reprap + metal lathe combo

Hello, I was looking at a pic of "Mendel Hardware plus Belts" at the reprapstores website and I have god this idea, to me it seems that almost all the hardware parts required for a Mendel can be made on a metal lathe, bolts, nuts, washers, smooth rods and threaded rods.

I thought that a RepRap and a metal lathe together can replicate more parts, in a RepLab kind of way.

I have no experience whatsoever with lathes and I don't know how bolts, nuts, washers and rods are industrially made, but I thought that it can be possibly cheaper to produce all the parts with a single machine, maybe the extruder parts too, I'm not sure if bearings can be made on a lathe, obviously a cnc one.


Does it even make sense to produce a bolt or a nut on a lathe? Will it cost a lot with electricity, lubricant and cutting blades replacement? Are the lathes economic just for custom parts and not for parts already made in an industrial way?

I know that the steel is pretty cheap if bought as scrap metal, something like 2 euro/kg, I think that all the reprap hardware can be less than a euro if bought in scrap metal. The complete hardware metal parts cost 200$.

Let's suppose that I want to replicate a lot of mendels to sell them or to give them to friends, does it make sense to buy a hobbyist lathe?

It almost certainly won't make economic sense, a good lathe is pretty expensive and it'll never be worth making bolts/nuts. For extruder barrels, knurling steppers /maybe/ it's worth it if you'll have another use for the lathe. I love my mini lathe, but it's not going to pay for itself any time soon. The trouble with scrap metal is that it's usually in weird shaped parts, so needs a great deal of human intervention, and you can't tell what grade alloys you're getting. Now using reprap parts to modify a lathe to be cnc - that I would love to have, and is on my long-term todo list.

Maybe to use a lathe on scrap metal was too optimistic, what can you use on lathes as a base?

I made some calculations based on the M8 nuts and washers, you need 104 nuts and 104 washers.

I found on the metaldepot site that a 9.5mm (3/8 inch) stainless steel rod can be bought for 5.6 euro / meter, I don't know if you can just buy one of those and put it in the lathe.

The density of steel is 7.8 g/cm3, so you buy steel for
5.6 euro / ( (pi * (9.5/2 mm)^2 * 1 meter) * 7.8 g/cm^3 ) to euro/kg =~ 10.12 Euro / kg

if you buy it in 9.5 mm rods, these are useful to make the M8 nuts and washers.

A A2 M8 steel nut for orbitalfasteners (this is the website suggested in the mendel assembly data sheet) cost 0.047 euro, an M8 washer cost 0.029 euro and it is 1.6mm thick.

Let's suppose that you can make a 1.6 mm washers from 2.0 mm of rod, it will cost you

(5.6 euro / m) * 2 mm =~ 0.0112 Euro (compared to 0.029)

If you can make a M8 nut from 7 mm of rod, it will cost you

(5.6 euro / m) * 7 mm =~ 0.0392 Euro (compared to 0.047)


plus all the machining expenses, that maybe are a lot more then the metal itself, I don't know.

It seems to me that it's a lot more convenient to melt the steel directly.

... or redesign the frame for much lower part-counts

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Viktor
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It won't be cost effective to produce your own hardware as stated above, but also the bolt or nut you make probably won't be as strong. For small nuts and bolts, the threads are usually rolled which improves strength and the bolt head is sometimes made by forging / die forming which increases the strength. Washers are generally stamped out from a strip or sheet using a press. As a general rule you can work out how a part is made by looking closely at the surface of the metal. There are light score marks in a direction on most surfaces which tells you whether it was cut with a tool, rolled (formed) and in which direction.

Viktor suggested creating a design with a reduced bolt count. I did see on here a great design that uses tie wraps instead of bolts and it was really quite good.

If you buy a hobby lathe, spend as much as you can afford. It is something you will only buy once in your life and you will have it for a long time. Its amazing when you have one how many little jobs you find for it, shortening bolts, making adaptors etc. etc.

I definitely agree with martin about getting the most expensive lathe you can, and i'd add that if you get one, spend a good deal of time oiling it properly, making sure everything is as tight as it should be. I shattered a couple of tools straight away because the toolpost wobbled slightly, so the tool was thrown into the piece.

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Autarkyboy
Let's suppose that I want to replicate a lot of mendels to sell them or to give them to friends, does it make sense to buy a hobbyist lathe?

Another thing to consider, is most of the parts (smooth/threaded rod, nuts, bolts, washers, etc.) are usually cheaper if you are buying in bulk. This way you can make several kits at once for less than making them all individually.

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[www.binaryconstruct.com]

jeffpark_ Wrote:
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> > Let's suppose that I want to replicate a lot of
> mendels to sell them or to give them to friends,
> does it make sense to buy a hobbyist lathe?
>
>
> Another thing to consider, is most of the parts
> (smooth/threaded rod, nuts, bolts, washers, etc.)
> are usually cheaper if you are buying in bulk.
> This way you can make several kits at once for
> less than making them all individually.

In this respect, a Rep-rapper cooperative makes sense. Is anyone selling these things as a package discount?

The "cooperatives" are already running. Ultimachine, Makergear, Makerbot, and and some of the saints on the forum are definitely not getting rich.

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repraplogphase.blogspot.com

spacexula Wrote:
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> The "cooperatives" are already running.
> Ultimachine, Makergear, Makerbot, and and some of
> the saints on the forum are definitely not getting
> rich.

I wouldn't underestimate the profits that some of these companies are making. Makerbots are $750 each. If Makerbot sells around 111 units per month I calculate that at $1million turnover per year. From their twitter and blogs I believe thay are shifting many more than this and that doesn't take into account spares and other stores items they sell. This doesn't sound like a small business to me.

Actually it is a small business. Turnover != profit. assuming that they're parts costs are $500, that's $250 per, which works out to 333K/year, which is enough to pay a two or three employees and the space rental. Since they have about 5 employees, their parts costs must be lower than $500. And that's still not leaving much room for any real profit.

Employees are expensive. Overhead will eat up profit at an amazing pace. Even with 20 employees I'd still consider them a small business, so if they where turning over <$20 Million/year, they'd still fall into the "small" catagory in my book. The IRS and other organizations have various definitions, but at ~$1M/year gross reciepts I think they'd all agree that makerbot is small.

Of course, I think at last report makerbot is turning over closer to 1000 units a month, which would give gross reciepts of 9M/year.

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I'm building it with Baling Wire

I don't understand why you would want to make your own smooth rods. The stock metal you'd buy to put into your lathe should already be a rod (or else it would be very difficult and dangerous to machine). All the lathe could possibly do is reduce the diameter, and alter the surface finish... but smaller diameter rods are generally cheaper, so it'd almost always be cheaper to buy the finished rod than the stock material you put into the lathe. And the surface finish you'd get from a little lathe would be far poorer than that from a commercial grinding machine. Not to mention the danger of long, thin spinning shafts becoming unbalanced and whipping around.

If you're somehow able to buy oversize shafts cheaply, the best thing to do is modify the Mendel STLs to accomodate them. The larger shafts will be stiffer, and so they'll make a better 3D printer.