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Mistakes to Avoid When Planning Accumulation

by Nercon Eng. & Mfg., Inc. on Jan 19, 2011

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This is a 45 minute on-demand webinar developed by Nercon about "Mistakes to Avoid When Planning Accumulation." It covers some terminology at the beginning, with advanced engineering topics covering ...

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Thank you for taking this webinar “Mistakes to Avoid when Planning for Accumulation – presented by Nercon. My name is Jessica Jacobson, and I’m your moderator, as well as developer of Nercon’s customer education programs and materials. For this recorded, on-demand event I would to thank Jim Streblow and Mike Weickert from Nercon who with years of experience in conveyor engineering, controls and application engineering, have helped to make this a very informative webinar.
Briefly, we’re going to discuss some conveyor terms and basics on accumulation and buffering. We’ll define the difference between accumulation and buffering. We’ll also give you examples of where they are used in the production line and the operational modes of both methods.
We’ll look at pitfalls and operational problems when equipment layout is not ideal.
Next will talk about the effectiveness of accumulation. We’ll look at how products should flow into and out of accumulation.
We’ll also look at the design criteria needed to clear buffering zones to allow for smooth product flow.
Another common mistake is incorrectly identifying the problem area that is causing the bottleneck. We have a couple of examples of problems and solutions that will improve line efficiency.
We’ll look at how to select the proper form of accumulation And how to avoid selecting the wrong method.
Then we’ll wrap up at the top of the hour with some questions from our recorded event.
To start…We’re going to cover some terms and basics. The first is accumulation. This re-circulating table shown here is accumulating products. Accumulation means temporary storage.
Buffering is the ability to collect products at one rate and discharge at another. The accumulator shown here has an expandable product path that provides buffering capabilities. The difference between the two is that buffering is for balancing your line and accumulation is for storage. A lot of times buffering is accomplished within the conveyor system and accumulation is normally accomplished by a secondary storage machine or piece of equipment.
Throughput is the output at the end of the line which is the number that management wants to know about. It takes into account the efficiency of the line, not necessarily the speeds and output of individual machines.
Sometimes called bottlenecks, to be more specific we refer to them as production constraints, these are areas in your line that are causing machines to wait or not operate at capacity. In a lot of cases the delays are expected like changing over a labeler.
By adding buffering and accumulation, you can keep product flowing to machines and minimizing those short, expected delays and by keeping a continuous flow – you increase throughput.
So how does buffering improve overall efficiency? Each machine on your line operates at different speeds and efficiencies. Without accumulation or buffering, a temporary stop in a machine may cause the whole line to shut down.
Here’s line production fault screen for that example. Wait times, jams, relay occurrences are tracked in addition to total down time for each error.
If we look at the main cause of faults it is a stop somewhere along the production line when one machine stops, the entire line comes to a halt.
By adding buffering solutions, whether it is controlled conveyors or accumulation equipment, We can allow upstream equipment to continue to run.
This is because most production interruptions are of short duration – less than 2 minutes.
Package equipment runs smoother and more efficiently when the equipment is not cycled on and off. On this fault screen, we went from almost 2 ½ hours to 39 minutes by adding buffering. That’s 110 minutes per shift but more than 2000 hours per year additional production for your line.
Do you have bottlenecks in your production line? If so, where do they occur? Upstream of Filler: The filler needs a steady and continuous flow, it’s typically a high speed, high volume machine. You really want to address bottlenecks before the filler and keep it producing. We’re going to talk about bottlenecks before and after the filler coming up in the presentation. Downstream of Filler: Anything downstream of the filler can also cause problems with shutting it down. We have an example of bottlenecks around the filler coming up in the presentation. Before or after the Labelers: Labelers, banders, case packers all require intermittent down times. The key is that all the machines need to operate together with buffering and accumulation to tie it together so the line runs smoothly.
Rule Number 1 Placing machines back-to-back in a production line or close coupling machines without planning for thresholds is one of the first mistakes we encounter.
Here is a typical line layout with multiple processes. The layout shows: The bottle unscrambler Cleaner and Rinser The filler Labeling Machines Case Packer and Taper And the Palletizer at the end of the line
We look at strategic areas in the line layout where we normally see problems due to close coupling. Bottle unscramblers do not have a steady output flow whereas the filler in-feed requires a steady stream of product. Due to the high speeds of most fillers, additional consideration needs to be taken for the overall distance between the unscrambler and the filler. The close coupling here often results in starvation of the filler due to the inconsistent output of the unscrambler.
Close coupling can cause issued with controlled stops. Certain pieces of equipment, such as the filler, need a controlled cycle stop, therefore storage or space is required to allow the equipment to come to a safe, efficient stop. This capacity may be as much as 10 – 20% of line speed. A filler speed of 600 units / minute may require storage capacity between 60 – 120 units, for example. Labelers also require a steady flow of product. Labeling machines also need supplies, glue, water, labels. Replacement or replenishment of these supplies often require a machine shut down.
Case packers, depending on the type of case, also suffer from intermittent down times. Also…Tray Packers, Overwrappers or Bundlers may need maintenance for a variety of reasons. Card board dust buildup Replenishment of heat shrink Replacement of carton or cardboard stock Maintenance with knives And jams So when planning your line, be sure that you have enough space between equipment to allow for these types of faults that could occur. If this layout there is insufficient space between the bander and the case packer to allow the bander and labeler to cycle stop without product backing up into the bander – this could cause product damage.
A well thought-out packaging line layout can also help to accumulate products during palletizer discharge cycles, not to mention down time due to maintenance. Later on in the presentation we will show you a preferred layout for this example.
Now for Rule Number 2 Accumulators require a specific layout for in-feed and discharge conveyors depending on the application.
This is the before example of an incorrect infeed and discharge for a bi-directional table. In this layout the bi-directional table is used for off-line temporary storage.
This layout, however, will choke product volume to when entering the accumulator Also, the layout also doesn’t allow enough room for the product to get out of the accumulator Both situations will most likely cause product bridging, which may lead to jamming and possibly product damage depending on the product.
Here’s an example of bridging on the top drawing, we see this happening when the product conveyors are not correctly specified feeding the accumulator. The product gets so jammed that it bridges between the guides and it won’t budge. On the bottom drawing is an example of how the product should flow into the accumulator.
This layout provides optimal performance for the proper conveyor infeed and discharge layout. Here, in the green areas, we have widened the conveyor both feeding into the accumulator and in the take-away path. This allows the product to flow and single file. Another advantage in this situation is that multiple conveyors relieve back pressure. The product also will have time to space and de-nest as it continues to go to other operations downstream.
Here is another question to ask yourself: What is the greatest roadblock you’ve encountered when planning production lines? Poll question comments: Not enough floor space: Sometimes this can be an issue, there are vertical accumulation solutions that we’ll talk about later. And sometimes conveyors equipment need to be relocated to allow for buffering and accumulation. Product Handling Difficulties: Not all products are created round. Some types of packages need special considerations for just handling the product let alone accumulating. While rounds, ovals, cartons and most uniform shapes have a number of equipment options, unfortunately products like bags, pouches or products with overwrapped packages, while equipment options are definitely available, they are a substantially high up-front purchase price. Initial investment: The bottom line is to analyze your waste, downtimes, labor and operational costs associated with those downtimes. If you have used a credible conveyor and systems application company and the cost for a new system outweighs the return on your investment, then it’s not a good investment. Maybe it makes more sense to make adjustments in areas that are more feasible or maybe you revisit the project at a later time.
Rule Number 3: Always clear downstream buffer zones between cycles.
A typical scenario we encounter is when the customer recognizes that he needs accumulation between production equipment. Let’s assume for this example that both pieces of production equipment produce at the same rate of 120 PPM.
Machine B stops for some reason – a jam or a paper change. The accumulation does its job and allows machine A to continue to run until the accumulator is full.
Machine B restarts and processes product at the rate of 120 PPM while machine A continues to deliver products at 120 PPM. The problem arises if machine B stops again and the accumulator is still full. We’ll be forced to stop machine A.
An improved design would be to plan for down-stream machines that are capable of running at a faster rate for short periods of time. This would allow for the emptying of the accumulator. In this example it would take 12 minutes to completely empty the accumulator. The monitoring of accumulation and the speed modulation of the packaging equipment will require a complex control system, but it will pay off in the increased efficiency of the line.
Rule Number 4: Identify the Right Production Constraint
To revisit our earlier layout, we promised to demonstrate how to fix these inefficiencies.
Keep in mind that in this close coupled layout example, every time one of those machines down stream of the filler stops, the filler must also stop. And remember the issues with the unscrambler - the intermittent product flow produces inconsistent flow of product to the filler and causes filler stops. As we’ve mentioned, the filler most often is a high speed, high volume machine, some people in the business call it the “money maker.” So when downstream machines stop, there is no room for the filler to keep producing; there is no where for the product to go. Then… when the filler ramp-ups or shuts down, product is often wasted from inconsistent fills not the mention the production time that is lost. It’s important to keep the filler operating at a steady pace and reduce all unnecessary down time.
At an initial look, placing an accumulation device in this location appears to be a good choice because it solves for the more common occurrence of downtime due to the case packer and palletizer. However… This location does nothing to address the downtimes associated with any of the upstream equipment. It does not address: The periodic servicing requirements of the labeler and bander This location does not provide buffering between the filler and labeler And finally, this location does nothing to provide for the controlled cycle stop of the filler
By placing the accumulation equipment in this location, it solves the accumulation needs of the labeler, case packer and also allows for a complete cycle stop of the filler.
To allow for the cycle stop needs of the labeler and the bander, as you can see from the dotted line, the conveyor distance was increased shown in green between the bander and the case packer and simple buffering controls were added.
To compensate for the intermittent product flow from the unscrambler to the filler we add some buffering conveyors and controls. We’ve also moved the cleaner so there is more room before the filler, as you can see from the dotted line. The amount required is dependent on the specific characteristics of the unscrambler and the filler. This is the maximum ROI solution to solve these inefficiencies. Let’s look at the numbers.
Mike: If you remember the close coupled example, we talked about the constraint issues in this layout.
Jim: … We look at the fault examples on this type of line, the downtime is significantly high because the machine downtime cause shut downs across the entire line.
Mike: This is the first option we looked at placing the accumulation between the case packer and the bander.
Mike … And looking at these numbers, we see a significant improvement in occurrences and down times, but the the upstream equipment could be showing more improvement. We have only shaved a few minutes off the fault screen examples.
Mike: And back to our maximum ROI solution for this layout where we moved the accumulator after the filler…
Mike: … Then we realize maximum efficiencies for the entire line. We went from ____ in the close couple example, to _____ in this preferred solution.
Here’s another question to ask yourself. What are common problems with accumulation equipment? Questions: It doesn’t Accumulate Long Enough: Be sure to calculate your downtimes accurately so the buffering and accumulation solution can be engineered for the best possible results. Depending on the line speeds, a lot product can accumulate in just a few minutes, and hopefully you have seen from our presentation example that you need space for buffering and accumulation. It was put in the wrong direction: Our last example showed a possible location, but not the best location for maximum ROI. We do see this happen, but you want to know your line performance data and also partner with a conveyor and systems supplier that has experience in your application. In-feed or Discharge Conveyor Incorrect: That’s one of the mistakes that we see that project managers may not realize how important the conveyor specifications are going in and out of the conveyor, that’s why we wanted to cover this topic. Again, conveyor specialists work with a formula to engineer the accurate conveyor specifications and there are often other considerations depending on the application.
Rule Number 5 – Choose the correct type of accumulator or accumulating conveyors. There are multiple types of accumulators available to use. They can be designed for FILO which is First in Last Out and FIFO, First in First Out and somewhere in between.
We talked a lot about packaging in this presentation, but sometimes storage is needed for handling bulk material. Bulk or processing lines can be designed for temporary storage and buffering; but is very different than accumulation for packaging lines.
Packages and containers run on some types of accumulators better than others. We look at the size, shape and stability of the product as well as taking other SKUs into consideration. This recirculating accumulation table for example can accommodate round and non-round or oval packages, but is not a solution for a carton because of how the table nests the products while being accumulated.
Some accumulation solutions like this bi-directional table can be controlled to constantly cycle on and off. This is an example of an accumulator that has buffering capabilities to balance the production line.
If product sequence in important you need to look into FIFO – First In First Out Accumulators This Flex Flow Accumulator is designed to gently handle products in sequence. It also offers a expanding product path which allows for buffering as well as temporary storage.
Sometimes available floor space can cause a problem when planning for accumulation, So consider the use of vertical space like in this vertical accumulator that can store large amounts of products in a small foot print.
This Serpentine Accumulator is designed for large capacity storage and can be controlled for on-demand buffering. In addition to large capacity, it is versatile and cost effective in high volume production lines.

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Nercon Eng. & Mfg., Inc. at Nercon Eng. & Mfg., Inc. 2 years ago

Mistakes to Avoid When Planning Accumulation Webinar Transcript

Mistakes to Avoid When Planning for Accumulation Nercon Eng. & Mfg., Inc. presents:
Outline
- Terms and accumulation basics
Jim Streblow speaking
Outline
- Terms and accumulation basics
- Avoid close coupling machines
Outline
- Terms and accumulation basics
- Avoid close coupling machines
- Proper accumulator in-feed and discharge
Outline
- Terms and accumulation basics
- Avoid close coupling machines
- Proper accumulator in-feed and discharge
- Buffering of downstream equipment
Outline
- Terms and accumulation basics
- Avoid close coupling machines
- Proper accumulator in-feed and discharge
- Buffering of downstream equipment
- Improper identification of the constraint
Outline
- Terms and accumulation basics
- Avoid close coupling machines
- Proper accumulator in-feed and discharge
- Buffering of downstream equipment
- Improper identification of the constraint
- Equipment selection specific to application
Outline
- Terms and accumulation basics
- Avoid close coupling machines
- Proper accumulator in-feed and discharge
- Buffering of downstream equipment
- Improper identification of the constraint
- Equipment selection specific to application
- Wrap up and answer final questions
Conveyor Speak Accumulation: The process of collecting products for temporary storage.
Conveyor Speak Accumulation: The process of collecting products for temporary storage. Buffering: The ability to collect products that can be delivered at a different rate than it is received.
Conveyor Speak Accumulation: The process of collecting products for temporary storage. Buffering: The ability to collect products that can be delivered at a different rate than it is received. Throughput: The true efficiency at the end of the line.
About Bottlenecks, Constraints
About Bottlenecks, Constraints
About Buffering Operation A Operation B Operation C Operation D
About Buffering WORST FAULTS FLT # Fault Name No. Occur HH MM SS
- 0 Waiting for Upstream 39 0 55 26
- Waiting for Downstream 20 0 32 44
- Discharge Jam 12 0 23 02
- Video Jet Not Ready 9 0 17 50
- Guard Door Open 4 0 04 37
- Product Out of Position 4 0 04 24
- Safety Relay Open 2 0 01 18
- Loader Overload 1 0 04 10
About Buffering WORST FAULTS FLT # Fault Name No. Occur HH MM SS
- 0 Waiting for Upstream 39 0 55 26
- Waiting for Downstream 20 0 32 44
- Discharge Jam 12 0 23 02
- Video Jet Not Ready 9 0 17 50
- Guard Door Open 4 0 04 37
- Product Out of Position 4 0 04 24
- Safety Relay Open 2 0 01 18
- Loader Overload 1 0 04 10
2 hours, 23 min., 31 sec.
About Buffering Operation A Operation B Operation C Operation D Operation A Operation B Operation C Operation D Buffer Buffer Buffer
About Buffering WORST FAULTS FLT # Fault Name No. Occur HH MM SS
- 0 Waiting for Upstream 15 0 14 07
- Waiting for Downstream 5 0 07 05
- Discharge Jam 8 0 05 10
- Video Jet Not Ready 6 0 04 06
- Guard Door Open 2 0 02 08
- Product Out of Position 5 0 05 02
- Safety Relay Open 1 0 01 01
- Loader Overload 1 0 00 58
About Buffering WORST FAULTS FLT # Fault Name No. Occur HH MM SS 39 min., 37 sec.
- 0 Waiting for Upstream 15 0 14 07
- Waiting for Downstream 5 0 07 05
- Discharge Jam 8 0 05 10
- Video Jet Not Ready 6 0 04 06
- Guard Door Open 2 0 02 08
- Product Out of Position 5 0 05 02
- Safety Relay Open 1 0 01 01
- Loader Overload 1 0 00 58
About Bottlenecks / Constraints
- What area in your production line does the most bottlenecking occur?
- Upstream of Filler
- Downstream of Filler
- Before the Labeler
- After the Labeler
- Before the Case Packer, Wrapper, Cartoner
Mistakes to Avoid # 1 Do not close couple equipment.
Mistakes to Avoid
Mistakes to Avoid
Mistakes to Avoid
Mistakes to Avoid
Mistakes to Avoid
Mistakes to Avoid # 2 Incorrect layout of in-feed and discharge conveyors for accumulator operation Bob Owen speaking
Mistakes to Avoid
Mistakes to Avoid
Mistakes to Avoid Bridging Preferred flow FLOW FLOW A close up of product traveling into the accumulator.
Mistakes to Avoid
About Bottlenecks / Constraints
- What is the greatest roadblock you’ve encountered when planning lines for peak efficiency?
- Not enough floor space for buffering/accumulation
- Product handling difficulties
- Initial Investment too high, payback not sufficient
Mistakes to Avoid # 3 Failure to clear downstream buffer zones. Jim Streblow speaking
Mistakes to Avoid
Mistakes to Avoid
Mistakes to Avoid
Mistakes to Avoid
# 4 Improper identification of production constraints Mistakes to Avoid
Mistakes to Avoid FLOW
Mistakes to Avoid
Mistakes to Avoid FLOW
Mistakes to Avoid FLOW
Mistakes to Avoid FLOW
Mistakes to Avoid FLOW
Close Coupled Layout FLOW
Close Coupled Layout WORST FAULTS FLT # Fault Name No. Occur HH MM SS 93 Minutes
- 0 Unscrambler Down 5 0 15 15
- Filler Waiting 30 0 07 20
- Filler Down 8 0 05 02
- Labeler Fault 5 0 12 50
- Bander Fault 7 0 09 37
- Case Packer Down 20 0 28 24
- Palletizer Down 10 0 17 59
Mistakes to Avoid FLOW
Layout with Accumulation after Labeler WORST FAULTS FLT # Fault Name No. Occur HH MM SS 68 Minutes
- 0 Unscrambler Down 5 0 15 15
- Filler Waiting 30 0 07 20
- Filler Down 8 0 05 02
- Labeler Fault 5 0 12 50
- Bander Fault 7 0 09 37
- Case Packer Down 5 0 11 34
- Palletizer Down 2 0 06 29
Mistakes to Avoid FLOW
Layout with Accumulation after Filler WORST FAULTS FLT # Fault Name No. Occur HH MM SS
- 0 Unscrambler Down 3 0 06 14
- Filler Waiting 12 0 04 30
- Filler Down 4 0 03 02
- Labeler Fault 2 0 04 50
- Bander Fault 3 0 05 15
- Case Packer Down 5 0 11 34
- Palletizer Down 2 0 06 29
42 Minutes
- What are some common problems that you have had with accumulation equipment?
- It doesn’t accumulate long enough
- It was put in the wrong location
- Infeed conveyor length incorrect
- Discharge conveyor layout incorrect
Mistakes to Avoid
Mistakes to Avoid # 5 Choosing the wrong type of accumulation technology
Mistakes to Avoid Accumulation technology is application specific. Do you need to accumulate bulk material?
Mistakes to Avoid What is the package or container? Reflow Accumulator
Mistakes to Avoid Does accumulation require on-demand cycling? Bi-Directional Accumulation Table
Mistakes to Avoid Is product sequence important? Flex Flow Accumulator FIFO
Mistakes to Avoid How much floor space is available? Vertical Accumulator
Mistakes to Avoid Do you need large capacity? Rolco Serpentine Accumulator A division of Nercon
Recommended Webinar: How to Choose the Right Accumulation Solution Nercon Eng. & Mfg., Inc. presents:
www.nercon.com