For machinery, if any problem could not be sloved by email, and customer need the service people to go to their place, it is convenient for customer, and the problem could be solved timely,

Contact customers within a few weeks of their purchases and ask if they have any questions about the product. Ask if the customer is happy with the purchase, and if not, what can be done to make things right. Taking a proactive approach to customer service is very important. In addition to gaining customer loyalty, you can get an early warning about any quality problems with your products. If you note that a particular product has a high number of customer complaints, you can take proactive measures to resolve those issues before more products hit the street.