This entry has some prerequisite reading: my entries of July 3, 19 and 22. Those posts will give you the necessary background to understand the following:
So… what are the downsides to ADR-First? In other words, why has that approach not (yet) gained more broad appeal historically?
First, and most broadly, the perception/reputation of the early ADRs still is the common perception today, and the biggest issues were reliability and price. Let’s take a look at both:
Older ADRs used water valves to actuate the knives of the cutterwheel. This led to two issues: First, they could not be actuated crisply enough to extend one knife blade alone, the minimum was two. In principle, the system needs to throw only one knife blade when cutting a defect that is near the end of a strip (the majority of defects fit this description). To throw that extra blade where there is no strip is to invite extraneous cuts, increasing white cube rates and decreasing product length. And that was the norm for ADRs built before 1999.
Further, since it was not possible to throw a single knife, it was therefore not economical to cut good strips to length (the processors/sensors didn’t provide for that anyway, but that is another matter). If for every cut a cube is created, the yield loss does not justify the other benefits.
Further, water valves had short lives. When actuated, they created “water hammer” (that banging noise in your house water pipes that happens when you shut off a valve quickly, and no hammer arrestor is installed). Water hammer did just what its name implies: hit the valve with a large force each time it was actuated; basically the force was the result of the water’s momentum being stopped suddenly. Remember from physics, mV=FΔt? V is high due to the high impact required to crisply drive the knives, and Δt is short, again to keep actuation crisp. The result? Force applied by the momentum shift was VERY high.
And the valves beat themselves to death, usually in a few months.
Further, the failure mode of the valves was relatively catastrophic in terms of yield: When a valve failed, it would fail “open”, directing a continuous stream of water to the knives of a row, extending all blades continuously. So, for that one lane of the system (1/44th of the total flow), all strips were turned into cubes and sent to co-product, until someone noticed the problem and replaced the valve. That is a significant yield loss in most applications.
The conclusion of the industry at the time? “Send only the strips necessary for cutting (defectives). Do not send any good strips to the ADR, if possible. The chances are too high that good strips will become by-product.” That perception largely holds today.
Even though ADRs since 1999 employ air valves, which both practically eliminate the catastrophic failures and enable single knife throws. Not to mention the savings in maintenance labor and parts.
ADR is a different solution today, folks. It truly is a system worthy of consideration of being used as a primary defect control device. More on price and payback next time.
Tim
Friday, July 25, 2008
ADR Valves: Old vs. New
Tuesday, July 22, 2008
The Solution to High Incoming Defects
Please refer to my posts of July 3 and 19 to get acquainted with some background on this subject.
ADR-first is the conceptual rearrangement of the potato strip processing line area downstream of the cutters. After sliver removal, all the product flows across one or more ADR for defect removal. Downstream of the ADRs (and nubbin graders), optical sorters can be placed to separate any defective pieces the ADRs might miss.
The principal benefit of this system is in defect removal. The ADR (with nubbin grader) removes about 80% of the incoming defects, but unlike the sorter-first arrangement, those defects are GONE from the system. Of the remaining defects in the line (20% of the incoming defects), the sorter removes about 80% (16% of incoming as the flow chart below shows). When those defects run through the ADR a second time, it removes about 70%, for an overall removal rate of about 93%. Compared to the status quo line that provides only 64% 
Keep in mind that this system (with performance shown above) is tuned to its highest efficient defect removal settings. And that those settings are not needed that high for most processors for much of the processing season. The beauty of this normal performance “headroom” (the difference between what is needed at the moment vs. maximum capability) is that it provides adjustability. So one can pass some minor defects intentionally most of the time and stay in grade. And those specific minors selected to be passed can affect yield quite positively compared to the sorter-first arrangement.
The system can also control length, as I described in my July 19 post. This will help yield and quality both directly (where length specs must be met) and indirectly (reduction in bag seal failures, segregation, etc.).
Note also that, with this line configuration properly sized, it is practically impossible to exceed rated capacity on either the sorters or ADRs. One of the huge limitations of the sorter-first line is eliminated!
But the strongest driver to move to this configuration is in regions where raw product quality is not well controlled, where much money can be made if poor quality potatoes can be made into high quality product. Where incoming defect levels can exceed 20%, 30% or even 40%. You simply cannot cost-effectively control quality for that incoming condition with sorter-first configurations.And even in areas where potato quality is good, processors are more and more asking for "zero defect product". This system will provide product quality very near to zero defect, at good yields. Look at the numbers: Sorter-first leaves 36% of the incoming defect in the product (100%-64%). ADR-First leaves 7% (100%-93%). That is more than an 80% reduction (100%-7%/36%) in remaining defects, compared to the current industry standard!
Keep in mind that the ADR, unlike the sorter, can tolerate and run efficiently with VERY high defect loads. Historically, ADRs have been received the reject stream of product from sorters, which often exceeds 80% defect. And it controls quality at those levels quite well. Most processors would consider incoming raw product that is 80% defects as good only for animal feed. You can set up your line to turn it into sellable product economically.
More soon-
Tim
Saturday, July 19, 2008
Further to July 3 (ADR-First)
If you have not read my July 3 post, please do so before reading this entry.
64% defect removal doesn't seem like much. Of course, you can argue, "I get better". But no one I have seen gets more than 85% on any sorter or ADR; if you were able to maintain that level, the system removal would be only 72%. At 20% incoming defects, that means your product still contains 5.5% defect after the sorters and ADR are done. Right on the cusp of acceptable grade. So, you might blend in some better product from a cleaner load and move on. If you have it.
But if your incoming defect load exceeds 20% by much, you have some difficult choices to make. And as the incoming defect rate gets higher, you start to encounter another problem besides trying to make grade: Your ADR can tolerate only so much flow. You have designed your line around 20% incoming defect, and at your nominal line flow, your ADR is at capacity. As incoming defect levels get higher (especially in late storage season), you send more and more product to the ADR. Sure, it brushes off the excess, but that doesn't help in the long run- that excess comes back around again, further adding to the load. Your system starts making more white cubes than it should, cutting (literally!) into your yield. Eventually, belts spread apart, cutters get jammed, knives bend and break, and you are looking at line downtime. These days, line downtime costs you a bundle.
Or maybe you slow your line down when you run high incoming defect levels. Ever look at what line slowdown costs you? If you have, it is shocking!
A couple of other areas to comment on, regarding the status quo line; both areas are related to missed opportunities for yield and product quality enhancement:
Modern ADRs are capable of cutting good fries in multiple pieces, using one knife throw per cut. Why might you want to cut good strips? Couple of reasons: First, some products have a length specification where too many short pieces ( less than 25mm) will cause you to be under grade on length, and that happens often with bins of short potatoes, especially in Europe. However, if the strips that are extra-long (say, greater than 150mm) can be cut in two pieces, the percentage of "long" pieces (e.g., over 75mm) goes up, even though the average length is reduced. Such a capability can make the difference between making grade or not.
The other mode can be even more significant. If you cut every strip that is longer than a maximum, product flows better in many ways. Every place there is a drop or gate, less segregation occurs, and you end up with more uniform product. Everywhere bridging has been an issue, is will be less of a problem, with no long fries to get hung up. Best of all, bagger jaws will close on product much less frequently, greatly reducing rework cost, film cost and improving bagger productivity. One could imagine shortening the actual bag length for any one quantity of product, again saving film and perhaps pasteboard. And shipping space. And....
Sure, you can send long strips to the ADR if you are using sorters with length sorting capability. But that is a lot more product to be sent to the ADRs, and they will likely not have the capacity to handle it when incoming defect levels get high.
You can also halve your whole potatoes prior to cutting, as an alternative to using an ADR to control length. But anyone who has modeled that approach knows that it increases the short pieces and slivers, compared to cutting whole potatoes. More yield and quality hits.
The other missed opportunity is in limiting the application of the intelligence available on modern machines. Modern ADRs can make very smart decisions about which strip to cut and which to pass. The classic example is a strip with a minor defect that is positioned such that removing the defect will result in an additional nubbin or short piece. If the grade of the moment can tolerate it, that defect should be ignored, and by doing so, yield and length profile will be enhanced.
Problem is, if you are only sending 80% of the defective strips to the ADRs, they often must remove every defect they identify, in order to make grade. If they were to be able to see 100% of the defects, often it will be possible to ignore a fair percentage of minor defects and still stay in grade. How much better that the specific minors ignored also reduce short piece count to maintain length profiles?
OK, I think I am finished (for now) with the issues of the status-quo system.
Next time, we will discuss the solution.
Check this entry again early next week- I will add some pictures to make things more clear.
Tim
Monday, July 14, 2008
Foreign Materials, Conclusion
I was doing so well at blog entries, writing no less than one per week. Then came the July 4 holiday here in the US, followed by a week of presentation-intense work. Lastly, I took a 3-day weekend to watch my youngest daughter play softball (also known as fastpitch). In the meantime, we sent out a "push" email, encouraging you all to read this blog and make comments (please make comments!!!)...
I'm back at it!
Before we go on the describe the ADR-First fundamentals, let's close out the foreign materials topic, last mentioned in my June 20 posting.
Remember that up to then, we had discussed implementing laser/camera combination sorting just prior to packaging, where it would protect the final consumer the best. Now, let's take a look at what would benefit the processor the best: pre-cutting (whole potato) foreign materials removal.
Of course, when foreign materials are removed from a whole potato stream, they are also removed from the resultant finished product. But the added benefit to the processor is the elimination of costly downtime to his cutters.
Without foreign material removal, cutters are constantly at risk from both hard items (stones, glass, metal) as well as other "junk" (fibrous roots/stalks, plastics). When cutters either bind up or break as a result, lots of bad things can happen. Of course, the flow through any one cutter can stop completely, reducing line productivity. More subtly, the cutter can break or be dulled in a way that still allows product to pass, but it is not cut to specifications. Often, this is difficult to detect, and so can affect quite a bit of product before it is corrected; it can thus become even more costly than a plugged cutter.
The solution: place an optical sorter just upstream of cutting, again using both cameras and lasers. As we mentioned in the June 9 post, both are necessary to eliminate the "crossover" in sensing specific items, like potato scab from black rubber. And, if both cameras and lasers can also analyze the shape of the object, a more clean separation of foreign materials can result.
Payback of such a system can be extremely fast, if you can calculate the true cost of cutter downtime.
Sometime, I will write more on whole potato sorting. I do plan to more immediately return to the ADR-First concept, which I think holds great untapped value for the industry.
Until next week-
Tim
Thursday, July 3, 2008
Cutting Out Defects
As I mentioned a few days ago, I made a presentation at the Potato Processing and Storage Convention in Warsaw last week. The presentation was on a "new" approach to defect control for potato strips, where all the product is sent to ADRs first rather than sorters. Over the coming weeks, I plan to discuss details of that presentation.
To begin, however, let's tell the short story:
It starts with the idea that, in potato strip applications as well as most others, sorters are not perfect. Neither are ADRs. That means that they neither removal ALL the defects that come in, nor do they remove the defects only: they also remove some amount of good product. There has been, and is, of course, an ongoing effort to improve both sides of that: defect removal rates and false rejection rates. But it is my impression that such efforts are nearing an asymptote: that theoretical limit beyond which further improvement is not possible without radical change of the concept.
If you haven't figured it out yet, this blog is a bit about radical change....
Most of the reason that sorters and ADRs do not remove 100% of all defects is that they image product while it is lying on a belt. It is not possible to image the face that is against the belt, so defects that are seen only from that side are missed. About 15-20% of all defects in any given load of strips falls in this category, so the highest possible defect removal is about 80-85% for on-belt systems. Because there are some other, more subtle causes for less than 100% defect removal, I tend to use 80% average removal as the standard number.
Most processors of strips send a flow of defects from the reject stream of the sorter to the accept stream of an ADR, so that the ADR can cut cubes of the defects and retain the rest of the strip for recovery. I will write more in coming weeks on those strip processors who do not use ADR. The ADR functions much like a sorter, removing about 80-85% of its incoming flow.
Problem is, the ADR only sees 80% of the total line incoming defects, so it actually removes only 64% (80% of 80%) of the incoming defects, maximum. See the image from my presentation:
64% doesn't seem like much, does it? And folks try to use various means to get better performance, such as double sorting and recirc (we will also discuss these later). And they usually get somewhat better defect removal, but at significant cost in yield.
And, to be sure, the above model tends to produce A-grade product if all parts stay in tune and incoming defect levels stay below 20%. When (not "if", for most folks) either of those get outside of spec, big problems can occur. Either the product goes out of grade, or the ADR is overflowed with product (with attendant yield and product quality hits, not to mention machine damage/downtime issues), or the line rate must slow down (cuts productivity). So the "if" that started this paragraph is a huge "if".
So some folks that are able to keep their machines in tune, and acquire good potatoes through storage season do just fine with the above plan, thank you! But there are others, and I must say that the number is growing, who do not enjoy such benefits. They process in regions where 20% incoming defect would be considered extremely clean, where 30% and up is the norm. They work in areas where skilled labor to keep systems in tune is difficult and expensive to acquire, and so often they do without- and suffer the consequences: poor product quality, poor yield or both.
So that is the problem... a system that is simply not capable to meet the needs of many new lines in new geographies, even though it is the historical standard of the industry.
Where do we go from here?
Read this blog next week!
Tim