CAD Drawing Import

Drawing Files

TouchDRO reads drawings in its own file format, which carries the geometry as true-scale coordinates. Right now, the only way to produce that file is SnapCAD, a CAD application with a built-in "Export to TouchDRO" command; the full path from SnapCAD to the machine is covered in the "Machining to a CAD Drawing" guide.

Direct DXF import is under development and coming later this year. Once it ships, you will be able to import a drawing from Fusion 360, FreeCAD, AutoCAD, or any other package that exports DXF, and everything described on this page will apply to it unchanged. In the meantime, SnapCAD's native format is DXF, so you can open a DXF from any other package in SnapCAD and export it to TouchDRO from there.

Because the coordinates are true scale, a drawing needs no scaling or calibration step on import. This is the main difference between a drawing and a reference photo, which carries no scale of its own and has to be calibrated against known points, as described in the "Reference Image Overlay" guide.

Loading a Drawing

A workspace holds one drawing at a time. The entry point is the "Drawing" row of the "Display" panel in the graphical view, described in the "Graphical View Display" guide. To load a drawing, tap the folder button on that row; this will open the system file picker.

A file that can be read opens the "Set Up Drawing" dialog. A file that can't is reported in the "Drawing Not Imported" dialog, which lists the problems found in the file and leaves the workspace untouched.

The Set Up Drawing Dialog

The "Set Up Drawing" dialog is where the drawing is positioned against the workpiece and its features are selected. Since the drawing carries true scale, it arrives already placed: the dialog opens with the drawing fitted to the preview, a datum mark on the point that will land on the workspace origin, and "Apply" available immediately. Everything else in the dialog is optional refinement.

Drawing Preview

The preview occupies the left side of the dialog and shows the drawing, the datum mark, and the snap points of every visible group. It responds to the same gestures as the graphical view: drag to pan, pinch to zoom, and double-tap to fit the drawing to the window.

Four buttons along the top of the preview change the drawing's orientation. Rotate left and rotate right turn it in 90-degree steps, and the two mirror buttons flip it horizontally or vertically.

To select a feature, tap it in the preview. The selection is marked on the preview and named on the status line. To clear it, tap the selected feature again, or tap an empty area of the preview. Only features belonging to a visible group can be selected, so a group whose eye is switched off in the "Snap Points" panel is not selectable either.

Position Readout

The Position Readout at the top of the control panel shows the current spindle or tool position for the two axes shown in the graphical view, along with a "set zero" button that zeroes both. It's there so a machine coordinate can be read, or an origin set, without leaving the dialog.

Reference Points

A reference point ties one feature in the drawing to one coordinate on the machine. Both "Reference 1" and "Reference 2" are optional, and each serves a different purpose.

Each section holds the same controls: a "Sub-Datum" selector, an X and a Y field, a synchronize button beside each field, and a lock button. The fields take the machine coordinate that the selected feature should sit at. The synchronize buttons copy the current position of that axis into the field, and the "Sub-Datum" selector fills both fields from a stored coordinate. The lock button accepts the reference. Once locked, it becomes a clear button that releases that reference and leaves the other one untouched.

"Reference 1" moves the drawing so that the selected feature sits at the stated coordinate. Its purpose is to put the drawing's origin somewhere convenient, which matters when the file was drawn around an origin that isn't practical to work from at the machine.

"Reference 2" is a sanity check on scale. TouchDRO compares the distance between the two referenced features on the machine against the same distance in the drawing, and reports a disagreement rather than stretching the drawing to fit. A plain mismatch is stated on a banner at the top of the dialog, in the form "These points are 2.40 mm further apart on the machine than in the drawing." A mismatch that lands on one of the common unit errors is named instead, along with what will be done about it: "Based on the two points you selected, this drawing is in inches, not millimetres. Apply will scale it ×25.4 to match." The conversion is carried out by "Apply", so a diagnosis that looks wrong can be overruled by correcting or clearing a reference point.

Two locked reference points also set the drawing's angle. TouchDRO takes the angle implied by the two stated coordinates, reports it on the status line, and rotates the drawing by that angle when it is applied. An angle too small to be distinguished from the precision of the two picks is treated as zero, and picking the two features further apart is what makes a small angle measurable.

Snap Points

The "Snap Points" panel lists the features TouchDRO found in the drawing, grouped by kind: points named in the CAD file, hole centers grouped by diameter, arc centers, and corners. Each row names its group and the number of features in it, such as "Holes - 6.0mm (13)". A group with no features in it is left out of the panel.

Each row carries two toggles, and they answer independent questions:

• The eye, "Show on drawing", controls whether the group is drawn on the preview. Since only visible features can be selected, it also controls whether the group can be used as a reference point.
• The circled plus, "Create as sub-datums", marks the whole group to be turned into sub-datums when the drawing is applied. A group is created in full or not at all.

The markers are useful on their own. A drawing shows a hole as its outline, while the machining happens at the center, and the snap point puts a visible mark exactly there. The same goes for arcs, whose centers lie away from the curve itself, with nothing else in the drawing to mark them.

Every group starts visible, except a corners group large enough to clutter the preview, which starts hidden. Only named points start marked for creation, since a named point is the one candidate a person placed in the drawing deliberately; every derived group starts unmarked, so nothing is created unless you ask for it.

Status Line

The status line below the preview reports what was loaded and what has happened since. It always states the number of shapes in the drawing and the overall area they span in machine coordinates, which is also the quickest check that a file arrived at the scale you expected. Three further notes are appended as they apply: the coordinate of the feature last selected, the angle set by the reference points, and any warning raised while reading the file, such as a lathe drawing loaded into a milling machine workspace.

Reset, Cancel, and Apply

"Reset" returns the drawing to the state it was in when the file was loaded, discarding the placement, orientation, and both reference points, so the setup can be started over without reopening the file. "Cancel" discards the import entirely. "Apply" stores the drawing in the workspace, creates sub-datums from every group marked with the circled plus, and carries out any unit conversion the dialog diagnosed.

Extracted Sub-Datums

Sub-datums created by "Apply" are named after their kind and numbered, in the form "6mm Hole 1", "6mm Hole 2", and so on. Each group is given its own tag, such as "Hole_6mm" or "Arc_Center", so hole centers of different diameters remain separately filterable instead of arriving as one undifferentiated set. A second import into the same workspace appends "_2" to a tag already in use, the same way the pattern functions do. Tags and the filtering they support are covered in the "Sub-Datum Tags and Filtering" guide.

Once created, these are ordinary sub-datums. They can be edited, retagged, and deleted like any other, and they are not removed when the drawing they came from is cleared.

The Drawing in the Workspace

An imported drawing becomes a layer of the graphical view, drawn beneath the sub-datums and the tool position. The "Drawing" row of the "Display" panel carries three controls in place of the folder button: the eye shows or hides the drawing, the half-opacity button dims it so the sub-datums and cutter stay legible against it, and the clear button removes it from the workspace after a confirmation.

The drawing's shapes are selectable. To make a shape stand out, tap it; the selected shape is drawn brighter than the rest of the drawing, like the circle in Fig. 1. The selection is only visual at this time, but it is a convenient way to mark the feature being machined.

A drawing that carries more than one layer lists them under the "Drawing" row, each with its own eye, so construction geometry or a reference-only layer can be hidden while the rest of the drawing stays up. The "Sub-Datums" row expands the same way, one row per tag. Both are described in the "Graphical View Display" guide.

How to Use

To import a drawing, follow these steps:

1. Open the "Display" panel and tap the folder button on the "Drawing" row
2. Select the drawing file in the system file picker
3. If the drawing's own origin isn't in a convenient spot, tap a feature in the preview, enter the machine coordinate it should sit at under "Reference 1", and press the lock button
4. Switch on the circled plus for every "Snap Points" group you want stored as sub-datums
5. Tap the "Apply" button

To use the drawing purely as a virtual layout, skip the "Snap Points" step and dim the drawing to half opacity once it's applied. The outline, slots, and hole positions are then visible in true position under the crosshairs, and you can mill to the drawing's lines the way you would mill to scribed layout lines.

Sometimes the drawing is square to its own frame, but the part on the machine isn't: a casting, or a workpiece held by its one flat surface, often sits at an angle to the table. In that case, use both reference points to align the drawing to the part:

1. Tap the first feature, enter the position where it actually sits on the machine, and lock it
2. Tap a second feature as far away from the first one as the part allows, enter its actual position, and lock it
3. Review the angle reported on the status line, then tap the "Apply" button

The drawing is rotated to match, so the stored geometry describes the part as it is clamped rather than as it was drafted. Note that two points close together can't resolve a small angle; the further apart the two features are, the more accurate the alignment.

For a complete worked example, from the CAD export to the finished part, refer to the "Machining to a CAD Drawing" guide.