The following is re-post found on the CAMWorks web site.

When I decided to write this blog, one guideline I made for myself is that the content would stay focused on technical trends and information and not become a forum for marketing and sales.  While the tone of this topic may sound like a sales promotion, it is not intended to be.  As many of you may be aware, Geometric recently released a new full machine tool simulation solution for CAMWorks.  This new simulation solution is the result of several years of strategizing, planning and developing.
What was wrong with the current simulation product that so much time and effort was spent to create an entirely new product?    The simple answer is that the new simulator offering has the ability to read and interpret G-code to drive the simulated machine motion.  This feature is not new to machine simulation. So, what makes Geometric’s new G-code simulator different and why is it important?
While the new CAMWorks machine simulator and other leading standalone simulator products are alike in that they process G-code, integrated machine simulator products offered by pretty much all CAM products read and process a neutral form of CL data.   This is a significant difference.  For anyone who has written or edited G-code manually you know it is not only critical to have the correct X,Y,Z and rotary axis values correct but also the proper use and format of G and M codes.   While the CL data that is generated from CAM systems do output accurate axis values, they do not provide CL statements for all G-codes available to a machine tool control.  This difference could prove disastrous on the shop floor if the integrated simulator is missing machine motion commands that are present in the G-code run on the machine tool.  In cases like this, the integrated simulator may show a safe and valid machine run but when the actual G-code is run on the machine, these missing codes could result in a costly collision.  A simple example may be that post logic is applied that outputs a parts catcher sequence after some predetermined conditions in the post processor.   When the G-code is read by the actual machine the parts catcher would activate but the CL data that is read by the CL machine simulator would not have enough information to emulate the parts catcher.
Similar example would be the ability of true G-code simulation to address sub-programs that will not be available in CL data simulation. If an uncommon CNC programming sequence occurs and the post processor logic has not been previously tested or if the G-code is manually modified for some reason, a simulator that processes G-code could help catch a mistake before it reaches the machine tool.  For machine simulators that take CL data as input, a potential problem may not be detected.
Does this mean that CL based simulators should not be used?  My opinion is that there are valid situations for their use.  First, if the machine environment is not overly complex, CL based simulation does deliver a consistently reliable result.  Second, depending on how the CL based simulator is integrated into the CAM system, the setup and simulation time may be faster than G-code based simulators.  Third, the cost of the CL based simulator is typically much less than G-code based simulators.
In the last couple releases of CAMWorks, Geometric has added significant new features and abilities to provide CNC programing for complex multifunction machine tools that are becoming more and more common in manufacturing.  The G-code programs that drive these machines can be very complex and catching these errors on a G-code based simulator becomes increasingly valuable to answering the big question “Will the G-code program run safely and efficiently on the machine tool it was written for”?   What sets the new CAMWorks G-code simulator apart from other simulators is that it provides the option of processing either G-code or CL data with the ease and simplicity of starting a simulation session offered by being integrated with CAMWorks.  When you consider that the CAMWorks G-code version is about half the cost of standalone G-code simulation products, the value is difficult to ignore.