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Difference between revisions of "Starting to draw"

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(Drawing the support beams)
(Drawing the support beams)
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* Via https://www.calculator.net/slope-calculator.html
 
* Via https://www.calculator.net/slope-calculator.html
 
we find out  
 
we find out  
 
+
[[File:Slopeexample.jpg]]
 
For the three beams we only have the length at this time:
 
For the three beams we only have the length at this time:
 
# 363 mm
 
# 363 mm
Line 88: Line 88:
 
Since we have three values of the triangle we can calculate the other values with  
 
Since we have three values of the triangle we can calculate the other values with  
 
* https://www.calculator.net/triangle-calculator.html
 
* https://www.calculator.net/triangle-calculator.html
[[File:Slopeexample.jpg]]
 

Revision as of 08:29, 6 November 2018

This page presents a simple sequence of creating a basic drawing, from a blank document to a printed design. It assumes that you have installed LibreCAD 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.

Sketching

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.

Example

We'd like to create a drawing of the following alumnium structure:

Librecadexample2018-11-06.png


CarportFreehand.jpg

Start a drawing

  1. Start LibreCAD
  2. First you might want to decide about your application preferences using Options/Application Preferences/Appearance
    1. For this example the background color has been changed to "white"
  3. Save the default "unnamed document 1" as "CarportEast" using the "File/Save" Menu
  4. Check that the save was successful by Quitting LibreCAD, and restarting it. The saved file "CarportEast.dxf" should show up in the "File/Recent Files" Menu
  5. Reopen the file and close the "unnamed document 1" by clicking the circled x in the tab.

Scaling

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 se the General Scale to 20 to achieve the scaling.

Construction lines

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.

  1. Create a new Construction layer with a name such as 'construction', and a colour of magenta or cyan or similar. The line's width should be '0'. Construtionlayerdialogexample.jpg
  2. Make sure Snap on grid is enabled.

Drawing Box

We'd like to create a 5000 x 1300 mm construction line drawing box in which our construction will be placed.

  1. Hit space to enter the command line mode - the cursor will jump to the lower right corner and "Command" will be in blue
  2. Type polyline or "pl" - you'll now asked for the points
  3. Specify first point: 0.0
  4. Specify next point: 5000,0
  5. Specify next point or [undo]: 5000,1300
  6. Specify next point or [close/undo]: 0,1300
  7. Specify next point or [close/undo]: close

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

Drawing the frame

Select the default layer in the Layer list by clicking on it Layerselectionexample.jpg

Add three more polylines in the default layer:

Command: pl (polyline)
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

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 PrintPreviewExample.jpg

Drawing the support beams

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 Slopeexample.jpg For the three beams we only have the length at this time:

  1. 363 mm
  2. 845 mm
  3. 1050 mm

But we can also see that we have two angles available:

  1. 14.57 degrees derived from the frame triangle
  2. approx 90 degrees at which the beams are attached on the top side

Since we have three values of the triangle we can calculate the other values with