Robotic Paint Automation for Smaller Industrial Operations
by Mark Freels
, Paint Business Development Manager, Robotics Division
ABB Inc. Posted 11/03/2008
Recent advancements have made paint and coating robots highly affordable and useable
Painting robots and industrial robots in general have a reputation of only being affordable to the largest and most technologically adept companies. Today’s reality, however, is far different as robots of all kinds are now highly viable for a full range of smaller, general industrial markets and applications. Robots, like other computer based equipment, become more affordable as the installed base grows. And with today’s industrial employee base having at least a working knowledge of graphical user interface (GUI), the ability to program and control robots has become more intuitive and user friendly for the novice programmer.
The 6-axis robot is a mature, stable product, the primary R&D costs of which have been well absorbed by the manufacturers and early adopters. Painting and coating robots are now positioned to help general industrial users increase competitiveness, product quality and workman safety, all while reducing the environmental impact associated with spraying many coating materials.
This article will help answer:
- What is a painting and coating robot?
- Is your factory a good candidate for robotic paint automation?
- If so, what advantages will automation bring to your operation?
What is a painting and coating robot?
“Painting Robot” is an industry term for a robot that has two major differences from all other standard industrial robots:
1) Explosion proof arms. Paint robots are built with explosion proof robot arms, meaning that they are manufactured in such a way that they can safely spray coatings that create combustible gasses. Usually these coatings are solvent based paints which, when applied, create an environment that must be monitored for fire safety.
There are several ways robot and applicator manufacturers maintain spark proof integrity in the spray environment. Positive pressure and intrinsically safe electronics are the two most common.
Terms such as ‘explosion proof’ can be a little startling to a paint robot novice. But, as an example of how safe automated paint systems are, all production model cars are painted with robotic automation!
For more specific information defining explosion proof environments see National Fire Protection Association code NFPA 33.
2) Self-contained paint systems. When paint robots were first designed, they only had one function – to work safely in a volatile environment. As acceptance and use expanded, painting robots grew into a unique subset of industrial robots, not just a traditional robot with explosion proof options. Painting robots now have the ability to control all aspects of spray parameters. Fan air, atomization air, fluid flow, voltage, etc, can all be controlled by the robot control system.
Is your factory a good candidate for robotic paint automation?
There are several limiting factors to robotic painting:
- Part presentation
- Amount of dissimilar parts
- Size and shape of the parts
Part presentation: Robotic coating does not require the highly accurate part presentation as more technical robotic applications such as arc welding and machining. Painting applicators usually require a tip to part distance of 10 to 14 inches. The more accurately a production conveyance presents a part to the robot, the more benefit of quality and material savings can be achieved. An industry standard request of part presentation can be assumed at 0.25 to 0.5 inches. The importance of tolerance will vary depending on the quality of finish required and cost of coating (material savings). For most standard applications a simple two hook part placement versus a single point hook provides enough stability to make robotic paint automation accurate and affordable.
Amount of dissimilar parts: Robots are very effective in a variety of painting systems; from those that involve only few parts to those that involve many hundreds of different parts. The primary environment where robots are not effective is in ‘job shop’ applications. An engineered piece that will be manufactured one time and never again is not a good candidate. Parts that will be manufactured over and over, even with major time gaps (months/years) between runs can be easily coated with today’s robotic technology. The robot memory will store part specific programs indefinitely and call for them when required.
Size and shape of the parts: A good rule of thumb is that if a man can paint a part there is a robot that can reach the same area. In certain applications, however, the size or shape of part is so unique that both man and robot may struggle to reach all surface areas. Other Limiting factors include:
- Very small parts: often the work is too fine to be done by hand or robot; some other process such as dipping will be more effective.
- Very large parts: the robot will need to be moved by additional track systems and extensions to reach all areas; often not viable for a smaller industrial operation.
What advantages will automation bring to your operation?
Quality and paint savings: Increased and more consistent product quality are the most widely regarded advantages gained by robotic automation of all types. For painting and coating robots the most complete analysis must dig deeper as the quality improvement cascades through the entire production system.
An industry standard assumption is that a paint savings of 15 to 30% is achieved when manual painters are replaced by automation. This savings is achieved in two primary areas:
- Film thickness tolerances of ± 0.2 mils are common with robotics. If a substrate requires 2 mils ± 0.2 and is regularly produced by hand at 3 mils a paint ‘loss’ of 50% can hit the producer with no knowledge of the additional expense. If the manual sprayer applies below minimum (e.g. 1.6 mils) the part will need to go through the system again or be scrapped. It is much more common to see the overspray situation because that will make it through inspection and need no rework.
- Trigger accuracy is the other major quality and savings impact. Industry standards of less than 200 ms trigger time are common. This allows the user to only apply paint to the part. When the applicator is repositioning the paint supply trigger is off, minimizing paint loss due to paint sprayed randomly into the air.
Savings achieved through film thickness tolerance control and trigger accuracy will relate directly to many other savings:
- Exhaust: Tolerance control/trigger accuracy directly reduces stack volatile organic compounds (VOC) volumes.
- Overspray: Reductions go directly to less filter usage or chemical usage with water wash booth.
- Reduced rework: Problems such as sags and modeling should be reduced.
- Reduced scrap: Less material to landfill.
GREEN is good: Paint robots have always been environmentally friendly. It is becoming obvious that carbon footprint impact will soon be the baseline for a good community employer, if not legally measured. When using robots there are the environmental savings already discussed, plus additional energy savings that are to be gained.
Example: a 10’x10’ spray booth at 120 FPM air flow is using 12,000 cfm to provide a safe work space for manual sprayers. If a robot is installed and air flow is reduced to 60 fpm, to maintain legal lower explosive limits (LEL), the user can immediately see a 6000 CFM savings. Again the savings start to cascade - a softer spray pattern using less paint flow volume is possible because of the lower air flow velocity, equaling more paint savings, less VOC exhaust, etc.
People first: All savings aside, many paint spray environments are very unfriendly to the workmen who occupy them. Chemicals such as Zylene, Toluene, and Diisocyanates are extremely unhealthy. Spraying the same product over and over can also result in a repetitive stress injury. Many employees initially see robots as a threat to their employment. In the case of many spray chemistry situations, the benefits of moving the robot in and the person out far outstrip the disadvantages. In most cases the employee is moved to a safer, more rewarding position.
While it is difficult to completely assess the installed cost for all industrial painting situations, as an example, a single ABB robot painting system can be purchased, installed and be fully operational for $100,000 to $150,000. The cost range is dependent on the size of the robot needed. Depending on paint usage, labor savings and increased quality/less waste, the full investment can be paid back between four months and one year. A well maintained paint robot can last for a long time, delivering savings that cover the cost of the system many times over!
The robot can be a great tool, but it is only a tool. The most common mistake is assuming that the robot is a paint expert. It is not. The expertise comes from support staff who keep the robot calibrated and at optimum functionality. With the combination of well trained staff and maintained robots, it will be very possible to increase quality and throughput while reducing cost and being a better corporate citizen.
Please contact Mandy Hermes at ABB Inc. Auburn Hills MI for additional information.
Call 248-391-8400 or visit www.abb.com/robotics.