I would place the boxes face side down on a conveyor and pass them over a rotary knife (say 10" diameter) which slices most of the way through the box, but leaves the back side intact. Subsequently on the conveyor, the slit is opened so the two halves of the box form a "V", and the contents slide out leaving the bag and box empty.

Cutting is relatively straightforward; even the humble box cutter can do that with a correctly calibrated blade protrusion. I don't think it much matters whether you open the box from the top or the bottom, but the bottom is always one wall high, so that seems like a pretty obvious place to cut. So, slice around the box, and lift the top part, leaving the bottom and the bags sitting on it.

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Thank you for the fast response.

@Compositepro , I also think a rotary knife would be a good idea but I don't understand how the two halves will form a "V".
Is it maybe possible to draw a sketch of it?

@IRstuff I think that when you slice around the entire box, there is the possibility that some carton comes with the bags when you empty the box.
Another problem is that the boxes got different dimensions, so when you slice around the entire box you always have to change the settings of the opener or is there an other way?

Watch these videos to see what I mean.

https://www.youtube.com/watch?v=REBhP0jjNCc

https://www.youtube.com/watch?v=gxNb0Vq3ffk

Thanks!
Hopefully those examples can give me some inspiration.

https://www.youtube.com/watch?v=iMqSJSTWYH4

I think that when you slice around the entire box, there is the possibility that some carton comes with the bags when you empty the box.
>> only if you just bad cutter or cheap boxes. If the box is cleanly cut, it should lift cleanly from the pile of bags and the bottom of the box.

Another problem is that the boxes got different dimensions, so when you slice around the entire box you always have to change the settings of the opener or is there an other way?
>> You stated that one dimension was fixed, which means that it could be placed perpendicular to the travel of the belt. A blade comes out and cuts the front, two blades cut parallel to the belt, which makes that dimension irrelevant, and some sort of sensor detects the back of the box, stops the side cuts and brings out a blade to cut the back.

It could be similar to 3DDave's video, only the cutting would be along the bottoms of the boxes, which would allow the belt to simply dump all the bags while retaining the bottoms of the boxes on the belt

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It is not clear whether the rice is to be removed from the bag as well. I assumed that both the box and bag are to be opened.

Guillotine cutter, falling into a sieve/separator/tumbler to remove carton and bag debris and to shake out the rice. 600 boxes per hour should be child's play.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

@Compositepro The installation only have to put the bag out of the box because there is already a machine that seperates the rice from the bags.

@orneynorsk Because rice bags may not be opened I think such a machine isn't achievable.

After some testing I think it's possible to open the box at the top with a rotating knife. Because when I use a normal knife it seems like the box doesn't got enough resistance and folds.
When I try to open the box at the bottom,I always cut in the bags because the box is very full with bags.

What is the easiest way to empty the box after opening it? I'm looking for a way to rotate the box 180°

Box cutting requires some amount of thought. If you're using a typical box cutter with the blade fully extended, then yes, you'd likely cut into bags. The cardboard of a typical box is rather thin, certainly less than 1/4 inch, so your blade should be retracted so that only 3/16" or so is exposed. Secondly, bags of rice, while compliant, are unlikely to get into the bottom corners of the box, hence, your cutter should not be cutting more than 3/16" up from the bottom of the box.

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After some testing it seems that a knife creates to much dust.
Seems like I have to find an other way to open the boxes.

What kind knife are you using?

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Paper dust generation is an unavoidable product of handling paper products. Even systems that don't cut paper will become contaminated. I worked with a mail handling system where the paper dust falling from envelopes needed to be frequently cleaned from the machines. It's understandable considering that paper and cardboard are made of paper dust; it just doesn't look like it because they are suspended in water during the manufacturing process.

There are various systems for blowing dust off things that should be clean and dust collection systems to limit the spread.

I'm using a rotating knife, with cut length 1cm.
You can't see the created dust, but in the lab they tested it and it creates to much dust for the consumer.
Maybe there are possibilities to open the box without cutting? Like 3DDave says, it will also generate dust but a filter can reduce it to a acceptable amount.

Is the rotating knife serrated? Generally, anything that rotates will have some level of frictional contact, which will generate dust

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Here are some possible solutions to the dust:
1. Slow the rotation of the blade.
2. Try different cutting edge geometries. Sharp and polished will minimize dust. Grind marks on the blade can act as sand paper.
3. Place a vacuum pick-up near the blade.
4. Humidify the cardboard before cutting it. It can be done in storage or as part of the cutting process with a little spray.
5. Make sure the blade rotates toward the outside of the box as it cuts.

If you are cutting the bottom of the box (easy location) I can see an issue of occasionally cutting the bag too (gravity hurts). This EE is picturing a spring loaded container that is as deep as your tallest box. So you'd move the box to be opened to the container, set it on the spring, and then have an arm push it down and hold it at a fixed height. Now when you cut the box gravity has pulled the bag away from the blade (gravity helps).

What would Rube Goldberg do?!

Z

Found the perfect thing (to take one's mind off the problem while still being on topic):

https://www.youtube.com/watch?v=7JyhWhgNXSc

My boss doesn't want to use a knife because he's afraid that it will influence the quality of the rice.
Weaken the box by humidify also isn't an option becaus of quality issues.
Now I'm more looking for an option to open the box at the top, where the box gets closed.

"My boss doesn't want to use a knife because he's afraid that it will influence the quality of the rice."

This seems like an important requirement. Please clarify how it's supposed to "influence" the quality of the rice.

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It will influence the quality of the rice, because it generates to much dust.
A static knife could well be an option, because it generates just a small amount of dust which can be filtered.

I don't understand why your boss cares about influencing the quality of rice once it has already failed quality checks.

You stated the rice was in plastic bags?

How can a knife generate more dust than what amounts to a saw?

A failed box requires extra handling anyway, to sort out good rice from bad, so dust would seem to be a minor issue.

Moreover, at the heart of the problem is the adage that you should find and fix faults BEFORE you have to take things apart to repair or replace them; that means that your company should be looking at how to eliminate boxing bad rice in the first place, which would therefore eliminate the need for a specialized piece of hardware for re-opening them. Your stated design goal of 600 (bad) boxes/hr is insanely ludicrous; how many boxes are expected to pass? If the percentage of failures is not less than 0.1%, then there's something seriously wrong in your manufacturing process.

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@JNieman there are little holes in the plastic bags, I think that's the reason why. I also don't really understand why it's not an option because like you said it already failed the quality control.

@IRstuff I think a saw generates more dust because it makes an back-and forth motion. It is pretty hard to fix the faults who generates the bad boxe because they are the result of human faults.

It's possible to open the box at the bottom or top side with a static knife. The next part is to seperate the ricebags from the box. Is there a possibilty with a twisted belt so the ricebags slide out of the box?