Well on this topic I'm going to talk a little about my project of a shredder that consists of shredding cardboard cores. In fact, the project has two parts; the 1st is the shredder and the 2nd is a screw conveyor that will transport the cardboard cups in a "Big Bag"
But I'm interested with the shredder.
Since the operation of a shredder is known, I will go directly to the connection with the screw conveyor. Indeed, below the shredding unit there is a sensor that will detect the presence of the cups and therefore the screw will transport the chips, i.e. the sensor plays the role of a contactor of the conveyor geared motor. For its operation; The cups are supported by an aluminum plate and the latter will touch the end of the sensor, its movement (the plate) is done using a spring hinge.
(see the design for a better understanding)
I found at this point a problem with the installation of this sensor otherwise its disassembly.
In short, if there is a possibility to improve the design of this machine or to correct mechanical errors, I hope that it will be good to finalize this project.
Thank you for sharing your project with us and asking for our opinion.
First of all, I see all the work done and it makes a big lot of hours of drawing and research of all the elements to get to this stage of the project.
Be careful not to go too fast because the plate that will trigger the micro-switch is not finished. As I see it in the drawing, there is no chance that the switch is activated. Because don't forget that shredded cardboard is very light.
I don't understand at all what these big M25 bolts and nuts are doing. In addition, they are in total collision with the contactor.
I am preparing a more complete answer for you tomorrow as well as some benevolent remarks.
Before talking about the manufacture of sheet metal, etc. etc... It would be good if we talked about functioning on the one hand and physical phenomena on the other.
In short, you don't want the worm screw to rotate all the time, but also you don't want it to do on-off all the time because you wouldn't save electricity by doing that (overconsumption at start-up) and the motor is not designed for that
1°) the screw in your electrical panel must not rotate when the shredder is stopped. For example your worm screw would stop "X" seconds after the shredder stops (unless you stop punching obviously which stops everything)
2°) your auger evacuates the entire stock contained in the "Assemble4" part in less than ten turns.
3°) Physical phenomenon: the cardboard reduced to the state of chips and dust is very light and the chips should have a grain size of less than 10 mm since the holes in the grid are 10 mm.
3-a) So you're going to have what's called a vault (the material is self-blocking) between your "Folded Sheet Metal7" and "Copy of Part4" part
3-b) In addition, the material will become stuck on "bent sheet"7.
Personally, I would not put the "Folded Sheet Metal7" piece and I would lengthen "Copy of Part4" up to 300 mm and I would put an angle greater than 45° on it (otherwise arch formation). The lengthening will also simplify your life for the choice of the return spring of your articulated plate.
For the spring, only one is enough and placed in the center, otherwise given the low weight of your shavings, your plate will remain immobile because you have to rely on the spring of the Switch.
Pay attention to the fanciful representation of your springs and the clearances necessary for the middle spring (you have a mega collision between the hinge and the springs)
You have to completely redesign this oscillating plate and the switch release because in addition you are in a very dusty and abrasive environment
Personally, I wouldn't put a switch at all. The screw should clear the chips all the time it runs + (Carton Volume /Screw Throughput).
I find the design relatively clumsy: impossibility to do some machining on the axes, countless number of screws, no play to allow the knives to be tightened,...
For the hoppers, you can make them in one and the same room.
For the oil pan, the design must be reviewed because as it stands, there will not be a drop of it... (impossibility of waterproofing)
I try to be indulgent and help Firass who, let's not forget, is a student in the 3rd year of Mechanical Engineering specializing in mechanical construction and manufacturing at the ISET of Nabeul in Tunisia".
That said, I encouraged Firass to create this topic precisely so that he could collect all the remarks and teach the contacts of the oldest or the most competent.
The housing that protects the two gears has already been improved compared to last week's version where there were no sidewalls, so all the abrasive dust from the cardboard would have worn out the gears. In my opinion it's now a grease box and not an oil box (to be confirmed by Firass) that's it given the game there is it's going to be mush in the box in less than three weeks.
I wouldn't put a MicroSwitch either because otherwise the motor of its worm screw will make perpetual stop and go. But I respond to his request.
Can you show us where machining is impossible STP?
There are other more serious errors in AMHA's system and we will quietly show them to him. :-) :-) especially since Firass partly takes into account what we suggest to him.
I'm waiting for firass' remarks because I discovered a very very big problem (I don't dare to say ) that will lead to the ruin of a part of the machine and even beyond.
So the two geared motors must be synchronized (on and off at the same time) and in this case the Switch is negligible.
Yes the cups are light but if we go back to the Switch with its characteristic that works when at least a force of 2.5 N, so if I were to lengthen << folded sheet metal7 >> with aluminum as a material its weight will exceed 0.25 Kg and therefore automatically the Switch will operate despite the fact that it does not have cups (on the other hand if the choice of tension spring is well determined with its aperture torque for a small angle it is between the initial state of the plate and the state of contact with the Switch, I hope it is the right choice, but to be reviewed) (I have already chosen badly for the <<copy of part4>> because of its net weight)
I used << folded sheet metal7 >> it's just to guarantee the support of the cups on << copy of a part4 >> at the end of the Switch.
Well and I'm okay with a single spring placed in the center and I find a spring hinge like that
" Arch formation" with "the grease box" to review with you.
@Yves T
Thank you for your answer
Good for machining the axes they are easy and I am confident that they are simple to make.
In fact, 3 operations of surfacing, grooving and drilling with a vertical milling machine, and other operations such as carriage, straightening and threading with a parallel lathe.
Yes, for the hopper, it's true directly by folding.
In short, I totally agree with you, but you have to do the simple thing to make it happen :)
I'm waiting to learn more mistakes in this project.
Here are the big problems that arise if I don't make a mistake.
I am convinced that the grate (hopper) will not hold the shock. I have made a simulation of the forces exerted on this grid and you will not stay within the limits of elasticity.
Indeed, putting this grid complicates everything because it will take several dozen turns before the shredded pieces manage to pass through holes that are only 10 mm Ø.
This is also due to the fact that your knives can let very large pieces pass through that will press on this grid inconsiderately. In addition, the large pieces will form a wedge before rising up and eventually being crushed by the vertical spacers.
As it takes several turns for the material to pass through the holes and the knives will continue to stuff downwards, I think that your hopper will leave (on vacation at the top of the Djebel Ressas) causing more or less significant damage.
But enough speeches you will find the different documents in the attached link.
It contains - An explanatory drawing of the tamping - A video that roughly explains where the problem is (take a good look at the top view) - A video of the simulation (you also have a safety factor of less than 1. - A 3D PDF that will allow you to look at the part of the machine that served as an example. To read the 3D PDF you need to
Double click on the file ==>Click option ==>approve the document ==> wait a few seconds for the little watch ==> then click on the blank screen==> the 3D appears ==> Then you have a button at the top left to rotate, zoom, etc...
The mouse wheel allows you to zoom in (3D mice do all the positions)
I tried to make modifications for the material in terms of material and shape.
I find a C.S of 1.7 In fact I chose the E360 with a thickness of 7 mm, and for the shape I eliminated the support surface at the top with a change of radius and a reduction of the number of holes, so that the pieces will pass through the holes in a progressive way to cause the variation of the distance between the tip of the knives and the surface of the knife. matter.
I'll put the result to validate by you
@gt22
Thank you for your answer
For the knives I used because they are recommended for this type of shredder machine because of its low rotation speed (it's 24 rpm) on the other hand the circular blades or routers are for other machines like Wood Router (very high rotation speed) so not the same case.
Yes, I have already put separating rings between the knives.
Thank you @gt22 for the VIBRANOR link I didn't know.
I put the link directly in my supplier bookmarks. :-)
Be careful for your solution with a carbide blade because the rotation of the knives is very slow (less than 60 rpm of memory)
For the story of the blocker intervals, I noticed it because in the first discussion with Firass because each knife had four teeth and I don't know why it changed to two teeth (weird ????)
For Firass to solve his problem, all you have to do is:
- Change the thickness of these knives by making them 8mm (since the holes in the grid are Ø 10
- that it modifies the shape by going to 5 teeth (the odd number favors chaos in the cutting)
- that he obviously changes the spacers between the knives on the two shafts
- And for the problem of the perforated hopper (bottom grid) it is enough to change the shape of the spacers that are fixed on the sides. It must fit the shape of the grid with holes in the lower part. This will prevent the build-up of material under the knives and the "wedge effects" that break everything.
Indeed, if the diameter of the knife is fixed (our case is 140 mm), 4 teeth require a large cutting torque since we obtain 9 teeth along a single shaft that they are working at the same time. ( also while maintaining the thickness )
Another thing, there is a problem with the penetration of the teeth in the material, in other words the chuck will move randomly on the knives and the latter are not able to attract it (I have already tested it before and I started with 1 tooth up to 4 teeth but I find that 2 teeth is the best for the reason I have says )
For the grid I find a problem to change its end with the sidewall because of the parts << against the blade >>.
I hope you saw the change on the grid ( ZIP before this answer )
Stupid question, what is the purpose of the perforated plate under the knife if not to cause jams?
The size of the chips is for me managed by the number of teeth. (simple example: circular saw blades)
In your design, how do you know that your "rectangular" chips from X wide to Y long will pass through your 10 holes? (knowing that X is in theory = to the width of the tooth and Y to the depth of the tooth)
For me, this perforated plate is a source of emm.. useless.
Look in detail at the circuit that a chip will take and you should come to the same conclusion.
I bounce back on what @ Yves T said (whom I salute)
I have the same conclusion as you about the jam and the diameter of the holes.
The mistake this design simply comes from that Firass has mixed two types of machine!
There are three main types: knife shredders/shredders such as those of Firass and others called knife shredders (although they are not knives) and finally hammer shredders.
The Firass shredder works at a slow speed (like that of scrap dealers), the so-called knife and hammer machines rotate very fast (more than 1500 rpm). The latter two categories use grids, while those of scrap dealers never use them.
CQFD
I bounce a second time on what Yves says about the thread and the groove.
Our friend Firass answered a little quickly and in my opinion next to it
As for the problem of the thread on the shaft, two things must not be forgotten, namely that the dies are conical at the inlet and that even by turning it over it cannot reach the stop of the shoulder because the thread of the die is not totally tangent to the face of the dies.
For the groove, apart from if you use a mortising machine or a carriage with a milling machine or lathe, I don't see how Firass goes about it.
Note that the groove could be made with a milling machine because the radius at the end of the groove is not annoying for the switchblade washer (if I understood the assembly correctly). Indeed the puck is currently mounted upside down in my opinion but hey.
I finish my suggestion and in addition if you have only one model of mandrel it is much easier because in addition if you put two vertical walls in the middle of your top hopper your mandrels will be nibbled from the small radius to the large one for priming. If your chucks are vertical, a big part of the problem is knives and engine power.
While waiting for me to finalize a remark.
I find that you are taking a big risk by securing your gears with a pin instead of a key. As you will have jolts and vibrations, if your pin takes a while, or little play, you will find it at the bottom of the tank.
Personally, I would never put a pin for gears with a higher modulus between 8 and 10. I didn't do the calculation of the shear of the clevis pin but it's the play that I remember. If your pin warps a little bit, it will stay in place.
Maybe my colleagues will give you more information and advice for gears
