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### Author Topic: worm gear cad design  (Read 15955 times)

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#### sparkyengle

• 63
##### worm gear cad design
« on: June 18, 2010, 02:07:01 PM »
Does anyone know of a cad program that can be used to design a wormgear that has a gradual increase in it's pitch the longer it is. The gear I am looking to design will have a 2" diameter, and be approximately 2' long. It will have a starting pitch of about 1/4" on one end and gradually increase to about 3/4" on the other end. Any design help would be greatly appreciated. Thanks...Andy.

#### Dan13

• 1,244
##### Re: worm gear cad design
« Reply #1 on: June 19, 2010, 06:47:52 AM »
Should not be a problem if you can write a mathematical expression for the helix you're describing

Daniel

#### Tweakie.CNC

• 7,909
• Super Kitty
##### Re: worm gear cad design
« Reply #2 on: June 20, 2010, 06:58:17 AM »
Can't help being curious but what would you use a variable pitch screw for please ?.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

#### RICH

• 7,361
##### Re: worm gear cad design
« Reply #3 on: June 20, 2010, 07:41:02 AM »
You could create one using 3d of a cad program ( haven't tried ) ie. you do a helix with a decreasing end diameter.
Now to get the gcode to cut it is a different story.....Mach threading is based on a constant pitch,  set by  feedrate over a distance...
Noot sure a if a math expression applied to something would work...
I don't know ....just some thoughts!

RICH

#### Ya-Nvr-No

• 985
##### Re: worm gear cad design
« Reply #4 on: June 20, 2010, 08:04:55 AM »
« Last Edit: June 20, 2010, 08:16:45 AM by Ya-Nvr-No »

#### stirling

• 2,188
• UK
##### Re: worm gear cad design
« Reply #5 on: June 20, 2010, 12:17:05 PM »
Here's a quick play around. X is axial and A is rotational Z gives the radius. The idea is that X moves in steps of a thou along the 2 in and the loop calculates the new rotation of A to vary the pitch. A starts at the .25 in pitch and finishes at the .75 in pitch.

pseudo code:

a = 1.44 (degrees)
x= 0.001 (inches)
G91
for int i = 0 to 2000
G1 Xx Aa
a = a - 0.00048
next

g-code:

#1000=1.44
G0 X0 Z1 A0
G91
M98 P1 L500
G90
M30
o1
M98 P2 L4
M99
o2
G1 X0.001 A[#1000]
#1000=[#1000-0.00048]
M99

Just kind of a starter describing the general idea. (I use two loops to give 2000 iterations because the limit in Mach of a loop seems to be around 998 or so).

Ian

EDIT: typo: I'd set Z to 10. Of course it should be 1 (as it now is)
« Last Edit: June 20, 2010, 04:29:52 PM by stirling »

#### sparkyengle

• 63
##### Re: worm gear cad design
« Reply #6 on: June 21, 2010, 06:20:33 AM »
Thanks Sterling. I'm soon finding out this is going to be way over my head.(logarithms and such). Maybe after I study more on writing code I will try what you are talking about in your example. Thank you anyway. Do you have any good suggestions on where to start for a noob wanting to learn g-code basics?

#### Graham Waterworth

• 1,877
• Yorkshire Dales, England
##### Re: worm gear cad design
« Reply #7 on: June 21, 2010, 07:52:31 AM »
Without engineers the world stops

#### khaled

• 17
##### Re: worm gear cad design
« Reply #8 on: December 22, 2013, 06:39:15 AM »
Hi there can anyone help me with G CODES FOR A 2 THREAD worm using ball end cnc milling its a 76mm diameter and the pitch is 27mm

#### RICH

• 7,361
##### Re: worm gear cad design
« Reply #9 on: December 22, 2013, 07:07:04 AM »
Not what you asked for but consider using the lathe to do it using alternate flank infeed.
FWIW,
RICH