helical gear interasses

[Polymar]

Good evening,
are at grips with a reducer on which gears turn for cylindrical precision with parallel axles. and so far everything ok, if it was not for some uncertainty due to the correct, indeed better to say working, calculation of the interassis. I have had to apply the correction of interaxes with annexed the variation of the head and primitive diameters, and apart from this on numerous books, especially school books, I read that even in the case of the gears of this type, the calculation of the dilasse is equal to that with straight teeth, i=(z1+z2)*m/2.
on the internet, downloading "academic" docs, it is written that in the helical i=m(z1+z2)/(2*cos(beta)), with beta that is obviously the angle of inclination of the helix. In my case, the entirety would pass from 81 to 82.5 mm, and being a detachment with m=3.75 (yes exactly, who preceded me years and years ago chose the modules later "vited"), this could be translated into an excessive game, synonymous with noise and early wear.
Would anyone advise me about this? I realize once again that school books say one thing, but then "to do well" things is another story. Thank you! ;-)

 

[meccanicamg]

first post all constructive data if you want assistance (module, tooth number, profile shift etc.).
as written several times look on khk gear that there are guides that really explain how you handle profile shifts and geometric parameters. Moreover with free regustration there is also the online computer (geometria, resistance to pressure flexye etc.).
You do this first round then you tell us.

 

[Polymar]

yes you are right, in fact my intention was to be able to calculate from the beginning the sizing of the entire transmission by thus escaping me from the "automatic calculators" (not only khk gear, but also kisssoft and camnetix). then maybe at the end, with some result in hand, I could check everything with what is available on the site you mentioned or with dedicated sw. It is true that today I have created from scratch an excel sheet in which it recalculates the sizing of gears and interaxes by setting the basic parameters and then I go to build the real 3d models on solidworks. Of course, it does not make sense to reinvent the wheel, but for the satisfaction of learning new methods and acquiring new knowledge also the old method of calculator with so much pen and paper, it certainly does not hurt. and after a rapid verification, the khk online calculator interacts with the propeller's angle of inclination. mission accomplished

 

[meccanicamg]

I also created several excel modules to get rid of proprietary software products. the formulas you are looking for are qui.
personally to have the right teeth with true profile, since I work a lot with freecad use profile shift with the fc gear module because otherwise I should do the construction of the complete evolver and it is a ball. then amount in solidworks. toolboxes are approximate and unreliable.

♪

 

[Polymar]

Hi, thanks for the link. I downloaded the web page last night and now was already making a xls sheet to speed up the calculation. really not bad as step-by-step guide, I still have to check everything but I would say I will follow almost certainly what is reported by khk. In the meantime I ask my former colleague if as soon as possible it makes me a sizing on kisssoft to have a further certainty of how much designed, in addition to the fact that it is possible to make a more precise wear calculation according to the lubricant. on yt there are many videos of solidworks on gears with evolving profile obtained from equation, so I don't know how much it is worth starting from a file imported from another cad system, for the simple fact of the evolving approximation->spline that weighs the model and generates approximations. I confirm by direct experience that the toolboxes are strictly avoided for the same reason you have also found. thanks and good day.

 

[meccanicamg]

I normally do 10 points for each side of the profile and using the actual profile that corrections are only right from geometry. then often working at zero game....I need certainties.

 

[Polymar]

10 points can be few or many depending on the module adopted, but generally the curves from equation work well in swx, sin that the recalculating time is considerable also with a cpu of several ghz. today I have finished my excel sheet which other does not do than perform the same calculations that are reported on the page of khk, and tomorrow I try some dimensioning and then check if with the corresponding models 3d I can make the square of the circle in the meantime my modus operandi of pen+carta+calculator has made me notice that the method of the cut-sweep of a straight line of beta grades external therefore to the evidence of the results, better to use a model based on the propeller rather than the projected trajectory, than to rigor of terms should be semmai "advertent".

 

[meccanicamg]

10 points can be few or many depending on the module adopted, but generally the curves from equation work well in swx, sin that the recalculating time is considerable also with a cpu of several ghz. today I have finished my excel sheet which other does not do than perform the same calculations that are reported on the page of khk, and tomorrow I try some dimensioning and then check if with the corresponding models 3d I can make the square of the circle in the meantime my modus operandi of pen+carta+calculator has made me notice that the method of the cut-sweep of a straight line of beta grades external therefore to the evidence of the results, better to use a model based on the propeller rather than the projected trajectory, than to rigor of terms should be semmai "advertent".

Just for these reasons, not wanting to knock me out to determine the profile, I use a free program that does it and rightly. Besides importing the step I do not have all the graphics problems of the native recalculator of solidworks....so all in all I can afford to have in the assemblies of the machines as well as the real teeth gears, without having to simplify them.
surely the swrep will never be like a long step propeller. correctly modeling a helical gear with true profile is not a walk. Moreover there is to be remembered that the outer diameter is not necessarily what is calculated with single wheel....in the coupled wheels you have a head cut due to the inranamenro. we have a post dedicated What about it?

 

[Polymar]

I have already verified the engraving of two "unaltered" gears having only the opposite propellers, and the result confirms that:
1. the trajectory to create the compartment between a tooth and the other should not be created with a sweep but with a loft, simply joining the initial section and that of sketch "derivata", with the propeller set as a line of half-works
2. the trajectory obtained by projection on the outer circumference is wrong, and the divergence from the real propeller is accentuated with "small" diameters and angles of 30 degrees

scrupulously sticking to these 2 rules, turning to pleasure the gears coupled with the "engineering" bond, it is possible to verify that in each normal arbitrary section to the axes there is never interference and the profiles always touch and only at one point only. logically the zmin condition must also be met according to the z2/z1 tooth ratio.

I will soon build the 3 gears and the first thing to perform as soon as they are delivered will be to compare them with my 3d models via an optical zwiss. will follow the assembly on the gearbox to make a preliminary test, of which the first part will be without oil to evaluate the silence/rumorosity, since I too in my case work at "zero game".

 

[meccanicamg]

I have already verified the engraving of two "unaltered" gears having only the opposite propellers, and the result confirms that:
1. the trajectory to create the compartment between a tooth and the other should not be created with a sweep but with a loft, simply joining the initial section and that of sketch "derivata", with the propeller set as a line of half-works
2. the trajectory obtained by projection on the outer circumference is wrong, and the divergence from the real propeller is accentuated with "small" diameters and angles of 30 degrees

scrupulously sticking to these 2 rules, turning to pleasure the gears coupled with the "engineering" bond, it is possible to verify that in each normal arbitrary section to the axes there is never interference and the profiles always touch and only at one point only. logically the zmin condition must also be met according to the z2/z1 tooth ratio.

I will soon build the 3 gears and the first thing to perform as soon as they are delivered will be to compare them with my 3d models via an optical zwiss. will follow the assembly on the gearbox to make a preliminary test, of which the first part will be without oil to evaluate the silence/rumorosity, since I too in my case work at "zero game".

Nice job to experiment. I like this approach. keep us updated.
but are you making gears with prototyping and 3d printer or with classic cut with maker?

 

[Polymar]

experimenting is the right term, first you have to be sure that the calculations are correct after the accurate understanding of the mechanism, then you have to ensure that the processed pieces are exactly the same as the mathematical model. made this functional test has a high probability of ending with a positive outcome. Based on automatic calculators and empirical methods is not really my style. and this time I leaned on excel, when I discovered that the most suitable application would be matlab. I end the bureaucratic part of the cards then forward everything to our manufacturer, who so far has always proved a good professional preparation, synonymous with reliability. all to create, if the method of design/industrialization/gluing is perfect, half measures do not serve

 

[meccanicamg]

How's the test going? have you already made the pieces or are you still in the design phase?

 

[Polymar]

hi, indeed now good night...
the delivery of the sampling of the gears with the parameters "correct" will be carried out, as established during the agreements taken at its time with the supplier, in the second half of the month in progress, in conjunction with the delivery of the normal production codes already planned in order to limit the expenses for a real sampling of 2 pieces by type (then 16 pz. in all), that would have required an urgent takeover of the money not indifferent and taking account the real problem is that to manage some modules (3.25 and 3.75) which are in disuse, complicates your life from beginning to end, so you can't go quietly to any dentator who should almost certainly buy the creators, but to turn to those who already have them in the house, who look randomly has so much to work and ask him a sampling is like to ask him the blood in the meantime I have ensured to make a carpentry therefore, for the moment, work in progress

 

[meccanicamg]

then we look forward to feedback. it was useless to say... but couldn't you use preferential forms?
then they are always the usual decisions of the high planes that of sensible they do not always have everything....contact the business....and they see of each.

 

[Polymar]

You are perfectly right, but this is not a novelty! I myself had proposed a remake of the transmission by adopting a module 4 (even 3.5 ...), but for many speeches this was not possible in order to avoid an overturn of the project, which is very dated as you certainly have drawn from those numeracci. Exactly, it counts the business, which in the end is what the 10th of the month gives me the salary. and it is also the reason why the commercials earn more than the technicians vabbè, we begin the week with the iot course, which is not of my favorites regarding the issues and not even the added value to my trade.

 

[Polymar]

Good morning to all, it has long been waiting for this fateful day, in which I can finally give you feedback of what had been discussed in the past with technical support of @meccanicamg .
had, the 3.75 module gears tern adapted to the interaxes of the box that had initially been designed for 3.25, works "perfectly well". the result was above expectations. silent transmission as there is no longer that "short" due to the incorrect teething that characterized old gears in style 13/6. I will never end up thanking @meccanicamg and all those who helped me solve this skyscraper, because coming to know of the previous flops of other technicians, I admit that at first I was not too confident in a success. and instead a little at a time I have gained confidence, calculated, verified, thought, reconsidered, questioned my knowledge of transmissions, with the result that I am now aware that the commitment but above all the determination to achieve the results, always pay.
Besides, there were concerns, when you know that your sampling would cost at least 10k to your company. because you know you're in the cross between the stars and the dust, if you can do it, you're a guru, if you're wrong, you're incapable. but someone had to do it, someone had to do it., and here I am confirming that sharing knowledge and opinions on a forum, it is not time lost but an opportunity to learn and grow professionally together.
@meccanicamg over the top.thanks and good day.

 

[PIETRO2002]

Good morning to all, it has long been waiting for this fateful day, in which I can finally give you feedback of what had been discussed in the past with technical support of @meccanicamg .
had, the 3.75 module gears tern adapted to the interaxes of the box that had initially been designed for 3.25, works "perfectly well". the result was above expectations. silent transmission as there is no longer that "short" due to the incorrect teething that characterized old gears in style 13/6. I will never end up thanking @meccanicamg and all those who helped me solve this skyscraper, because coming to know of the previous flops of other technicians, I admit that at first I was not too confident in a success. and instead a little at a time I have gained confidence, calculated, verified, thought, reconsidered, questioned my knowledge of transmissions, with the result that I am now aware that the commitment but above all the determination to achieve the results, always pay.
Besides, there were concerns, when you know that your sampling would cost at least 10k to your company. because you know you're in the cross between the stars and the dust, if you can do it, you're a guru, if you're wrong, you're incapable. but someone had to do it, someone had to do it., and here I am confirming that sharing knowledge and opinions on a forum, it is not time lost but an opportunity to learn and grow professionally together.
@meccanicamg over the top.thanks and good day.

How nice to read something positive! !

 

[meccanicamg]

This is a good feedback.
we are here available to science and technology.

 

[Polymar]

follow an infinity of tests to verify the new toothing, but already "dry" the noise is really very limited. of course the model under observation is module 3.75 with change of interaxes on a 3.25.

 

[teseo]

hi guys I reconnect to this discussion because I have a problem definitely easier solution than the post, then I have two simple gears with 1:1 ratio with a spreadsheet that I got or copied now I don't remember from you, I know that I have to have a toothed wheel made and so far everything ok, but I would like to have zero game....and 25mm interassemble I can type go also to 25.2 25.3 but not less than 25, how can I do, I had thought to do in offset of the profile of the wheel, is it correct? How can I quantify this move to have a zero game or almost?

Thank you.