Jump to content

Recommended Posts

Posted

From a book, there is a shape shown as below.

autocad_problem.jpg

 

It is shown for showing how to use "pedit" but not mention how to draw it. It should be drawn using polyline command.

 

Is there any easy method to draw it accurately.

 

The inner shape is at center position of outer shape.

 

The inner shape should be draw using "rectangle" > "chamber" command. However, don't know how much to chamber. There should be a easy way to do it instead of any calculation.

 

Any help is appreciated.

Posted (edited)

PEDIT is a command that allows one to change lines and arcs to polylines and it also has the added option of joining consecutive lines and polylines into one continuous entity.

 

Drawing accuracy can be enhanced via the use of ORTHOMODE and OSNAPS.

 

The command for the cut corners of the inner shape is actually named CHAMFER.

 

Start the exercise by drawing a rectangle using the dimensions given for the larger of the two objects. That would be 140x160.

 

Chamfer all four corners using a distance of 20.

 

If you used lines to create your rectangle then use PEDIT to turn them into polylines and the JOIN option to create a single continuous polyline.

 

Offset the rectangle (with chamfered corners) a distance of 30 units to get the interior rectangle of 80x100.

 

Now finish off the exterior rectangle by creating one of the arcs. You can use this arc (mirror and copy or array and move) to create the other three. Trim as necessary then dimension it all. Done.

Edited by ReMark
Posted

Despite ReMark's overlooking the phrase "this should be drawn using the polyline command", I drew the outside shape with this command sequence

 

 

Command: pl

PLINE

Specify start point:

Current line-width is 0.0000

Specify next point or [Arc/Halfwidth/Length/Undo/Width]: 30

 

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: a

 

Specify endpoint of arc or

[Angle/CEnter/CLose/Direction/Halfwidth/Line/Radius/Second pt/Undo/Width]: s

 

Specify second point on arc: @15,30

 

Specify end point of arc: @-15,30

 

Specify endpoint of arc or

[Angle/CEnter/CLose/Direction/Halfwidth/Line/Radius/Second pt/Undo/Width]: l

 

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: 30

 

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: @20,20

 

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: 20

 

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: a

 

Specify endpoint of arc or

[Angle/CEnter/CLose/Direction/Halfwidth/Line/Radius/Second pt/Undo/Width]: s

 

Specify second point on arc: @30,-15

 

Specify end point of arc: @30,15

 

Specify endpoint of arc or

[Angle/CEnter/CLose/Direction/Halfwidth/Line/Radius/Second pt/Undo/Width]: l

 

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: 20

 

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: @20,-20

 

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: 30

 

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: a

 

Specify endpoint of arc or

[Angle/CEnter/CLose/Direction/Halfwidth/Line/Radius/Second pt/Undo/Width]: s

 

Specify second point on arc: @-15,-30

 

Specify end point of arc: @15,-30

 

Specify endpoint of arc or

[Angle/CEnter/CLose/Direction/Halfwidth/Line/Radius/Second pt/Undo/Width]: l

 

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: 30

 

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: @-20,-20

 

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: 20

 

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: a

 

Specify endpoint of arc or

[Angle/CEnter/CLose/Direction/Halfwidth/Line/Radius/Second pt/Undo/Width]: s

 

Specify second point on arc: @-30,15

 

Specify end point of arc: @-30,-15

 

Specify endpoint of arc or

[Angle/CEnter/CLose/Direction/Halfwidth/Line/Radius/Second pt/Undo/Width]: l

 

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: 20

 

Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: c

Posted

Draw a rectangle using the dimensions option to get your outer shape. Use the chamfer command to add the corners. Offset the outer shape to get your inner shape. Draw an arc and center it on the edge. Copy said arc and past it to the centers of the remaining edges (rotate arc as needed). Trim the lines and then use PEDIT to join it all together.

 

HOWEVER, there is insufficient data to create the chamfer on the inner shape. When you offset the outer shape, the inner chamfers are smaller than what is shown in the image.

Posted

If you are going to draw the shape using the polyline command then there would be no need for using the PEDIT command. The teacher should make up his/her mind.

Posted

Thanks. ReMark, eldon and SuperCAD.

 

Sorry for misleading to say "It should be drawn using polyline command" that I think myself, because "Polyline" command is just illustrated before "PEdit" command within the book.

 

Thanks eldon for full details to draw the outer shape using polyline.

 

"offset" command is not mentioned yet in the book. I've tried using "rectangle" and then "offset" without the arc yet, the corners of inner shape is not that expected:

 

unmatched_result.jpg

 

So I think it is not possible to have the result looks like that in the book.

Maybe it just use it for demonstration of using PEDIT only.

 

Anyway, I know how to draw this now. Thank you!

Posted

By proportion the missing dimension for the inside chamfer it 10.

Missing Dim.jpg

Posted
By proportion the missing dimension for the inside chamfer it 10.

 

Thank you for your reply.

How to determine the inside chamfer by proportion accurately or by estimation?

Posted

Short answer is, you can't. 10 is purely a guess since the dimension is not stated on the image. Number one rule in reading drawings is never guess a dimension. If you can't figure it out by deducting other dimensions you need to ask what it is.

Posted

Whilst I would in no way gainsay the previous post, there is a case here for observation. One could argue that the length of the arc cut-out on the outer shape lines up with the flat length of the inner shape.

LinesUp.jpg

Posted (edited)

If you can prove to your teacher that it was not possible to finish the assignment whithout making an assumption (the missing dimension vs the offset result) you might get a higher mark.

Edited by JD Mather

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Unfortunately, your content contains terms that we do not allow. Please edit your content to remove the highlighted words below.
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...