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Engineering drawings are documents prepared on
reproducible material for providing information that is pictorially or
textually presented, or the combination of both for the purpose of
describing the physical and functional requirements of an end-product.
SolidMasters
generates and updates *.DWG or
*.DXF files for users of AutoCAD or other CAD systems. Since most of our
projects end up in production, the value of having an accurate and up to
date documentation package at the end of the project cannot be
overstated.
Checking Drawings, guidelines and services.
In order that the drawings may have a high
standard of excellence, a set of instructions, as given in the
following, has been issued to our checkers, and also to the draftsmen
and tracers in the engineering department of
SolidMasters.
Inspecting a New Design
When a new design is involved, first inspect
the layouts carefully to see that the parts function correctly under all
conditions, that they have the proper relative proportions, that the
general design is correct in the matters of strength, rigidity, bearing
areas, appearance, convenience of assembly, and direction of motion of
the parts, and that there are no interferences. Consider the design as a
whole to see if any improvements can be made. If the design appears to
be unsatisfactory in any particular way, or improvements appear to be
possible, call the matter to the attention of the chief engineer.
Inspect the drawing to see that the
projections and sections are made in such a way as to show most clearly
the form of the piece and the work to be done on it. Make sure that any
worker looking at the drawing will understand what the shape of the
piece is and how it is to be molded or machined. Make sure that the
delineation is correct in every particular way, and that the information
conveyed by the drawing as to the form of the piece is complete.
Tolerance Accumulation per Section 2.6 of ASME Y14.5. You maybe asking yourself right now, “What is Tolerance Accumulation?”. Tolerance accumulation, or tolerance stack-up, is the dimensional variance between two features of a part based on the tolerance range of the intermediate dimensions. How you apply dimensions and tolerances to features on a part can have a huge effect on the finished part. Today we will look at some simple parts and how different methods of dimensions can give you dramatically different results.
Check all dimensions to see that they are
correct. Scale all dimensions and see that the drawing is to scale. See
that the dimensions on the drawing agrees with the dimensions scaled
from the lay-out. Wherever any dimension is out of scale, see that the
dimension is so marked. Investigate any case where the dimension, the
scale of the drawing, and the scale of the lay-out do not agree. All
dimensions not to scale must be underlined on the tracing. In checking
dimensions, note particularly the following points:
See that all figures are correctly formed and
that they will print clearly, so that the workers can easily read them
correctly. See that the overall dimensions are given. See that all witness lines go to the correct
part of the drawing. See that all arrow points go to the correct
witness lines. See that proper allowance is made for all
fits. See that the tolerances are correctly given
where necessary. See that all dimensions given agree with the
corresponding dimensions of adjacent parts.
Be sure that the dimensions given on a
drawing are those that the machinist will use, and that the worker will
not be obliged to do addition or subtraction to obtain the necessary
measurements for machining or checking his work. Avoid strings of dimensions where errors can
accumulate. It is generally better to give a number of dimensions from
the same reference surface or center line. When holes are to be located
by boring on a horizontal spindle boring machine or other similar
machine, give dimensions to centers of bored holes in rectangular
coordinates and from the center lines of the first hole to be bored, so
that the operator will not be obliged to add measurements or transfer
gages.
Study the sequences of operations in
machining and see that all finish marks are indicated. See that the finish marks are placed on the
lines to which dimensions are given. See that methods of machining are indicated
where necessary. Give all drill, reamer, tap, and rose bit
sizes. See that jig and gage numbers are indicated
at the proper places. See that all necessary bosses, lugs, and
openings are provided for lifting, handling, clamping, and machining the
piece. See that adequate wrench room is provided for
all nuts and bolt heads. Avoid special tools, such as taps, drills,
reamers, etc., unless such tools are specifically authorized. Where parts are right- and left-hand, be sure
that the hand is correctly designated. When possible, mark parts as
symmetrical, so as to avoid having them right- and left-hand, but do not
sacrifice correct design or satisfactory operation on this account. When heat-treatment is required, the
heat-treatment should be specified. Check the title, size of machine, the scale,
and the drawing number on both the drawing and the drawing record card.
See that the part can readily be assembled
with the adjacent parts. If necessary, provide tapped holes for eyebolts
and cored holes for tongs, lugs, or other methods of handling. Make sure that, in being assembled, the piece
will not interfere with other pieces already in place and that the
assembly can be taken apart without difficulty. Check the sum of a number of tolerances; this
sum must not be great enough to permit two pieces that should not be in
contact to come together.
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Service Tags: cad drafting services, drafting design services, mechanical engineering drawing, as built drawing, Engineering companies in Orange County, 3d cad modeling Los Angeles California, Consulting firms Orange County, Product development Los Angeles, 3d finite element analysis. |
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