Automatic Spline Calculations or spline drawing 2

[broacher]

Hello,

I have to first say that,i am really surprised about issues in this forum ! What a great site is this !

I am working as a young engineer in Turkey.We are manufacturng broaching tools.

The important issue for me is,i am looking for a program that will calculate or give us dxf automatically.I used some lisps given in this site,but i couldn't find any properly working.

We have a new project.We will make a new machine that will dress the tools cnc controlled.For to give this data to machine,we need a program to calculate or draw automatically.

I will be very appreciated to have great ideas given from you.I hope,i could tell you what we need.

Just we will enter pressure angle,module,z,Lw,e.t.c. and it will make a correct (very small tolerance) drawing for us.

We are drawing manually now.The attached lisp doesn't work correctly for some values i have given.Are the dimensions in inch ? Can this be the problem?

I am waiting for your kind help and answers.

Thank you.

Enver DEMIR

 

[dinjin]

The program was for inch dimensions. It should be obvious by the default tooth thickness. Accept all of the defaults and see what happens. If it still does not work properly, you may not have enough decimal places set before you use the lisp program. You can always use the 1 dp as the default and then scale the finished drawing accordingly using 0,0 as the centerpoint. If that does not help, let me know. The program says enter the dp which is the diametral pitch which indicated it uses the inch system.
The program could also be modified or shortened so that it does not draw the complete number of gear or pinion teeth.
If you can stop the program before it make the array you would have the external gear tooth profile. To create an internal gear form, you would have to enter the tooth space and reverse the addendum and dedendum to get the tooth space profile. I hope that makes sense to you.

 

[dinjin]

Someone else has told me that the program does not work for high pressure angles. What is the pressure angle of your
spline? It might also be easier to have an involute drawing
with the base diameter equal to one and then scale that accordingling and rotating the profile one half of the arc space angle or one half of the arc tooth angle. You would then have to truncate the profile by drawing the major and minor radii of the splines, gears, pinions, or whatever.

 

[broacher]

Dear dinjin,
I couldn't write your handle because ? have forgotten it.What i was looking is you !

The programme works in default mode.Attached you can see your default spline in autocad.

I want to ask you;
1-)The do=m*z in metric but in drawing Dp.z=do ?

According to this is module and DP same?

2-)dg(Basic circle)=do*cos P.A. There is no problem in your programme.?t calculates.

3-)The addendum and dedendum are given as Add.=1 and Dd=1.1571 in default.But if you take dimensions from drawing,you see the Dd.=26 and Add.=22.553

If i divide these numbers to 25.4 (mm to inc),it doesn't give me the correct values that i entered ?

Where am i wrong,can you please tell.

 

[dinjin]

I would change the program for the dedendum to default to
1.25 ie to the new standard. This program was written long
ago when the 1.1571 was the standard for full depth teeth. I think using 1 module would work the same as 1 dp but I have not tried that. If it does work then you can simply scale everything by the module ratio. The radius portion of the program does nothing and could have been eliminated. Let me know if this works.

 

[dinjin]

I just realized that the 22.553 is the base diameter.
The program can only draw from the base diameter out to the
outside diameter. The program cannot draw the fillet radius or any portion below the base diameter. You have to fudge the fillet radius. Also it cannot draw in the undercut if it would have one or more simply said needs one.
Most splines are not a problem as they are generally double stubbed forms or at least use 1/2 the addendum and dedendums. Do not know what kind of spline you are using.

 

[gearguru]

broacher,
convert the module to diametral pitch first:

Diametral Pitch = 25.4/module

There is plenty of online info about the gear/spline geometry and the calculations.

dinjin, if the module = 1.0 then the DP = 25.4

 

[dinjin]

Gearguru,
I know the conversion factor. I think the program would
work for 1 module the same way it works for 1 dp if you
assume the default units are metric. It is nice to hear from you again. I hope you were not snowed in and business is good.

 

[broacher]

gearguru,

Thank you firs of all.I found late but there is no problem.I divide 25,4/m and then divide it by 25,4 to inch and i get what i need called DP

Dp*m=25,4,you are correct.

dinjin,

? just understood as i told gearguru above.Now,i can draw with using module or either D.P.The problem is only for dedendum and addendum.Other all values can be reached correctly.

We generally work with fiat norms,peugeot norms,din 5480,ansi e.t.c.There are lots of works that we use splines.We are manufacturer of broaching tools.

Dinjin,what can i do for getting addendum and dedendum from the programme.What happens if ? draw add and dd circles manually.I think it wokrs.

Do you have anyy suggestion for a revision on programme.Can i make a cahnge in lisp to get dd and add correctly.

Thank you for your efforts and knowledge.

 

[Occupant]

Has anybody checked the curves on these splines? Afterall, we are talking "involute splines" here and if I'd make broaches, I would confirm this first.

 

[gearguru]

broacher,
to divide 25.4 by m and then to divide the result by 25.4 is the same as to calculate 1/m isn't it?

dinjin,
I prefer not to mix module and DP and mm/inches, they are different animals. Our friend broacher has to be very careful, he is designing expensive tools.

 

[dinjin]

I guess I could very easily revise the program for metric
gears, splines, etc. as it would take so little effort.
It is a simple text lisp program that works in ACAD and draws involute splines. For splines, I think I should use .5 times the module for the default addendum and maybe use .625 times the module for the default dedendum.
I will post the revision to this thread. I might as well delete the fillet radius portion as it does nothing and was kind of for information purposes in its development.
I do agree that having two separate programs for inch and metric makes a lot of sense as it is very easy to confuse the output. The only trouble I see is that the units must then be clearly defined. Thanks for the suggestions!

 

[broacher]

Dear Occupant,

Yes,we are working on involute splines.Our pressure angles are not constant as 30 in gears,it changes to standart and e.t.c.

I am new to working and i am a new graduate of mechanical engineering.I have been working for 6 months and now i am responsible of a project.

gearguru,
you are right my friend.? explained what i did to get correct,1/m is enough

dear dinjin,

Your programme works wit few errors.Tha add and dd are wrong and i manually draw these circles and then trim.

Yesterday we had an appointment in this issue with our technic department.I need to calculate the involute values to give servo control for dressing automatically.

Can anyone help me for calculating these points,for example 7-10 points for involute tooth forms.Is there any method or excel programme e.t.c.But becareful,i say calculating not drawing.

Can the geartrax in solidworks help me ? I only need point calculations (A programme that helps me to calculate these points automatically or easily)

Thank you so much.I know,i ask many questions but i really need.This development is too important for us.We will design a special machine for profile grinding.dressing e.t.c. will be cnc controlled.

Many thanks to everyone.

 

[gearguru]

broacher,
why don't you look in some books about the theory of gears? There is a lot of them and the calculation of an involute coordinates is the basici one.
dinjin is very generous...

 

[dinjin]

broacher,
I think gearguru is right. Revising the program for you would actually be a disservice to you. You will miss out in the learning experience without understanding what the program does. The program was written for full depth diametral pitch gears and the default values were the standards that existed when it was written. If you do not realize the difference between internal verses external gears and how they are somewhat mirror images of each other.
I gave you the basic information in an earlier post on how to modify the input to let it work for you. The program can be used to create spline drawings or stub gear teeth but you have to know how to adjust the addendum and dedendum values for it to work. Good luck in your growth and development.

 

[broacher]

Dear Gearguru and Dinjin,

Thank you for your efforts.? am studying hard to learn what i need.I will try to revise the programme,i started to learn what it makes by exercising a lot.

I will buy mechanic's handbook,i will have it in 1 months,i think.We have lots of books but not have a book like this.

Dinjin,the last question,dou you have an excel programme for calculating just coordinates x and y.

In another post,i saw this.How do you calculate these points,by using the formula manually or do you have any programme.

I really need this information.Thank you.

Best Regards,


at point X=-1.690885 Y= 7.350665 Z= 0.000000
at point X=-1.693748 Y= 7.367844 Z= 0.000000
at point X=-1.697442 Y= 7.396875 Z= 0.000000
at point X=-1.701055 Y= 7.438197 Z= 0.000000
at point X=-1.703616 Y= 7.492355 Z= 0.000000
at point X=-1.704068 Y= 7.560010 Z= 0.000000
at point X=-1.701227 Y= 7.641947 Z= 0.000000
at point X=-1.693744 Y= 7.739084 Z= 0.000000
at point X=-1.680055 Y= 7.852489 Z= 0.000000
at point X=-1.658317 Y= 7.983384 Z= 0.000000
at point X=-1.626330 Y= 8.133159 Z= 0.000000
at point X=-1.581440 Y= 8.303379 Z= 0.000000
at point X=-1.520415 Y= 8.495787 Z= 0.000000
at point X=-1.439287 Y= 8.712295 Z= 0.000000
at point X=-1.333145 Y= 8.954966 Z= 0.000000
at point X=-1.195867 Y= 9.225962 Z= 0.000000
at point X=-1.019774 Y= 9.527449 Z= 0.000000
at point X=-0.795173 Y= 9.861437 Z= 0.000000
at point X=-0.509750 Y=10.229495 Z= 0.000000

 

[Occupant]

Hi,
I don't know where I got this, but it is in German. When you run it, it produces a *.dxf file and also one called Zahnrad.txt. When you open that file, the first set of numbers give you the coordinates of points for the involutes of the left and right flank of the top vertical tooth. The others are probably also there, but I haven't looked.

 

[dinjin]

I do have an excel program that does do the coordinates but it assume you know enough about gears, spline, pinions, etc. to input the correct information. I did not create the excel program and not certain where I got it on the internel. The author of it is simply named Mick and it might be Mike Bull's program. He was kind enough to share several of his excel sheets in the past. I do not know how to post it to this forum. It is for module gearing.
I assume you mean Machinery's Handbook. It is a good reference. Dudley and Buckingham also have some great basic gear books. I have been to Istanbul and Ederne but did not get a chance to see much of the commercial side of your Country.
If you use my program successfully, you should have no problem getting the coordinates by simply windowing one side of the involute and simply type list to have it list the coordinates in ACAD. The program basically calculates coordinates and uses the pline command to draw the involute.

 

[dinjin]

The coordinates listed looks like something that I furnished to someone. I simply input his data into the program, it drew the gear, and I windowed in on I think the right side of the involute tooth to get those coordinates.
I then simply copied and pasted them to a text file.

I looked at Occupant's Zahnrad program but it did not create a text file for me. I was impressed with the drawings that came up as I entered new numbers of teeth to
see if it showed pointed teeth or not. Tho my last name is of German origin, I was not certain about all of the German text so was not certain what else to enter in some of the data fields to see how the profile changed. Someone did a lot of work creating that program for sure.

 

[gearcutter]

Occupant,
A star for you. Thanks for that little app.

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181