Magento:: Join Product Table with custom collection

Grid.php of your custom module

protected function _prepareCollection() {
	  
	$collection = Mage::getModel('warranty/stickerid')->getCollection();
	// join product table
	$entityTypeId = Mage::getModel('eav/entity')
			->setType('catalog_product')
			->getTypeId();
			
	$prodNameAttrId = Mage::getModel('eav/entity_attribute')
			->loadByCode($entityTypeId, 'name')
			->getAttributeId();
			
	$collection->getSelect()
			->joinLeft(
				array('prod' => 'catalog_product_entity'), 
				'prod.entity_id = main_table.product_id',
				array('sku')
			)
			->joinLeft(
				array('cpev' => 'catalog_product_entity_varchar'), 
				'cpev.entity_id=prod.entity_id AND cpev.attribute_id='.$prodNameAttrId.'', 
				array('product_name' => 'value')
			); 
	$this->setCollection($collection);
	return parent::_prepareCollection();
}

Show product name in grid:

protected function _prepareColumns() {

    $this->addColumn('product_name', array(
        'header'    => Mage::helper('warranty')->__('Product Name'),
        'align'     => 'left',
        'width'     => '120px',
        'index'     => 'product_name',
    ));
    
    return parent::_prepareColumns();
}