This page presents a simple sequence of creating a basic drawing, from a blank document to a printed design. It assumes that you have LibreCAD installed and have opened it to a new default blank drawing. It introduces quite a few LibreCAD concepts, and links to other pages that explain these.
You can download and unzip Carport.zip to compare your results with what the authors of this document saved.
The first part of any design is a freehand sketch on paper. This is quick and simple and so allows for greatest freedom in the design process.
We'd like to have an A4 drawing on which a scaled version of the 5000 x 1300 mm construction fits.
A4 is 297 x 210 mm so if we make the 5000 mm be shown as a 250 mm long line we'd be set. That is a 1:20 scale.
Via the menu Options/Current Drawing Preferences/Dimensions we can set the General Scale to
'20' to achieve the scaling. And set
'Landscape' for the paper direction.
The first lines of any technical drawing are the
construction lines, setting out the locations of all lines without specifying any line types, colours, etc. All straight construction lines are of 'infinite' length — i.e. they extend off the screen in both directions.
We'd like to create a 5000 x 1300 mm construction line drawing box in which our construction will be placed. Since we want precise positions for this box we'll use the Command Line Mode and create a Polyline. Note: Command Widget must be displayed (Widgets, Dock Widgets, Command Line).
'clear' in the command box if the state of things is not like that)
'polyline' or “pl” - you'll now be asked for the points
Zoom out with the View/AutoZoom menu item You should now see a 5 x 1.3 m rectangle at 1:20 scale
Try printing the page with File/Print - the printout should be empty since the construction layer will not be printed
For the frame we would like to create three “rectangles” that represent the sides of the frame. Each side has 40 mm width, so we simply take the three corners of the triangle:
and shift the coordinates by 40 mm accordingly.
Add three more polylines in the default layer:
pl 0,0 5000,0 5000,40 0,40 close 4960,0 4960,1300 5000,1300 5000,0 close 5000,1300 5000,1260 0,0 0,40 close
Should you have made a typing error you might want to use the “undo” command to remove the latest drawing item that didn't go as you intended. Hint: You should type these commands to learn the process but in future you can copy/paste multiple commands using the special command action on right of command line.
You might want to save your result with File/Save. This time if you print things out with File/Print the result should be visible. You can also check what the print looks like with File/Print Preview which will open up a new tab
To support the transition from the freehand sketch to the LibreCAD CAD drawing you can optionally insert a scanned version of your freehand drawing as an image.
The next three polygons are a bit more tricky. We need to find out the positions to use from the dimensions we measured. Fortunately for the math there are helpers on the internet:
we find out
For a triangle to be calculated we need three values.
For the three beams we only have the length and slope 14.57 degrees at this time:
But we can also see that we have two angles available:
Since we have three values of the triangle we can calculate the other values with
We'll add the triangles in the construction layer using LibreCAD's capability to use relative and polar coordinates
pl 0,0 1443,0 @363<104.57 close
The values are from the triangle calculator.
We repeat this for our other beams
0,0 3359,0 @845<104.57 close 0,0 4174,0 @1050<104.57 close
You'll find a saved version up to this step in the 'CarportEastStep2.dxf' file in the zip file mentioned above.
For the beams we could now also calculate the points for the corresponding polygons. We do not need that much precision here so an alternative is to draw the beams with the mouse using our construction triangles as guiding lines.
see https://github.com/LibreCAD/LibreCAD/issues/1036 for the question how the close button could be improved
We can make the point calculation easier by using relative coordinates.
1443,0 @30,0 @363<104.57 @-30,0 close 3359,0 @30,0 @845<104.57 @-30,0 close 4174,0 @30,0 @1050<104.57 @-30,0 close
The basic construction elements are now in place.
You'll find a saved version up to this step in the 'CarportEastStep3.dxf' file in the zip file mentioned above.
da 0,0 5000,0 0,-100
Hint: If the dimensions are not shown clearly then check Options > Current drawing preferences > Dimensions.
We keep adding dimensions:
da 5000,0 5000,1300 5100,0
You'll find a saved version up to this step in the 'CarportEastStep4.dxf' file in the zip file mentioned above.