Request for assistance for the finalization of the shredder project

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21

Hello

Two remarks: the teeth of the knives should not attack the material at the same time along the length of the shaft but should be offset in such a way that your mandrel is simply sucked up. (In other words, only one tooth of the motor shaft and the secondary shaft touches the mandrel.) If not, chances are your chuck will jump for a long time before being sucked up by your grinder.

No pins for the sprockets. In principle, the minimum bearing area between the key and the pinion must be at least equal to the bearing surface of the pinion teeth.

UNLESS you want to create a torque limiter, in which case you have to size the pin so that it gives up to the desired torque.

I haven't done any calculations and I'm not asking you for the power of the motor but seeing the 3D of the engine I assume that it is at least 5 to 6 Kw for 1500 rpm, I have the feeling that it's greatly over-dimensioned to shred cardboard not to mention the reduction gear which multiplies the torque by about 20. All this to say that I think you will be able to grind washing machines if you run out of cardboard... (Hihi)

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22

Hello Yves

In reality, if you look at the assembly, there is a kind of disc torque limiter. This will prevent the engine from burning if it jams. :-)

 

23

Good evening

Totally agree with you

I will change the pin solution by a parallel key with 2 circlips in both sides of the wheel (spur gear). Indeed, as Zozo says, there is a risk of gambling in case of shocks...

The geared motor has a power of 11Kw with a maximum torque of 4332 Nm so as Yves T says  to grind washing machines ...

@Zozo

I would like us to decide  on the geometry on the knives.

Kind regards 

24

Hello Firass

I made you a new shape for the 3-tooth knives but above all they are mounted in alternating angular.

You should have the piece in the morning with the proposed assembly plus an animation that shows you how the chuck will be crunched.

See you later

 

25

Hello everyone and Firass

Here are the images of the knives and their operating dynamics. The knives on one side are not all aligned but offset by 60° one knife out of two (this is in line with Yves' remark)

This 1 out of two offset has the effect of having less effort on the trees and facilitating shredding.

I'm doing the animation, which will follow in the afternoon.

@ Firass   Be careful, your center distance between the two shafts is 1 mm wrong , which means that your primitive diameters will not be superimposed and this will create jolts and shocks on the gears because of the artificial play you create in this way.

 

 


dynamique_dechiquetage_vue_1.zip
26

@ Firass and @ all those who have an interest in this subject

Here's a little animation that's a little simplified.

 


animation_dechiquetage_v1.mp4
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27

Hello Zozo,

I am very happy with your solution. 

Indeed, you have improved the knives for several reasons (if I have understood correctly the phenomenon of cutting with the effect of "eagle's beak" pliers) the cutters will be very small because of the center distance (I think it will be 127 mm instead of 128) in addition the shape of the knives with the rings (work as blade and lamé tale it is according to the photo "operating knives").

Another thing, according to the "dynamic shredding" photo, there is an alternation between the teeth in a way that 2 teeth fix the chuck and 3 teeth crush the chuck and so on...

So to confirm your solution, I would like to know the section of the active part of the knife that will crush the material and the number of teeth that are aligned for a single shaft.

NT: Your quality of explanation is enormous and well simplified, thank you!

Kind regards 

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28

The knife is 10 mm thick and the rings 12 mm. But we both have to make them thicker in due proportion if we want to play it safe.

I didn't do a simulation because I don't know the (real) force it takes to shear the thickness of the mandrel in one go.

I think that if you work on the shape of your hopper, you could better control the shredding since luckily we always have the same object to shred. This fact allows us to specialize a more hopper, something impossible if it were a universal machine.

29

Which version of SW do you have if it's SW 2018 it's easy I'll send you the sub-assembly: otherwise I'll send you a drawing in PDF format and you just have to redo the shape of the knife in less than 10 minutes.

:-)  :-)

 

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30

Hello Zozo,

Well, we can estimate the shear force by the product of the shear stress for the mandrel (we will take 6.4 Mpa) with the sheared section for example like this (Sc=774 mm²)

But you need a volume (the hopper) that will occupy certain numbers of the mandrels, otherwise, you can then know the shredding rate of this machine. 

We have the same version of SW :-)

Kind regards 

31

Firass

I don't know if you remember but at the beginning of our discussions I was asking for the force needed to get through the 18 mm thickness  of the mandrel.

I would like a force measured concretely by putting weights on a tool (a jack with a pressure gauge will do (in the absence of a penetrometer) and not from a theoretical calculation to which I give no credit because kraft cardboard is really special.

You have to be careful because after a few centimeters of grinding the tube will bend in half. In other words, the two edges of the small ray will touch. From this moment on, three or six knives will have twice the thickness to cut.

In addition, the cylinders formed by the mandrels are costy, so bending the cylinder in half will require significant effort (data that we don't know yet but that you could experiment with by putting weights to crush a mandrel in the radial direction. Can you find this value by measuring in real life? 

That said, I don't know if you know it, but a cardboard chuck crushed in the radial direction, but the material loses its coherence because the Kraft disintegrates because the different layers of each winding no longer stick together. This phenomenon facilitates cutting. But even with this phenomenon, you have to slice 36 mm of cardboard in pliers mode.

For the number of Crunchable Mandrels simultaneously, if you modify your hopper as I suggest, then the number is four,  however, Three seems more reasonable to me. Look at the joint assembly

You don't need to crunch more than 15 x 3 per hour (I think three minutes per chuck). We do not know how many of them must be destroyed at the present time????

Attached are your parts in the assembly  in 2018  version :-)


assemblage_des_couteaux_avec_moindres_efforts.zip
32

Hello

Firass, have you thought about why you need to modify the top hopper and have you been able to model something.

I'm trying to go step by step so as not to drown you but there's still a huge OS in your design.

1°) The motor is not fixed on the same profiles as the sides that support the shafts of the knives.

2°) you don't have an elastic coupling between the output of the motor shaft and the disc torque limiter. While the simulation shows that you have a slight radial fexion at the end of the shaft that holds the knives. You have also put articulated bearings which is wise.

3°) you have no chance on welded mechanics to have any parallelism between the engine base and the profile that supports the shafts of the knives. Especially since you went to put your engine at an antiquity with the frame and you don't have any gusset or strut on your frame. Your frame will move in the axial direction by several millimeters or even centimeters

4° You have not provided any mechanical system to make the alignment between the two shafts (motor shaft and knife shaft)

Remember that the adjustments are at least H7 in the coupling

So here is the problem you have to solve in my opinion.

Kind regards

PS Can you really make this machine??
Or do you only have to produce a complete design file.
If your tutor (teacher) or your supervisor in the company are good, they shouldn't accept the assembly of the engine like that given the level of diploma you are aiming for.
Good luck

 

33

Good evening

I think you need to add a lid at the top of the hopper so that the mandrels will be blocked when shredding, so that the opening volume will be reduced.

For the coupling I will eliminate the torque limiter by a removable elastic hub coupling because the hub of this limiter is insufficient for two keys with the knife shaft (but the problem is the motor will be damaged during an overtorque!!).
Is the displacement of the frame due to the vibration resonance of the motor?
I think that the rigidity of this frame is satisfied when we talk about a safety factor of 3 (result after simulation) without gussets.

Really for the alignment system I have no idea but I'll try to look for it.

For me it's just study and design but the realization to review the company in the long term  (if the machine is beautiful).

(I think this project has an infinite number of mistakes with you)

Thank you Zozo for your attention.

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34

Hello Firass

No, there are not an infinite number of errors, you have made very good progress and you are making the necessary changes.

If you put an elastic coupling it will be fine but I think it would be better to consider shims under the engine to have an alignment as close as possible. Indeed, with mechanically welded frames, it moves quite a bit during welding and it is quite difficult to have a millimeter or less. It is better that the engine mount is 5 to 8 mm lower and put shims for upward alignment.  The elastic couplings are forgiving but not too much anyway.

For the protection of the motor, you have to see the manufacturer or an electrician because there are systems that cut off as soon as you exceed a certain load for X seconds. (this plays with the amperage which increases if it blocks). I put it on the electric actuators and it works well safely.

For the hopper you will find a proposal attached

It's up to you to adapt it!

The idea is that the mandrels go down as vertically as possible and that each mandrel remains separate from the others for as long as possible.

In the proposed model what matters would be to respect the orange faces, Be indulgent because I did it in a hurry like a bully. It's just to suggest an idea, but it's up to you to see how you make it happen.

You're pretty much done now and that's not bad at all.

Courage, the finish line is not far away. :-)  :-)

 


asm.zip
35

Hello Zozo

Good idea
but I don't know why you add this extra part, my question is are there any problems if the mandrels touch each other?

Otherwise you have reasoned on a single case (vertical mandrel) and then you have forced the operator to put them in this position, while he will throw the mandrels at random so possibility the case of (horizontal mandrel).

It's just so that the operator has the freedom to use this machine so no constraints.

Yes, don't forget that this part has an advantage to avoid chucks hitting the hopper wall, plus that on welds.

In my opinion I think the hopper remains open like the universal machines.

(I respect your idea, but just to make it simple)

For the safety of the motor, how does the electric actuator work?

I really only know mechanical, hydraulic and pneumatic cylinders, but this is the chance for me to learn new solutions with you.

Kind regards 

36

Hello

For the hopper I don't share your point of view but it's not important, you're right to do what you think. Practice makes you strong at swearing!!!


Especially since the machine will not be built in the near future.

However, I made this proposal only because it limits the effort on all the knives. In addition, I am not convinced that if a chuck comes horizontally, the knives can shred it easily, but as soon as the knives have managed to grip the mandrel, you will have the maximum effort because the chuck will bend in half by the crushing. With the vertical water solution, instead of having two thicknesses over 500 mm, you will have it on one diameter so the efforts will be much less.

Operators who throw it in bulk or throw it vertically doesn't make a big difference, especially since you still haven't told us how many they are supposed to destroy per hour.

To end the conversation on the subject you say (( are there any problems if the mandrels touch each other ? ))

No problem if they touch each other before they start to be taken by the knives. Once one or two are caught by the knives, it doesn't matter anymore since the mandrels can't interpenetrate each other. FIFO First In Firts out method - in other words, the last one caught by the knives cannot double the one who was grabbed first by the knives.

The simplicity of the so-called universal hopper should not be opposed to the robustness and reliability of the process.
I'm a proponent of the KISS keep it simple and stupid method, but from experience, unreliability will always cost more than a barely more sophisticated hopper.

Especially since with the vertical method the effort will be less on the hopper.

In fact, to decide between us on this point, we would have to have the machine and do tests with bulk and strictly vertical ones. We would see what the engine would say in terms of effort and depending on the case it would be enough to modify the hopper in the direction I propose or not.

Which brings me to the question you ask (( For the safety of the motor, how does the electric actuator work? ))

I told you that you had to pick up on the variation in amperage. This is what specialized electronic boards do and which cut off the power relays that supply the engine at the predefined time in advance. (it's almost the same as the thermals on the power relays). I can't tell you much more but the engine manufacturer must know this because depending on the power the problems are not the same. Moreover, it is outside my area of expertise. This must not be an esoteric solution because my three electric actuator manufacturers do it.

There you have it, keep us informed of the grades you will get.

Kind regards

PS: for those who have followed us so far and who don't have the SW2018 I'm posting some pictures that have fueled the discussion on the hopper :-)  :-)
We don't get paid a lot but we have a lot of fun :-)

 


vues_tremie_-_mandrin_verticaux.zip
37

Here's the ASM for animation.

Kind regards 


machine_complet.zip
38

Can you send us report and design

39

Hello

We can also deliver the parts to you and free of charge

However, in our countries it is customary to say  "Hello" and also "aychek / choukrane" (شكرا). 

besslama

 

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