Cfrgtkky

How can a bold arrow be bent correctly?

I use the following code, but it looks horrible:

tikzset{%

    thick arrow/.style={

    -{Triangle[angle=90:1pt 1]},

    line width=1.0cm, 

    draw=gray

    }

}



tikzstyle{software} = [draw, text width=10em, minimum height=6em, text centered, line width=1pt, color=mydarkblue, fill=mylightgray, text=mydarkblue, font=normalsizebfsffamily]



centering





begin{tikzpicture}[node distance = 6em]



node[software](softA) {Software A};

node[software](softB)[left = of softA] {Software B};





draw [thick arrow] ($(softB.north)+(1,1em)$) [bend left=45] to ($(softA.north)+(-1,1em)$);



path [decorate,decoration={text along path,

text={|footnotesizebfseriessffamilycolor{white}|DATA A},text align=center}] ($(softB.north)+(1,1.5em)$) [bend left] to ($(softA.north)+(-1,1.5em)$);



draw [thick arrow] ($(softA.south)-(1,1em)$) [bend left=45] to ($(softB.south)+(1,-1em)$);



path [decorate,decoration={text along path, text={|footnotesizebfseriessffamilycolor{white}|DATA B},text align=center}] ($(softB.south)+(1,-1.5em)$) [bend right=45] to ($(softA.south)+(-1,-1.5em)$);





end{tikzpicture}

Here is what the code creates: the arrows are very strangely bent and don't look curved properly and uniformly.

I do not know yours documentclass{...} and usetikzlibrary{...}. You may want to consider this source where you can add the two rectangles.
My code is an adapt of this code.

documentclass{article}

usepackage[margin=0.3cm, paperwidth=3.3cm, paperheight=3.3cm]{geometry}

usepackage{tikz}



defarrow{

  (10:1.1) -- (7:1) arc (7:120:1) [rounded corners=.8] --

  (120:0.9) [rounded corners=1] -- (130:1.1) [rounded corners=.8] --

  (120:1.3) [sharp corners] -- (120:1.2) arc (120:5.25:1.2)

  [rounded corners=1] -- (10.4:1.05) -- (8:1.05) -- cycle

}



tikzset{

  ashadow/.style={opacity=.6, shadow xshift=0.1, shadow yshift=-0.07},

}



defarrows[#1]{         

  begin{scope}[scale=#1]



    draw[color=gray, left color=gray, right color=gray] [rotate=210] arrow;



   draw[color=yellow, left color=yellow, right color=yellow]  [rotate=20] arrow;

  end{scope}

}



begin{document}

begin{center}

  begin{tikzpicture}

    arrows[1];

  end{tikzpicture}

end{center}







end{document}

or you take this example at the link Drawing a diagram of a three-cycle.