************* HELP FILE FOR THE MACRO "Flat_pattern" ************

               (THIS FILE IS READ-ONLY. HIT ESC TO RETURN TO ME10)

                        Written by Darren C. Haverstick
                     Paul Mueller Company   Springfield, MO
         Phone: 800-683-5537 Ext 725    Email: dhaverstick@muel.com

          My company makes a variety of products out of plate and coil steel.
     Often-times, we have a fitting intersecting a cylindrical shell and we
     need to precisely cut the hole in the shell that the fitting will go
     into. We do this by making a flat pattern of the 3D surface of
     intersection, place it on the shell, and cut around it. We also make a
     pattern to wrap around the outside of the fitting so it can be cut to
     accurately fit the shell. While creating these flat patterns might be
     easy in a 3D graphics package, doing it in ME10 is tricky. This macro
     uses rotational matrices and a descriptive geometry technique to get the
     job done.
          "Flat_pattern" will create the flat pattern of the surface of
     intersection between a fitting of some particular cross-section and a
     cylindrical shell. It also will create a flat pattern for a repad to go
     around the fitting at the point of intersection. A repad is simply a band
     of material welded onto the shell to reinforce the fitting/shell
     intersection.
          You are given a choice of five cross-section types for your fittings:
     1) Circular 2) Elliptical 3) Oval 4) Rectangular with Square Corners 5)
     Rectangular with Round Corners. The associated MI file, "CROSS_SCTN", is
     loaded by the macro "Flat_pattern" to give you a graphical representation
     of these cross-sections and the dimension values you must enter to define
     them.
           By answering a series of questions, you will tell the macro how your
     fitting is positioned in 3-dimensional space with respect to cylindrical
     shell. A macro named "Draw_views" is called several times to generate
     graphics which clarify the questions and aid you in answering them. Once
     all the questions are answered, you can pick "DRAW PATTERN" from the
     display table. This will start the macro calculating points along the
     perimeter of the cross-section you chose and place them in 3D space. These
     perimeter points are then projected through the cylindrical shell and the
     points of intersection a determined. The points of intersection define the
     boundary of the 3-dimensional surface of intersection. Using a descriptive
     geometry technique found in any drafing book, the macro takes the 3D
     points, determines the relationships between them, and "flattens" them out
     in to 2D space. The result is a flat pattern of the surface of
     intersection.
          "Flat_pattern" can then take this process a step further by using the
     same 3D boundary points to create a pattern to wrap around the fitting
     itself. The fitting can be cut by this pattern so that it fits snugly
     against the shell.
          To load all the necessary macros into memory, invoke the macro,
     "input_macros". Enter "Create_pattern" on the command line to start the
     macro "Flat_pattern" or you can enter "Flat_pattern 'START PROGRAM' ''".
     "Flat_pattern" makes use of display tables and logical tables. Clicking on
     the right column of the display table will cause the macro to prompt you
     for data. When enough information is entered, you can pick "DRAW PATTERN"
     from the display table to generate a flat pattern.
           There are two variables in the macro, "Flat_pattern", which are used
     to set directory paths to certain associated files. The variable
     "Help_dir" defines the directory path where the text file "onlinehelp.txt"
     resides. The variable "Library_dir" defines the directory where the MI
     file "CROSS_SCTN" resides. By default, both of these variables are set to
     "./".
     _________________________________________________________________________

     GLOSSARY OF TERMS

     ELEVATION VIEW: The elevation view is defined as the view you have if you
     looked at the cylindrical shell with it standing on one end. The shell's
     appearance in this view wil be rectangular. The global Z axis corresponds
     to the shell's radial (centerline) axis and is positive in the "UP"
     direction. The global X axis is positive in the "RIGHT" direction.

     HOLE: This is the hole that will be cut into the cylindrical shell to
     accomodate a fitting, of some defined cross-section, that will be welded
     onto the shell at some defined orientation. The flat pattern for this hole
     can be made to correspond to the intersection of the fitting and the
     shell's outer surface or the fitting and the shell's inner surface.

     NORMAL ORIENTATION: A fitting is "normal" to the shell when its radial
     centerline intersects the shell's radial centerline in the top view and
     the fitting's radial centerline is perpendicular to the shell's radial
     centerline in the elevation view. Since the surface created by this type
     of fitting/shell intersection is not dependent on the fitting's top view
     angular location, the fitting's top view angular location is ignored.

     REPAD: This is a thin "collar" of material that is welded onto the shell
     around a fitting's perimeter. It is added to give the fitting/shell
     intersection more strength. A typical repad is .25" thick and 3" wide. The
     calculations done to generate a flat pattern of a repad are based off of
     the repad's centerline of material thickness. If a repad is .25" thick
     then its centerline of material thickness is .125".

     GENERAL ANGLE ORIENTATION: The "general angle" orientation has no
     predefined conditions about the fitting's rotation in any view plane. The
     angle of rotation entered for the fitting in the top view plane or the
     elevation view plane can be any value, as long as it's physically
     possible. "Tangent and "normal" are particular cases of the general angle
     orientation and have predefined conditions which force the fitting to be
     tangent or normal to the shell in the top view plane.

     SWAGE: Swaging a hole is the process of extruding material around the edge
     of the hole up through a collar to form a "lip" around the hole. This lip
     makes the shell stronger around the hole. The material used to make this
     lip is accounted for by the difference in size between the finished hole
     and the smaller hole that is actually cut.

     TANGENT ORIENTATION: A fitting is "tangent" to the shell when its outer
     surface becomes tangent to the shell's surface at some point in the top
     view. With this type of fitting/shell intersection, the fitting's top view
     angular location is determined by the diameter of the shell and the size
     of the fitting.

     TOP VIEW: The top view is defined as the view you have if you looked down
     the cylindrical shell's radial (centerline) axis. The shell's appearance
     in this view will be circular. The global Y axis is positive in the "UP"
     direction and the global X axis is positive in the "RIGHT" direction. In
     the tank business, however, the angular coordinate system does not
     correspond to the standard angular coordinate system in the XY plane. "0³"
     is in the standard 90³ position, "90³" is in the standard 0³ position,
     "180³" is in the standard 270³ position, and "270³" is in the standard
     180³ position.
     _________________________________________________________________________

     DISPLAY TABLE CONTROLS

          To enter data, click in the box that is on the right side of the
     question you want to answer. You will then be prompted to enter the
     necessary information.

     AUTO ENTER: When this box is picked, you will be asked whether you are
     making a pattern for a repad or a hole. Questions will then automatically
     be asked, based on the answers you gave to previous questions. When the
     pertinent questions have all been answered, the macro will stop.

     DRAW PATTERN: Picking this box will erase all the geometry on your screen
     and draw a flat pattern of a hole or repad based on the shell/fitting
     information you entered. If the pattern type you chose was a hole, you
     will also have the option of creating a flat pattern that can be wrapped
     around the fitting. By cutting the fitting according to this pattern, it
     will fit snugly to the hole cut into the shell.

     TABLE OFF: This makes the display table, "data_display", and its connected
     logical table, "data_table", pop down or disappear. It also creates a
     display table that pops up in the top lefthand corner of the screen that
     will allow you to pop the display table, "data_display", back up.

     DEL TABLE: This deletes all the display tables and all the logical tables
     that were created by this macro.

     HELP: This opens the help file, "onlinehelp.txt", in the ME10 Editor.