Ishikawa Tikz 图

Question

我想创建一个像下面这样的石川图（鱼骨图）：

我曾尝试用 Tikz 实现它但似乎有点困难。

\tikzset{
  ishikawa/.style = {align=center, inner sep=0pt, text centered,
    %font=\sffamily
    },
  matter/.style={   % Wirkung=Betrachtete Störgröße
  rectangle,minimum size=6mm,very thick,draw=red!70!black!40,top color=white,bottom color=red!50!black!20,font=\itshape
  },
  level_1/.style={      % Haupteinflussfaktoren
  ellipse,node distance=60pt,minimum size=6mm,very thick,draw=red!50!black!50,top color=white,bottom color=red!50!black!20,font=   \itshape
  },
  level_2/.style={      % Nebeneinflussfaktoren
  rectangle,minimum size=6mm,font=\itshape,font=\tiny
  }
}
\begin{tikzpicture}[->,>=stealth',level/.style={sibling distance = 5cm/#1,
  level distance = 1.5cm}
]
    \node (Grund)       [matter]    at ( 12,0)      {CPA};
    %   \path[draw,->] (0,0) -- (Grund)
        \draw [->,very thick] ( 0,0) -- (Grund);
    \node (tl_1_1)      [level_1]   at ( 0,5)       {Material};
    \node (bl_1_1)      [level_1]   at ( 0,-5)      {Methode};
    %   child{ node [level_2] {msndfbdejfsdlfksf}}
    \node (tl_1_2)      [level_1, right=of tl_1_1]  {Maschine};
    %   child{ node [level_2] {msndfbdejfsdlfksf}}
    \node (bl_1_2)      [level_1, right=of bl_1_1]  {Mensch};
%       child{ node [level_2] {msndfbdejfsdlfksf}}
    \node (tl_1_3)      [level_1, right=of tl_1_2]  {Messtechnik};
    %   child{ node [level_2] {msndfbdejfsdlfksf}}
    \node (bl_1_3)      [level_1, right=of bl_1_2]  {Mitwelt};
%       child{ node [level_2] {msndfbdejfsdlfksf}}
\end{tikzpicture}

这会产生我的顶层框，但我不知道如何从那里绘制到我的主要箭头的路径。下层箭头也存在同样的问题。

有人可以帮我吗？！

欢呼杰罗德