Bean Cutters: The reality

Folks, sorry for the hiatus- You will definitely see me posting weekly going forward. Change you can believe in!

Let's have a chat about bean cutters. For those of you who don't know, a number of potato strip lines today run with bean cutters in lieu of ADRs. Bean cutters are devices that can be configured to cut a segment off of one end of long, thin objects (like snap beans, which is what the machines are made to cut). There is no selection of which end will be cut- it is a blind, random cutting of one end of the strips that enter the device. Typically, folks set them on strip lines to cut 15mm at a whack, but that is an adjustment that can be anything you wish.

They set their lines up with optical sorters, sending the rejects to one or more bean cutter. The remnants are then sorted again, the pass stream going to the blancher, and the rejects to the bean cutter again.

There is, of course, no mystery as to why people have done this. Let's be honest- ADRs are expensive and bean cutters are cheap. Easy math. No one wants to pay out big bucks if there is another way to get the job done. And, if you are an equipment supplier who does not offer ADR, what choice do you have? You sell what you can deliver! Tout its value! And who doesn't want low capital cost?

The problem is, just like the oil filter ads of a couple decades ago, "you can pay now or you can pay later". And the amount you "pay later" is, let's just say, eye-opening. Just like those filter ads of yesteryear.

I have spent the last couple of days modeling what a sort-then-bean-cut line does to potato strips. Without going into all the details, if you did to people what bean cutters do to potato strip yield, you would be in the slammer 20 years-to-life.

Just look at your average, pedestrian potato strip. 7mm cut. 75mm long. No criminal record. Defect on one end, like 15% of his relatives (5% have a defect in the middle, but that is jumping ahead). When he runs through the sorter, he is rejected and sent to the bean cutter. SNIP! He loses 15mm in length. Now, half the time, his defect end is cut off, and he passes into the blancher his second time through the sorter. Would that it were always so simple!

(Ever wonder which end is YOUR defect end?)

Problem is, half the time, the wrong end is cut. Whoops, there goes waste. A white cube down the drain! But wait, we're not done... the strip comes back around through the sorter, where 20% of the time he is missed and passed into the blancher! Holy cow! You mean, I could lose a white cut, and still pass the defect? Yep. Happens all the time. And even if the right end was cut the first time through the bean cutter, the good remnant can be rejected back to the cutter if it is lying too close to a defect going through the sorter. WOW! You mean, everything can go right, all through the cutter, but I can still end up making white cubes? You bet.

And we're STILL not done. If the wrong end is cut the first time, and the strip is successfully sorted to the cutter the second time, what are the chances the wrong end is cut again? 50%! But the strip is now only 60mm long and getting shorter. Recovery of the remnant is getting less and less valuable. And if the wrong end is cut a second time, there is also a 20% chance that the defect passes through the sorter into the blancher. And on and on it goes, until we have a big pile of nubbins (including some actual defects), and compromised product quality.

I think you get my point.

Next time, I'll work through some of the actual numbers with you. As you can tell, I was having a bit of fun with this tonight. Next time, we'll get serious. Promise!

Tim

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