@Carl Love 

Yes I do. When I enable/disable this option, the only difference is the number of the steps.

@acer 

I found what you are talking about. In my case a suden change happens around 2696 numpoints. I couldn't find out the reason from your previous post.

Yet the left plot is not fine. I mean you can compare it with the results of more graphical and less mathematical softwares. See the bellow image as an example. No matter how much I magnify this image, the quality keeps intact. But why in the world a plot made by maple has these steps that we cannot control.

@Mac Dude Yes I guess it is related to the system one is using. I see the plots on my laptop smoother than on my PC. However it's not at all fine. Still it's visible that the lines and curves are consisted of smaller pieces. The problem is that we cannot control these pieces.

@Markiyan Hirnyk 

Now it looks fine because the view has changed. However this is not an option for me. I need to present my work with maple and there are a number of plots with favorite ranges that I cannot change. So my problem is not to export with high quality. More than anything, I want to know what the origin of the problem is. It seems maple is making the computations with a very high precision, however it is not somehow able to plot the results in a optimized curve.

Thank you guys anyway. If you have any more comments, I would love to see them.

@Markiyan Hirnyk 

I did it, but still i get exactly the same plot. Up to gridrefine=8, and still ziro change.

@acer 

No! no significant change even with 10000000 numpoints!