Codeigniter submit form not working, blank page

I'm attempting to submit a form with codeigniter and when i submit the form a get a blank page. Where did i go wrong?

View

echo "<form class='order_ctn_parent' method='POST' action='add/insert_orders'>";
//inputs
echo "</form>";

Controller

class Add extends CI_Controller {

    public function __construct()
    {
        parent::__construct();
    }

    public function index() {

    }


       public function insert_orders()
    {
        $this->load->model('order_model', 'order');

        $this->order->insert_orders();
        redirect('view_orders', 'location');
    }

}

Model

class Order_model extends CI_Model {    
public function insert_orders()
        {
        $DB2 = $this->load->database('orders', TRUE);

                $timber_array = $this->input->post("timber_choose");
                $products_array = $this->input->post("product_choose");
                $qty_array = $this->input->post("quantity");
                $price_array = $this->input->post("price");
                $qty_array = $this->input->post("quantity");


                $loop = 0;
                foreach($products_array as $product) {

                    $price = str_replace("£","",$price_array[$loop]);

                    $data = array(
                       'product_code' => "",
                       'timber_type' => $timber_array[$loop],
                       'product' => $product,
                       'quantity' => $qty_array[$loop],
                       'price' =>  $price
                    );

                    $DB2->insert('timber_order_products', $data); 

                    $loop++;
                }
        }
}

Try something like this

?>//end of php

<form class='order_ctn_parent' method='POST' action='<?php echo base_url()?>add/insert_orders'>

</form>

and load model in __construct(), like this

public function __construct()
{
    parent::__construct();
    $this->load->model('order_model', 'order');
}

and no need of check $DB2 = $this->load->database('orders', TRUE);

and Codeigniter insert should be Like This