Rebuilding And Retrofitting Robots
By Mark Stephen, Managing EditorUmair Abdul, Assistant Editor
Shakespeare's Hamlet famously wondered whether it was better to be or not to be. When it comes to robots and automation, the question facing many of today's plastics processors looking to do more with...
Shakespeare’s Hamlet famously wondered whether it was better to be or not to be. When it comes to robots and automation, the question facing many of today’s plastics processors looking to do more with their machinery is whether it’s better to rebuild or not to rebuild. And while they’re pondering that question, here’s another, closely related: when does it make sense to retrofit older robots and automation with new controls?
For many plastics manufacturers, the rebuilding and /or retrofitting options have probably never seemed more plausible than right now. With large numbers of relatively inexpensive used robotic and automation equipment available at auction, the temptation to purchase a unit that’s almost-but-not-quite-right, with the idea that it can be tweaked to perfection, is strong. “Upgrading or retrofitting applications has become an option that a lot of our customers are requesting, as they try to avoid investing in new capital equipment,” said Brad Lemieux, sales manager with Yushin Automation representative En-Plas Inc. “Typically, they buy the standard off-the-shelf robotics not knowing what the future is going to bring, then upgrade as necessary.”
THE DOWNSIDE
There’s no mystery, of course, as to what processors want to accomplish. “Most customers want their robots to offer higher speeds and acceleration rates, better accuracy and repeatability, as well as capable of handling more payload,” said Bill Egert, vice president, engineering for Logic One Robots, a supplier of new and rebuilt robots. “For controls, they tend to want more user-friendly operator interface.”
But are rebuilding and retrofitting the right strategies to achieve these ends? Most importantly, when all the factors are considered, will the cost of rebuilding or retrofitting the equipment amount to the same — or more — than the price of a new unit?
According to robot and automation suppliers, the first question for processors considering a retrofit or rebuild to answer is whether the equipment is, from a mechanical point of view, even worth the effort. A good history of preventative maintenance for a robot or automation equipment doesn’t guarantee that a rebuild can be done, but it helps. “In theory, a robot can be 20 years old and still be cost-effective to rebuild if the mechanics are solid,” said Bill Egert.
A poor maintenance record, especially on an older machine, is usually the deciding factor in stopping a rebuild or retrofit project cold. “If the machine is in poor shape, usually because proper maintenance procedures haven’t been followed, we will advise a customer against trying to rebuild for that reason alone,” said Jim Healy, vice president of sales and marketing with automation manufacturer Sepro America Inc.
An obvious point, but often overlooked by processors, is that determining if a robot should be rebuilt is easier if the unit is actually operational. “It’s always simpler to evaluate the robot if it’s running, as opposed to sitting on a skid,” Healy continued.
If a robot or piece of automation equipment is in good working condition, other questions follow. “The company performing the rebuild or retrofit will want to know what the make and model are, what size press it’s on, and then application questions about what the customer wants the unit to do after it’s been rebuilt,” said Bill Egert.
According to Egert, a rebuilder might shy away from working on an unfamiliar make of machinery. “We don’t always know enough about the more obscure robot brands to proceed with a rebuild,” he said.
THE DOWNSIDE (CONTINUED)
Another hurdle involves the age of the machine. Indeed, age can be the decisive hurdle -at least from the rebuilder’s point of view, regardless of maintenance history. “If a robot was not built with at least a ten-year lifetime on the mechanics, it’s probably not worth rebuilding,” Egert said.
Key problems in rebuilding older equipment are the availability and cost of spare parts. “Most robot and automation manufacturers maintain an inventory of spare parts for older models and, once depleted, can be expensive to have custom manufactured,” said Christian Weiss, technical sales, robots and automation at equipment manufacturer Wittmann Canada Inc. “On the controls side, for example, it’s not always possible to make a new controller work on an older system because older systems are not always backwards-compatible.”
Assuming spare parts are available and not prohibitively expensive, the focus may shift to whether the rebuild or retrofit is cost-effective in the larger sense. According to Bill Egert, a full rebuild of an older robot with new motors and servo drives can cost up to US$35,000, a total that approaches the cost of some new units. “Because newer robots have decreased greatly in price, and the technology in the drives and controls has improved substantially, there may actually be no cost benefit to retrofitting or rebuilding as opposed to simply buying new equipment,” said Christian Weiss.
Indeed, according to some automation providers, substantial rebuilds of older machines are invariably too expensive. “If a robot requires a significant rebuild, it’s almost never a good idea,” said Joe Corturillo, engineering manager at Wittmann Canada.
“If a processor is trying to increase the robot’s vertical stroke, for example, they’re probably looking at an investment almost equal to the cost of a new robot.”
Rebuilds, in particular, often have hidden costs and inconveniences, as well. “If the decision is made to go ahead with a rebuild, the robot usually has to be taken off the press and shipped to the rebuilder’s facility,” said Jim Healy. “This translates into cost of freight back and forth, as well as a good deal of machine downtime.”
THE UPSIDE
Given these factors, is a rebuild or a retrofit ever a good idea? Under certain conditions, suppliers say, the answer is yes. “Rebuilds can be cost-effective on larger tonnage machines performing pick and place operations, where cycle times are not as critical, and we’ve performed these rebuilds successfully in the past,” said Jim Healy. “Generally speaking, the larger the robot is, the more cost-effective it can be to rebuild.”
On the retrofit side, most robots that are less than five years old still have functional controls, and thus can be retrofitted to perform some additional operations without too much trouble or expense, according to Joe Corturillo.
Within these parameters, there are real benefits to be gained by rebuilding or retrofitting robots and automation units. “Many processors have modified their robots to have more vacuum systems and gripper circuits, allowing them to pick and place multiple products and package or separate cavities in quality control situations,” said Brad Lemieux.
Also, rebuilding robots or retro fitting with servo motors can increase speed by 100 per cent or more while improving repeatability from 2-3 mm to 0.25 mm, according to Bill Egert. “Servo controls can also increase payload capacity, and improve low-speed jogging and motion with smoother, more repeatable stepping,” he said. “New servo controls offer many special features that allow for better in-mold and post-mold operations, increasing the number of jobs that can run on a press.”
When retrofitting controls, Egert advised, processors should be wary of using displays that overload the system with information, display excessive messaging, and have a tendency to lock up.
In the end, if the decision is made to rebuild or retrofit either a robot or piece of automation equipment, equipment suppli-ers stress the importance of involving them in the process. “The danger in trying to rebuild robots without professional help is that robotics gives you the perfect chance to fail, because it combines mechanics, electronics, and software, and also interfaces with the injection molding machine, mold, downstream equipment, production workers, and setup and maintenance technicians,” said Bill Egert. “Unlike
a passive machine that sits in a corner performing a simple function, an automation system basically takes the place of a person on the production floor for up to 24 hours a day.” CPL
RESOURCE LIST
En-Plas Inc. (Toronto);
416-286-3030
Logic One Robots (Addison, Ill.);
Sepro America (Pittsburgh, Pa.);
412-459-0450
Shadow Automation Inc. (Uxbridge, Ont.);
905-649-2652
Wittmann Canada Inc. (Richmond Hill, Ont.);
888-466-8266
Anplast Inc. (Anjou, Que.);
1-800-387-4590
In dire economic times like these, an inefficient operation is every processor’s worst nightmare. Unfortunately, however, many companies are also finding their budgets constrained in leaner times, and many have had to cut back on the amount they spend to maintain their plant’s equipment.
There was a time, and it’s still true today, where everybody had their own maintenance crews who would maintain their equipment,” noted technical support manager Bill Collis of Universal Dynamics Inc. “I think gradually we have been seeing a trend where people are getting rid of their maintenance crews.”
When it comes to dryers, suppliers note that downtime or inefficient drying often boils down to poor or improper maintenance. A few quick and easy preventative maintenance steps can help ensure that your drying system is running optimally, or help identify inefficiencies in your drying process.
“Typically, processors don’t even touch the dryer until they have a problem with a part, and then they start to investigate,” explained Joe Corturillo, engineering manager for Wittmann Canada.
Here are a few pointers to stay ahead of the curve, and avoid any unpleasant surprises when it comes to your dryers.
Check and replace your filters. Most suppliers identify poorly maintained filters as the number one culprit for drying inefficiencies. “This is often the primary cause of poor drying said Charles Sears, president of Dri-Air Industries, Inc. “Not only does it affect the dryer performance, but without adequate air flow, the material will not heat up to the proper drying temperature.”
Equipment manufacturers advise that you regularly inspect the process and regeneration filters, and clean or replace them if necessary. Suppliers note that some processors don’t even use regeneration filters on their machines.
“Some people think regeneration filters are not important, but in many of these plants you have dryers and grinders next to the machine, and sometimes these grinders generate a lot of dust,” said engineering manager Kalhan Tavakoli of Universal Dynamics. “When the plastic dust gets pulled into the regeneration system, the plastic dust melts and fuses itself to the desiccant.”
Maguire Canada’s Brian Davis explains that the regeneration filters on Novatech dryers are exposed to avoid this “out of sight, out of mind” mentality.
How often should you check your filters? It depends on who you ask, but it can also depend on the material you are running through the machine.
“If the material is dusty, has an additive in it, or has a plasticizer in it, you may have to clean the filter every shift,” said Dri-Air’s Sears.
Check your dew point. If your machine is not already equipped with a dew point meter, portable ones can be purchased for periodic checks of dew point levels. One supplier compared being without a dew point meter to operating an automobile without a speedometer.
“If you’ve got a bad dew point, your first line of defense is to check the desiccant,” said Maguire Canada’s Davis.
Davis also recommends that processors check their desiccant once a month, which is relatively easy to do with a beaker test.
Check for ambient air leaks. Suppliers also recommend that plant managers check their equipment for any leaks that may let ambient into the process, affecting the air flow and pressure in the system.
“It’s supposed to be a closed system, and if you’re bringing ambient air into it, you are reducing the efficiency,” said Maguire’s Davis.
Wipers and seals should be checked and not allowed to degrade. Brad Lemieux, sales manager at En-Plas Inc., also recommends that processors check for leaks at the hopper -most commonly the lid or access door of the hopper -or for leaks inside the dryer (bed seals, hoses and heater boxes) if the machine isn’t maintaining dew point.
Additionally, Jamie Jamison, product manager for dryers at The Conair Group, recommends that operators check all the hosing to ensure that there are no cracks or holes letting air into the process.
“Collapsed air hoses will reduce air flow and compromise dryer performance,” said Jamison. “Frayed or damaged hoses may draw wet ambient air into the closed-loop drying circuit, causing premature desiccant loading and resulting in high dew points.”
With larger dryers, Universal Dynamics also suggests that customers ensure they are using proper ducting made for the pressure the system will be under.
“Seamless ducting is important in large dryers for maintaining pressure,” said Collis “We find that people think that normal house ducting will be sufficient, but it doesn’t get you there.”
Check your air temperature. If you’ve made sure your filters and hoses are clean and in good shape, but notice that material is still not drying properly, check your drying air temperature. The drying air temperature should be monitored and controlled at the inlet of the hopper rather than at the dryer outlet, and the sensor should be positioned in the center of the air duct to prevent false readings.
“A low drying temperature at the hopper inlet may be caused by something as simple as an improperly adjusted controller, or something a little more sinister like failure of heater elements, heater contractor, thermocouple or controller,” said Conair’s Jamison.
Check your heaters. “When you check heaters, you are checking for continuity, to make sure you don’t have any breaks in the heating element,” said Wittmann’s Corturillo. “As long as the heater is producing the air temperature that is required for regeneration, you are usually fine.”
According to Sears at Dri-Air, heaters can fail at any time and greatly affect the operation of the dryer.
“Also, fuses and relays to control the heaters can fail, making the dryer ineffective,” said Sears. “It is easy to spot a failed process heater but the failure of regeneration heaters are not apparent until the dew point is affected and defective parts are molded.”
Sears adds that some newer dryer models include circuitry to check the status of the heaters, but circuitry is not easy to add to an existing dryer.
Although these steps seem simple enough, they will go a long way in helping you ensure that your dryer runs efficiently and provide early warning signs if problems do arise. You should also follow your manufacturer’s specifications, contact a representative and use the maintenance schedule checklist on pg. 10.
CPL
RESOURCE LIST
Conair (Cranberry Township, Penn.); www.conairnet.com;800-654-6661
Hamilton Avtec Inc.(Mississauga, Ont.); www.hamiltonavtec.com;905-568-1133
Dri-Air Industries, Inc. (Windsor, Conn.); www.dri-air.com;860-627-5110
Plastics Machinery Inc. (Newmarket, Ont.); www.pmiplastics.com;905-895-5054
Maguire Canada Inc. (Vaughan, Ont.); www.maguirecanada.com;866-441-8409
Motan Inc. (Plainwell
, Mich.); www.motan.com;269-685-1050
Dier International Plastics Inc. (Unionville, Ont.);
905-474-9874
Thoreson-McCosh Inc. (Troy, Mich.); www.thoresonmccosh.com;248-362-0960
Universal Dynamics, Inc. (Woodbridge, Va.); www.unadyn.com;703-490-7000
Resource Polytec Inc. (Vancouver, B. C.); www.resourcepolytec.com;604-454-1295
Wittmann Canada Inc. (Richmond Hill, Ont.); www.wittmann-canada.com;888-466-8266
Anplast Inc. (Anjou, Que.); 1-800-387-4590
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Buyer Beware: Auctions
With the recent wave of consolidation in the industry, there has been a glut of used equipment in the market, with new auctions taking place on an almost weekly basis. But according to major suppliers, buying a dryer off the auction block may be more trouble than it’s worth.
Buying a dryer on auction is not the same as buying a second-hand dryer, because you can’t test auctioned equipment before buying it.
“At an auction, you can’t plug the dryer in,” noted Brian Davis at Maguire Canada. “Also, you don’t know how well it’s been maintained.”
Davis points to one major processor that went under last year and had its capital equipment auctioned off. He notes, however, that the company had had to cut its entire maintenance budgets eight months before it went under.
When a processor purchases a piece of used equipment from a supplier or distributor, the “buyer beware” is often taken out of the equation.
“We completely check over every used piece of equipment we sell and either completely refurbish the unit so it runs and looks like new or at the very minimum give the customer a checklist of potential concerns,” noted Brad Lemieux at En-Plas Inc.
If purchasing drying equipment at an auction, customers should try to check seals, filters and hoses to get a sense of the dryer’s maintenance record. Additionally, make sure that the cabinet control wiring is intact, and look for warning signs like rusted out boxes.
“The very least a person can do at an auction is check the quality of the steel,” said Davis. “That way, you will at least get a good shell.”
Suppliers also advise potential buyers to do their research before going to the auction, noting that dryers are often sized and engineered for a very specific application.
Once the equipment has been purchased, you want to clean up the dryer, including the hopper, and replace the filters and the desiccant.
“With the seals, go through and check if they are pliable and soft because you don’t want to start with air leaks,” said Corturillo.
Additionally, manufacturers also warn that equipment on the auction block can often be older, and savings on the sticker price may be lost when running the equipment at your plant.
“When you are buying an older product, you know it’s not the newest technology,” said Corturillo. “So odds are it’s not as efficient as the technology available today.”
