## Re: hard to retrofit taig lathe for CNC? To powerfeed or not powerfeed

Expand Messages
• Ken- may i ask your algorithm for computing path accounting for the 1/2 diameter of the tool as the offset? i was going to just find the coordinate
Message 1 of 53 , Feb 3, 2012
Ken- may i ask your algorithm for computing path accounting for the 1/2 diameter of the tool as the offset?
i was going to just find the coordinate perpendicular to (and at the right distance from) every 2 points on the ideal involute path.

--- In taigtools@yahoogroups.com, Ken Cline <cline@...> wrote:
>
> Hi Tony,
>
> I am aware of Gearotic, but I like my DIY approach. My gear design program handles some unusual design cases and produces exactly the dxf and g-code I want.
>
> FYI, here's a session running it to calculate a 12-tooth, 24tpi, 20 degree spur gear (an image of the calculated gear is also displayed in a pop up window):
>
> [~/src/involute]% involute -n 12 -P 24 -phi 20
> phi = 20.000000, P=24.000000, p=0.130900
> r=0.250000, r_b=0.234923, r_r=0.234923, r_o=0.291667, r_f=0.012501
> a=0.041667, b=0.015077
> angular displacement = 0.000000
> [~/src/involute]%
>
> The fillet radius, 0.0125, is smaller than I would want to attempt with a standard end mill, so I would use a more conventional approach at this pitch/modulus and smaller.
>
> My program uses a rule-based inference engine to match gears, allowing a lot of flexibility in the specification of mating gears.
>
> On Feb 3, 2012, at 12:36 AM, Tony Jeffree wrote:
>
> > Ken -
> >
> > Art Fenerty (of Mach 3 fame) has developed a package called "Gearotic" (
> > http://gearotic.com/ ) that can generate the necessary G-code to cut
> > involute spur gears using an end mill. The only constraint is that the end
> > mill needs to be no larger than the space between adjacent teeth, so that
> > tends to limit the technique to cutting gears with a large module size.
>
>
>
> [Non-text portions of this message have been removed]
>
• Hi, The side lead screw is the best that you can do with the little taig as the base is filled with concrete. Many larger lathes also have this on the side
Message 53 of 53 , Feb 5, 2012
Hi,
The side lead screw is the best that you can do with the little taig as the base is filled with concrete. Many larger lathes also have this on the side without any apparent problems.

Regards,

A.G

Sent: Sunday, February 05, 2012 8:40 AM
To: taigtools@yahoogroups.com
Subject: [taigtools] Re: hard to retrofit taig lathe for CNC? To powerfeed or not powerfeed

I've finally gotten the whole rig setup and even turned a little piece for testing.

I gotta say, the rack and pinion is terrible. backlash is quite significant, although from a purely manual perspective it doesnt really matter as long as you have dials everywhere and measuring actual movement. However the z resolution isnt as great I suppose.

Im definately going to add some sort of leadscrew to my setup and take out the geared handle.

This leads me to a followup question. From the few CNC retrofits and powerfeed version that I have seen, they seem to put the leadscrew on the front side of the lathe, near where the rack and pinion resides.

With regards to this, isnt this setup not as ideal, given that any leadscrew will be further off-center from the tool-holder bed? In the ideal world, the leadscrew should be centered along the center of the stage so that you dont get excessive friction at opposite corners of the dovetails of the bed, given that there is always going to be some gap spacing on the dovetails?

--- In taigtools@yahoogroups.com, Tony Jeffree <tony@...> wrote:
>
> I haven't tried the g-code output features yet, so I can't comment on that.
> As you say, a fun program though!
>
> Regards,
> Tony
>
>
>
>
> > Hi Tony,
> > I have down loaded the trial version of the software you mention and it
> > indeed does have the limitation that you mention so for small scale gear
> > cutting it is hopeless and it also doesn't seem to generate any code on my
> > computer perhaps due to it being a trial version but it is fun to generate
> > data as you mention.
> >
> > regards,
> >
> > A.G
> >
> >
> > From: Tony Jeffree
> > Sent: Friday, February 03, 2012 7:36 AM
> > To: taigtools@yahoogroups.com
> > Subject: Re: [taigtools] Re: hard to retrofit taig lathe for CNC? To
> > powerfeed or not powerfeed
> >
> >
> >
> > Ken -
> >
> > Art Fenerty (of Mach 3 fame) has developed a package called "Gearotic" (
> > http://gearotic.com/ ) that can generate the necessary G-code to cut
> > involute spur gears using an end mill. The only constraint is that the end
> > mill needs to be no larger than the space between adjacent teeth, so that
> > tends to limit the technique to cutting gears with a large module size.
> >
> > It is a fun package to play with because it can sim arrangements of
> > multiple gears & also draw out non-circular gears and (more recently) clock
> > escapements too.
> >
> > Regards,
> > Tony
> >
> > On 2 February 2012 21:05, Ken Cline <cline@...> wrote:
> >
> > > On Feb 2, 2012, at 9:23 AM, juangelt wrote:
> > >
> > > > therefore, a cutter with TRAPEZOIDAL teeth can cut any size gear of
> > that
> > > pitch at any resolution one desires - something i find really wonderful.
> > >
> > >
> > > Of course you can also cut gear teeth with a plain old end mill. I make
> > > credible approximate-involute gears this way, sweeping the end mill
> > across
> > > the face of each tooth several times to cut facets. Using a ball end
> > > cutter leaves nice bottomland fillets that eliminate stress concentrating
> > > angles at the base of the teeth. I have designed and used this technique
> > > to make custom gears that mesh at multiple pressure angles (e.g. mating
> > > with two gears of the same overall size but differing number of teeth).
> > >
> > > It is worth mentioning that these approximate-involute approaches tend to
> > > leave a little extra material n the gear teeth, getting closer and closer
> > > to the true involute form as more facets are cut. Gears made to this
> > shape
> > > will therefore interfere with each other, and therefore won't mesh at
> > they
> > > true pitch radii. Widening the rack-cutter's teeth, changing its angle,
> > > its position when cutting, or a combination of these techniques will
> > > produce gears that mesh at the design distance.
> > >
> > > Compare this to the standard numbered involute gear cutter approach: Each
> > > numbered cutter produces a smooth involute shaped profile, which never
> > has
> > > extra material on the tooth so that the gears produced never interfere
> > when
> > > run at their pitch radii. The deviation from ideal shape arising from
> > > using a small number of cutters to produce al gears is not usually a
> > > problem because the involute shape allows the gears to still mesh at
> > > constant pitch angle and angular velocity ratio, albeit with a small
> > amount
> > > of backlash (and small change in pitch angle).
> > >
> > > By the way, we have examples of complex mechanical gearing at least two
> > > thousand years old (e.g. the Antikythera Mechanism). Hand cut gears with
> > > crudely controlled profiles proved serviceable in ancient times. Involute
> > > gears were first proposed by Leonhard Euler in the 1700's.
> > >
> > >
> > >
> > >
> > > [Non-text portions of this message have been removed]
> > >
> > >
> > >
> > > ------------------------------------
> > >
> > > To Post a message, send it to:
> > > taigtools@yahoogroups.com
> > >
> > > To Unsubscribe, send a blank message to:
> > > taigtools-unsubscribe@yahoogroups.com
> > >
> > > Let the chips fly!
> > > Yahoo! Groups Links
> > >
> > >
> > >
> > >
> >
> > [Non-text portions of this message have been removed]
> >
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
> >
> >
> > ------------------------------------
> >
> > To Post a message, send it to:
> > taigtools@yahoogroups.com
> >
> > To Unsubscribe, send a blank message to:
> > taigtools-unsubscribe@yahoogroups.com
> >
> > Let the chips fly!
> >
> >
> >
> >
>
>
> [Non-text portions of this message have been removed]
>

[Non-text portions of this message have been removed]
Your message has been successfully submitted and would be delivered to recipients shortly.