Help in Making Helix Gear

[ReMark]

If you loft 2D lines you get surfaces.  Make sure your tooth is a single, continuous polyline.

Edited November 11, 2023 by ReMark

[Cad64]

I'm not a gear maker, but here's my suggestion. This is just a quick and dirty example. If you need this gear to actually work, you will need to do all the necessary calculations.

[BIGAL]

This may be useful.

2Dgear.lsp

[basty]

10 hours ago, BIGAL said:

This may be useful.

2Dgear.lsp 16.58 kB · 0 downloads

 

What should I do with this 2Dgear.lsp file?

[basty]

12 hours ago, ReMark said:

If you loft 2D lines you get surfaces.  Make sure your tooth is a single, continuous polyline.

 

As I already told you, the gear tooth is a regular triangle. I do make a Region on the triangle and then Loft it. I created the triangle using Line command, not Polyline.

Edited November 12, 2023 by basty

[ReMark]

3 hours ago, basty said:

 

What should I do with this 2Dgear.lsp file?

The lisp routine will draw a 2D profile of an involute tooth gear.  Use the Appload command to load the routine.  Once loaded it can be invoked by typing 2DGEAR at the command line.  Follow the prompts and enter the data for the gear.

[basty]

41 minutes ago, ReMark said:

The lisp routine will draw a 2D profile of an involute tooth gear.  Use the Appload command to load the routine.  Once loaded it can be invoked by typing 2DGEAR at the command line.  Follow the prompts and enter the data for the gear.

Thank you.

[basty]

Unfortunately, I think, the shape of the gear tooth is not involute (see the attached image please).

I measure the diameter using vernier caliper of the most outer gear is 58.3 mm.

The amount of the tooth is 34 and it's a, I guess, a plastic gear.

The gear is damage and I need to find its replacement.

I don't know what is its pressure angle.

 

Edited November 12, 2023 by basty

[ReMark]

What is the gear used in?  Types of gears: Spur, Helical, Rack, Bevel, Miter, Worm, Screw and Internal.  Each type has specific uses.  Take a picture of the gear straight down and post it.

Edited November 12, 2023 by ReMark

[lrm]

@basty  

1. The reason that you were having a problem creating a region from your 2D gear profile is that he object is an Associaive Polar Array.  The region command will not work with this object type.   When creating the full gear profile issue the "AS" (associatiive) option and answer NO. This will create a polar array which you can turn into a standard polyline and region.
2. It is difficult to tell from the image but it does look like the gear tooth profile is an involute.  Note that the tooth profile is maintained in the direction of the helix angle not in the plane perpendicular to the axis of the gear.  Beta in the image below is the helix angle.   Simply lofting two gear profiles as suggested in other posts will distort the tooth profile. To maintain the correct tooth profile you can extrude a single 2D tooth profile as a solid object  and then subtract it from a solid cylindrical blank for the gear.
   
3.  Check out aorund 16:40 in this video to see how a helix gear is cut by drive a cutter with an involute outline in a straight line at an angle beta.

[lrm]

Here's a step by step process.

1. Create a 2d gear profile from the program posted by @BIGAL and use it to create a shape that can be used to "cut" the gear.
   
2. Extrude the "cutter" profile and a circle to create 3D solids.
   
3. Rotate the cutter by the angle beta and bring it in contact with the gear blank.
   
4. Make a polar array of the cutter making sure that it is NON-associative.
   
5. Subtract the cutters from the blank yielding the helx gear.
   

[basty]

2 hours ago, ReMark said:

What is the gear used in? 

 

It's a component of paper shredder machine.

 

2 hours ago, ReMark said:

Types of gears: Spur, Helical, Rack, Bevel, Miter, Worm, Screw and Internal.  Each type has specific uses.

 

I don't know. It should helical gear (at least that is what I read on Google).

 

2 hours ago, ReMark said:

Take a picture of the gear straight down and post it.

 

See the attached pictures please.

 

 

Edited November 12, 2023 by basty

[ReMark]

I would draw the entire gear in 2D.  I would then copy the gear in the Z axis and offset it the required degrees to achieve the helical aspect.  Then I would loft the two profiles to create a 3D model.  Any other feature of the gear (ex. - center hole, etc) would be executed upon the 3D model.  Note: when you create the 2D profile it must be a single continuous entity.  Do NOT turn it into a block.  I used this method to create the helical gear shown below.  The hole and keyway were created after the gear.

Edited November 12, 2023 by ReMark

[basty]

I don't understand what block is. Your tooth profile of the gear appear to be involute curve. How to draw the profile of my gear (which is not an invoute curve) and what is its pressure angle? Do anyone here is Mechanical Engineering student? Please help me make this gear.

 

Edited November 12, 2023 by basty

[ReMark]

You have been using AutoCAD since 2014 and you don't know what a Block is?  How is that even possible?  Well, if you don't know what a block is then I guess there is no point telling you not to create one.  I have to agree with Irm... your gear tooth profile is involute.  The pressure angle of a gear is defined as... "the angle formed by the radial line and the line tangent to the profile at the pitch point."  Twenty and twenty-five pressure angle gears are typically the most commonly used today.  For maximum strength applications pressure angles as high as twenty-eight to thirty degrees have been used.  I suggest you try twenty and twenty-five first.

 

Here's an idea.  Draw your gear's 2D profile then print it.  Cut it out with an Exacto knife then lay your real gear on top of the paper gear and see how they match up.

Edited November 12, 2023 by ReMark

[BIGAL]

Why are you asking, take the broken one to a good machine shop and they will work out what it is very quick. If your thinking just 3D print one it may not last. A lot of pressure in those paper shredder gears, by people who put 5 sheets in when sign says max 3.

[basty]

10 hours ago, ReMark said:

You have been using AutoCAD since 2014 and you don't know what a Block is?  How is that even possible?  Well, if you don't know what a block is then I guess there is no point telling you not to create one.  I have to agree with Irm... your gear tooth profile is involute.  The pressure angle of a gear is defined as... "the angle formed by the radial line and the line tangent to the profile at the pitch point."  Twenty and twenty-five pressure angle gears are typically the most commonly used today.  For maximum strength applications pressure angles as high as twenty-eight to thirty degrees have been used.  I suggest you try twenty and twenty-five first.

 

Here's an idea.  Draw your gear's 2D profile then print it.  Cut it out with an Exacto knife then lay your real gear on top of the paper gear and see how they match up.

 

Why you keep telling me the profile of the gear tooth is involute? Can't you see on the picture? It's a triangle isn't it? Or maybe it's so small so that it looks like a triangle?

[ReMark]

Or... maybe it is so worn that some teeth have broken off.  Did you do as I suggested re: creating 2D profile and directly comparing to actual gear?  FYI - I'm off to the mountains of Tennessee this morning to hike for a couple of days.  By the time I return I expect you to have figured this out.  Good luck.  

Edited November 13, 2023 by ReMark

[basty]

49 minutes ago, ReMark said:

Or... maybe it is so worn that some teeth have broken off.  Did you do as I suggested re: creating 2D profile and directly comparing to actual gear?  FYI - I'm off to the mountains of Tennessee this morning to hike for a couple of days.  By the time I return I expect you to have figured this out.  Good luck.  

 

Do you mean create the 2D profile using 2DGear.lsp or I should measure the dimension of the tooth using vernier caliper all by myself?

Edited November 13, 2023 by basty

[lrm]

@basty    Zooming in on the gear image you posted it is difficult to delineate the tooth profile from the 3rd dimension of the tooth.  In the image below I have roughly shown what I think is the tooth profile in yellow and its depth in red.  If you add some side lighting to the gear before taking the picture you may be able to see the involute more clearly.

 

I think you should consider @BIGAL 's suggestion to bring the gear to a machine shop to duplicate it.  If you still  want to create a 3D model in AutoCAD then yes, use the gear lisp program to create the 2D profile of a tooth and then use the method I outline to create the gear keeping in mind that the involute shape of the tooth is NOT in a plane parallel to the face of the gear but at an angle beta as discussed before.  

Good luck!

@ReMark Enjoy your hike!  I've enjoyed hang gliding the valleys of Tennessee near Dunlap.