Gear DXF Help v3.2

GearDXF supports the design of Spur, Internal and Rack gears which can be exported to 2D DXF and SVG or 3D OBJ and STL files.

Menu Bar • Export (Ctrl+S): Saves the gear design to a 2D DXF or SVG file of your choosing. (See Export.) • Extrude (Ctrl+E): Opens the Extrusion window with an ability to export 3D STL files. (See Extrusion.) • Reset: Resets the gear properties to default values. • Zoom to Fit (Ctrl+F): Causes the gear image to fill the Gear View. • Adjust tool: A mouse tool for dragging left or right within the Gear View to change the selected gear property value. (The properties in grey may not be changed.) The mouse can also be used with key modifiers for panning and zooming, as shown in the Status Bar. • Pan tool (hand icon) (Ctrl+P): A mouse tool to pan the gear image within the Gear View. • Zoom tool (magnifier icon) (Ctrl+M): A mouse tool to zoom in or out on the gear image within the Gear View. • Settings (gear icon): Opens a window to edit program settings. (See Settings.) • Select Spur Gear, Internal Gear or Rack Gear: Select from three different types of gears that can be designed, each with its own properties. • Select units of Inches or Millimeters: Changes the units of measure by which values are displayed and the units that are written when exporting data files. You can enter values with explicit units of either mode regardless of the selected mode. There is also a Settings option to Suppress Units Display. • Information (Ctrl+I): Shows an About box with copyright and other information about GearDXF. • Help (F1): Links to this online help file.

Gear Properties Displays the gear properties and allows the values for most to be modified. You can enter units (e.g., ‘cm’, ‘mm’ or ‘in’), if you like. By default, the units are those selected in the Menu Bar. A dropdown Scrubber Bar can be used to manipulate most properties with mouse interaction where the arrow keys and page up/down keys make small and large changes in the values, respectively. Or hold down the Shift key for small changes to become large ones. Using the mouse in the Gear view to change properties has similar characteristics.

Module (M) and Diametral Pitch (DP) are two ways (Metric/Millimeter and Imperial/Inch, respectively) of expressing the same concept of how wide the teeth are (or how many teeth there are per inch), with an inverse relationship between the two: DP = 25.4 / M. As M increases, DP decreases, and the gear gets larger. Thus, the output properties for circular gears (Tip, Pitch and Root Diameter) are all tied to the M/DP. Changing one changes the others. Gear manufacturers generally restrict their products to a few common values for M/DP. So, designing a gear for a specific Tip Diameter, for example, may result in a non-standard M/DP and an inability to mesh with retail manufactured gears. Similarly, the Length of a Rack gear will grow as M increases (DP decreases).

Pressure Angle is also an important gear design parameter. Values of 14½, 20 and 25 are typical where 20 seems most common with good strength and power transmission qualities.

Clearance is additional spacing between the teeth along the arc of the Pitch Circle. Essentially, the tooth profiles are rotated about the center by an angle that would create that distance, one half to each tooth profile wall.

There’s a fundamental rule of designing gear drive systems that mesh properly: The Module (Diametral Pitch) and the Pressure Angle must match for all meshing gears in the system! Gears should also be mounted so the pitch circles (or pitch heights) meet tangent to one another for the best efficiency and least backlash. For example, the centers of two spur gears should be separated by a distance equal to their combined Pitch Diameters divided by two. GearDXF now allows small amounts of Clearance to be added between gears to avoid jamming. Alternatively, a small amount of separation between gears may be help. Some of the precise geometry of the tooth profile may also be lost with the imprecision of 3D printing or other CAM processes, so some tweaking may be required to get good results.

GearDXF copies the Module (Diametral Pitch) and the Pressure Angle as the gear type is changed to help insure the consistency of these gear meshing properties across the gears in a design.

See http://en.wikipedia.org/wiki/Gear#Nomenclature for additional details about gear nomenclature.

Status Bar Provides feedback during operation of the program, describing how to use the mouse buttons and key modifiers to adjust gear properties or modify the Gear View.

Gear View Shows a live view of the gear as its properties are changed. Using tools from the Menu Bar and the mouse you can zoom in to view a specific portion of the gear or view it in its entirety. Settings

Many program settings allow for customization of the Gear View display, colors and styles.

Export The Export button invokes a Save dialog for selecting an export file format and file name. The following output formats are currently supported:

• DXF file: The AutoCAD Drawing Interchange Format (DXF) is widely used for the exchange of 2D design data between CAD applications. Setting the DXF Export Options > Save Curves As Lines property will cause the cubic Bezier curves, used for spur and internal gear tooth profiles, to be approximated with line segments of roughly the length specified by the Curve Segment Length setting. Used by default, Bezier curves are smoother and more precise. But this option is useful for programs lacking support for Bezier curves when importing DXF files. • SVG file: The image format was developed by the World Wide Web Consortium (W3C) and is growing in popularity as a 2D image format for the web. But as a scalable vector format, SVG is also valuable as a simple and non-proprietary exchange format for vector data. SVG supports lines, arcs and Bezier curves. But seen primarily as an image format, some programs that read SVG files may arbitrarily scale the data as an image viewer, requiring some manually scaling be applied to restore the designed dimensions and units in the file. Currently, SVG export only outputs path information and omits styling information for colors, lines and fills, etc. SVG output is targeted toward machines and processes, like routers and vinyl cutters, that are only interested in paths. • STL file: The STL (stereolithography) Format is a popular exchange format for 3D objects, often used with 3D printers and slicers. • OBJ file: The Wavefront OBJ File Format is another 3D exchange format has been adopted by many of the same products and applications as STL files. It has the added benefit that, along with its companion MTL (material) file, it can provide color information for software that can make use of it. The 3D Viewer application, provided with every installation of Windows 10, is a nice viewer for color OBJ files. • Image files: 2D images of the designed gear may be exported in JPG, PNG and TIF image file formats. PNG is growing in popularity throughout the web as a 2D pixel image format and is essential where retaining transparency is required. The ‘Options…’ button in the Save dialog may be used to control the pixel Size of the output.

Both the STL format and the 3D view model support only triangular faces with straight line edges. Arcs and curves in the gear design are approximated with line segments of roughly the length specified by the Curve Segment Length property in Settings. Extrusion

The Extrude button launches the Extrusion window, generating a 3D model of the gear being designed. The window remains open, updating live as the gear properties are changed. The Status Bar across the bottom right describes the mouse button and key combinations that can be used to manipulate the view and the gear thickness. Selecting a tool changes the priorities, but all the tools are available at all times with a given button & key combination.

• Zoom to Fit (Ctrl+F): Resets the 3D view and causes the gear image to fill the Gear View. • Orbit tool (‘O’): Click and drag the mouse to move the camera view in orbit around the gear. • Pan tool (‘P’): Click and drag the mouse to pan the camera view over the gear. • Lift tool (‘L’): Click the gear face and drag up or down to increase or decrease the thickness. This is a visually interactive alternative to modifying The Top gear property in the Gear Properties panel. The updated value is also displayed in the Status Bar window in the bottom left. • Scroll wheel: Zooms the gear view in and out.

You can observe the effect of the Curve Segment Length Settings property live in the Extrusion window. Smaller values creating many smaller segments may slow down 3D model generation and rendering, causing reduced responsiveness and larger export files. Gears with large numbers of teeth may have the same effect.

GearDXF Release Notes • Version 3.2 o fix: Incorrect value display using the Scrubber for properties with units of ‘Inches’. o added: ‘Clearance’ gear property adds additional backlash clearance between teeth. o added: Additional export formats for 3D OBJ, JPG, PNG and TIF. All export options centralized under the main window Export command. o moved: Curve Segment Length from Gear Properties to Settings property. o added: Pan Tool and Tool selection commands and Status Bar help to Extrusion window. o improved: Internal Gear tooth profile received minor corrections. • Version 3.1.2 o fix: Problems when Windows' Region settings for 'Decimal symbol' and 'Digit grouping' were not '.' and ',' respectively o fix: 'Diameter' rings showed up in extrusion; and should draw on top of gear o fix: Scrubber large change increment o fix: Tooth end cap arcs became full circles as tooth edges overlap with large Pressure Angles o added: Splash screen o fix: Top value display for extrusion was fixed at mm, now displays according to units set o added: Change Top value by right-clicking the top surface in the Extrusion window and dragging up or down o added: “DPI Awareness” – GearDXF should look better when scaling is set to other than %100 in Windows “Display settings” • Version 3.1.1 o Copy the Module (Diametral Pitch), the Pressure Angle and Curve Segment Length as the gear type is changed o Add Rack Gear Length property. • Version 3.1 o Added 3D extrusion and STL export. o Moved ‘Curve Segment Length’ from program setting to gear property to visualize live update in the Extrusion window. • Version 3.0.1 o Fixed bug with tooth profiles crossing below the Base Circle. (E.g. with large number of teeth.) o Added SVG as an output format for saving gear profiles. • Version 3.0 o Added support for Rack and Internal gears o Modified ‘Root Fillet Radius’ to better fillet root corners o Added grid to view o Added ‘Edit Preferences’ dialog o Added preferences to control display colors and styles o Added ‘Save Curves as Lines’ option for DXF output o Removed support for annotations layer • Version 2.2 o Added ‘Module’ property as metric corollary to ‘Diametral Pitch’ o Improved tooth profiles with Bezier curves o Added property trackbar and Gear View mouse UI mechanisms for changing property values • Version 2.1.1 o Fixed bug related to large numbers of teeth • Version 2.1.0 o Modified gear profile so that first tooth is aligned with positive X-axis o Added Bore Hole property o Made output 'Diameter' properties modifiable (all cause changes to Diametral Pitch) o Allow grid selection to determine property manipulated using the mouse o Added Help file o New setup mechanism (old setup no longer supported by MS Visual Studio)