing is water jet but with added abrasive particle, such as silicon carbide or aluminum oxide
This increases the material rate removal of the product
The machine is a little more complicated cause it needs to mix the contents
References
www.nd.edu/~manufact/pdfs/Ch26.pdf - Supplemental Result
Kalpakjian • Schmid Manufacturing Engineering and Technology © 2006
www.storkvecousa.com/ technology/2_etch.htm