How to Avoid the 6 Most Common Pitfalls of Robotic Palletizing System Startups
Ollie Langhorst | 07 June 2018
“Garbage in, garbage out.” This well-known phrase from the computer science industry is worth considering when it comes to automated material handling. As it applies to robotic palletizing systems, the system outputs, particularly built pallet quality and throughput rates, are directly tied to the quality of the system inputs. So, whether building a new plant or retrofitting your existing one, if your system will include a robotic palletizer, there will be much to plan for to ensure a smooth startup. Two major aspects that can get overlooked, yet negatively affect the startup process of new robotic palletizers, include poor system input quality and lack of available resources during startup. By considering the following points, your firm may be in a stronger position to avoid the scheduling headaches, unforeseen costs, and timeline impacts that poor commissioning phase planning can cause.
1. Product Quality
Dimension Variance The first thing to consider when it comes to system inputs is product dimension variance. Uline, one of North Americas larger cardboard box suppliers, states that for box dimensions, “acceptable manufacturing variance is ± 1/8.” However, the engineers designing your robotic palletizing system’s End of Arm Tool (EoAT) will base their design on the listed case dimensions and tolerances agreed to in the Functional Scope Document (FSD). Even with an innovative and robust EoAT design, the commissioning team will likely struggle if your cases are outside of the agreed upon tolerances. For example, if a relatively large number of cases are being picked at once, and many of the cases have dimensions that are out of spec, then the EoAT may not engage with the pick as designed. This can result in dropped products, or worse, crushed product during placement. While it may be possible to correct this with some fancy program changes, chances are hardware changes will be in order, and this could even mean a tool re-design. Imagine the delays that could be caused if commissioning has to swap out hardware because the cases aren’t the right size. So, be sure to verify that the cases being provided to the robot cell are what was specified in your signed FSD.
Case Geometry Another aspect of product quality worth mentioning is case geometry. If the robotic palletizing system will be handling cardboard cases, then it would be wise to have your firm’s case erectors tuned up before commissioning begins. One commonly seen issue with built cardboard cases is when a case should be a rectangular prism, but instead is formed into an oblique rectangular prism. In other words, the top and bottom of the case is shaped like a parallelogram instead of a rectangle. Irregularly shaped cases can cause the material handling system to interact poorly with the product. For example, the relative length of a row of cases may change considerably if many cases are oddly shaped. Like with poor case dimensions, this can degrade the pick-place cycle. Again, a good commissioning engineer may be able to accommodate for this with programming changes. However, it is likely that the built pallet won’t look very neat, and some demanding end customers may view the quality of the built pallets as indicative of the product quality. To avoid potentially increased cycle times and reduced quality of your built pallets, make sure that your cases are correctly shaped. Crowning and bulging, whether on the top, bottom, or sides of cases, can also be challenging for a commissioning engineer or team to accommodate. Bulging typically happens from over packing a case, but crowning can also occur as a function of cardboard thickness, relative humidity in the cardboard, and the number of perforations per unit length along flap folds. Even if case flaps aren’t perforated, press scores that aren’t deep enough can also cause flaps to tend to spring back to their unfolded state. In relatively long cases, this can lead to an almost football like shape. Crowned cases make built loads increasingly unstable as the height of the load increases. In turn, the built load may require reduced conveyance velocities and accelerations or tier sheets between layers, ultimately impacting cycle times and project costs. At worst, load instability may even mean the built loads aren’t conveyable. Finally, just like with case dimensions that are out of specification, odd case geometry can cause product drops, which will impact the system’s throughput. Though you may have to spend some extra time working with your case vendor, taking the time to dial in case geometry and dimensional variance is an investment worth making.
2. Pallet Quality
Pallet management may seem low on the list of things to consider during a system startup, but with an automated robotic palletizing system, a certain amount of care must be taken for the typical pallet dispenser to work correctly. For instance, pallets that are stored outside are likely to get wet at some point from the weather. Wet pallets can stick together, especially if temperatures drop below freezing.
Pallet Dispenser Issues Typical automatic pallet dispensers are designed under the assumption that each pallet can move independent of the others. Frozen pallets can stick together, but so can ones that have excessively damaged boards, or protruding nail heads. And if the pallets stick together, it’s likely that the pallet dispenser will be destroying pallets, instead of dispensing them. By designating a space near the pallet dispenser where pallets can be brought to dry out for a day before being put into use, you will help ensure that useable pallets are available for running the system when needed. Of course, staging pallets near the system may need to be added to a line operator’s start or end of shift responsibilities, and don’t forget to remind your forklift drivers that they will have to load the pallets into the dispenser as needed.
Pallet Size Variance Despite the lack of a globally accepted set of pallet dimension tolerances, section 6.2 of the Uniform Standard for Wood Pallets as set forth by the NWPCA is a common guide used in North America. However, as with case size variance, the FSD will act as the final say in what the system’s engineers design to. Just as moisture can cause them to stick together, wet wood pallets can also potentially swell to dimensions outside of specified tolerances. But regardless of how it occurs, such variance, especially in pallet height, can affect the build quality of the pallet loads due to where the robot places the product. For example, if the pallet is shorter than the system was programmed for, then the product will be dropped from a height greater than normal causing the built pallet to look sloppy. Conversely, if the pallet is too tall, the product will be smashed down into it. What’s more, if the robot EoAT is designed so that the product is supported from underneath, then overly tall pallet heights may lead to crashing the EoAT into the pallet. Given the considerable cost increase of adding pallet height sensing to a system, most firms choose to opt out of this option. So, it would be prudent to ensure that your pallet supplier has provided your firm with quality pallets before the start of commissioning. However, if getting your supplier to do this is proving to be too much of a hassle, then consider this: Bastian Solutions has recently released a line of dimensionally stable, automation grade pallets. Using Bastian Solutions’ Rogue pallets can eliminate many of the headaches associated with pallet management, which is one less thing to slow down the commissioning process.
3. Quality of Other Inputs
Slip / Tier Sheets The basic robotic palletizing system will of course utilize product and pallets. However, there may be other inputs to the system worth having on hand and dialed in. Slip or tier sheets are common for many palletizing systems, so be sure to have enough of the correctly sized sheets available for startup. After all, the last thing you want to do is go digging in the back of your warehouse for them after commissioning has started. Also, the typical robotic palletizer running slip sheets requires relative sheet flatness. If the environment you plan on storing your slips sheets in will see drastic humidity changes, its nearly guaranteed they will warp, degrading system performance. Pallets of sheets stored in parked trailers are a great example of this scenario.
Print and Apply Machines Given the need for many manufactures to track product through the supply chain, label print and apply systems are another common item seen in automated material handling systems. If a third party, independent of the system integrator commissioning the robotic palletizer, is handling scanners and labels, make sure that those systems are dialed in. Poor adhesive quality on labels may mean that they accidentally peel off during conveyance, and dirty print heads can cause the location that labels are applied to on the cases to vary. These two issues can mean that product doesn’t get scanned correctly, further slowing down the commissioning process, and operations in general. Another label related point to consider: if your data management system doesn’t have all the label data preloaded, your timeline may slip. Just imagine what would happen if a label change required authorization from corporate, and the authorizing parties were on vacation!
Case Sealing and Stretch Wrapping A couple additional items worth dialing in before commissioning a robotic palletizing system are case sealing and stretch wrappers. Taping machines and type of tape need to be tuned up to minimize back-to-back cases, tape creases, and proper tape adhesion. If gluing cases, make sure that enough glue is being applied so that the bottoms of the cases won’t pop open due to accelerations seen by robotic handling. If your system is going to employ a stretch wrapper downstream of the robotic palletizing system, ensure that you have enough stretch wrap of sufficient strength in your facility to ensure that testing and production can run smoothly. Your system integrator should be able to recommend a quality stretch wrap if you aren’t sure which type to order.
4. Product Availability
While ensuring quality inputs to the system is important, perhaps equally important is having the necessary product available. Depending on your situation, it may be difficult or impossible to have production change product types without considerable advanced notice. So, it will be in your best interest to have all the SKUs you intend to run through the system available for testing. Otherwise, you may have to schedule your system integrator to commission the system in phases as product types become available. The obvious downside of doing this is the difficulty that rescheduling can entail. However, another aspect to consider is that highly complex systems tend to be tightly coupled, meaning that small changes to the system while testing one product type can affect how the system performs when running the others. So, to successfully commission a system in a timely manner, having all SKUs available is a major plus. Be sure to have sufficient quantity of the various products you will be running on hand to simulate actual production rates as well. After all, to meet the rates that high throughput systems run at, you will likely need more than a pallet or two worth of product handy. Finally, make sure that the product has been freshly packaged, as product that has been sitting in the back of a warehouse, or freezer, will give different results compared to recently run product.
5. Additional Staffing
It’s one thing to have enough product type for testing, but what about staffing? The typical commissioning process for a robotic palletizing system requires the commissioning engineer to make minor software and hardware tweaks. To do this, the engineer needs to have their eyes on the system while it is running. This can be difficult to impossible if the commissioning engineer must induct product into the system by hand, which can add unforeseen time to the startup schedule. Instead, consider designating an in-house system expert who can act as a liaison for managing the additional labor needed for testing. Plus, the in-house expert can shadow the commissioning engineer, learning valuable troubleshooting techniques along the way.
6. Odds and Ends
A few more items to consider as your firm moves towards the commissioning phase of a robotic palletizing system implementation.
Are the interlocks with upstream/downstream equipment in place? If not, will this impact the systems’ ability to run in a manner representative of full production? Do your end customers or other logistic requirements demand labels out on all the cases? Hitting the commissioning team with this requirement after the FSD’s ink is dry will likely require a change order at best, and if the system wasn’t originally designed for this requirement, throughput could be majorly impacted by the change.
Will employee turn-over potentially cause you to lose a shift system expert? Do you have the staffing needed to hand palletize while final tweaks are being made to the system? Answering these questions before the commissioning team gets onsite will help ensure that your go-live stays on schedule, which translates to money in the bank.
Here’s another one: does the commissioning team have access to all the necessary points of contact at your facility, including maintenance, shift leaders, designated system experts, fork truck drivers, etc.? A commissioning engineer could lose a half a day’s worth of testing or more trying to track down the right person needed to move the testing process along. If you are managing capital projects for your firm, why not create an SOP with pertinent site contact information, along with system, safety and training expectations. Providing this document to your system integrator before commissioning will help guarantee smoother communication and startups. Robotic palletizing does one thing very well, in that it accurately repeats each cycle. This requires repeatable product induction into the system, which hinges on the consistency of system inputs and ultimately dictates commissioning success or failure. Now, one could argue that many of the aforementioned issues should be caught before the system ever gets to the field. However, if the system inputs that are sent to the system integrator’s testing facility are not representative of what will be run at your facility, then the commissioning team will likely have to spend additional, unforeseen time tuning the system to accommodate those discrepancies, delaying your go-live date. If a chef is only as good as their ingredients, then it could be said that a commissioning engineer is only as good as the quality and availability of the resources needed to run the system. By working with an experienced system integrator, and making sure that you have done the necessary preparations suggested above, you will maximize the likelihood of a smooth startup for your new robotic palletizing system.
4/13/2020 08:15 PM
It is very informative. Thank you
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