Help with densifier for material inside BigBags

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In summary: The forklift is the best available option for now and it is the cheapest.In summary, the engineer is trying to find a way to compact particles inside a BigBags without using a vibration table. He is looking into various mechanisms, but is having trouble deciding on the best option. The material is plastic shredded scrap, and the engineer is concerned about the durability of the mechanism.
  • #1
teun-lll
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TL;DR Summary
Help with choosing the right mechanism for high load 'shaker'
Hey there. I am hoping you guys are willing to share some experience/knowledge.

Im a young engineer and i would like to expand my knowledge on mechanical engineering.
Currently I am trying to develop a densifier for material inside BigBags.
The bigbags are loaded with particles up to a total of 700kg. The bb are hanging in some clamps. The basic setup is shown in the attached file.
I came to the conclusion that i want to shake the bigbag to get the result i need. I tried putting it on a vibration table but this was not effective enough.
I want to raise the whole bb in its loops. Then drop it like 100mm and catch it again. this way the wieght of the material pushes down the material below. I've been looking at cam shafts, crankshafts, unbalance motor, gear racks and spur gears, custom mechanism with a cilinder that hooks and unhooks, pneumatic bellows and so on...
But i have a hard time deciding what mechanism would be best for minimal energy consumption and minimal maintance.
Im not asking for a full design, but i would like a head start in what general direction i can go. I really hope someone can help me out!

I hope I've been clear enough. Otherwise please ask for more information. Thank you!
 

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  • #2
Hello @teun-lll , :welcome: !

Is this an exercise or an attempt to re-invent the wheel ?
Or are you prepared to make good use of already available knowledge so you can stand on the shoulders of your ingenious predecessors ?
(Better well copied/stolen than invented poorly :wink: )

A little https://www.knauer-engineering.com/fileadmin/image/Ruetteltische-Ruettelboecke/Videos%2BProspekt/Brochure%20Vibrating%20tables.pdf can do no harm ! ('unbalanced motors and bigbags')

1606818181649.png
 
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  • #3
Thanks for the response. like i said before, a vibration table does not work with our product. The vibrations don't travel trough the whole bag. I have tested this option by renting a table like your example. I try not to invent the wheel again but i don't see another available option.
Maybe this helps:
Currently we shake the BigBags with a forklift. We raise the bag ca 5-10 cm and then we drop it. This is an expensive option.
 
  • #4
I re-read your post and find experiments with vibrating don't meet expectations.
Perhaps the density of the material isn't sufficient ? Is it compactable ?

I would expect raising and dropping won't be much better: only the bottom layer gets enough pressure to compact.

Wouldn't compaction from above be more efficient ? When we lived in the US, the trash compactor in the kitchen was a revelation -- hadn't seen that in Europe.

Note also that unloading becomes more problematic when compaction is indeed successful !

[edit]saw your reply. What is the material ? 700 kg/m3 isn't all that much.

Had more fun googling. Big bag compactor is taken litterally and goes in the wrong direction :-p

But some are more to the point: https://www.emde.de/en/bulk-materials/big-bag-handling/big-bag-compactor/
 
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  • #5
BvU said:
I re-read your post and find experiments with vibrating don't meet expectations.
Perhaps the density of the material isn't sufficient ? Is it compactable ?

I would expect raising and dropping won't be much better: only the bottom layer gets enough pressure to compact.

Wouldn't compaction from above be more efficient ? When we lived in the US, the trash compactor in the kitchen was a revelation -- hadn't seen that in Europe.

Note also that unloading becomes more problematic when compaction is indeed successful !

[edit]saw your reply. What is the material ? 700 kg/m3 isn't all that much.

Had more fun googling. Big bag compactor is taken litterally and goes in the wrong direction :-p

But some are more to the point: https://www.emde.de/en/bulk-materials/big-bag-handling/big-bag-compactor/

haha thanks for sparring with me. The Whole bb weighs 700kg and contains plastic shredded scrap(not fines or granulate). Fun fact, i also tried compacting the material with the compactor you just sent. I pressed the particles in the big bag with this screw. The results were ok. I got the compression i needed but the bb were shaped badly and a great forces was needed to keep the screw running. Besides this i think the screw will wear out fast.

I know for a fact that the material is compactable since we use a Linde forklift to get the right result. Vibration is just too weak. I want to try avoiding a press mechanism since the machine is going to be operated semi automatically. For safety reasons i want to avoid a press if possible. You are right that the top part of the bigbag will be less compressed when shaking. But with forklift method this is not a big problem. I am trying to find a substitude for shaking with a forklift. Only a Linde forklift is capable of shaking like we do, and now we have one of those reserved fulltime just for this activity. This needs to be changed.

You are also right about it being harder to unload. But this is not a problem. Our client wants it this way.
 
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  • #6
You will probably need more vigorous action, but can you apply the shake table idea while the bag is being filled?

Of course shaking mostly rearranges the shredded material without deforming it very much. The forklift drop probably does both, and the compactor just deforms the pieces.

The misshapen bag problem from the compactor can be solved by enclosing the bag as is normally done in a home trash compactor.
If the bag extraction is vertical, probably need two of the enclosure walls to be movable to release the bag. If extraction is horizontal, one hinged wall is also needed for forklift access.

Cheers,
Tom
 
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  • #7
Thanks Tom. I've thought about enclosure walls for the compactor. Yet i would still be left with the screw being under high force and it will probably wear fast.
I'm also scared that a very aggressive shaker table doesn’t work because the particles keep jumping around instead of moving to a "gap". I am able to apply the shaker table idea while the bag is being filled. This works especially well in the first part of the filling. The more material the less effect it has.

I want to look at some replacement for the forklift to achieve, like you said, both compression and deforming. So i want to shake the bag more aggressively than a shaker table.
So what would be a good way to achieve a linear, vertical motion, with a relatively low frequency and 5-10cm displacement. I’m now trying to see if a crankshaft or camshaft would be best.

Thanks again guys. I hope yall can see this like a fun puzzle, because i do! I just wish to finish the puzzle sometime soon ;)
 
  • #8
teun-lll said:
Yet i would still be left with the screw being under high force and it will probably wear fast.
Use a bigger screw. (Careful who you say that to and in what context. :wink:)
Or maybe a ball screw, the ones with re-circulating ball bearings comes to mind.
Or use hydraulics. Your idea of a crank also sounds possible.

A cam maybe and maybe not. I suspect you need a downward acceleration of one G or greater, you need solid coupling on the downstroke to get the 'or greater.' But a cam is cheaper than a crankshaft.

teun-lll said:
...shaker table idea while the bag is being filled. This works especially well in the first part of the filling. The more material the less effect it has.
That's expected, shredded anything acts like a distributed spring.
How about shaking the whole bag horizontally?

Cheers
Tom
 
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  • #9
Tom.G said:
Use a bigger screw. (Careful who you say that to and in what context. :wink:)
Or maybe a ball screw, the ones with re-circulating ball bearings comes to mind.
Or use hydraulics. Your idea of a crank also sounds possible.
hahaha! Bigger screw is not a bad idea... Do you mean that i can use a ball screw to raise and then drop somehow?
I'm thinking about testing a hydraulic shaker. Maybe with a very low frequency, high amplitude.
Tom.G said:
A cam maybe and maybe not. I suspect you need a downward acceleration of one G or greater, you need solid coupling on the downstroke to get the 'or greater.' But a cam is cheaper than a crankshaft.

There are so called snail cams. They allow for rapid downward acceleration. I think i need 1G not more or less. The bag won't drop faster than G allows and i don't want to catch it on it's second rotation.

I was also thinking about a system like shown in the attachments.
The yellow plate moves freely. The blue one rotates continuesly. Every rotation the red pin(and also the yellow plate) gets pushed around by the blue cam. Once it passes it's dead center on top, the yellow plate and the connecting rod can fall freely until it reaches its bottum position, waiting for the blue cam to push it around again. The BigBag hangs in a "hanging" which is connected to the slider. The slider gets moved by the connecting rod. Do you think a system like this could be robust enough?

Tom.G said:
That's expected, shredded anything acts like a distributed spring.
How about shaking the whole bag horizontally?
Yeah exactly! i did not try horizontally yet. Next week i will try to shake it more vigorous with a shaker table with a 4 pole motor instead of a 2 pole. If this does not work i'll try a hydraulic shaker.
Im also thinking of an easy way to test the horizontal shaking. Maybe i can use a forklift with sideshift.

But thanks Tom, I really enjoy sparring sessions like this. Glad I signed into PF!
What is your professional background? You seem to have experience.[/QUOTE][/QUOTE]
 

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  • #10
teun-lll said:
Im also thinking of an easy way to test the horizontal shaking.
I think the main problem with the vibration table is that it relies on the weight of the material compressed, while the vibration actually works against that weight (keeping the stuff 'floating').

Solution: put the table on the top of the bag. Maybe you can even weight it down.
You may need to put the bag into a compartment with solid walls, though...

Ps.: alternative solution: put the walls of that compartment on hinges and add an excenter so the walls could 'slap' the bag from the sides. This might also require additional weight from top.
 
  • #11
Rive said:
I think the main problem with the vibration table is that it relies on the weight of the material compressed, while the vibration actually works against that weight (keeping the stuff 'floating').

Solution: put the table on the top of the bag. Maybe you can even weight it down.
You may need to put the bag into a compartment with solid walls, though...

Ps.: alternative solution: put the walls of that compartment on hinges and add an excenter so the walls could 'slap' the bag from the sides. This might also require additional weight from top.
Hey Rive. I really like the way you think. Outside the box... nice!
However, I can not put the table on top because it needs to vibrate while being filled.
But i agree that it needs some weight in order to work.

But in conclusion:
Im going to try a more vigorous shaker table
I will try horizontal shaking with a forklift with sideshift
I will look into making easy accessibel compartment walls to shape the BB and help coordinate the compression.

I will update you all if this is done.
@Tom.G I'm still curious for your response if you have the time.
 
  • #12
Hi @teun-lll, I got busy yesterday and didn't get on-line, hence the delay.
teun-lll said:
I was also thinking about a system like shown in the attachments.
The yellow plate moves freely. The blue one rotates continuesly. Every rotation the red pin(and also the yellow plate) gets pushed around by the blue cam. Once it passes it's dead center on top, the yellow plate and the connecting rod can fall freely until it reaches its bottum position, waiting for the blue cam to push it around again. The BigBag hangs in a "hanging" which is connected to the slider. The slider gets moved by the connecting rod. Do you think a system like this could be robust enough?
Last question first: almost anything can be "robust enough" with enough material in it. I am a little confused about its operation though. If the bag is suspended by the Green shaft at the bottom, at the most the spring will allow the bag to free-fall for a short distance. But you don't need the spring. When the pin gets past TDC, the bag will free-fall anyhow,
teun-lll said:
What is your professional background? You seem to have experience.

I'm retired now, but my back ground is mainly Electronics product/systems development. I was one of those guys that got called in when a company didn't have the in-house capability available for a new product, product upgrade, or needed to make a new product actually work. Also a bit of mechanical knowledge (I did my first engine rebuild as a teenager).

I guess a generalist with focus on Electronics would be the closest description. I've worked on stuff ranging from controls for an anti-aircraft gun to the first magnetic-stripe reader for credit cards, control systems for punch presses to a warehouse for sugar and corn syrup (railroad cars in, tanker trucks out, about 22 miles of control wiring and 35 pgs of "D" size (22x34 inches) schematics, took 3 yrs, the documentation ran 4000 pgs). Then I retired!

Now PF keeps my brain working. :wink:

Cheers,
Tom
 
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  • #13
Tom.G said:
Hi @teun-lll, I got busy yesterday and didn't get on-line, hence the delay.

Last question first: almost anything can be "robust enough" with enough material in it. I am a little confused about its operation though. If the bag is suspended by the Green shaft at the bottom, at the most the spring will allow the bag to free-fall for a short distance. But you don't need the spring. When the pin gets past TDC, the bag will free-fall anyhow,
Allright i think i have to explain my idea a bit better. The spring needs to change so that it just absorbs some of the shock from falling. I want to do this so there would be less sound and less wear. In the example i sent it accelerates the green shaft on its way down. I indeed don't need this.
I like this mechanism because of the freefall feature. Otherwise i have to match the rotational speed of the crank/cam so that the pin does not go up when the bag is still falling.
If i want a 5 cm displacement. I think i need about 90 rpm so the bag will still fall all the way down before getting picked up. This would be without the freefall mechanism.

Tom.G said:
I'm retired now, but my back ground is mainly Electronics product/systems development. I was one of those guys that got called in when a company didn't have the in-house capability available for a new product, product upgrade, or needed to make a new product actually work. Also a bit of mechanical knowledge (I did my first engine rebuild as a teenager).

I guess a generalist with focus on Electronics would be the closest description. I've worked on stuff ranging from controls for an anti-aircraft gun to the first magnetic-stripe reader for credit cards, control systems for punch presses to a warehouse for sugar and corn syrup (railroad cars in, tanker trucks out, about 22 miles of control wiring and 35 pgs of "D" size (22x34 inches) schematics, took 3 yrs, the documentation ran 4000 pgs). Then I retired!

Now PF keeps my brain working. :wink:

Cheers,
Tom
Sound interesting. I always have respect for "generalist" who can problem solve for matters they are not specifically experienced with. Its a mindset that i stive to obtain over the years with experience. Good that you keep your brain from dusting up and instead share your knowledge. You gave me some new insights that i want to look into. If you wish i can update you when the final system is up and running.
 
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  • #14
teun-lll said:
Im also thinking of an easy way to test the horizontal shaking. Maybe i can use a forklift with sideshift.
Put a shake table on edge and prop it up with a few forklifts. You may have to rig a temporary shelf/platform and/or wall for the bag. Details left to the implementer. No nearby observers though in case the shaketable falls over!
teun-lll said:
If you wish i can update you when the final system is up and running.
Yes, I would appreciate that. It's always nice to know the final results, whether successful or not. We often learn more from the not-yet-successful ones!
teun-lll said:
Its a mindset that i stive to obtain over the years with experience.
A wide-ranging and general curiosity helps a lot... and do take advantage of opportunities when they arise so you don't get stuck in a complacent rut.

Cheers,
Tom
 
  • #15
teun-lll said:
I can not put the table on top because it needs to vibrate while being filled.
How do you fill the bag? There is some kind of hanging flexible pipe or funnel for this, or... ?
 
  • #16
Tom.G said:
Put a shake table on edge and prop it up with a few forklifts. You may have to rig a temporary shelf/platform and/or wall for the bag. Details left to the implementer. No nearby observers though in case the shaketable falls over!
This sounds like a fun test. If the shaker table returns with the 4 pole unbalance motors i will also try this!

Tom.G said:
Yes, I would appreciate that. It's always nice to know the final results, whether successful or not. We often learn more from the not-yet-successful ones!

A wide-ranging and general curiosity helps a lot... and do take advantage of opportunities when they arise so you don't get stuck in a complacent rut.

Cheers,
Tom
Allright, I will update you. I made a prototype of the mechanism i was talking about. I see that i might not need a spring at all. The rotating motion of the freely rotating backplate will damp the fall by going back and forth around its resting position. Ill have to check for wear though. You can see a video of the prototype here(too big to upload on PF):

(The material in the small bag is not the material we need to load in the actual BB's)
Ill be good with the curiosity haha. I am interested in a lot of (or too much) stuff.
But ill update you then as soon as i made some relevant progress.

Thx!
 
Last edited:
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  • #17
Rive said:
How do you fill the bag? There is some kind of hanging flexible pipe or funnel for this, or... ?
We fill the bag from the top with a conveyor belt. We hang the BB like the drawing in the attachment(without the springs)
 

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  • #18
teun-lll said:
We fill the bag from the top with a conveyor belt.
There is a thing called 'vibro compaction'. It's usually used on soil, but I think you can adapt it (without the water part, of course).

The point is, that the 'pin' makes room on the bottom with vibration (pushing aside the material below and using the weight of the material on top) so you can keep the top feed.
Maybe even with four 'pins' in one go.
 

1. What is a densifier and how does it work?

A densifier is a material that is used to increase the density of a substance. It works by filling in the gaps between particles, making the material more compact and reducing its volume.

2. Why is a densifier needed for materials inside BigBags?

BigBags are large, flexible containers used to transport and store materials. These materials can often be bulky and take up a lot of space, so using a densifier helps to reduce their volume and make them easier to handle and transport.

3. What types of materials can be densified inside BigBags?

A variety of materials can be densified inside BigBags, including powders, granules, and even liquids. Some common examples include cement, fertilizer, and plastic pellets.

4. How is a densifier applied to materials inside BigBags?

The densifier is typically added to the material inside the BigBag using a specialized machine or equipment. It can be applied in different ways, such as spraying, mixing, or coating, depending on the type of material and the desired level of densification.

5. Are there any safety or environmental concerns when using a densifier for materials inside BigBags?

It is important to carefully select a densifier that is safe for both humans and the environment. Some densifiers may contain harmful chemicals, so it is crucial to follow proper handling and disposal procedures. Additionally, using a densifier can have a positive environmental impact by reducing the amount of packaging and transportation needed for the materials.

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