First? repstrap in finland...

I'm constructing a mcwire style cnc with the arduino based electronics. I now have almost all of the electronics, and have ordered steppers and bearings from the RRRF. I have threaded rod and nuts form K-Rauta and some springs. I'm trying to find PTFE (Teflon) strip from Etola to use as a linear bearing. Then I'll have to find some hard wood and/or aluminum rail...

Bebek (Helsinki) carries everything but the L293D (with the protecting diodes), TIP120 and the opto switches (I'm getting them from the RRRF), according to their website. When I get to building an extruder, I'll have to figure out those two. You should try ordering at least the L298 and L297 as free samples, which should save you over 30

I bought a 22x27 cm 4 mm thick piece of PTFE from Etola for a bit under 20

I just got some aluminum bar/beam and the like for free. I'll hopefully get something to form the stages etc. in place of the lasercut parts. I'm still waiting for the stepper controller kits to order the electronics and bearings, but I have built a somewhat working board and have some ol' n' dirty skate bearings to test the x stage.

Hello,

I just found RepRap, and it certainly seems a nice thing to have. In 2004 I made DIY CNC machine, it's working area is about 500 x 500 x 300 mm's. It can work on aluminium, wood and plastics. Last sprint I converted my small 12x7" metal-lathe for CNC, it's working nicely now, small parts can be made quite easily on it. But RepRap would be very nice thing to have around, especially for small plastic gears and similar small things.

Do you have working RepRap yet ? If there is anything I could help, I would be glad to help. I'm thinking if it would be possible to use just the reprap nozzle in my CNC-machine, and manufacture rest of RepRap parts on it ?

I have made proto-circuit boards with my another homebuild CNC-machine some years ago, so they could be possibly made with it too.

That should work; you can even use the router to make the extruder head parts.

What kind of steppers do you have on the CNC machine? You may need some bipolar stepper motors. If you are lucky, that's what you have, or you can rewire them in bipolar mode.
[reprap.org]

Note that RepRap can't do pieces with features smaller than 1-2 mm yet (because we're depositing filament ~0.5mm wide), so it isn't useful for small gearteeth. If we ever figure out how to deposit thermoplastic using a inkjet printhead, that will change.

I have at last something working: [picasaweb.google.com]

It is an x-y positioning table based on mcwire. I'm using the rrrf stepper boards and the sanguino with the gcode interpreter from svn. With the v 4.7 (in ubuntu 8.04) avr-libc the function strtod crashes, but I upgraded to the 6.2 from 8.10 and now it seems to work. I'll up some vids soon.

Not a repstrap yet, but after I get simple plotting done, I'll get to the third axis...

Sorry, the actual versions are 1.4.7 and 1.6.2, respectively.

elmom: Looking good.

I also started on a similar McWire inspired plywood based platform while waiting for my Bitsfrombytes laser cut parts. It's on hold now as I'll use the electronics and steppers for the bitsfrombytes machine, but it seems like a simple and cheap design.

For the Z axis, I planned to use a 2" by 4" or similar piece of wood, attached with metallic beam attachments (about 1 euro, like these but supporting the beam on more sides [www.taloon.com] ) to the base, and supporting the Z-axis and write head above the middle of the platform.

I used aluminum U-beams meant for hanging curtains as the rails, you can buy them for 10-20 euros at normal hardware stores, with plastic sliders included (similar to this: [www.curtainpoles4u.co.uk] ). By using the plastic sliders you avoid the need for bearings, and also get a design that keeps the Z axis platform attached to the rails. There might be some loss of precision though.

I just took a look at the parts lister and that seems to solve my confusion about where and what to get. How much did the parts cost you total?

Elmo:

I'm ordering my Arduino-board or kit this week, but I have not yet
decided which one to order: the standard Duemilanove (with USB-port),
or either Boarduino or Sanguino (this latter has a larger microcontroller,
for possible future versions of RepRap, as they say?).

However, I reckon that I need also this USB->TTL cable with it:
[sanguino.cc]
[store.rrrf.org]
with the extra price of $20.

Is there anything else in the cable than the wires?
Can I do it by myself?

Cheers,

Antti

Kartturi: I would recommend the sanguino to be a bit more future-proof, since the arduino only just has enough space for the firmware. The cable contains a usb-serial convertor, which is probably not worth making, since the parts aren't much cheaper, and its well made, so you can plug it straight in without smd soldering and extra boards. I have found the sanguino excellent on a breadboard, because tinkering is so much easier.

Thanks James for an excellent bit of information!

Elmo,

What's the status of your McWire RepStrap nowadays?

Just today I found six aluminium rails, 58,5 cm long,
3 cm wide, but only 8,5 mm thick. (From Kumpula's
library actually! Left for salvaging at the bottom
floor). Otherwise would be ideal, but I'm afraid they
are not thick enough, when I look at the images
at [flickr.com]

But of course it depends on the dimensions of the roller bearings.
Any good place in Helsinki to get those?
(Could get ones from any used skateboard, if they haven't worn out yet?)

More general question:

How much more difficult is to build Darwin 1.0 than McWire based RepStrap,
assuming that I can order or get the plastic parts of the Darwin from
somewhere? Which one is more precise in action?

I have a 2D table working and have the structure for the third axis mostly (nothing new functionally, see my old pics: [picasaweb.google.com]# ). I bought my bearings from rrrf, hard to find them much cheaper. Used ones should work initially (don't pay much), but you might want to upgrade later if you find the urge to push the machine's limits.

I think a robot made from stiff continuous material (like McWire) can be made more precise, but without a pillar drill and good measuring aids and/or experience (of which I have none , a Darwin is easier to make precise enough. Of course, getting all the non-plastic bits for Darwin can be fiddly.

About your find. You could use some board (anything cheap and straight) under the rails if you find them too bendy. Like my base structure.

Elmo: I don't think they would bend, as the rails feel stiff enough.
However, I'm afraid that as they are only 8,5 mm thick, the roller
bearings might not have enough contact with them, and might "slip off".
How thick are your bearings? (I.e. the "height" if you just lay them on the table).

BTW, at what times you are in Kumpula? It would be nice to meet you
and talk face-to-face.

.. Antti