Some newbie questions.

Hello,
I'm interessed on constructing a RepRap machine, but I have some questions first:

What is the pros and cons of a RepRap Mendel over a common DIY CNC machine? How much weight can RepRap supports for the extruder?

I live in Brazil, then I'd like to know any cheap shop (inside or outside Brazil, but with good shipping prices) that sells:
-Motors
-Plastic (ABS)

Where can I get the belt and the gears/pulleys to the RepRap for cheap? I just found the belt on a RepRap (or at a MakerBot) shop. But it was expensive.

What is the mechanism used on Z-Axis (up and down)? I didn't found any belt, it's screw driven? If yes, where can I find the part that goes on the platform (that I just forget the name)?

Last, there is any way to make the final printed part don't have (or just don't shows) the printing lines? Like in the image below:

As i'm thinking on making some mechanical parts (like a piston and a cylinder) it need to be plain (and air-tight, as in the last example).
I'm thinking on a plastic paste that is used on Styrofoam and Depron, that makes the surface plain and uniform (airplane-modeller experience)

Sorry if I commited any english mistake, my english it isn't perfect.

Newbie here my self (and you English is MUCH better then my Portuguese)

The Rep Rap can be modded into a CNC. People have used different toolheads.

Z Axis is screw driven, Y&X are belt.

As for belt and pulleys, a little math (and maybe firmware tweak) can fix for not being able to find the 'right' size pulleys.
(a 2:1 ratio is the same if the drive motor is 10mm and driven is 20mm or is 20mm & 40mm)

As for extruder weight, probably not a whole lot, but up the 8mm rods to 12mm (and even add in hardening and the flex will diminish.

As for making air tight cylinders, not going to happen without secondary boring operation.

Print lines aren't going to go away; keep in mind this is a fairly low-tech method.

Yes, I know that there is alot of people using others toolheads, but a CNC needs a bigger area, then, if there isn't pros on doing a RepRap, I would make a CNC with an extrudder.

Also, what diameter it's the RepRap X/Y pulleys, it's 45mm? I only know the pitch (5mm, right?).

A big advantage to a RepRap is that it can print its own parts, so if a part breaks, you can easily print a new one (or have a spare set handy). However, if a CNC machine has a part break, you'll have to get a new one.

... with a CNC-machine you can mill replacements (or enhancements) too, but if the machine (reprap or CNC) is broken, then it can't do anything, so you have to fab some spare parts as potential replacements before they break

---

Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

"Print lines aren't going to go away; keep in mind this is a fairly low-tech method. "
Yes, I know that, but how this guy made this parts:

Did he sanded those parts?
I noticed that on transparent ABS it shows alot of lines, but on white it just just a little. I think if I make a mm thicker then I can sand to get a smoother surface, with a caliper to check. Did someone have any other idea?

Edited 1 time(s). Last edit at 01/22/2011 05:16AM by Francoo.

Who can tell from the size of that photo?
The bolt is 10cm long!
Looks a lot like "Large Threaded Bolt and Nut by ub3rgeek" auf Thingiverse.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Ok, then.

But I still can't find the theared rod for the Z-Axis, does anyone knows some shop that sells it word-wide? At good prices?

The threaded rod is the hold up? Check electrical supply shops. Its also used to hang conduit, lights, and other stuff. In the States its called All-Thread.

I have seen it called studding as well in New Zealand.

David

Sorry for the huge number of questions, but still do not understand a thing. mIn the z-axis, is used a common threaded rod? (of which are found in hardware stores). Because in this thread, a guy sayed that normal threaded rods don't work well...

Yes. It doesn't work well on X or Y, but Z doesn't need to move quickly, it just needs to move up a layer height at a time. A leadscrew would still be better, but threaded rod works well enough and leadscrews are more expensive and harder to come by.

Francoo Wrote:
-------------------------------------------------------
> Sorry for the huge number of questions, but still
> do not understand a thing. mIn the z-axis, is used
> a common threaded rod? (of which are found in
> hardware stores).

By Jove! You've got it!

But make sure you use good A2 stainless steel and not BZP for the z-axis.
For all other threaded rod pieces that make up the frame (and the measuring jig if you make it) BZP threaded rod is fine (and considerably cheaper) but for the z-axis drive rod you need high grade (A2) stainless steel!

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

BZP wears out or something? Gah... Looks like I'll have to go to the hardware store again...

AND all of your round bar for the X, Y and Z axis should also be high quality A2 stainless steel.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Outch! Getting A2 steel bars here in Brazil it will be hard...
There is any alternative to it?

A2 stainless steel is also known as 304 stainless steel.

Might be easier to find people selling 304 than A2 - not everyone uses the A2 naming convention.

Notes:
316 is also usable (it's marine grade, usually more expensive), but you may find that easier to get in some places than 304 (eg: anywhere that has a big shipping industry), simply due to volume purchases by suppliers.
For the smooth rod, you can use 5/16th inch imperial (7.9375mm) instead of 8mm, as the difference is too small to be a problem. DO NOT do this for the threaded rod, as the thread pitch is different.

Ok then, i'll have to buy the bars outside (about 45 bucks everything).
For the theared rod, the Brazilian manufacturer gives this table for sizes:

What it's the one that Mendel uses? M8?

Yes, metric mendel uses M8 threaded rod.

There is an imperial version which might be worth looking into if you can get imperial studding more cheaply, but the metric version is the more common.