Conveyor Blog

In our previous line analysis examples we looked at a linear packaging line and another with multiple paths. Today we’re looking at a puck system.

A puck system is used to move unstable products through a packaging line. They’re popular in the cosmetics and personal care industries and can be purchased from a number of vendors such as Advantage Puck. The pucks and the products are separated at the end of the line and the pucks must be conveyed and reintroduced back to the beginning. A puck system provides a unique challenge for our line analysis calculation because stoppages in the line affect the flow of pucks upstream and downstream simultaneously.

Let’s look at a simple example of three machines.

Three machines in a packaging line with a puck return system.

Like any normal packaging line, this line has a constraint. Machine A runs at 300 products per minute (ppm) and the line can’t go any faster than that. Machine B accepts products from Machine A and sends them to Machine C. Machine C performs some sort of operation on the product, removes the product from the puck, and returns the empty back back to Machine A. If any machine malfunctions, all other machines must also shut down. Normally we can add an accumulation to help protect the constraint from the downtimes on other machines like this:

We added an accumulation table between Machines A and B to improve throughput, but does it help?

Unfortunately, Machine A requires a steady stream of empty pucks from Machine C to run. Downtimes on Machines B and C interrupt this stream, so despite having an accumulator downstream to allow A to keep running, line production shuts down anyway.

Downtime on Machine C cuts off the flow of empty pucks to Machine A, shutting down the whole line.

The same thing happens for downtime on Machine B.

We solve this problem by placing a second buffer upstream from the constraint in the empty puck return conveyor.

A second accumulator primed with empty pucks will allow the constraint to keep running.

If we have downtime on B or C, the second accumulator that was pre-primed with empty pucks will start emptying out and the original accumulation table will start to fill up at a rate of 300ppm. If the malfunctions on B or C are corrected before these tables empty out or fill up, then no production has been lost and throughput has been increased.

If B or C malfunctions, the first accumulator starts to fill up and the second starts to empty out, but the important thing is that Machine A keeps going.

Some important notes and questions:

How big should the accumulation tables be?
Both tables should hold enough products to handle the longest average repair time of any non-constraint machine, plus the number of pucks in transit.

Do the tables have to be the same size?
If you have two tables, they must be the same size because they are emptying out and filling up at the same time.

Does the second accumulator have to be in the empty puck return section?
No, but for the majority of cases it is the best place. Otherwise you will have to remove all the empty pucks from the system at the end of a shift or allow empty pucks to pass through machines without products in them. It makes sense from throughput standpoint and an operations perspective to accumulate all the empty pucks on accumulator 2 at the end of the shift.

How many pucks should I put on the system?
Fill the accumulation table prior to Machine A with empty pucks and don’t put any more on. Adding more pucks will decrease the line’s throughput.

A bag in a bottle? This should have been the cover story for this month’s Packaging Digest. The debate about which packaging strikes the greatest balance between environmental concerns and customer convenience got more interesting with Ecologic’s bag/bottle hybrid.

A plastic bag inside a paper bottle

“In principal, Ecologic is a bag-in-bottle with the consumer interface being almost identical to standard packaging,” says Julie Corbett, founder and CEO of Ecologic Brands, Inc. “The Ecologic bottle offers enhanced functionality [over bag-in-box formats] as it is easier to pour, hold and grip.”

The bottle is a biodegradable, paper-based, rigid container that houses a plastic bag inside. Once in a landfill the paper container breaks down quickly leaving the much smaller plastic bag. What I love about this packaging is that it addresses some of the concerns that bottlers and machinery manufacturers have had for years in that weaker and/or flexible packaging reduces the ability to fill, pack, and ship the products efficiently, requiring more overall energy usage on packaging lines. I haven’t seen any of these bottles yet in person, but if this trend continues I think it could eventually see widespread adoption.

We’re exhibiting today at Westpack at the Anaheim, CA Cenvention Center, along with Package Devices. Stop by for a demonstration of our Infinity Rx Accumulation Table.

This year for Christmas I received a fantastic book, The Visual Display of Quantitative Information by Edward Tufte. It reviews best practices for charts, graphs, and tables that opened my eyes to how data should be presented.  In it he discusses how to improve your data-ink ratio, eliminate chart junk, and tell how honest a chart is. He also came up with an graphical invention called sparklines, tiny graphs meant to be embedded into text and tables. If you’re a chart nerd like I am, definitely check it out.

We keep track of the queue levels at every operation in our facility. Here’s a good example of how we were able to reduce 12 charts down to three without losing any information.

Before

After

Big thanks to this nifty Excel AddIn for getting Sparklines to work properly.

In my previous post about throughput line analysis, I discussed the case of how to size buffers in a simple, linear, production line. What do you do if you have machines that run in parallel, such as two labelers?

A simple packaging line with multiple paths

Each product can take one of two paths through this packaging line. Throughput varies depending on the rates and efficiencies of each machine like a normal production line, but here you have something different. If one of the labelers is down, production can continue at a slower rate. How do you calculate the throughput of this line?

Note that the line will run normally at 500ppm, unless one labeler is down. Then it runs at 300ppm.

A linear production line has only one running state: The state when all machines are operating. The throughput of a linear line is calculated with the following formula:

Throughput = Machine #1 Efficiency * Machine #2 Efficiency * … Machine #N Efficiency * The Max Rate of the slowest machine

Where N is the total number of machines.

By multiplying each machine’s efficiency together you are calculating the percentage of time that all machines are operational. We can also use this formula to calculate the frequency of a state when one or more machines are non-operational. This simple non-linear line has three running states.

State 1: Filler On, Labeler 1 On, Labeler 2 On, Packer On (This produces at 500 ppm)
State 2: Filler On, Labeler 1 Off, Labeler 2 On, Packer On (This produces at 300ppm)
State 3: Filler On, Labeler 1 On, Labeler 2 Off, Packer On (This produces at 300ppm)

ppm = products per minute

Now we need to calculate how often the line is in each of these states. State 1 is calculated like the linear packaging line. Just multiply each efficiency together:

0.98 * 0.95 * 0.95 * 0.94 = 83.14%

Our line runs in the optimal, 500ppm state 83.14% of the time.

To calculate the percentage of time in the other states, we need to multiply each efficiency together for running machines and (1 – the efficiency) for all non running machines:

0.98 * (1 – 0.95) * 0.95 * 0.94 = 4.38%
0.98 * 0.95 * (1 – 0.95) * 0.94 = 4.38%

So State 1 occurs 83.14% of the time, State 2 occurs 4.38% of the time, and State 3 occurs 4.38% of the time. This is independent of any duration of time, so we if we want to set it to throughput in terms of products per minute we multiply the state percentage by the overall line rate in that state and add them together.

The line is down and not producing anything during the other 8.1% of the time.

So that’s how you calculate the throughput of a simple, non-linear packaging line. The calculations get more complex as you increase the number of machines, so later we’ll look at some shortcuts on how to cut down on the math. If you’d like one of our sales engineers to stop in a do a free line analysis for your packaging line, call us today.

Scientists in Korea have figured out a way to circumvent the costly production of polylactic acid (PLA), which is used in the production of biodegradable, eco-friendly plastics. They’re using E. Coli bacteria. .

Before, we had to go through a two-step fermentation and complicated chemical process of polymerization. This time, we metabolically engineered E. coli and fed it with biomass. Then PLA could be accumulated right away in the E. Coli cells, ending up with a one-step process.”

Every year we all get together and have a holiday luncheon the last work day before Christmas. We invite retirees, welcome new people who we’ve hired recently, and talk about our goals and performance for the year. One year my Dad decided that there was too much talent the room to let it go to waste, so he created the Garvey Gong Show. Three judges are chosen and the rest of the employees get up and perform any kind of talent they have, whether it’s telling jokes, playing music, karaoke, ventriloquism, etc. Today is the 8th Garvey Gong Show and it’s something I look forward to every year.

The contestants are warming up

I saw this photo on the Packaging Diva Blog today. It gives you a sense of the immensity of the packaging industry.

A familiar sight from an unfamiliar angle

Food and Beverage Packaging Magzazine posted an article today where they quoted various luminaries of the conveyor industry about speed, safety, and sanitation. They also quoted me.

Garvey general manager Ben Garvey concurs. “For us, the biggest difference between food and beverage markets is the speed—beverage lines run two to four times faster than a typical food packaging line. Overall conveyor construction is similar, because of contamination concerns. They all require easily cleanable conveyors.”

Read the entire article here.

Practical Winery and Vineyard’s latest cover story has a great shot of the huge wine barrels made by Oak Cooperage.

Practical Winery and Vineyard

We have installed many of our Infinity tables in the wine industry in California and Australia. They raise throughput by protecting fillers from downtime on labelers and casepackers.