Contour Cutting for Laser, Plasma and Waterjet

Contour cutting is the operation for machines that cut with a beam or a jet rather than a rotating tool: laser, plasma and waterjet. It differs from contour milling in two ways that matter.

What makes it different

The beam has to be switched on and off. Specific lines are defined in the postprocessor for starting and stopping the cut. CamDRAW writes them at the beginning and end of every contour, so the laser fires as the cut begins and stops before the machine travels to the next one.

There is no cutting depth. A beam cuts through in one or more passes rather than stepping down in increments. The depth fields are replaced by a cutting height and a pass count.

Creating the operation

Select the objects in CorelDRAW, then click the sixth icon in the row of six in the Toolpaths section of the CamDRAW docker. It is the last of the six.

Contour adjustment

Tool center places the path on the line, inside or outside. For parts you are keeping, cut outside; for holes, inside. The offset uses the beam diameter stored with the tool, which is how kerf is compensated.

Machining direction is same or opposite rather than climb or conventional, since there is no rotating cutter.

Both directions allows either.

Show tool diameter draws the path at the real beam width, which is the quickest way to check that small features are not being cut away entirely.

Machining parameters

Three fields, and the first two have checkboxes.

Safety height is where travel moves happen. The checkbox lets you switch it off entirely, which suits machines where the head does not need to lift between cuts.

Cutting height is the Z level where cutting takes place. This too can be deactivated if your machine controls the height itself, as many plasma systems do with automatic torch height control.

Number of cuts is how many times each contour is traversed. More passes for thicker material.

Being able to switch the two heights off is the point here. A machine with its own height control does not want CamDRAW commanding Z.

Leads and tabs

Two collapsible sections below contour adjustment, both specific to cutting work.

Leads & Transitions adds an entry and exit to each contour so the pierce point sits off the finished edge. Entry and exit are set separately, and each can be tangential, made of an arc plus a straight segment, or purely linear. Position places them as a percentage along the contour, where 0 is the start and 100 the end.

Tabs interrupts the contour so small bridges of material remain, holding parts in the sheet until the job finishes. Set the Width of each bridge and the Number per contour. With Automatic position switched on the positions are distributed for you; switched off, the tabs appear as red dots on the CorelDRAW page and can be dragged anywhere with the mouse. Scaling only changes how large those dots are drawn and has no effect on machining.

Tabs and leads can be combined.

Sequence and allowance

Sequence sets automatic optimisation by shortest path, or the order the objects sit in on the CorelDRAW layer.

Allowance offsets the contour by a fixed distance, useful for adjusting fit on material that burns back.

The tool

Laser, plasma and waterjet tools are created in the same tool library as cutters. The Diameter on the Dimensions tab is the beam or jet width, and it drives the kerf compensation.

On the Other tab, Pierce time defines how long the beam needs to penetrate the material before movement begins. It is available in the postprocessor as a placeholder, so it can be written into the program where your control expects it.

The Tabs tab of the tool list holds a default tab width for that tool.

Checking before you cut

Generate the program with the G1 G2 button in the NC program section and look at the 3D view. Cutting paths appear in blue and rapid moves in red, so a lead sitting in the wrong place or a contour cut in the wrong order is visible before the machine runs.