less expensive steel for reducer

[Massimo694]

Hi, as an examination project I was required to design a gearbox assigned power and engine speed. I would like to realize the least expensive reducer possible, could you recommend the least expensive material for making it, or could you recommend the most reliable catalogs? (indicatively the minimum hardness that I need for the realization of toothed wheels is 460hb but I'm sure I can lower it further in case there is a convenient material)

 

[meccanicamg]

first you can use niemann in the three separate volumes to study the chapter dedicated to the "minimum volume" of a reducer and then establish how much you stand and what relationships to do.
for the determination of gears the niemann volume 2 treats the iso/din rule of quacbe year ago but it is fine. would be better to evaluate with iso 6336:2019.all sorts out for a spartan comparison you can use lewiss to determine the module and use the hertz theory more or less modified to evaluate hardness/duration.
on the forum find many gearboxes already done and find many tips.
other source to have an online computer with so much jis theory we have khk gear which is free.
if you want to make solid modeling you can use freecad in its current version 0.20,1 with workbench fcgear. I use it at work because I build gearboxes as under the stage of special machinery and we find well.
regarding the costs of materials you must keep in mind that at least one hardening thermal or chemical treatment can be associated with each material.

2018 prices were the following for material in the remediated status in bar:c45e = 1,05€/kg
39nicrmo3 oppure 42crmo4 = 1.72€/kg
s275jr = 0,75€/kg
18crnimo7 = 1,85€/kgat c45 and 42crmo4 you can do nitriding, tempering, or nothing.
at 18crnimo7 you make cementing and tempering.
You're doing nothing at s275jr.

mechanical characteristics are remarkably different as fatigue and wear resistance.

a material that costs little, it is worth little and need for larger dimensions.
you need to do a careful analysis of the whole process.

 

[MassiVonWeizen]

so you would like to have for every single component, which you don't tell us what they are and how you designed them, the cheapest material?

 

[Massimo694]

for now the project is in very embryonic phase I was interested only to know what was the least expensive material (at mass parity) to use for a toothed wheel (the most solicited of the reducer) that could bear certain superficial tensions, now I do not know if we will treat the reduction of volumes in the future with the professor since the objective of the project is the only respect for the dimensional relationships to vary of power and number of turns of the engine, reduce the cost is my curiosity. in this regard you might recommend to me where to get it, and could you tell me where to find a catalog containing the materials you mentioned? I am literally on my first day of mechanical design.

 

[meccanicamg]

the three volumes of niemann are practically out of sale and are found almost exclusively in the library of engineering universities.

if you work with the rules iso 6336 treats all design, including materials and their treatments, as well as voltage values permissible to bending and wear. has different parts, and each explains something specific.
If you look This is what discussion can be found for example the characteristics of the materials indicated in ISO 6336-5. read well all that there are links that explain well.

an industrial mechanical reducer transmits high pairs in reduced volumes.
already the type and conformation of the axes can determine more or less compactness.
if you turn at higher regimes you have a more accentuated wear and you can not use normalized materials.

equal weight, an iron gear holds practically nothing. using hardened carbon steels then you already have a considerable load capacity even if it is a little "fragile" with time and strong stresses. hardened steels are a good compromise of resistance-wear-cost. cementing steels are the top of the range for strength.

another free book that is on the net is written by bonfiglioli and is manual of the motor....where you find the calculation formulas for gears according to the first version of iso 6336.

if you provide us with more details (power/giri input, reduction ratio, number stages, type of use and field of use.....) we can also make a reasoning.

We don't want to replace you, but if you want concrete help, you need to share information.

 

[meccanicamg]

returning to your first post, a steel with 460hb i.e. 48hrc or 490hv which is equivalent to a breaking load of 1600mpa means that the tooth at heart possesses this characteristic.
according to iso6336-5 you can see that we are talking about steels from the top of range to descend.

In particular, by making the heat treatment simpler and cheaper than the tooth induction tempering, we have the following materials that according to iso 6336-5 behave in an equivalent way.
clearly the least expensive is the c40...then the c45....the 42crmo4 and in the end the 39nicrmo3.but everything depends on what you have to do.

 

[ultratech]

I add only one info.

the weekly tg with price trends for application you can see:

https://www.siderweb.com/siderwebtv/playlist/plpx7kspv3rv0emzv2e833ipusl3aqdeg5/video/0/pagetoken

the site is very interesting but it is better to register:

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[MassiVonWeizen]

I am literally on my first day of mechanical design.

If so (would you like your presentation so as to give consonant answers with your knowledge) would not be the case initially to do the task in a basic way and only then implement it with improvements? otherwise there is the risk of getting lost in a juniper only because the variant of the material and treatments should be considered in calculations.

 

[Massimo694]

probably it’s a bit early to deal with these problems, as the project is passionate about me but I’m trying to acquire as many notions as possible. as you asked for the data are the following, input power 32 kw, input speed 260 rpm, the reducer consists of two stages the first coupling has a transmission ratio similar to 0.3478 the second is similar to 0.322, and it is used to transmit the power to a porter. I also do not know why we were forced to use pinions with 17 teeth and only if necessary to increase them.

 

[meccanicamg]

From what you write, I can tell you that you will have gears that will have strong loads due to low turns. you have the advantage that you do not turn to high regimes and therefore the heat produced and the accuracy of the scratches can be not considered in the first approximation.
the fact that the track imposes a minimum number of teeth 17 means that they do not want to make you work with the undercut, that is with the base of the tooth excavated due to a number of teeth lower than the cutting interference of the tool. This leads you to simplify the issue, as I imagine you have no idea what the profile shift is.
If you can use helical teeth, then not straight teeth, you can improve transmission conditions and conduct ratio (number of teeth in socket).

this exercise is a nice toy that if faced by degrees and starting from simplification and parameterization in excel will give you good satisfactory results.

However if you want to estimate costs you have to parameterize gears like cylinders, calculate their weight for cost/kg and then treatments. go vary the values in excel and get a varied scenario.

 

[Massimo694]

perfect thanks to a thousand of the elucidations, last question, what radius to use to parameterize the dentate wheels as cylinders? and where can I find the catalogues of steelworks, what are the keywords or names of the most popular catalogues? thank you so much in advance for the availability I apologize for the trouble

 

[meccanicamg]

As for the parameterization of the toothed wheels you could use the primitive diameter as a cylinder diameter, because the teeth are half full and half empty, at least in the first approximation and then will be the same type of "empty" on all the sampling you will weigh.

If you look at the discussions we have made about steels you would see that the most common manufacturers are id or metallurgical veneta, lightfin and rodacciai. on their site there are pdfs with technical characteristics. if you then contact them you can also give an indicative cost. Tell him you're a student and what you need, so they know how to get the information. of this time the prices are crazy and the material not always available but you need a comparative average price and not a special batch of material x diameter y.

In any case, of steels marketed and therefore at medium cost are those that I have indicated to you. Other alloy steels are less findable and therefore more expensive and mechanically is not that they are so different.