There are many Digital Readout systems (DRO) available, but most of them just show coordinates of the tool. They require calculations at every step and are not very continent. The idea of this project is to see drawing together with instant “live” distances to its elements from lathe cutting tool. The process of turning becomes just following the line on the computer screen with XY hand-wheels. Such WYSIWYG technology makes lathe turning very simple and allows to make parts of any shape.
Hardware
The X and Y scales are modified tire tread depth gauges, the modification includes ribbon band and strong neodymium magnets. The scales can be easily attached/detached for cleaning and positioning. Scale communication protocol and pinout is available at https://www.instructables.com/id/Reading-Digital-Callipers-with-an-Arduino-USB/
Fig.1 Gauge (scale) modified with ribbon band (to return the pin) and magnets attached with double side tape. Connectors are soldered to the board.
Both X and Y scales are served with single Teency LC board, connected to scales via level shifters.
Fig.2 connection diagram.
Mini lathe is modified with a steel bracket (to attach Y scale) and 5mm aluminum plate (as a pusher of X scale).
Fig.3 Lathe modification
Software
The software (Windows 10 tested, should work also on Win 7 and Win XP) makes parsing of DXF files, draws them on the screen together with the tool. It also shows distances from the tool to the nearest DXF lines. The software automatically scales the drawing to fit the screen. For continence half of the part or the whole part can be shown, or the image can be flipped vertically if it is required by part turning.
DXF parser (designed for Solidworks DXF) supports lines, polylines and arcs. Option “splines as polylines” must be checked in the “options” of the dxf export dialog. Please see how to prepare DXF drawing at 2:17 of this video.
Fig.4 Interface in overview mode, in this mode image is automatically scaled to the screen. Touch control, upper bar: (1-4)East, west, north and south directions of distances; (5) half/whole image; (6) overview mode or zoomed at the tool center; (7-8) 2 buttons for zoom level (visible in zoom mode); (8-9) X and Y references. Numbers can be entered with virtual touch keyboard (appears automatically on focus), or any of the vertical or horizontal lines can be selected with touch at it (selected element is shown in green). Y numbers can be halfed on enter; (10) flip vertically; (11) load DXF file. Status bar shows screen coordinates in mm with touch of the screen. Click to touch bar shows raw input from COM port.
Fig.5. In zoom mode center of the screen is the tool center. Bar at left shows 1mm scale. Zoom can be altered with + and – buttons.
Some parameters (like colors, thickness etc), zoom level, scales directions can be adjusted with self-explanatory *.ini file. The ini file must be located in the same to application folder.
Parts
1. Scales: amazon
2. Teency LC: pjrc.com (details) or amazon
3. 4 channel Level shifter sparkfun or amazon
Software
Free open source software, requires link to this page if used or modified.