Large part automation: a holistic approach
- June 2, 2015
Automation starts with specific manufacturing goals that must be realistic, achievable and well defined. Most importantly, they set the groundwork to effectively determine the appropriate level of automation needed as well as which jobs and/or operations would benefit most if automated.
Defined goals, especially when processing large workpieces, also dictate whether to automate part and/or tool handling, since both can involve significantly heavy loads. Shops must then decide if some type of connectivity and monitoring is needed. They must also take certain steps to ensure the automation has all it needs to truly run unattended and lights out.
Plan for automation
Ideally, shops should plan for automation at the time of machine acquisition. Machines equipped and configured for automation early on can save time and the cost of having to retrofit after the fact. Such automation preparedness can simply be automatic doors, built-in robot interfaces and any other necessary options such as larger tooling capacities and special workholding systems. Or, if future automation needs are uncertain, shops can opt for those machines that make adding automation as easy and inexpensive as possible.
Determine the appropriate level of automation Various degrees of automation range from a simple hydraulic assist lifting system or a conveyor belt with vision sensors to barfeeders, gantry loaders, articulated robots and palletized systems. While all these apply to small and medium-sized parts, large parts tend to narrow the choices to the hydraulic assist lifting, beefy two axis gantries (spanning over one or multiple machines) and robots (either stationary or on a rail system).
Choose the ideal jobs for automation
Part weight, amount of part variations and batch/lot sizes are key considerations when evaluating what jobs to automate. The ideal scenario is high-volume-per-year jobs produced in low-to-medium-volume re-occurring batches at scheduled intervals. These batches should also have as little variation–in terms of part size, processes and features–between part numbers as possible.
Small batch sizes of very different part numbers would be inefficient and costly in terms of automation. This is because job changeovers must be kept to a low minimum, and workflow should be such that automated cells run and produce as long as possible between necessary job changeovers.
Big parts need big automation
In addition to large-scale automation, big parts require much more careful thought as to how they are presented when loaded and unloaded from a machine tool.
Also, simple fixturing with large parts eliminates having to maneuver them around into complex setups. So, shops should avoid multiple sequencing where parts are clamped and unclamped numerous times during processing. However, the end of arm tooling on either articulated or gantry robots can be as simple or as complex as needed to efficiently load and unload parts. And again, workpiece size, weight and shape will dictate the best tooling.
Consider up and downstream operations Machining cycle times tend to be a bit longer with large parts, so shops must give careful thought to upstream and downstream processes.
Could, for instance, a robot perform other tasks within those peripheral processes while parts are being machined? And with that, will giving the robot additional duties require that it rides on rails or travels overhead to serve those other processes and pieces of equipment? Or, could the robot tend several of the same types of machine tools running similar parts? And will there ever be a need to take automation off line to manually run occasional small lot size jobs? The answers to these questions will inevitably help further maximize automation utilization and help justify its cost.
Move more than just parts
Tooling (cutters and holders together) for large part machining can be heavy, so shops should consider using automation to also transport tooling where needed. Robots could also change fixturing–such as chuck faceplates or machining centre fixture plates–to accommodate a wider range of parts, while also automating the fixture changing process.
Keep an eye on automation
Cell controllers together with advanced connectivity, such as through MTConnect, provide the capability to run automated operations from one common location and communicate with all the equipment and devices involved. These networks can also communicate any problems occurring within the cell and provide a channel for OEMs to log in remotely for system troubleshooting/diagnostics and lend any other needed assistance.
Prepare for true lights-out automated operations
Having enough parts in queue and stationed within reach of the automation is critical, especially when running multiple short cycle time jobs. There must also be enough space for staging the raw parts and storing them once finished. Sufficient tool storage capacity is also needed, as are efficient chip evacuation and coolant level maintenance.
Assign automation ownership
Shops should designate a person or persons, at the shop floor level, as the lead or champion of an automated system or cell. This in-house person would attend all necessary OEM training sessions and be responsible for any system part additions or changes in terms of new programs and setups.SMT
by: Jason Fights, assistant engineering manager of sales and engineering.
Paul Robinson, engineering manager of sales engineering.
Rob Vieth, automation project engineer, Mazak Automation Systems.