topic Offsetting a shape that has a round corner made with Fillet command in AutoCAD Forum

Offsetting a shape that has a round corner made with Fillet command

Anonymous — Sun, 04 Jul 2021 09:28:23 GMT

There is an image that I have attached to this post, in that image the left middle shape is made by several lines and arcs which are then joined together by 'join' command.

The upper left corner of the middle shape which is 90 degree arc is made by 2 intersecting lines and then the 'Fillet' command gives it the round 90 degree shape

The outer and inner shapes in the left side is made by using 'Offset' command on the middle shape but there is a difference in outer shape and inner shape rather than the size.

The 'Offset' command has treated the middle shape in a way that the upper left corner is sharp has no round shape but when it comes to the inner shape, the 'Offset' command treats the corner as a round shape

On the left side I tried to do the same thing but this time I used 'Polyline' command instead of drawing lines and curves and joining them by 'Join' and this issue didn't happen

Why does this happen with 'Fillet' command and also different reaction to inner and outer offsets ?

Re: Offsetting a shape that has a round corner made with Fillet command

GustavoUbriaco — Sun, 04 Jul 2021 15:26:43 GMT

Hi!

In your example both figures are different, try to make them equal and you'll have the same results

the arc dissapears because is too short in the offset result when the arc moves to left side they dicrease, to righ side they grow.

Re: Offsetting a shape that has a round corner made with Fillet command

Anonymous — Mon, 05 Jul 2021 05:33:53 GMT

First even if what you are saying is true, the outer offset and inner offset are still different from each other !

And why shouldn't offset treat my left side shape differently from the right side shape based on the size ?

Re: Offsetting a shape that has a round corner made with Fillet command

S.Faris — Mon, 05 Jul 2021 08:56:58 GMT

The reason why you are loosing your arcs while offsetting it inwards is because your Arc radius is less than your Offset value. For example you cannot offset a 200mm radius arc towards its center with a value equal or more than 200mm.

In simple words, An arc cannot have a negative radius value.

Re: Offsetting a shape that has a round corner made with Fillet command

Anonymous — Mon, 05 Jul 2021 09:08:21 GMT

Actually the arcs are getting offset inwards properly despite the reason you mentioned !

I'm having problem offsetting objects outwards as it's shown in the attached image

Re: Offsetting a shape that has a round corner made with Fillet command

S.Faris — Mon, 05 Jul 2021 09:23:47 GMT

Eventhough you are offsetting outward. It is towards the center of the arc right? That's the error

Re: Offsetting a shape that has a round corner made with Fillet command

Anonymous — Mon, 05 Jul 2021 12:59:03 GMT

So you mean when the shape get offset outwards, the radius of the circle in the corner also increases, and if the sides of the corner get smaller than the circle radius then that quadrant of the circle can't fit in the corner and as the result AutoCAD makes that corner sharp. Did I get you right?

Re: Offsetting a shape that has a round corner made with Fillet command

S.Faris — Mon, 05 Jul 2021 13:02:49 GMT

Exactly. Since a negative value Arc is impossible. Autocad 0 Degree fillets the corner where you previously had the arc.