service process：
Each maintenance steps：

• Failure item part number and serial number required 
• Receive the maintenance unit and allocate the maintenance number
• Assembly the damage part and inspect the malfunction cause ( confirm if valid warranty)
• Offering the cost with the detailed list of parts and labor charge
• Check the internal inventory and send the stock if any in time
• Obtain customer’s consent or send back the unit to customers in original state
• Purchase the spare parts and carry out the repair work
• Preserve the replaced parts in GTP for 4 weeks or send back to customers as request
• Discard the replaced pars after 4 weeks.