Re: [Emc-users] Encoders

[Chris Albertson]

On Fri, Jun 15, 2018 at 7:58 PM Gene Heskett  wrote:

> On Friday 15 June 2018 20:20:20 jeremy youngs wrote:
>
> Aerotech mentions
> using 741's (op-amps) but the gain of a 741 above 10 hz falls like a
> rock, and that leaves the nyquist phase v stability angles in doubt.


If the paper suggests using a 741, then the paper is very old.  Today you
can of course buy better op amps.   And of course today a micro controller
can precisely measure an qucoder at any speed from zero up to some MHz.
If you can, the simplest way is to connect the digital encoder to the mesa
card, let it keep the position count then use that any way you wish,
possible to create the analog output you want

I would not build an analog, op amp based digital rate the analog output
converter even with modern op amps.  That is not the best solution in
2018.  A digital counter is the way to do.  It is easy to make and as exact
as you want.   But I think the existing FPGA based hardware should be able
to count and you'd not need to actually build anything.
-- 

Chris Albertson
Redondo Beach, California
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Re: [Emc-users] Encoders

[Gene Heskett]

On Friday 15 June 2018 20:20:20 jeremy youngs wrote:

> Always another hurdle . Lol. I abandoned the h bridge plan for now as
> I am lacking sufficient power supply. I have 2 aerotech 4020 linear
> drives . The issue is they need tachometer feedback and it appears
> though the drive isn't configured for armature feedback. So the
> question is, is there a readily available device to convert 1000 ppr
> to an analog signal @7v /1000 rpm ?
>
> The drive is configurable to torque mode, would it be easier to set
> drive in torque mode and tune servo in Linux CNC with 7i90 ?
> Thanks

Put a 1000 line encoder on the motor, and use the encoders in the 7i90 to 
do a position servo. The aerotech drive is line powered, 20 amps max, 40 
volts max. And it has inputs for an encoder, taking lcnc out of the 
circuit if you'd like. But I'd druther put the encoder into linuxcnc, 
and let it calculate the pwm or pdm drive needed for a position null. I 
think it would be more precise, and possibly faster. Aerotech mentions 
using 741's (op-amps) but the gain of a 741 above 10 hz falls like a 
rock, and that leaves the nyquist phase v stability angles in doubt.

I don't see a reason why, if the correct motors are used, that it cannot 
be made to work.



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Re: [Emc-users] Encoders

[jeremy youngs]

Gmail is queing my messages for some reason. I apologize if this double
posts.

Always another hurdle . Lol. I abandoned the h bridge plan for now as I am
> lacking sufficient power supply. I have 2 aerotech 4020 linear drives . The
> issue is they need tachometer feedback and it appears though the drive
> isn't configured for armature feedback. So the question is, is there a
> readily available device to convert 1000 ppr to an analog signal @7v /1000
> rpm ?
>
> The drive is configurable to torque mode, would it be easier to set drive
> in torque mode and tune servo in Linux CNC with 7i90 ?
> Thanks
>
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Re: [Emc-users] Encoders

[jeremy youngs]

Always another hurdle . Lol. I abandoned the h bridge plan for now as I am
lacking sufficient power supply. I have 2 aerotech 4020 linear drives . The
issue is they need tachometer feedback and it appears though the drive
isn't configured for armature feedback. So the question is, is there a
readily available device to convert 1000 ppr to an analog signal @7v /1000
rpm ?

The drive is configurable to torque mode, would it be easier to set drive
in torque mode and tune servo in Linux CNC with 7i90 ?
Thanks
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Re: [Emc-users] Interesting gear hobs

[andy pugh]

On 15 June 2018 at 06:57, Roland Jollivet  wrote:

> What's interesting is that they make the gear in two parts. (2012). Maybe
> today they use a CNC and use one piece.
> That helicopter looks like a solid chunk of metal.

They have to do that to be able to fit in the tooling to make the
gear, but if they had used the Palloid (rather than Cycle-Palloid)
process that wouldn't have been an issue.

The comments blame the weld for the aircraft falling out of the sky.
But I think I have seen another video that says the problem is with
the epicyclic gearbox.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

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[Emc-users] Interesting gear hobs

[Roland Jollivet]

I thought I'd try find videos of palloid cutters in use, but found this
instead;
https://www.youtube.com/watch?v=oD4jKBOIBwc

What's interesting is that they make the gear in two parts. (2012). Maybe
today they use a CNC and use one piece.
That helicopter looks like a solid chunk of metal.




On 14 June 2018 at 21:04, andy pugh  wrote:

> On 14 June 2018 at 19:51, Henk du preez  wrote:
> > I think those can only be used to cut a specific size gearset with
> specific
> > ratio.
>
> This article:
> http://gearsolutions.com/features/high-performance-gear-
> cuts-a-path-to-stronger-bevel-gears/
>
> Seems to suggest that the wheel and pinion are cut with the same
> cutter, so I think that they can hob any bevel at the 3.5mod tooth
> pitch.
>
> --
> atp
> "A motorcycle is a bicycle with a pandemonium attachment and is
> designed for the especial use of mechanical geniuses, daredevils and
> lunatics."
> — George Fitch, Atlanta Constitution Newspaper, 1916
>
> 
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