How is the process selection method: from screening to slection
Screening:
- First screening based on:
- Shape
- mass,size
- section thickness
- tolerance nad rougness
- material compability
- production volume
- Cost estimation for the particular process avoiding the most costfull.
cs = cmateril + Ccost forming tools/ n +(Cpapital over time + Coverhead over time) /n
selection:
- Collection of accurate information on processes
- specification on process/ machines for the component
- communication with process providers (machine suppliers. tool suppliers etc.)
- Preliminary risk assessment (quality of parts etc.)
What are the disadvantages of a screening methods?
- Overlooks or gives poor guidance on a process chain
- Have to quite a large extent poor/outdated/wrong data on processes
- Higher level of information “out” than “in”
- Cost estimates difficult
What are the product cost management tool PCM software used for?
- Not always for direct process selection
- For determining cost for different processes
- used to analyse design changes and influence on cost
- custom control (above) = includes desiction of machine setting etc
What are the three most important things for environmental ascpects? and what is the dilemma?
Economy, society, anvironment
Both economy and society are constrained by environmental limits
The dilemma: sometimes an improvment of one can lead to compansation of another
What is the remanufacturing process acording to 6R
Ordinary:
Pre-manufacturing, manufacturing, use, disposal, landfill
But after use instead goe to recycle, recover, redesign, remanufacturing and then it can be reused
also imprtant with reuse and reduce
what work can be involved in the remanufacturing process?
- sorting
- inspection
- Disassembly
- Cleaning
- Reprocessing
- Replacement
- Reassembly
Often processes
- Advance cleaning and chemical “machining”
- Welding
- laser deposition and/ or 3D printing
- physical vapor deposition (advanced coating)
- Simpler coating
What is important in process for a better invironment?
- Reamnufacturing
- Process for light- weight materials
- Process for demanding applications as more efficient engines
- Processes for new products as fuel cells
What is the checklist for M.P assessment of sustainabilty ?
- Environmetal aspects:
- Energy consumption, toxins and pullutants, materia utilization
- Aspects of importance for economy:
- Material removal rate, speed, tool life
- Aspects of importance for society:
- Potential hazards and risk factors, general operator health
what is a radar chart?
What is the life cycle analysis?
a tools for the “big” picture:
- Assessing the environmental impact (different aspects) during the “life” typically of a product
- Typically from cradle to grave= from rawmaterial to disposal or rycycling
- Examples of factors: energy use [MJ], Global warming potential [kg Co2 eq], water use [kg], solid wate [kg], acidification [kg SO2 eq], land use [m^2]
What is the energy in metal forming? which are the influencing factors?
W = sFds for homogen deformation
In additional to the ideal forming ther is always:
- friction (tool surface) and shearing
- Heating energy if hot formning
The influencin factors:
- The base material
- Deformation (how much forming is made)
- Hot/cold formning
- complexity (shearing) hard to define
- serfaces /lubrication
- a thin chip gives realtively high contribution of friction
curring energy cunsumption: Wc=Kc*V
cutting power Pc=Fc*Vc
In addition should as well be accounted for the energy of pumping cutting fluids
What is the energy for unconventional machining?
Specific energy w: w=w/v
often is used something similar to metal cutting
For jet/beam/wire cutting : typically better to quantify energy per area produced
Generally not that energy efficient processes in themself:
- Laser: loses energy in the laser source
- AWJ: loses energy in the energy transfer water to abrasived
- EDM: losses erngy in that only a small part of the hot sparks is “used”
however:
— thery are ehn comparing a manufacturing sollution with other technologies quite effective in creating a geometry
what is the surface topography?
Surface topography is the local deviations of a surface from a perfectly flat plane. The topography of a surface is known to substantially affect the bulk propoerties of a material
What are the functional surfaces?
- Appearence:
- Roughness affects; reflectivity, gleam, subjective appearance
- Tribology
- Roughness affects; Friction, wear, fatigue life- surface pitting, sealing, oil consumtion, noise
- Fluid machnics
- Roughness affects; ship performance, aircraft performance, fluid transfer
What is the measurment techniques? and what are the advantages and disadvantages of 3D
- 2D- incresing the stylus tim means decresing roughness values, it can miss some rougnesses if the point is to big for the dipping
- 3D
+ Visualisation- imergery of the surface
+ Functions are in 3D most often
+ Statistics (much more data) - Cost and time
- More for R&D than production
Why do we need a filtering ? And what is high pass and low pass filter?
- There are specific wavelengths (requencies) for each application which affect the function of the surface
- A surface measurment needs to be filteres in order to analyze these wavelengths
- ISO-standard specifies high-pass cutoff length of 8mm,2.5mm, 0,8mm, 0,25 mm
- Measurment profiles should have a length of 5 cut offs (samling length)
Filters which stops short wavelengths but passes long wavelengths are termed low-pass
(=passes low frequencies)
Filters which stops long wavelengths but passes short wavelengths are termed high-pass
(=passes high frequencies)
What is the surface parameters? and why do we need more than one?
Its important to have different values beacuse for example many urfaces can have the same Ra value but be very different. längre dippor, kortare, jämt djup
- Ra value (ampltude parameter) avrage raougness
- Skewness (statistical aplitude parameter)
- The bearing area curve (hybrid functional parameter)
What is the relation between USL, LSL and VOP
to target in the mittle is the performance target on the left side is the Upper control limit and the lower control limit. these is the voice of the process VOP. the right side is the Upper specific limit and lower spcific limit that is the voice of the customer VOC. if the production its important that the left and right side limits match otherwise their will be waste and rework that çreates cost,
What is the variation definition
The std is the distance between the mean and the steepiest point on the normal distribution chart
what is the process capabilty and 6 sigma
When UCL and LCL is within the USL och LSL
improvment straegies to make this decrease variation (std)
om move the process tomard to the center mean, it is hardest to fix the mean.
what is cp and which values is of intrest?
Capability for process
Cp = specification width VOC / process variationVOP =
(USL-LSL) /6sigma
benchmarks:
cp =1.0 limit,
cp = 1,33 ok
cp = 1,67 good most important
What is Cpk ?
Centered capability measure
Cpk = minimun (Cpu,Cpl) min ([(USL-u)/3sigma],[(u-LSL)/3sigma])
how close you are to target
allways cpk <= Cp
What is the goal of the statistical process control?
Control = Based on post experience we can predict whitin limits how it will vary in the future
- Control the process so it remains stable
- To avoid over control of process
- Fins and eliminate special causes of variation
What can a maesurment sysem analys be used for?
- To take decisions:
- On single unit :
- Go/no-go variation <30%
- On process behaviour:
- Control charts
- variation <20%
- On single unit :
- Measurment system:
equiment (gauge) + operators (human factor) + procedure - Measurment system anslysis, MSA:
- is a set of statistical techniques for determining the error of a measurment system, commonly called R&R studies.
