The Dado Loop (DDL) command is designed to close the contours of dadoes, grooves, mortises, pocket or rabbets. When you prepare the contours for machining flat parts on a CNC milling machine, you are probably faced with the task of forming a closed loop, which the cutter must go through to cut a dado or pocket. The contour should be such that the milling cutter catch all the material in the dado. And cutter should come out of a part. And cutter should approach into a inner corners. And the contour can not have bottlenecks, thinner than a milling cutter. 

This program will help you to make this work simple and fast.

The program only works with drawings from lines and curves lying in the XY plane. Similar work directly on solids can be done by the program CNC_Prepare.

Features of the program

• • Closes the contours of the dadoes, pocket or rabbets in the loop using fragments of the outer contour of the part.

  • The program itself finds the outer contour of the part. It should be a closed polyline.

  • The program can call the Inside Corner command to form milling cuts in the corners.

  • The program extends the contour if it is too narrow for the given cutter. And if it can not expand, it will issue a warning.

  • The program will add arcs to the edge of the part for the complete exit of the cutter from the part to the outside.

  • The program can work with the diameter of the milling cut equal to zero - in this case the contour are simply closed along the contour of the workpiece, without expansion and approaches to the corner.

  • The dado loop is assigned the NC_Inside layer, so that the technologist understands that the loop should be processed by the cutter's passage inside the contour.

  • You can specify the depth of milling in the settings. This number will be added to the layer name and Thickness property.

  • The program will identify the contours of the pockets that can not be traversed by the specified cutter at a time and placed in the NC_Pocket layer, for spiral processing or scanning.

  • The command has flexible settings, all options can be disabled, the layers can be renamed.

  • You can use layers from a template file.

Read about downloading and installing the program here.

To run the command, you will have to register account and top up your account balance or receiving bonuses.

Then you can activate one of the licenses:

• • Annual license - 10 EUR.

  • Unlimited license - 50 EUR. Free updates for 1 year.

  • The trial period is 20 days.

Description

Usually, before using this command, the part (solid) is laid out in the XY plane with the Lay command, then a flatshot is made using the Flat command (FLT), then all the curves are processed by the Outside Loop command (OSL). After that, the outer contour of the part becomes a closed polyline. Now you can close the loops of the dadoes and pockets - call the DDL command.

• • At the beginning of the work, the command requests the diameter of the cutter to ensure that the loop is passable. The default diameter is 8mm or half an inch (depending on the drawing units). When entering the diameter, you can also select the Settings option to bring up the settings dialog.   

Note that by changing the diameter of the milling cutter in this command, you change it in the other contour processing commands (Outside Loop and Inside Corner).

• • The program then requests the objects of the dado contour. These can be arcs, lines, polylines, elliptic arcs and splines. You can select two parallel contours if this is the groove in the middle of the part.

  • Next, the program itself searches for the main contour of the part. Without it, work is not possible. The main contour must be a closed polyline and the dado contour you select must end exactly on the contour of the part.

  • Then the program builds a loop so as to ensure the passage of the milling cutter of the specified diameter, but minimally to cut a remnants to sawdust. In addition, the program makes milling cuttings at all internal corners of the dado contour (the "Inside Corner" command is called) to provide a full dado so that rectangular parts can be inserted into the groove.

  • The finished loop is closed in the polyline.

  • The program operates on a cycle, again requesting contours for the next dado, until you press Esc.

The program checks whether the "meat" of the part remains after the cutter has passed through the contour. If it remains, the loop is assigned the NC_Pocket layer. This is necessary for a spiral milling or for scanning. The check does not always work - be sure to check the result.

Watch the command line - there are displayed all the messages of the program.

Settings

You can bring up the settings dialog by selecting the TUNE option or use AvcOptions palette on CNC tab. 

All options have a tooltip.

There are many settings and for your convenience, you can use ready-made sets of settings, which I call CNC-Style. You can create up to 9 styles. You can switch the current style in the header of the settings window. And during the work of the command, you can call the SwitchStyle option and select the style by its number.

Attention! The current NC style affects all contour commands. Switching the style in one command you will work with this style in all other command too.

The operation of the command is affected by all options from this window, except for the Detailing section. A layer management and a layer template can be set on the A>V>C> tab in the Common Options section.

Known Issues

• • To form a loop, use the shortest path along the contour of the part. If a rabbets is milled on three sides of the part, then this algorithm does not work, the loop will be done incorrectly! The program has no information about the 3D-geometry of the original part and therefore the problem is unsolvable. However, you can redo the contour of rabbet so as to form 3 short loops instead of one long one.

  • When expanding the dado under the cutter, only the ends of the dado are checked; make sure that there is no narrowing in the middle of the dado.

  • It is impossible to close the contours of the dodoes with branches and intersections. The program accepts no more than 2 contours at the input, and each branch is a new isolated contour. You can break the branched dado into a few simple ones, just by cutting it with a line in a suitable place.

Special thanks: This program is based on the source code writed by Sergey Donskov.