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i'll weigh

  • Thread starter Thread starter Jeffcott
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Jeffcott

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Hello, everyone.

I designed a tape for a weigher with the following specifications:
- tape width 350 mm
- tape length 500 mm
- total weight tel 300 g
- teflon tape on steel top
the same slides on two rolls diameter 30 mm

I was then given a cc engine with the following specifications:
- power 60 watt
- number of laps 3300 rpm
with relative gearbox characterized by:
- number of laps 536 rpm
- i = 6
- performance of 0.9

I then finally determined the max transferable weight on the tape that resulted to me equal to 5 kg.
I then take advantage of the forum to ask confirmation to you all and if possible its steps for verification.
 
I did not give other data as the belt transmission I decided to carry out it with a transmission ratio equal to 1 with diamentro pulleys of 30 mm.
 
Jeffcott said:
Hello, everyone.

I designed a tape for a weigher with the following specifications:
- tape width 350 mm
- tape length 500 mm
- total weight tel 300 g
- teflon tape on steel top
the same slides on two rolls diameter 30 mm

I was then given a cc engine with the following specifications:
- power 60 watt
- number of laps 3300 rpm
with relative gearbox characterized by:
- number of laps 536 rpm
- i = 6
- performance of 0.9

I then finally determined the max transferable weight on the tape that resulted to me equal to 5 kg.
I then take advantage of the forum to ask confirmation to you all and if possible its steps for verification.
Click to expand...
How fast do you need those 50 mt/min?

greetings
Mar
 
certain sampom, and neither can the rest not be changed. everything is related to the number of pieces/hour.
 
newly verified design:
the tape allows the passage of 140 pcs/min for which, having an interasse equal to 500 mm, has a speed of 1.17 m/s=745 rpm. the total weight transported is 3 kg and the weight of the tape is 300 g. I have a coefficient of friction (hypotized) pairs to 0.4 while the steel rollers have diameter 30 mm. this tape will work 24 h. greater problem is the overheating and accessibility of the brushes of the dc motor, so I chose a motor and a gearbox definitely oversized, but that meet the requirements required. solution of this design is the choice of the s1 gear motor characterized by an output torque of 1.7 nm, 811 rpm output and a service factor of 4.7. observation to be made about the oversize is that the excess speed can safely be handled with a suitable card.
 
At this point I consider the previous question:
tape for a weigher
- tape width 350 mm (not relevant given)
- 500 mm
- total weight tel 300 g
- teflon friction coefficient on steel plane equal to 0.04 (I have some doubt about this value)
- rollers with a diameter of 30 mm
dc engine s1 with the following specifications:
- power 60 watt
- number of laps 3300 rpm
reducer characterized by:
- number of laps 536 rpm
- i = 6
- performance of 0.9

incognity will be the weight that can be transported.
 
How much data! but why do you have doubts about the friction coefficient? cmq from incompetent I would be curious to know how to solve the question you have placed. Hi.
 
atofras said:
How much data! but why do you have doubts about the friction coefficient? cmq from incompetent I would be curious to know how to solve the question you have placed. Hi.
Click to expand...
the friction coefficient despite that it does not depend on the forces at stake, as they taught us, this is not exactly truth.

the fact that a conveyor belt is tensioned more or less, substantially changes friction between tape and roller. so also the weight of the material on the tape itself can change the friction values a lot. I want to remember that the tape is not a deformable body and the more it increases the load the more it deforms, just like a road tire, increasing the contact area and the microstructure deforms. That's why the friction changes.

However if you are in the project phase you just oversize. if you are in the process of verification I would say that it is good then to consider all the variants, but there is no wonder if you are away from reality even 50%.
 
Jeffcott said:
At this point I consider the previous question:
tape for a weigher
- tape width 350 mm (not relevant given)
- 500 mm
- total weight tel 300 g
- teflon friction coefficient on steel plane equal to 0.04 (I have some doubt about this value)
- rollers with a diameter of 30 mm
dc engine s1 with the following specifications:
- power 60 watt
- number of laps 3300 rpm
reducer characterized by:
- number of laps 536 rpm
- i = 6
- performance of 0.9

incognity will be the weight that can be transported.
Click to expand...
I also see that value for teflon/steel (is all teflon? the reverse is not "telate"? . However let's leave it a moment to lose, at the limit you see after how to add the coeff.

in theory that motorization/reduction would be able to drag to the engine roller a total mass of 6.36kg.

the calculations, very simple, are these:

torque motor cm=p/ω=60/(3300*2dic/60 = 0.1736 nm
Reduced torque cr=cm*i=0.1736*6=1.0416 nm > *0.9= 0.937 nm
f=cr/r=0.937/0.015= 62.46 n > /9.81= 6.36 kgand then check with that friction if we can drag the tape without slips, according to the indications of mechanicmg. then surface wrapped in contact etc..
I usually rollers so small I only use them as crazy reinviers ("penes" even much smaller.. obviously with suitable tapes; ask the supplier). to the tow drum use larger diameters, so even more round, than that "high" rotation speed is certainly not friend of friction.
the larger ones of tapes very wide and long I make them rubber.
then sure, with the pretension generally "adjusted" everything, but on such a small axis and (relatively)long if you exaggerate risks of inflectioning the roller with abnormal loads on the bearings. rather for so reduced diameters I would put a full tree mounted in supports on the sides. the bearings will be "external" (so load on the inner ring) and you can oversize them to pleasure (in that tube you are forced to put small stuff) and avoid the complications of pipe, post, center etc..

One thing,
say that the operation will be 24h, but do you mean in a continuous way without continuous stops and repairs?
because in case the service factors may vary a lot.

greetings
Marco:smile:

p.s. maybe I made some confusion between this and your other bearing post.. But I think you're talking about the same application. - Wrong?
 
then look what I found between my documents in the pc (he posted it some time ago it seems to me):View attachment CALCOLO NASTRO TRASPORTATORE.raris a simple and comfortable excel and the results are aligned to what was said before.
and apparently friction is already considered in the general "compute".

you try and see a little

greetings
Marco:smile:
 
I agree with you mechanicalmg but my doubt remains on the friction coefficient, I have already asked for information elsewhere but without any result. What about you? What value would you attach to this coefficient in the design phase? I'm going through the head to use 0.4 as in the previous design. . I look forward to your opinion! I was also about 6 kg, but my doubt about friction remains. cmq I will continue to study the problem and make you participate in the results. soon and thank you again.

pierluigi
 
sampom touched a painful key!
Unfortunately both motor and the reducer, at least for this single application, I have been imposed since last in stock (there is a complete use of the goods in stock so we are imposed what remains, always that is feasible of course) regarding the rest instead, for needs of various nature are bound to these spaces and sizes, the speed instead is the minimum required for the number of pieces/hour that must pass on the load cell. As regards the service factor, it must be said that this machine will work just 24 h a day but I could not consider any value having no reference to the engine (brand or manufacturer). Unfortunately, they are recently in design and for others they are alone and without experience you will understand therefore that I find not a few difficulties sometimes even for the simplest problems (in appearance even stupid) in every way thanks again for your answers. :smile:
 
According to me with 0.4 you should go well seeing here in the company I see that often is used that value.and try to call who produces the tape to know from them any prorpio characteristics to avoid slipping disadvantages?? They should usually have faced these things and should have tables.
 
Jeffcott said:
I agree with you mechanicalmg but my doubt remains on the friction coefficient, I have already asked for information elsewhere but without any result. What about you? What value would you attach to this coefficient in the design phase? I'm going through the head to use 0.4 as in the previous design. . I look forward to your opinion! I was also about 6 kg, but my doubt about friction remains. cmq I will continue to study the problem and make you participate in the results. soon and thank you again.

pierluigi
Click to expand...
the sprimetnale solution is the only one I recommend every time we talk about friction coefficient.
You send a sample of a span x a span. you put on 6 or 10 kg (about the load coming out). put on a tilted plane with the treated steel plate as it will be the tape bottom and mix the formed angle and revenues the static friction coefficient that is the worst in point phase.
static friction coefficient makes

fa = tan (angle)
 
Forgive me the question, perhaps surprised. for the development of the cloth I limit myself to the sum of the diameter of a roller for the double of the [D(rullo)+Interasse x2] ?
how do you take into account the fact that the tape will be tense?
 
Jeffcott said:
Forgive me the question, perhaps surprised. for the development of the cloth I limit myself to the sum of the diameter of a roller for the double of the [D(rullo)+Interasse x2] ?
how do you take into account the fact that the tape will be tense?
Click to expand...
Usually the tape is ordered along a value of 99.5% of the theoretical development. assumes that, once tensioned, it will extend to an additional 0.5% of development. clearly they are not precise numbers but so much these tapes always have rollers for tensioning.
 

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