Print and Apply – Five Essential Design Considerations
In my previous article titled “Automated Label Applicators – Is the ROI right for you?”, I explored major topics that need to be considered from the financial standpoint of the Print and Apply (P&A) system. Keeping in mind that complexity equals more cost, this article will explore the engineering side of P&A systems. To take an accurate view of the system, not just the printing unit, I will touch on the P&A hardware, the conveyor requirements, quality control, the software functionality and the integration scope of work.
P&A Hardware
When looking at the applicator, the first consideration would be whether the label is going on the top of the box (top apply) or the side (side apply). This is dependent mostly on the end user company requirement, however, side application tends to be the easier of the two. This is because the box can always be justified on the conveyor and will be a consistent distance from the applicator regardless of size. A top apply would have to be adaptable to each box height running down the system, requiring a more complex mechanical system.
The second major consideration is the number of applicator devices and the control/quality check that follows. Normally for faster paced systems that run 20+cartons per minute, two P&A units are suggested to go inline of each other. This is to allow for faster conveyor speeds, having each machine label every other box, and to ensure that in the case one of the machines were to break or require maintenance, that the system could continue to run. Even for systems that run at a lower carton per minute pace, a second machine is not necessarily a bad idea as long as the payback period is decent.
Conveyor Requirements
Many people I talk to simply say to me that “conveyor is conveyor”. That statement is both partially true and partially false. Conveyor hardware itself, which includes the side channel frames, the rollers, and the sensing equipment, is all very similar. The part of conveyor that differs from company to company is the engineering that went into it. I can buy a piece of conveyor online at a variety of internet re sellers and chances are that it will work for its intended simplistic purpose: moving a product from A to B in a straight line. When you start requiring more complex tasks such as justification of boxes, zero pressure accumulation of product, and orientation of product, the engineering that goes into the conveyor matters heavily.
I could go on for paragraphs talking about how the engineering design of a conveyor system matters; however, that would be a tangent of the purpose of this article. For information about that, go to this link <here>. Back on topic, for a P&A system there are two major requirements for the conveyor. First the conveyor prior to the P&A machines must justify the product to one side. This usually means skewed/canted rollers and a guardrail with low friction rails.
Once this has been accomplished, the second requirement is that the conveyor properly tracks the product to allow the P&A to trigger the label applicator at the right time. This requires a belt conveyor to avoid product slippage and some photo eye controls to track the product. With these considerations, the P&A system should run smoothly from a hardware standpoint.
Quality Control Checkpoint
After passing through the P&A machines, usually the system will look to do a quality check. Since this is done via scanner and software, I figured this would be a good segue point into the software portion of the article. The QC station can be a variety of things, but normally in a fully automated system, this consists of a scanner on the conveyor and some type of discharge mechanism for the labels that fail the check. A simple way for empty boxes would be to use an air blade which blows the box off of the conveyor into a QC bin. If the box already has product, usually it becomes a pusher that discharges the box off of the mainline and onto a quality control line for manual inspection.
Could you get away without including this to reduce cost? Yes. Should you? Not if throughput is a concern. The advantage that quality control discharge lane provides, is that is does not stop your whole system when a label fails. This allows for the mainline to continue operation until the QC lane is full, which probably indicates a bigger problem anyway. But how does the system check the labels? That leads us right into the software discussion.
Software Considerations
Software is often an overlooked, undervalued and surprisingly expensive part of material handling solutions. When buying a WM System, an important factor to remember is that if you intend to automate your warehouse at some point in the future, you need to make sure that have strong integration capabilities with hardware (usually a WCS module), and that they have an open architecture that allows integration with other software. A number of companies make claims that they will void agreements or charge for services where you integrate with another company’s equipment or software and that should not be the case. For a P&A system I mentioned the requirements of a WCS module in the early part of this article. That module functions as a high speed interchange with the WM System. WM Systems are not generally designed to have a large number of small strings of data leave and enter the system every few seconds. That is exactly, however, what a P&A requires. Each label requires a check against the order it is references to, whether it be a license plate for the box or the shipping label for the order. A WCS acts as a buffer and gives/takes large chunks of information from the WMS while handling the piece level information for each carton/order. WCS are designed to interact with the hardware on the ground level to allow for the fast communication required to label every box as it passes by the P&A at 60+ feet per minute. In this type of application, network latency to a large WM is enough to cause the P&A to miss the application timing to hit the box. This all ties into the integration of a system as a whole.
Choosing an Integrator
As a disclaimer, currently working for an integration engineering firm probably colors my view; however, I believe having a single integrator is the best way to make sure you have a system that works well. When you piecemeal out a design to multiple vendors and have an integrator tie them all in, it puts a lot of risk on the integration house and you probably end up paying the same amount of money as you would have should you have had them design the entire system. This is generally because risk translates to padding, not because an integrator is not skilled, but because they have no control over any of equipment vendors who, once they sell their equipment, have no skin in the game to help, modify or generally play nice.
Either way, it is important that the scope of work and a strong understanding of your goals is translated between you and the integration partner before the project starts. It does take additional time, but walking through these points early leads to a lot less frustration and considerably fewer change orders in the long run of the project.
I hope this article was helpful. Feel free to email questions or constructive comments to scott.ichikawa@cognex.com.