Gear Generation software 1

[gearman1234]

I have a 12 DP,20 deg standard tooth thickness semi-topping hob. I want to know how much tip chamfer variation would be obtained in hobbing gears 64 Teeth and 27 teeth.

I would appreciate if anybody can give information about the softwares available.Demo as well as paid.

 

[diamondjim]

You might try using the lisp program below
and draw a hob tooth centered at 0,0
with the addendum down and the pitch line
also at 0,0. Block this drawing and call
it hob.dwg. Then pull in the lisp program
and follow the prompts. Include the topping
hob profile in the hob profile. I would change
the color of the hop topping profile so you can
see its effect.


(defun c:HOB ()
(command "SNAP" "OFF&quot
(setq cpg (list 0 0))
(setq ntg (getreal "\nEnter number of teeth on gear: &quot)
(setq ngh 18)
(setq odg (+ 2 ngh))
(setq pdg (getreal "\nEnter generating pitch dia of gear: &quot)
(setq dpg 1.000)

(setq xi (/ (* -0.25 pi pdg) ntg))
(setq mx (/ pi ngh 2))
(setq sph (list (* -48.0 mx) (* 0.5 pdg)))
(setq rot (/ -180.0 (* ntg ngh)))
(setq cnt -51)
(setq pt1 (list (* -2.2 odg) (* -1.85 odg)))
(setq pt2 (list (* 2.2 odg) (* 1.85 odg)))

(command "OSNAP" "OFF&quot
(command "SNAP" "OFF&quot
(command "zoom" "w" pt1 pt2)

(while (< cnt 51)
(progn
(command &quot;INSERT&quot; &quot;HOB&quot; sph 1 1 0 )
(command &quot;rotate&quot; &quot;W&quot; pt1 pt2 &quot;&quot; cpg rot)
(setq sph (list (+ (car sph) mx) (cadr sph)))
(setq cnt (+ cnt 1))
))
)

 

[diamondjim]

Please note that when you draw the addendum
of the rack it must be equal to the dededum
of the part you are cutting. Is this topping
hob similar to FMCs standard hob cutter?

 

[Gearhead]

UTS offers software for your problem.

http://www.uts.com

They do offer a trial if you qualify.

 

[Spurs]

I use software from Web Gear Services Ltd.

I like it cause it runs on Excel and is very easy to use.

Their web site is

http://members.rogers.com/webgear/home.htm

 

[gearman1234]

Thank you very much for the information. Since I have autocad LT I can not use LISP. But I tried to plot the coordinates and then match the rack and gear. But rotation of the rack tooth seems to be a problem.

 

[diamondjim]

I could probably run the program
for 27 and 64 teeth and e-mail it
to you. You would have to enter
the hob profile at 0,0 in the individual
drawings, explode it, and redefine it with
the modification as needed to
have the topping profile included and
then redefine the profile as hob.
It will ask if you want to redefine
the hob. answer yes and the drawing
will change to reflect the hob change.
I would change the color of the hob
topping profile change so you can track
it in your drawing.

 

[diamondjim]

Just saw this on another post:

...Maybe You can buy the Lt-Extender (

http://www.lt-extender.de/englisch/frameset.htm

), and then You can use *.lsp-files ( Thread555-48939 )

 

[gearman1234]

Thank you very much diamondjim. I downloaded the LT-Extender and ran the LISP program as per your program but there looks like some problem as I am not getting the generated gear tooth even after entering the number of teeth and the pitch dia. All I get is a hob tooth which is rotated along a curve. I would appreciate if you could run the program and email it to dschitale@usa.net. I would again try to run the program.

 

[diamondjim]

The hob lisp program is only for
1 dp system, so you have to convert
your data to this system.
You can scale the drawing afterwards.
i.e. the pitch diameter and number of
teeth will be the same unless you are
trying to account for backlash.
Hope this works for you.

 

[diamondjim]

Will also run the programs in acad10
and send them to you.

 

[gearman1234]

Hello Diamondjim,

Thank you. I got your emails. I also tried the LISP program and I got the gear generation profiles. This is the program I was looking for.

As these profiles are for 1 DP gears, I am trying to figure out how to convert the program for other DPs and pressure angles.

If you have that information I would appreciate if you coukld send me that.

 

[diamondjim]

All you have to do is redefine the hob drawing
for the different pressure angles.
You would need several involute drawings
similar to the one for the 20 degree pressure
angle for comparison purposes.
The hobbing action is the same.
Tip rounding is .005/.015 for 12 dp gears
per section 5-39 of Dudley's book.
Tip Relief on a hob can be as much as 33 percent
relief on the cutter and vary from 2 to 3 degrees
or be a blended arc accomplishing the same.
The same is true of stub verses full depth gears,
just redefine the hob with the stub proportions.

Draw everything to the 1 dp system and then scale them
to size i.e. if 12 dp scale by 1/12. I layout every
thing to 1 dp for determining the y or Y factors
especially for modified addendum gears. You might
try laying out a 16 tooth pinion to see how
little the hobbing relief effects the small pinions.
Using the 1 dp system also helps me think of percent
changes more readily. Something I did not explain is
that when it asks for center distance, you can use
something other than the true center distance to
allow for backlash or modified addendum teeth. The
program assumes the pitch diameter and center distance
is the same.

The program will also do Gates sprockets if you
redefine the hob per their recommendations.
Again I convert all of their dimension to the 1 dp
system and then scale after the program is finished.

Hope this helps. It is nice to see the simulated
hob in action by just using the regen command.

 

[gearman1234]

Diamondjim--

I am requesting this after a long time but I was just wondering if you could explain to me the LISP program which you have written. Is it possible to know how the program is developed? I am learning AutoLISP and would like to develop progrma for my own application based on things learnt in this program.

Thanks

 

[diamondjim]

The hob program was developed by following
the recommended way in some gear books to
develop the trochoid radius by drawing in the
hob profile and rotating the paper about the
centerline and then move the hob horizontally
to the right and draw it, rotate the paper
the same amount etc.
I have done the same with pinion cutter profiles
to develop other trochoids and to check involute
interferences and see how they cut eternal or
internal gear profiles.
I often do these manually and record each step
and then develop a program to emulate the manual
drawing steps. Using blocks of the profiles
allows acad to generate the individual steps
and you can determine the degree of precision
of the interval between steps by varying the
progam to your need.
Good luck with the lisp programming.

 

[gearman1234]

Thank you Diamondjim.

I am waiting for my 1st AutoLISP programming book to be shipped. I will review all these steps after I get that book.

 

[luky]

mr. gearman i have the same problem.
got a hob with semitopping but don't know what the tip chamfer is if i change the number of teeth from 18 to 33.
could you help me?
i've read that you with the help of mr. diamondjim got a result.
best regards
luca

 

[gearman1234]

Hello luky

1) I tried with the manual method on AutoCAd and it worked perfectly well. It can tell me exactly how much chamfer , radius etc. is generated by any hob on a gear. Butit is very time consuming. That is why I am working on AUTOLISP. There is program developed by Diamondjim in one of the replies in this thread.

2) I have a request for Diamondjim.
I have written my own program in AutoLISP but it does not seem to work for the iteration.
I was jsut wondering if it possible for Diamondjim to go over it.

Here is the program.

(defun c:HOB()
(command "SNAP" "OFF")
(setq cpg (list 0 0))
(setq ntg (getreal "\nEnter number of teeth on gear: "))
(setq dpg 1.000)
(setq pdg (getreal "\nEnter generating pitch dia of gear: "))
(setq rolrad (/ pdg 2))
(setq rolangdeg (getreal "\nEnter Roll Angle of the tooth from OD to BD: "))
(setq numtgt (getreal "\nEnter number of tangents: "))

(setq rolangrad (/ (* rolangdeg pi) 180.0))

(setq theta (/ rolangrad numtgt))
(setq pt2 (list -3 4))
(setq pt3 (list 3 7))


(setq rgt 3.0)

(while (<= rgt numtgt)

(progn
(setq pt1 (polar cpg (atan (- 1.570796327 (* rgt theta))) (/ rolrad (cos(atan(* rgt theta))))))
(command "INSERT" "HOB" pt1 1 1 0)
(command "rotate" "W" pt2 pt3 cpg (* rgt theta))
(setq rgt (+ 1 rgt))


))
)

 

[diamondjim]

Not certain without going over the
whole program. I would call the
program something other than
hob to see if it is a name conflict
with the insert "hob".

 

[diamondjim]

My first suggestion does not work.
It is hard to find someone's logic
by just examining the lisp program.

(setq rgt 3.0)

what are you trying to accomplish by
this?
I would use (/ pi 2.0) for the 1.570796327 value

If you did this initially by inserting each step,
do you have that drawing available?