What am I doing wrong here?

[ArtF]

Hi:

  I think helical bevels were turned off until straight bevels were tested. As yet, they havent been with the new code. They require a
milling bit tapered at the pressure angle. The problem with bevels is they are very hard to cnc, while 3d printing them is easy, cnc'ing them
requires a special blank as well as the tapered bit. The older code used a stright flute and worked, but peopel wanted smaller bevels so we
switched to tapered bit and as yet it hasnt tested out. I plan to offer a new improved version in the fall for cnc bevels, but till then your limited to straight ..

Art

[Mooselake]

Art:

I don't have a 4th axis so this is mostly academic, but why do you have to have a special blank?  Wouldn't it be easier to make one that's somewhat close (bandsaw to the general diameter, say, from the proper thickness), then mount it in the 4th axis and mill it to the proper diameter/shape?  Could this be something that GM could do for you?

Be gentle, way out my depth here.

Kirk

[ArtF]

Kirk:

  Its due to the angles involved, getting a smooth blank of the right size in a 4th axis would take a very long time..
take multiple tool sizes to do it efficiently..basically a pain in the ass. Its why special machines make bevels, you rarely mill them
or make them any other way..

  Now 3d printing seems the way to do.. Im of the opinion even to print one to use as a mould is probably quicker and better quality than trying
to machine one...

Art

[JamesTSG]

Good for quick prototyping and yeah making a plug or mold, but problem is that most additive materials and techniques aren't up to the requirements that a bevel gear train needs.  If not peak loading, then long-term wear, not even metallic sintering.  And even then with most of them, you will still have to machine finish the gear faces...


Very cool stuff nonetheless.

Thanks,

-James

[ArtF]

James :

All true. However, using additive methods for moulds is pretty good for bevels if one needs the strength
and I suspect a nylon bevel is pretty strong for most applications for small mechanisms. ( Windo blind winders and such).

  Im seeing many posabilites. I printed a bearing this week, runs pretty well so I can see where
GT will have to offer parametic bearings for printing, hinges..and a variety of other 3d objects.. HOW one
deals with making them Ill leave up to the user. Its possible to download models of many things these
days, but GT will concentrate on proper mathmatics of models and parametric ways of creating them. Ill
focus on output options that reflect whats possible for each model type.

 
Art

[JustinO]

I'm happy with a nice quiet, free running gear train. My needs are not for high speed or high torque -- just kinematic synchronizing. I really need SMOOTH accurate geometry though. I think the resolution of 3D printers will have to come up pretty far before they work for me. Heck, even the highest definition video still shows artifacts of the discrete pixels.

If you  want to loose sleep, read up on how they design gearboxes for aircraft -- helicopters and the V-22 Ospray in particular. The requirements were high power, light weight, and super reliability. Easy!

--Justin

[ArtF]

Justin:

  I woudlnt be too sure...

  Ive so far printed spur gears, involutes, helicals and bevels in Nylon and ABS. These are as good
as any wooden gears Ive made, and are as accurate as Id expect from CNC'ing them from metal. They mesh smoothly and are incredibly detailed. In fact the involutes are the best Ive ever made because the printers resolution seems to as good or better than most cnc'ed gears. Admittedly you wouldnt want to
drive anything heavy, but the nylon helical is as capable as any Ive used in industry in things like Kodak XRay developers and such. If your into kinematics primarily, Id have to say the right 3d printer woudl amaze you with what it can presently do...
  We've been discussing building an example board here with a motor driving a huge chain of gears, at least one of every type GM can make. Its probably worth doing as a video example of what GM can do .. Youll probably see one before too long..
Art

[Ken_Shea]

Art,
Would love to see more examples of your prints as time permits.

While I know the build size suits yout testing purposes sure wish they had a 8x8x8 minimum build platform.

The mendel and off spring don't seem to come close to comparing what you posted of your first prints.

Thanks
ken

[ArtF]

Ken:

  Ill try to post some more pics of the things Ive printed tomorrow.
From what Ive observed so far, the problem isnt the process, I too was not
impressed by many of the web examples I ve seen...and its why I held off
so long. But, it appears to me those problems are primarily of extruder size,
which is now down to .3mm or so.. and the methods the software uses for things
like supports and such. TO make the support easily removable I suspect took awhile to
develop. Also doing hollow itesm took some thought..but the software is pretty seamless
at that as well. They claim of course its due to their special ABS.. I disagree, in fact I lowered
the temperature of mine with a resistor in the sensing circuit, and am now using normal ABS
from repraps..same quality really. So its mostly software which woudl differentiate between a
really good 3d printer and an OK one. Luckily the one I picked seems to have pretty good software.
  Ive heard of much tinkering that has to be done, but I havent found that as yet. All but one print
has turned out perfect and its totally seamless for the mmost part. I print from my desktop,
the unit beeps and anywhere from 20 minutes to 3 hours later it beeps again and you open
the door to your piece. Removing supports has been as easy as using a fingernail for the most
part. I printed a bearing yesterday...loose balls, but it rotates freely. ( Bearings will be in GT..)

  Anyway, Ill see if I can post more photos of what I print as I go..

Thx
Art

[Ken_Shea]

Looking forward to seeing them when yiu are able.


Thanks