Advantages of pc based machine controllers:

• High and increasing performance year on year if the PC is replaced or upgraded
  
  
• Low part price
  
  
• Networking capability
  
  
• Great flexibility due to availability to a large variety of plug in cards
  
  
• Unlimited memory
  
  
• The PC can perform many other functions
  
  
• Touch screen compatibility
  
  
• Incorporates familiar menu systems
  
  
• Customised Human Machine Interface
  
  

Disavantages of pc based machine controllers

• Often high installation and setup costs due to added system complexity and a probable requirement for a computer development engineer
  
  
• Generally compromised system performance
  
  
• "PC" crashes result in lost time & materials
  
  
• The timely operation of the PC operating system is critical for highest system performance
  
  
• PC compatibility problems when the PC fails. New PC's and operating systems are not necessarily compatible with older systems and software
  
  
• Generally compromised system reliability as PC's are inherently much less reliable than dedicated industrial quality controllers, e.g. hard and floppy disks fail
  
  
• Harsh environments require industrial components and enclosures that increase total parts cost
  
  
• Requires external drivers, connectivity, and machine safety components
  
  
• Complex systems require a number of cards that have to be integrated
  
  
• Potential warranty issues when third party cards are plugged in the PC
  
  
• Making the system work can involve specialist product developers
  
  
• System support has to be obtained from multiple sources
  
  
• If system problems are encountered who takes the ultimate responsibility?
  
  
• Real total system lifetime costs are usually higher
  
  
• An expert is required to support the system, they can move on leaving you in a fix
  
  

Standalone non PC Based Machine Controllers

Advantages:

• 'Industrial Robustness' is integrated into the design when systems are well designed and manufactured
  
  
• Easy installation
  
  
• High hardware reliablity
  
  
• Reliable operation - no PC 'software' crashes
  
  
• Well designed systems give higher machine performance for the same price
  
  
• Meets high "Machine Safety" regulations.
  
  
• Single source procurement and support - Responsibility path is clear, the system supplier is responsible
  
  
• Low "Total" lifetime cost
  
  
• Compact enclosure holds all components
  
  
• Easy maintenance - modules or complete controller can be easily shipped for repair
  
  
• Less component distribution, fewer sub systems to connect and integrate
  
  
• System does not rely on software operating systems
  
  

Disadvantages:

• Control panels are very inflexible -
  
  
• In low volume special applications standard control panels are unsuitableŘ In low volume special applications standard control panels are unsuitable
  
  
• Control panels may use languages that are not understood by the machine user
  
  
• Custom control panels and supporting software is very expensive
  
  
• For single enclosure integrated systems there is a limit on the size of drivers that fit into controller
  
  
• Front panel and menu structure can be complicated, especially if many applications can be supported
  
  
• Finite memory in the controller limits size of jobs that can be retained in memory
  
  
• Systems generally use proprietary operating systems making it difficult if not impossible to change system specification or customise system features
  
  
• Part program size may be limited by controller memory

Combination system: PC plus controller

Advantages:

• Provides most of the advantages of PC's without most of the disadvantages
  
  
• Provides most of the advantages of stand-alone controllers without most of the disadvantages
  
  
• Almost any PC can be used including desktops, laptops, and touchscreens
  
  
• With suitable 'virtual control panel generation software' password protected control panels can be produced to suit any application, any operator's skill level, and in any PC supported language
  
  
• Provided part programs can be streamed to the motion controller in the background their size is unlimited
  
  
• Usually there is no software to develop
  
  
• Support problems are minimised by using almost any PC which is readily replaced if it breaks
  
  
• System operation is far less dependant on the PC
  
  
• It is easier to integrate additional functions in the PC as more computing time is available when the machine control is implemented externally
  
  
• The timely operation of the PC and the PC operating system is far less critical, time critical operations are performed by the motion control
  
  
• If the motor drivers are external to the motion controller there is no motor/driver size or type limitation

Disadvantages:

• Applications are limited to those supported by the motion controller
  
  
• The virtual control panel software supplier must provide support for upgraded and new operating systems e.g. Windows XP