Re: [Emc-users] Maybe a minimally printed harmonic drive?

[Sam Sokolik]

36 hours - For this purpose I think we are good.

http://electronicsam.com/images/greenmachine/IMG_20210320_072206.jpg

Next I think a destructive torque test and then maybe some actual
cutting...  I need to finish the face plate first though.

On Fri, Mar 19, 2021 at 11:16 PM Chris Albertson 
wrote:

> If you wanted a more durable part, you can send the STL file out to a
> service that prints it in stainless steel.  You might change the design to
> reduce the bulk because they charge by the gram for the steel.
>
> SpaceX is printing pre-burner parts for their new Raptor engines.  If
> anything needs to be durable it is rocket engine parts.  I've read about
> turbine engine blade retainers being printed in Inconel too.   It is not so
> expensive if you think to reduce the weight of the parts.
>
> On Fri, Mar 19, 2021 at 5:10 PM Gregg Eshelman via Emc-users <
> emc-users@lists.sourceforge.net> wrote:
>
> > 3D printing fixtures to hold things you've 3D printed can be done the
> same
> > way. Put two cubes side by side with a bit of gap between. Position the
> > object at the divide so that it's half embedded in each cube, with no
> > undercuts. Subtract the object from both cubes. Print the cubes and you
> > have blocks to clamp in a vise to hold the object for more operations
> like
> > drilling, tapping, pressing in threaded inserts etc.
> >
> >
> > On Friday, March 19, 2021, 10:53:55 AM MDT, Chris Albertson <
> > albertson.ch...@gmail.com> wrote:
> >
> >  When I first saw this, my idea was to print the internal tooth gear
> > "backward" as a mold that makes up the central space in the aluminum
> > housing, then pour in an epoxy/glass composite paste.
> >
> > I've seen this done on other projects, the most complex is a prosthetic
> > hand I'm slowly working on.  The designer made the "finger bone" in 3D
> > printed plastic, then you put it inside a hollow 3D printed mold and pour
> > in polyurethane resin which "over-molds" the plastic core.  It makes a
> > very tough non-slip fingerpad.Seeing this got me thinking about what
> I
> > call "hybrid design" what you combine 3D printing with metal and resin
> > casting.  It sounds complex but if you have a 3D CAD system and a printer
> > mold-making is nearly trivial, Use the part you want to make and subtract
> > that from the inside of a brick.
> > ___
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> > https://lists.sourceforge.net/lists/listinfo/emc-users
> >
>
>
> --
>
> Chris Albertson
> Redondo Beach, California
>
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Re: [Emc-users] Maybe a minimally printed harmonic drive?

[Gene Heskett]

On Saturday 20 March 2021 09:57:11 Sam Sokolik wrote:

> 36 hours - For this purpose I think we are good.
>
> http://electronicsam.com/images/greenmachine/IMG_20210320_072206.jpg
>
> Next I think a destructive torque test and then maybe some actual
> cutting...  I need to finish the face plate first though.

Looking pretty good Sam, but the color of the lube I can see makes me 
want the recipe.

FWIW, some of the first failure may be from the UNK lube migrating out of 
those huge bearings, this stuff is known to do strange things when 
exposed to petroleum based Lubes, even if just the fumes. I've seen and 
used the vegetbale grease sold as crisco and gotten away with it for 
limited time.

That has the looks of something with moly or graphite in it?

Can you share that info?

Thank you Sam S.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] Maybe a minimally printed harmonic drive?

[Sam Sokolik]

Currently I am using Vaseline...  The black is plastic wear...

On Sat, Mar 20, 2021, 1:43 PM Gene Heskett  wrote:

> On Saturday 20 March 2021 09:57:11 Sam Sokolik wrote:
>
> > 36 hours - For this purpose I think we are good.
> >
> > http://electronicsam.com/images/greenmachine/IMG_20210320_072206.jpg
> >
> > Next I think a destructive torque test and then maybe some actual
> > cutting...  I need to finish the face plate first though.
>
> Looking pretty good Sam, but the color of the lube I can see makes me
> want the recipe.
>
> FWIW, some of the first failure may be from the UNK lube migrating out of
> those huge bearings, this stuff is known to do strange things when
> exposed to petroleum based Lubes, even if just the fumes. I've seen and
> used the vegetbale grease sold as crisco and gotten away with it for
> limited time.
>
> That has the looks of something with moly or graphite in it?
>
> Can you share that info?
>
> Thank you Sam S.
>
> Cheers, Gene Heskett
> --
> "There are four boxes to be used in defense of liberty:
>  soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> If we desire respect for the law, we must first make the law respectable.
>  - Louis D. Brandeis
> Genes Web page 
>
>
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Re: [Emc-users] Maybe a minimally printed harmonic drive?

[Gene Heskett]

On Saturday 20 March 2021 14:52:51 Sam Sokolik wrote:

> Currently I am using Vaseline...  The black is plastic wear...
>
Humm, I've heard its not recommended, as it's petroleum based. I won't 
have that wear evidence though, this Dremel 3d45 came with clear PETG, 
and although I've two spools of it, one about used up now, when thats 
used up I'll install the 2nd, and I've some bright green PETG to rewind 
on the first of the special 3/4 kg spools this thing uses.

These slightly smaller Dremel spools have RFID chips in them so they can 
tell the printer what its eating. At least enough to display it. But 
cura still runs the show.

I have not carved any alu for a housing yet, next on the agenda here as I 
wanted a final size check from these innards first.

I'd post a pix, clear stuff is wierd looking, but when I turned on the 
camera an hour back it yelped for a battery and died.

And as a reloader, I have a couple oz of moly powder I may sprinkle a few 
grains of into a teaspoon of crisco just for S & G's. But with 
everything made from PETG, its surface is hard and polished, so the 
contact friction seems to be quite low anyway.  Nothing like PLA for 
friction.

Thanks Sam S.

Take care abd stay well now.

[...]

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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[Emc-users] Std D-flatted motor shaft, how is size of flat determined?

[Gene Heskett]

Greetings all;

When making what I intend to be a tight (for PETG) press fit to a 
D-flatted motor shaft, how is the size of the flat determined?

It seems to me there ought to be a std math rule for that, but I've not 
found a reliable reference.

Thanks all.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] Std D-flatted motor shaft, how is size of flat determined?

[andy pugh]

On Sun, 21 Mar 2021 at 01:12, Gene Heskett  wrote:

> It seems to me there ought to be a std math rule for that, but I've not
> found a reliable reference.

Why do you think that? Surely the manufacturer can make any flat that they want?

I would measure the actual shaft (flat to rounded opposite curve) then
dimension my sketch to that actual number (my printer shrinks holes,
so I wouldn't make it any tighter deliberately)

-- 
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, 1912


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Re: [Emc-users] Std D-flatted motor shaft, how is size of flat determined?

[Gene Heskett]

On Saturday 20 March 2021 21:21:56 andy pugh wrote:

> On Sun, 21 Mar 2021 at 01:12, Gene Heskett  
wrote:
> > It seems to me there ought to be a std math rule for that, but I've
> > not found a reliable reference.
>
> Why do you think that? Surely the manufacturer can make any flat that
> they want?

This is true, but most of this stuff has a best practices doc buried 
someplace on or in this planet.

> I would measure the actual shaft (flat to rounded opposite curve) then
> dimension my sketch to that actual number (my printer shrinks holes,
> so I wouldn't make it any tighter deliberately)

So does mine, if I want a 8mm bolt hole, I draw an 8.25mm,but a bar 100mm 
long measures 99.8. Doesn't coorolate all taht well.

Thanks Andy. Take care and stay well.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] Std D-flatted motor shaft, how is size of flat determined?

[Chris Albertson]

I use a reamer to make accurate holes in 3D printed parts.  You can fudge
the hole size all you like but you never get a perfect fit. Same with
threaded holes.  I print the threads but clean them with a tap by hand

If you want a perfect D-hole, print an undersized hole, ream it on the
lathe or drill press then place the saft in the hole and fill the gap with
JB-Weld. (put something on the shaft to keep epoxy from sticking)

That said, my preference is to make metal hubs and to print the outer rims
of gears and pulleys then epoxy the hub to the ring.  The holes on printed
pulleys always fail. Maybe because the motor gets hot but the holes seem to
enlarge over time.

3D printed parts usually do require some hand work to finish.   It is not
unlike making parts from metal castings. Usually there is some machine work
required

On Sat, Mar 20, 2021 at 9:14 PM Gene Heskett  wrote:

> On Saturday 20 March 2021 21:21:56 andy pugh wrote:
>
> > On Sun, 21 Mar 2021 at 01:12, Gene Heskett 
> wrote:
> > > It seems to me there ought to be a std math rule for that, but I've
> > > not found a reliable reference.
> >
> > Why do you think that? Surely the manufacturer can make any flat that
> > they want?
>
> This is true, but most of this stuff has a best practices doc buried
> someplace on or in this planet.
>
> > I would measure the actual shaft (flat to rounded opposite curve) then
> > dimension my sketch to that actual number (my printer shrinks holes,
> > so I wouldn't make it any tighter deliberately)
>
> So does mine, if I want a 8mm bolt hole, I draw an 8.25mm,but a bar 100mm
> long measures 99.8. Doesn't coorolate all taht well.
>
> Thanks Andy. Take care and stay well.
>
> Cheers, Gene Heskett
> --
> "There are four boxes to be used in defense of liberty:
>  soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> If we desire respect for the law, we must first make the law respectable.
>  - Louis D. Brandeis
> Genes Web page 
>
>
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> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users
>


-- 

Chris Albertson
Redondo Beach, California

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Re: [Emc-users] Std D-flatted motor shaft, how is size of flat determined?

[Gregg Eshelman via Emc-users]

There should be some equation that can give the width of a flat on a shaft if 
you know the diameter of the shaft and the distance from the flat to the round 
side opposite.
*lightbulb* The flat is the shame as a chord. So what you want is to calculate 
the length of a chord. https://byjus.com/maths/chord-of-circle/

On Saturday, March 20, 2021, 7:24:16 PM MDT, andy pugh  
wrote:  
 
 On Sun, 21 Mar 2021 at 01:12, Gene Heskett  wrote:

> It seems to me there ought to be a std math rule for that, but I've not
> found a reliable reference.

Why do you think that? Surely the manufacturer can make any flat that they want?

I would measure the actual shaft (flat to rounded opposite curve) then
dimension my sketch to that actual number (my printer shrinks holes,
so I wouldn't make it any tighter deliberately)  
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