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1  General Category / Bevel Machining Discussions / Re: Machining Bevels. on: May 09, 2015, 10:34:57 PM

Here is another paper on spiral bevel gear generatio n and inspectio n.

Also Klingelnb erg method is in a spread sheet with macros that create tooth form for Solid Works IGES inport.

Chuck in Wyoming

2  General Category / Newest Rev Release / Re: Release of GM Version 4.20 on: October 29, 2011, 10:33:37 AM

Watching your video on the clock,  the way you created the gears for a specific reduction .   When designing a pair of gears it would be nice if you added mode for a fixed center distance and fixed number of teeth and had GM calculate the pitch to make it work.   This can be calculate d by hand but why? 

Perhaps a popup window to input shaft center distance, clearance and the number of teeth, then calculate and display the pitch.

3  General Category / Suggestions for Future / Re: Upcoming development season.. on: October 08, 2011, 10:26:40 PM
cycloid rotor page link..... lets try again.  I am not used to this posting system. _rotor_co nstructio n_-_2_lobes.svg

I tested it this time..... .

4  General Category / Suggestions for Future / Re: Upcoming development season.. on: October 08, 2011, 11:04:56 AM

 The Roots Compresso r is easily generated it is simply 2 meshing circular arcs forming a cycloid centered on a circle around the shaft of each rotor.

_rotor_co nstructio n_-_2_lobes.svg" target="_blank"> _rotor_co nstructio n_-_2_lobes.svg

If you do add this to GM you should make the pitch circle and the tooth size adjustabl e.   This will change the compressi on ratio.

You will also need to have a clearance allowance and you may want to add turbulenc e seal groves to the rotor tips but that doesn't need to be in the generator program.

Of course the Roots MUST be driven by a 2 matched gears outside the compressi on volume.

If you make them spiral you must consider the angle, too much angle and they won't pump any air. 

5  General Category / Suggestions for Future / Re: Upcoming development season.. on: October 02, 2011, 10:47:48 AM

Randy has an interesti ng idea.   If you build a profile design tool that would allow you to design just about any cutter profile on a large graph paper like screen.   This would be like an optical comparato r with a 20X or 50X magnifier .   You could also assist the designer with involute or other computed curves. 

Once designed the program could convert the profile into Gcode for one of several tool machining setups.

With a fly cutter tapered endmill or formed endmill and a 4 axis cutting Gcode program you could do a number of small gears from spur to helical and bevels.

You may want to add several types of worm/worm wheel designs to the wish list.

6  General Category / Suggestions for Future / Re: Upcoming development season.. on: October 01, 2011, 08:13:39 PM

While I do have an interest in bevels I understan d your prioritie s.

The next thing I think you should focus on is to allow spur, helical and worm gears with fine pitch for the modellers .   This would lead to using the tapered engraving tools and fly cutters.   

The ability to grind both endmills and fly cutters is the logical solution to small gears. A 2D grinding process with the grinding wheel position set below the cutting edge to provide clearance would be easy to do.  Just allow for a grinding wheel diameter and  X, Y or Z alignment . Of could cnc the full clearance but with the correct setup you wouldn't need to.

Formed tools would also allow faster gear cutting.  While productio n shops will likely invest in productio n gear cutting equipment there is a market between one off gears and short run productio n.   Other ways to speed up the process in metal gears?

And the list of things you could add never ends..... .

7  General Category / Newest Rev Release / Re: tutorial doesn't match latest release? on: August 20, 2011, 09:31:30 AM

If you do a setup in the 4th axis so you can rotate the tool you could do the  relief cut and rotate the tool 10 degrees make the next relief cut and continue around in 10 or 15 degree cuts. This would automatic ally solve the relief problem and make a full 3D relieved endmill.

For 2 or more teeth just repeat the tooth and relief process as many times as you need.

An option to use a grinding wheel in stead of the endmill to form the tool would be nice.  That way we can grind carbide blanks or hard tool steel.  I have been making single point carbide taper endmills in the 4th axis with a Dremel Tool diamond cutoff wheel. It takes lots of passes at 0.0005"/cut but on a 1/8" cutter it isn't too bad.

It would also be nice to be able to make fly cuter forms in addition to end mills.  This too may be best done in the 4th axis.  Anyone wanting to CNC gears this way will already have the 4th axis setup at least X or Y aligned.

8  General Category / Newest Rev Release / Re: Version 3.47 online. on: June 27, 2011, 11:23:05 AM

You got it!  You have to unwrap a string on the diameter  not the tangent of the angle.  I think I made the same mistake back in 1974 when I made my first spur gear this way.  Punch cards and FORTRAN days..... BOY am I glad that is gone by.

You may be ahead of the game if you start by doing simple spur gears and not jump in to bevels!

Be sure you account for the compound angle the cutter makes with the rotated bevel tooth.  This will change the angle you need to rotate the gear to get the desired involute contact angle.  I assumed you had this worked out when you said your code was independe nt of the angle of the cutter.  But now that you are requiring a pitch angle cutter I wonder if you have it covered.

If you want me to look at a section of code just send it off list.

I didn't see any of the example attachmen ts but it sounds like they are old info now. 

9  General Category / Newest Rev Release / Re: Version 3.47 online. on: June 26, 2011, 06:13:17 PM

I was looking for a diversion from a rather tricky embedded processor project.

The intersect ing rack rotates as the bevel rotates, this complicat es the rack generatin g method but it should still work.  Rotate the gear to the next involute shaving angle and calculate the end points. The changing pitch complicat es the calculati on of the tool path end points!  The Z must be moved with the changing pitch and must follow the pitch cone.  Also as the gear rotates the pressure angle generatin g has a 3 way compound angle with the cutter.

After some thinking, the only way I can visualize the spiral bevel is to do a 4 axis move cut with the tapered endmills. I don't see any way to do a simple linear move.  It looks like you will have to do short line segments along the tooth and do 4 axis move for each segment to maintain the involute contact with the cutter.

If you place an imaginary zero thickness crown  gear scaled for 2 diameters on the tooth cone and connect the dots for a given involute angle.  The X, Y, Z and A will have to move to keep the contact angle of the cutter at the involute angle.  The error in angle is controlle d by how far apart the crowns are in the calculati on.  Using the rolling rack idea at each end of the cut and rotating the gear to adjust the involute angle then compute the X,Y and Z to connect the endpoints .  With the angle change and the X,Y,Z change you can generate the G1 X.. Y.. Z.. A.. move.

instead of the crown gear it may be easier to use an imaginary flat spur gear tooth normal to the bevel cone, scaled to the changing pitch for each point and connect the dots.

This is much like strait endmills but at least it still has the advantage of fewer passes for the same generatin g step angle on the involute.  Spiral tooth bevels are just another level of complexit y with the same setup.

10  General Category / Newest Rev Release / Re: Version 3.45 released on: June 20, 2011, 07:50:21 PM

OK now you have forced me to add a stepper to my dividing head and give it a try.  My current A axis can't be tipped up at an angle.  I just have too many projects. ......ret ire and take it easy?

11  General Category / Newest Rev Release / Re: 3.42 online on: June 13, 2011, 09:09:52 AM

Looks like a great start on bevels with tapered cutters. I really like the ability to use any taper, solves the problem with a limited number of stock taper endmill angles.

This should allow us to cut just about any pitch with large endmills or small engraving cutters.

12  General Category / Bevel Machining Discussions / Re: Machining Bevels. on: June 03, 2011, 09:44:36 AM

For small pitch we have the engraving tools.  These should work for about 20DP down to about 80DP

The stock sizes of 30 are close to 14.5 and the 40 are spot on for 20 pressure angles.

They are easy to make yourself and can be made for larger pitch from 1/8", 1/4", 3/8" or 1/2" drill rod.
With a Gcode generator program we can make any size we want with a 4 axis CNC!  I have made cutters in the lathe by turning them off center for clearance heat treating and grinding a cutting edge rack tooth endmill cutter for 6DP.

A basic spec for the cutter in sizes of 1/8" and 6mm:

13  General Category / Bevel Machining Discussions / Re: Machining Bevels. on: June 02, 2011, 08:13:37 PM
Looking for 20 degree stock taper endmills.  not much out there!
I have been grinding single flute taper endmills,  I will put together a program to generate the Gcode.

I did find an interesti ng link:

Side not I am building a 1/4 scale Shay Loco.

14  General Category / Bevel Machining Discussions / Re: Machining Bevels. on: June 02, 2011, 07:34:10 PM

You are on track,  I wonder if you will be back to point to point calculati ons on spiral bevels?  The compound angle may mess up the "simple" rack generatio n method when you start rotating the gear. I have been thinking about it and can't get my head screwed up enough to visualize it!  Oh well get the strait cut bevels working and then we can discuss spirals.  I can see how the helical spur gears will work but that is a much simpler setup.

And yes 40 degrees included or 20 per side,  here is a catalog link:
3-Flute 15 deg. Per Side End Cutting Tapered End Mills

15  General Category / Bevel Machining Discussions / Re: Machining Bevels. on: May 30, 2011, 07:42:11 PM
Art, John and Archie,

Art's lifting pass is NOT the generatin g method used.  John and Archie are on track, I would add that a shaper cut  tooth is formed by a cutter on each side of the rack tooth that is split and mounted on a tapered slide.  The tapered slide forms the cone of the bevel and the gear is rotated and moved by the shaper as if it was a thin rack tooth.  The machine then takes care of the involute generatio n.

Art, just keep the pitch cone center point aligned with the tool path offset at tool edge and move the rack tooth past it to generate the gear.   By keeping a point on the pitch diameter of an imaginary crown gear in constant synchroni zed motion with an imaginary rack tooth. Then rotate and adjust the path to keep the offset surface of the cutter on a line to the gear pitch center point.  If the cutter is rack tooth form of the desired involute the generatio n is automatic, you just have to rotate and align the gear with the cutter.

Look at this gear shaper video:

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