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Geek Culture / How to build complex mechanisms?

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Dark Java Dude 64
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Posted: 23rd Dec 2014 23:42
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Greetings folks! So recently, I have gotten into mechanical engineering, and I have designed (mainly in my mind) a new type of mechanical gearbox. For those curious, it is one of those nifty infinitely variable transmissions, or IVTs (it doesn't actually have any gears ). So yeah, I have been wondering how I might be able to build a real gearbox according to my design. The design is rather complex, and at a very rough estimate, I would guess about 40 or so moving parts (not counting individual bearings and such). It has many parts that would be sensitive to manufacturing inaccuracies, including cams, cam followers, clutches, etc, and certain parts that have to be placed at very precise angles and positions.

I have thought about 3D printing, but I am not very sure that would give the types of tolerances the gearbox would need for proper operation. Scaling the gearbox to large sizes would allow those same tolerances to bear a much less significant effect on the operation of the gearbox, but of course, 3D printing larger objects is more expensive.

I don't have access to any machining tools that I could use to manufacture parts, and most machining services I have looked at boast pretty lofty prices.

I have even thought about emulating 3D printing myself by cutting sheets of paper to very exact shapes, and then gluing those together in layers. But of course, that has some obvious issues I probably don't need to mention.

Perhaps I could solve some issues of poor 3D printing tolerances by adding things like rubber bushings to fill gaps, incorporating more part flex into the design (to ensure reliable contact between cams and cam followers, for example), and perhaps even modifying the parts once I receive them.

So why do I want to manufacture one of these gearboxes? Just for fun! I'm not looking to make a ton, just one to play with and to prove (or disprove ) that my design works. No big deal if I can't make one, but I would love to if possible. Since I have become stuck on the logistics of doing so, I have come here in hopes that maybe someone would have some suggestions.

So yeah, does anyone have any suggestions for how I could go about building a small, complex gearbox? As of the current, I am looking more toward the 3D printing side of things, especially if I am willing to pay a little money to get it right.

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bitJericho
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Posted: 27th Dec 2014 04:47
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3d printing is very accurate, to within a millimeter if you do it right and have the right printer. Expect to pay a lot though for a proper one.

What you should do is design it in CAD, you can then have it machined or printed. If you go to school for such things you then have access to their equipment so you can manufacture these types of things. Without shelling out for school, you would have to buy these tools yourself (imo a much wiser investment)

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Dark Java Dude 64
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Posted: 27th Dec 2014 05:04
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Quote: "3d printing is very accurate, to within a millimeter"
True! I suppose the inaccuracy of 3D printing was a misconception I had for a bit. Shapeways' strong & flexible material supposedly has accuracy up to 0.15mm, which is totally sufficient if you ask me. I have some other high key projects going right now, but when those finish up, I am definitely thinking about printing a gearbox to my design.

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code master
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Posted: 27th Dec 2014 08:57
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Quote: "Without shelling out for school, you would have to buy these tools yourself (imo a much wiser investment)"


Which is the wiser investment, school or purchasing tools?


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Dar13
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Posted: 27th Dec 2014 18:52
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Quote: " Which is the wiser investment, school or purchasing tools?"

I suppose the answer would depend on your goals. If it's a hobby, probably the tools. If you're pursuing this as an aside on the way to being a professional, I would think the school would be better long-term.

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bitJericho
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Posted: 28th Dec 2014 04:35
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Quote: "I suppose the answer would depend on your goals. If it's a hobby, probably the tools. If you're pursuing this as an aside on the way to being a professional, I would think the school would be better long-term."


It would depend on the country probably. You don't want to be saddled with 60k un-forgiveable debt in the US.

You could invest 10k in tools and books and become your own one man manufacturer. Or you can go to school. Whatever floats your boat I guess.

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Dark Java Dude 64
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Posted: 28th Dec 2014 05:01 Edited at: 28th Dec 2014 05:04
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And then I suppose, for a person like me who just wants to build one little mechanism, shelling out money to another company to just do the part making for me is the wisest investment.

On a somewhat random note, how does extrusion printing methods (as you would find in a DIY or consumer purchased machine) compare to the sintering methods seen in professional 3D printing machines? I personally find the actual sintering process to be way more interesting; the extrusion process is just a glorified hot glue gun. I believe the sintering methods are also generally stronger, and can be manufactured with greater accuracy, etc. But then of course, the extrusion machines are more accessible to the average individual (assuming the average individual doesn't have $30k to shell out for a 3D printer ).

Quote: "You don't want to be saddled with 60k un-forgiveable debt in the US."
is it possible to obtain student loans via a bank, instead of the government? Do colleges simply not accept loans from banks, or do banks just not accept loans to pay colleges?

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Indicium
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Posted: 28th Dec 2014 05:36
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Quote: "is it possible to obtain student loans via a bank, instead of the government?"


What difference would it make?
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bitJericho
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Posted: 28th Dec 2014 06:00 Edited at: 28th Dec 2014 06:04
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Quote: "What difference would it make? "


Because a regular loan can be forgiven in cases of bankruptcy or various other reasons. A loan backed by the government called a "student loan" in the US is unforgivable except with death or if you're on permanent disability and the government so chooses to forgive your debt for you.

AFAIK you can get a normal non-government-backed loans.

If you wish to use $30k printers and you don't wish to own one yourself (ie, do a startup), then sure, school sounds legit. Pay for it out of pocket though.

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Indicium
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Posted: 28th Dec 2014 14:35
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Quote: "A loan backed by the government called a "student loan" in the US is unforgivable except with death or if you're on permanent disability and the government so chooses to forgive your debt for you."


Wow. I did not know that at all.
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Phaelax
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Posted: 28th Dec 2014 18:08
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Quote: "3d printing is very accurate, to within a millimeter"


We have different opinions of what accurate means! But then, I was a machinist and so my tolerances were only permitted maybe 1/1000th of an inch.


"I like offending people, because I think people who get offended should be offended." - Linus Torvalds
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Dar13
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Posted: 31st Dec 2014 03:02
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Quote: " Because a regular loan can be forgiven in cases of bankruptcy or various other reasons. A loan backed by the government called a "student loan" in the US is unforgivable except with death or if you're on permanent disability and the government so chooses to forgive your debt for you."

I believe even private student loans are unforgivable except by the same means as federally-backed loans. The quick Google search I did on the subject seems to say the same thing.

Basically, student loans are really really crappy.

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Dark Java Dude 64
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Posted: 31st Dec 2014 03:48
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Quote: "I believe even private student loans are unforgivable except by the same means as federally-backed loans."
Does that mean banks are somehow using the precedent set by the government as an excuse to treat people that way? That's sad.

Funny how student loans are a vital step in today's economy, and yet, they can't be forgiven. We live in a society, especially here in America, where people are effectively pushed through cookie cutters; you are expected to go to college, get a degree, and use that degree as a dull sword in the battle that is the job market. Then, once you get a job, you are expected to work for somebody else, and hope that your pay might be enough to pay off your student loan, let alone other vital things you need to buy. Why is it that society punishes itself like this? Also, part of me says that colleges have a part in this, because that's gotten pricey lately.

This thread has derailed a little! It is my thread, and I suppose I am just fine with this new topic.

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Dar13
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Posted: 31st Dec 2014 04:12
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Quote: "Does that mean banks are somehow using the precedent set by the government as an excuse to treat people that way? That's sad."

Yeah, this will be my last post on this topic(we have gotten kinda off-topic ). The deal with the student loans is that they are a special kind of loan allowed to be made by the federal government by any lender. That special categorization gives it certain characteristics such as its unforgivableness. The reason it's unforgivable is because the target of these loans, students, have no credit history when they need these loans. Thus it's a large risk for these lenders to give these loans and the unforgiveability is meant to give lenders some assurance they'll have some return on investment.

At least that's how I understand it. There might be some issues with what I said so don't take it as gospel.

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The Zoq2
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Posted: 31st Dec 2014 12:12
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Reading this makes me really glad I live in a country with free education

The only thing have to take loans for in sweden is living expenses which makes sense and we get a part of that money for free. 2700 SEK are given to us for studying and we can loan another 7k each month.

Quote: "3d printing is very accurate, to within a millimeter"


I'd say it's even more accurate than a millimeter. My family got a 3d printer DIY kit for christmans and after spending a week building it and a day or so configuring it, I can print things that are accurate to around half a milimeter (I think). You can get some impefections depending on what you print but it's fairly accurate.

Say ONE stupid thing and it ends up as a forum signature forever. - Neuro Fuzzy
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Dark Java Dude 64
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Posted: 31st Dec 2014 20:17
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Shapeways' most accurate material claims accuracies of
Quote: "± 0.025 - 0.05 mm for every 25.40 mm"


Pretty accurate if you ask me!

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