I gota hand it to you Randy.. you really like to try to paint yourself in the best light.. trying to smear people, just to 'win'. The uninformed will be easily fooled... I and many others know the real truths. Manipulation of wording, doesnt equate to truth. Maybe you should go into Politics instead of machining? You will make more more, and you will bend more people over at the same time.
Steve, as usual, you demonstrate that you seem to have very little idea as to what you are talking about. Those inner "voids" are intentional and the outer skin uniformity on a non-working surface is of no consequence other than cosmetic.
There is no way to Verify the internals. 3d extrusion printing like this, does not lend well to solid innards due to the way it comes out, without any pressure to form a strong bonding.. and the very circular shape of the output material, lends itself to inner voids and poor quality strength as a result.
The outer skin just reveals this fact. It shows the tool pathway, and all the weak points that such a poor pathway presents. I think its unprofessional to have a voided edge, and yes, it still is an edge which provides strength to the outside edge of the teeth. If they chip off, it then exposes other edges to chip and wear down.. and that chip can take off more than one layer. So, the idea that its a Non working surface, is just bull.
If each internal layer uses that same tool path.. it would be clear to see which teeth are well supported, and which ones, were poorly supported.
There are no "voids" on the working surfaces. When making parts from plastic, solid parts are more prone to deformity due to uneven shrinkage as the materials cool. Parts with a dense, but not solid, uniform internal support structure, not only make them very strong, but also dimensionally stable.
To a degree, good support can be had with good structure. However, a solid gear will be stronger. Im fairly certain, expansion and contraction will only be a factor with larger metal gears. If your talking about plastic extrusion effects, then maybe I agree. But thats my whole point.. these layered extruded gears are just horrible substitutes.
IMO, it would far more effective to mold a very long version of the gear, and use machining to slice it into several gears, then use a jig to bevel sand sharp corners down, using the central shaft hole.
The versions of Laser based 3d printing, out of the powder material, is far more suited to producing usable gears... and pretty much anything else, in a much more professional and usable format.
These parts are exactly that, low strain parts. They are not doing any heavy work whatsoever. The reason the original parts broke is quite simply due to the poor design of the original nylon gear. The wall of the original gear was too thin, and when pressed onto the hub, put this thin wall under constant stress. As the parts aged, they became brittle and the thin wall snapped, just like an old rubber band. If you look at the photos, and compare the RAM replacement, you can see that the hub wall thickness has been decreased from the original, allowing for a thicker wall on the nylon part.
I agree on the reasons why the originals failed. However, that was after like +20 yrs. Its funny how you say low strain, then failed under strain. heh. But yeah, I know what you mean. Plastics dont seem to last forever. But poor design can make parts fail far before the age of material degradation.
In your case, your using the original metal part... meaning that the gear wall is the same thickness, hence the same flawed design.. with a much weaker gear.
As for metal replacements in an existing nylon gear chain, this is probably one of the worst things you could do. Metal is very hard and unforgiving. Machining processes to cut it also result in very sharp edges. Any misalignment of a metal gear against a plastic one will result in the metal gear chewing away at the plastic one, whereas gears made from materials with similar properties are more likely to wear together and mesh.
Im very aware of this fact. Which is why I would sell the gears in a pair. Its no doubt that the larger gear is old and capable of cracking at any time. So why bother replacing one.. when you could replace both at the same time, and not have to worry about touching the thing for a very long time? This is how I work on Pinball machines. Why go thru the long process of taking apart a flipper assembly to replace the bushing.. when other parts could have wear? That will just cause the new bushing to get torn up quicker.. as well as not produce the accurate performance needed for the game to play properly.
Plastic gears are fine. They are light and smooth, need little to no lubrication in this application.. but the results are pretty much the same as things fail. Teeth chip and break. In the case of metal gears, the assembly needs to be very solid, as metal teeth clashing at offset angles, is unforgiving... where as plastics have some deformity flex, which can often handle without too much wear.
As far as I know, theres no reason why water jets cant cut a set of plastic gears, producing a far better part.
Obviously it would be better to improve the design, to eliminate the weak wall. Not easy or cheap, as the collar has to be machined.
Then again.. what if the part was completely missing? They would need that collar.
I still just dont understand the desire to make bare minimal efforts on things that should be excelled in superior quality and passion.
You did great to get the tron handles produced... but here?
If your unwilling to make quality parts... why not just buy out the stock that was made from David?
As for your "deeper knowledge".....I remain skeptical and I'll just leave it at that
I wouldnt say Im an expert in any one area... but that my combined experiences with a multiplitudes of areas, has given me a high level of knowledge and perspective, than the average Joe.
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Topic: Atari Yolk 14 tooth gear Repoductions (Read 13024 times)
