CMM And CAD Flashcards
What does CMM stand for
Co-ordination measuring machine
What does GD&T stand for?
Geometric dimensions and tolerancing
Coordinate measuring machines are versatile because they are capable of recording measurements of complex profiles with high sensitivity (0.25nm) t or f?
True
4 important features of CMM
-hollow box construction of all moving members for maximum rigidity
-map of systematic errors in the machine is built up and fed into computer so error compensation is built up into software
- all machines provided with their own computers and user friendly software
-thermocouples are incorporated throughout the machine used for compensation of temperature gradients thus providing increased accuracy and repeatability
3 different coordinates on CMM
-Cartesian coordinate system
-polar coordinate system
-spherical coordinate system
The ___ coordinate system enables you to locate a point or coordinate in space so that the software in the machine can interpret it.
Cartesian
___ coordinate system was developed for ease of use when drawings were dimensioned with angles. It was easier to program the part that was angularly dimensioned directly using a polar coordinate system than it was to calculate the point values in x and y
Polar coordinate system
The ___ coordinate system on a cmm is a coordinate system for 3 dimensional space. This coordinate system is seldom used. Most drawings are built on the Cartesian coordinate system
Spherical coordinate system
4 Main pieces or elements of a cmm
-Main structure
-probing system
-control unit w computer hardware
-software for 3d geometry analysis
5 types of main structure for cmm
-cantilever
-bridge
-column
-gantry
-horizontal
The __ arrangement combines easy access and relatively small floor space requirements. It is typically limited to small and medium sized machines
Cantilever
The ___ structure over the table carries the quill (zaxis) along the x axis. Sometimes referred to as the traveling bridge. It it claimed that the bridge construction provides better accuracy l, although this advantage maybe offset by the difficulty of making 2 members track in perfect alignment. By far the most popular construction
Bridge structure
The ___ type machine is commonly referred to as a universal measuring machine rather than a CMM. Usually considered a gauge room instrument rather than a production floor machine
Column type
In a ___ type of arrangement, arms are held by 2 fixed supports. This type is particularly well suited to vertical large components and it allows the operator to remain close to the area of inspection
Gantry style
The open structure of the __ arrangement provides optimum accessibility for large objects such as dies, models and car bodies. Sometimes referred to as layout machines. Some have a probe arm that can rotate like a spindle to perform tramminf operations
Horizontal
CMM can sense or touch the surface using a variety of devices such as these 2
-touch trigger point
-analogue measuring probes
A ___ employs a form of kinematic (movement) location to retain stylus in a highly repeatable manner. A typical mechanism consist of 3 cylindrical rods, each of which is pressed against a pair of balls. This action constrains all 6 degrees of freedom of the stylus
Touch trigger probe
The ___ is sometimes used in situations requiring extreme accuracy with rapid movement. It is an inductive measuring system meaning that it uses electric current to measure proximity to a target. It is non contact
Analogue measuring probes
3 parts of a probe
-stylus
-head
-probe
__ is the process of predicting the selling price of a workpiece. It’s a firm price that the machine shop gives to a customer before starting the job
Estimating
___ are the expenses associated with running a machine shop. It includes both fixed and variable costs
Operating costs
Fixed costs, also called overhead, include those expenses that are incurred whether or not the workpiece is produced. These expenses include these 3 things
-plant and equipment depreciation
-fire,theft and liability insurance
-salaries for staff not direction involved in production ie secretary, foreman and managers
__ include those expenses that are incurred only if the workpiece is produced. Consists primarily of material and labor costs
Variable cost
Begin the process of material cost by performing a __. It involves reffering to the lost of materials on the drawing to find the sizes and types of material needed for each workpiece. Add a cut off allowance to each part
Material take off
Determine the __ by multiplying the amount of material needed for each wp by the total number of wp to be produced
Material requirement
A __ acknowledges the fact that a certain percentage of workpieces is scrapped during production. Factors include
Skill of operator
Type and condition of machine tools
Type of work
Scrap allowance
Allowed 5%-10%
___ are the hourly expenses of paying a machinist to produce the workpiece
Labour cost
___ refers to the overall sequence of machining and production
Job planning
___ refers to the step by step sequence of all operations that are required to produce the workpiece such as heat treating, welding and assembling. Once the process is planned, the estimator can determine the cost of each operation
Process planning
The final estimate given to a customer is the __
Selling price
The shop rate includes all cost and profit related to labor. T or f
Trhe
5 steps to estimating the cost of labor are
-make a process plan
-prepare a machining sequence
-calculate how many extra wp to start to allow for scrap allowance
-Multiply the total # of wp including scrap allowance by the time it takes to make 1 piece
-multiply the total time for the job by the hourly rate of the shop
Most common types of gauges that you see in general use. 7 of them
-cylindrical plug
-plain ring
-taper plug
-taper ring
-thread plug
-thread ring
-snap gauge
3 factors that can affect a gauges reliability in checking a part are
-gauge dimensional accuracy
-gauge geometric form
-gauge surface finish
ANSI or American national standards institute recommends that gauge tolerance be 5% of features tolerance, t or f?
True
7 examples of gauge geometric form that might need to be tightly controlled include
-straightness
-parallelism
-cyclindricity
-circularity
-perpendicularity
-profile
-flatness
If the feature is subject to GD&T form control, you can use 5% of the features gd&t form tolerance as the gauges for tolerance. T or f
True
Triangles naturally form 2 groups, which are
Right triangles
Non-right triangles
