By Dennis Collin
When training AutoCAD I frequently get many questions about the hatch command. This is usually relating to such matters as the scale of hatch pattern, error messages in creation and the ability to modify hatch boundaries when perimeter objects change. One thing I stress to users is to NEVER use the explode command on hatch. I always jokingly refer to that function as the “Friday Afternoon Command”!
With recent AutoCAD updates hatch entities are much more versatile and many of these adjustments can be easily accommodated via the ribbon menu, in terms of hatch pattern, colour and scale. The most common issue I find is when an area of hatch needs to be modified to accommodate an island of new geometry which has been created since the hatch. Many untrained users either explode the hatch into separate lines (unforgivable) or redraw the hatch from scratch (better!), but there is an easier way, by adding a new boundary to an existing hatch entity.
In the example image in figure 1, it is required to remove the area of hatch from the red rectangle. This is an easy process. Simply select the existing hatch and choose the select boundary option marked in figure 2 and press <ENTER>. The Hatch object should display as per figure 3.
If the cut-out function doesn’t work, check the hatch options menu and check that the island detection is set to normal or outer. This will ensure AutoCAD’s hatching algorithm respects internal boundaries.
Alternatively, it is also possible to use the trim command on regular hatch objects, this tends to work best with the manual boundary selection method.
Hatch elements have all kinds of purposes from illustrating materials, hazard areas or just for simple area calculation and display, but if the explode command is used then all this clever functionality is lost making the resultant drawing a lot more problematic and tedious to work with.