Senhas aleatórias

Procedure TForm1.Button1Click(Sender: TObject);
var
i:integer;
const
str='1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ';
max=6;
begin
Edit1.Text:='';
for i:=1 to max do
Edit1.Text:=Edit1.Text+str[random(length(str))+1];
end;
end.