IT-390Operation%20Estimating

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IT-390 Operation Estimating
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Introduction

• Products - manufactured in a series of steps
• Saw - rough size, milling, grinding, deburring,
  assembly
• Each major step of the building process, is
  referred to as an operation
• For estimation, it is convenient to break down
  the whole

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Introduction

• A product estimate, as we will see in Chapter 8,
  would just be a string of these operation
  estimates put together, with overheads added
• Process
• 1) Rough saw
• 2) Mill
• 3) Grind
• 4) Deburr
• 5) Assembly

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Introduction

• Estimate creation - blueprint/process plan
• This combination describes part and build
  sequence
• Break design down into small, discrete portions
  and then assign labor and material

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Operation Cost

• Sources for estimate request
• Common routes are
• RFQ (request for quote) from customer
• Work order from customer
• Production planner
• Foreman's request
• Work simplification savings
• Employee suggestion
• Marketing request

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Operation Cost

• These become an RFE (request for estimate)
• RFE will have
• Design drawings
• Period of activity
• Specifications
• Quality requirements
• etc.

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Operation Cost

• Estimator now employs "microanalysis" to arrive
  at a cost
• Microanalysis - operation broken down into finer
  elements or subdivisions both physically and
  economically and calculated for each
• The aggregate of these then becomes the cost

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Operation Cost

• Different schools of thought for an operation
  cost
• Combination of direct labor and direct material
  only
• Should include "nonrecurring initial fixed costs"
  or "tooling
• Method is company policy
• If operation cost is direct labor direct
  material only, tooling is absorbed in overhead

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Operation Cost

• Level of detail debate
• Greater detail, more expensive estimate
• Dilemma of a job shop
• Average job shop - capture 5. Why?
• First, bidding is competitive, so they may just
  lose bid
• Secondly, many times a company considering
  outsourcing will use this information in make or
  buy decision
• Thirdly, is current company giving them a "good"
  price
• Why spend the money/time (waste) if only
  capturing 5?
• Survival

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Manufacturing Work

• Classifications
• Mass production, moderate job shop
• All three deal in volume and treated the same

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Manufacturing Work

• Breaking down further
• Machine - which is self explanatory
• Process - chemical or fusion
• Bench - assembly

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Manufacturing Work

• Initially - gather together engineering drawings,
  marketing quantity, specifications, standard
  time data
• Know the processes
• When a process is developed for a job, estimates
  are also developed for the direct labor time
  using Ch 2 methods

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Manufacturing Work

• Preferred - standard time data, and break jobs
  into elements reflecting standard data
• This time data will include estimates for both
  cycle time time and set-up
• Cycle time is time a part stays at each station
  or process
• Set-up time is the time required to prepare our
  machine, process, or bench
• The larger the volume of parts to be run in a
  batch, the less significant Set-up time is
• Because of this, it is quite often ignored in
  mass production

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Nonrecurring Initial Fixed Costs

• Tools and test devices used prior to running
• These types of devices are "nonrecurring initial
  fixed costs" or "tooling"
• This tooling is built once
• They are up-front costs, just as machines are,
  and are depreciated, just like machine are

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Tooling Examples
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Nonrecurring Initial Fixed Costs

• Perishable tooling is an expense - absorbed in
  overhead
• General rule for tool building
• The tool must pay for itself
• pay comes in many forms

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Nonrecurring Initial Fixed Costs

• Tooling as a cost - manufacturer/customer
  decides
• Should a tool be built? see Eq. 7.19 (pg. 333)

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Nonrecurring Initial Fixed Costs

• Eq. 7.19 (pg. 333)
• Where,
• N of units mfg per year
• a labor cost savings per unit compared to
  another operation
• t overhead rate (burden) applied against the
  labor that's saved
• SU annual set-up cost,
• I annual allowance for interest on investment,
  decimal
• T annual allowance for taxes, decimal
• D annual allowance for depreciation, decimal
• M annual allowance for maintenance, decimal

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Nonrecurring Initial Fixed Costs

• Problem 7.7 (pg. 341)

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Metal Cutting Operations

• Manufacture - composed of set-up and cycle time
• Table 7.4 (pg. 313) (Set-up Times)
• Companies strive to compile this
• Simplifies Estimators job

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Metal Cutting Operations

• Cycle time is a bit more involved, it includes
• Handling time
• Machining time
• Tool changing time

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Metal Cutting Operations

• Handling time - time to load / unload the machine
  and to advance / retract the tool with respect to
  the part
• Time for part inspection
• Table 7.5 (pg. 315) (Std Time Data)
• Times are in minutes and have PF D allowance
  built in

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Metal Cutting Operations

• Machining time - time when the tool is
  cutting/removing chips
• The basic machining time equation 7.2 (pg. 305)
  is
• tm machining time, minutes
• L length of cut, inches
• D diameter, inches
• V cutting speed, feet/minute
• F feedrate, in/revolution
• N rotary cutting speed, rpm

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Metal Cutting Operations

• Table 7.2 (pg. 307) (rough and finish machining
  values)
• Times listed - turning and facing, milling,
  drilling, and tapping
• Use table for "V" and "F" values in our equation
• Also Reference "Machinist's Handbook et al

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Metal Cutting Operations

• Tool changing time - when machine is stopped to
  service dull cutting tools
• In addition - cost is also incurred for the
  eventual replacement of the tool

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Metal Cutting Operations

• Tool changing time - found from stop-watch time
  study or standard data tables
• Table 7.5 (pg. 315) (Machine Operation Change
  tool)

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Metal Cutting Operations

• Concerned with cost this adds to my part
• Frederick Taylor - not only first use of time
  study, but the invention of high speed steel

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Metal Cutting Operations

• He also discovered relationship between tool
  life/cutting speed
• Ref. Eq. 7.6 (pg. 308)
• T average tool life, minutes
• V cutting speed velocity, ft. per minutes
• n, K empirical constants for different
  combinations of cutting tool/part material
• Some typical values of "n" and "K" are shown in
  Table 7.3 (pg. 309)

algebraically
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Metal Cutting Operations

• Tool Changing Cost - eq. 7.7 (pg. 309)
• Tool Changing Cost
• Co direct labor wage, / minute note!!
• Tc tool changing time, minutes
• Tm machining time, minutes
• T tool life, minutes
• Note All are in minutes, including labor.

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Metal Cutting Operations

• Tool Cost - eq. 7.8
• Tool cost per operation
• Ct total cost,
• tm machining time, minutes
• T average tool life, minutes
• Table 7.3 (pg. 309) - sample time and costs for
  tool changing times tool costs

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Metal Cutting Operations

• Problem 7.9 (pg. 342)
• Problem 7.17 (pg. 344)