Automating and integrating CADCAM into shopfloor data systems (MRP)
Many companies will comfortably spend a five or six figure sum on a Production Control software (MRP) system but find a black hole of invisibility of jobs that enter their CAM system. Management or Sales unsuccessfully trying to obtain information on the status of an order, other departments trying to locate parts that possibly have not even been programmed yet into CAM system etc. These are day-to-day occurrences for many manufacturers. Perhaps you’re one of them, or are just about to take the plunge into shop floor data management. Find out the common pitfalls and how to avoid them.
This article was provided on a geographically exclusive basis to several technical trade magazines worldwide in the sheet metal fabrication and aerospace/composite industries.
CNC programming and nesting for cutting of sheet or roll-based materials differs from other manufacturing processes as a nest of components cut say on a laser, waterjet, knife cutting or punch press machine can contain many parts spanning many orders. Compare that with milling or turning where orders are generally made on a per-part basis and you begin to see the problem. The usual scenario is that orders are placed into an MRP system, material is ordered, orders are printed and physically sent to manufacturing for CNC programming and production. Here the CNC programmer needs to interpret the paper order for each component, locate correct CAD drawing (geometry) for it, import it into his CAM system and prepare it for nesting. To maximise material and processing efficiencies, forward looking companies will employ powerful ‘free form’ nesting systems, which by default, produce best results when given a mix of components of various sizes. To achieve this, orders have to be consolidated. This however, presents a number of problems – to start with, every component ordered and its manufacturing information has to be entered into the ‘order’ list of the nesting system. If production orders arrive on paper, this obviously is a time consuming and error prone manual task. Secondly, to maintain any visibility over production, management (and often sales), need real-time feedback from the shopfloor. Again, with the above scenario this can only be achieved by manually entering relevant CAM and shopfloor information, this time into the MRP system. There are also other problems, ie. maintaining reliable component/material traceability, etc.
Full automation – the Holy Grail
Ideally, your CAM system should communicate directly with your MRP system, automatically fulfil any orders received from it and immediately report back on the actions executed and results obtained. This means that there must be a direct and automatic link between these two systems. However, to achieve full automation, the CAM system must also be able to locate the component geometry files associated with the order, apply tooling or profiling to them, nest all parts for a given material, thickness and CNC machine, generate correct CNC code and report back to the MRP that this has been done – all without human intervention. Although such a level of automation is seen by some as prohibitively expensive, it is simple to justify such an investment if you can quantify the time you are currently spending to manually perform these tasks. Return on investment is often measured in months or even weeks, not years.
Of course, a chain is only as strong as its weakest link, and if the CAM system cannot perform above tasks well and without error, then you may end up spending more time fixing problems than what you tried to save in the first place.
What you need for Full Automation
If you decide to opt for full automation then you need a CAM system which is able to deliver such automation (while being able to support all of your CNC machines) and can also seamlessly communicate with your MRP system. That is, it should be able to understand commands from the MRP system and send back relevant information in a format the MRP system can understand. As in majority of cases each system will have its own (and incompatible) databases, a special translation module will need to be implemented to facilitate a link between these two systems.
Finding a happy medium for your business
There are companies which either cannot justify such an outlay, or feel that their business is not suited to full automation. However, they can still take advantage of automatic communication link between their MRP and CAM systems and go for lesser automation on the CAM side (with the right CAM vendors you should be able to upgrade your CAM system at any time in the future to make it more or even fully automatic). Let’s take a look at each element of the CAM and nesting process, the problems often faced and what you should look for to overcome them:
CAD import: Many CAM systems will provide the ability to either draw components or import from popular CAD systems. Importing files often brings problems due to the quality of the CAD file. For example lines may not be joined or arcs may not be ‘true arcs’, instead comprising of dozens or even hundreds of short lines segments. Some higher end CAM systems will be able to ‘clean’ such CAD files within predefined tolerances, saving a considerable amount of time. The part is then ready to apply tooling or profiling information.
Tooling/profiling the part: Some CAM systems apply tooling/profiling information to parts on the nest, however this can create significant problems, especially if one or more parts are changed or need to be made on another machine. If tooling information is stored within the component file then tolling information for every available machine can be stored, making the part available for automatic nesting at any time and on any machine without any further considerations.
Sequencing and simulation: Very often what appears to be the optimum cutting path does not take into account manufacturing constraints, such as parts that may become loose as the sheet becomes more structurally unstable. Being able to either manually or automatically apply logic to the cutting order of general and finishing cuts that separate the parts from the sheet, or apply unloading or tagging commands depending on part orientation can make the difference between a job that can run unmanned and one that requires constant attention or, worse still, can damage parts or the machine itself.
Nesting: This is the area that can yield the most immediate savings if automated correctly. An efficient nesting engine will be able to take into account individual part characteristics that must be applied, such as nesting at restricted angles, or if they should be nested with other components. The ability to specify ‘filler parts’ is also useful, allowing you to utilise otherwise wasted material for frequently used components.
CNC code generation: The reason you have a CAM system is to generate CNC code, and while your system may have all of the bells and whistles up to the point of code generation, if it cannot make accurate CNC program using a reliable postprocessor then it defeats the object. Ensure that your CAM system has a tried and tested postprocessor(s) to support all of the required features of your machine(s).
Reporting: Your CAM system’s ability to report back to MRP on each job’s status completes the circle. This will either be a case of CAM updating files within the MRP system, or the MRP reading updates from within the CAM system. This will consist of information such as material used, actual material utilization, parts created, material used per part, material/parts scrapped, estimated processing time, etc.
Although the initial aim of a CAM system is to automate the generation of NC code as much as possible rather than writing it by hand, there are many more processes where human intervention is not necessarily required. Is your programming department currently automating all of the areas it could? By breaking down each stage of the process you can get a much clearer picture of where improvements could be made. Once any initial costs have been recouped, which can often be over a much shorter period then you may think, then your company can enjoy the additional and ongoing profits.
For more information visit www.jetcam.com.