There are a number of scenarios in which a glue purge may help restore a poorly functioning printer. 

  1. If the system has been shipped by air pressurisation and/or thermal cycling of the system while in transit can impair the glue performance. 
  2. The longer a system is stored without use the more likely it is that you’ll encounter a glue system that has blockages or glue that is out of date. 
  3. Glue has a shelf life unopened of 1 year and should be used within 6 months of opening for best performance.  You may need to replace out of date glue. 

There's a procedure attached below.