Contraptor

Sure, I can try it out (as is on your sketch) if you include it.

Thanks for the quick reply!

Rethinking my future requirements, I'm aiming at minimum (woodwork) dimensions of 30"x18"x5" (LxWxH).

However, even using the RepRap motors, the CNC would be much faster than I doing the routing, carving, cutting, rounding, etc. manually.
Of course the larger the CNC, the more power is required to move the router.
I have no clue whether the motors are powerful enough to move almost twice the weight.

I'm pretty skilled in software dev. - Do you think, the arduino hardware is not capable of handling larger motors, or is this a pure driver (software) issue?

A few more points:
Is there any info on how well the transformation from CAD-format (e.g. dxf) to G-Code works? - I had a look at the specs and there're also codes for changing the CNC tools etc. I'm curious if this actually works with the Contraptor/RepRap software stack.

Has anybody of you guys ever tried using models generated in Blender with Contraptor?

Have you considered using Contraptor to reproduce itself (metal CNC'ing itself).

schoeftinger

Your dimensions should be "doable" however there would be quite a bit of tweaking here and there to be done. Sorry for the confusion but when I refer to a stepper driver I am referring to the PCB board that "drives" or "powers" the motor. Like this, http://www.thingiverse.com/thing:760

I have never used blender to design stuff. Google Sketchup works very good for our purposes. Perhaps when we create an contraptor extruder blender will be required.

For metal CNC'ing. YES! very much so. :) In fact Vitaly created a contraption for making the angle you can see it here: http://www.garagefab.cc/contraptor/what-can-be-built/perforaptor Its older and from what I remember it didnt really work super great but hey its a start. There are also a few other options. Like, getting a proxxon rotary tool instead which is suppose to be more powerful etc. And lastly you would need to slowly remove material in small steps. Not like a giant 1/4" thick cut at a time like you can do with mills etc.

Personaly I have not converted any DXF to Gcode but I think you can look on the reprap forums or post there for input.

Hope that answers a few questions. Thanks for being active in the contraptor community. Let use know / see what you build. We are attempting to grow a list of contraptions!

Ril3y

More powerful motors would require more powerful driver boards (like Geckos as James mentions below). The driver board interface is typically simple: digital pulse steps the motor, so in principle Arduino should be able to control the boards. Cdegroot mentioned inexpensive 3-axis board (Xylotex) in another thread, maybe he'll try it with Arduino :)

To go from DXF to G-Code, you need CAM software. I've been using CamBam recently and there are other free/open source alternatives out there too. Once I have functional mini CNC, I hope to get to documenting the software chain. Arduino G-code interpreter supports very basic subset of G-Code - straight lines, circles, pauses. No advanced stuff like tool changing (you'd need a tool changer for that too:).

As far as Blender - we'd love to see Contraptor components converted to other 3D formats since not everyone prefers Sketchup. Blender, being open source, would be a great start.

Hi again,

thanks - I'll need the luck! ;-)

I've already had a look at the other contraptions - including your mini router.
Why did you change the design for your cnc so radically? - Stability?

Besides that, I'm struggling with ideas how to fix the workpiece to the cnc table, while routing.
Large CNCs kind of suck the workpiece and therefore don't require additional clamps, etc..
However, when using clamps the workpiece might start moving around on the cnc table (once the part of wood where the clamp is fixed is cut off).
Neither is it feasible to attach a clamp somewhere at the center of the workpiece or attach it from beyond (using screws or whatever means).

How to you fix your work pieces on the mini cnc?

Before starting some actual work, I think I'll need to clarify a few more issues, such as this.

Another thing: given your response times, I assume you guys are either American night owls or europeans, right?
I'm asking because it appears that you support each other with building your contraptions…
BTW, I'm in Austria

Hi Schoeftinger,

I'm simply trying different designs, T-slot is useful with larger sizes and it is also faster to build with. On the other hand it's more expensive than angle so there isn't as much flexibility in trying different designs. One of the goals for this particular design above was to build a mini CNC router for cutting 12"x24" size of plywood/MDF/acrylic with Dremel/Proxxon.

Regarding workpiece clamping - with the mini-router, I milled the material in shallow passes - about 1/32" - so the cuts were gradually made deeper without disconnecting the milled part. Deeper passes are difficult for Dremel anyway, and this allows the workpiece to be clamped at the corners. The table can have the grid of holes drilled and tapped for clamping screws.

I can't speak for everyone here but Riley and I are American night owls, correct :)

Good… then on with the questions. ;-)

On the reprap page (http://reprap.org/bin/view/Main/Generation3Electronics) I saw that they have a new mainboard (V1.2) and new stepper drivers (2.3).
Do you actually use the original reprap board or is your arduino board something else?

The reprap site says, the new stepper driver can control motors up to 2A.
I'd select the following NEMA 23 motor:
http://uk.farnell.com/jsp/displayProduct.jsp?sku=4743167&CMP=e-3e6f
Do you think this particular motor may be powerful enough?

Since buying multiple sets of hardware will become very costly, I'd be happy to choose appropriate hardeware from the beginning.
Please let me know, if you have better motor/stepper driver proposals…

As soon as I have a shopping list, I'll sort out the total costs and go on…

Thanks for all your input!

Hi Schoeftinger,

We're currently using Reprap v1.2 Stepper Driver Boards to drive stepper motors and Arduino as controller. We have not tested Reprap v2.3 stepper board with Contraptor steppers - so I can't really say that they work, but unless overheating of the board is an issue, they should.

The motor you linked has higher torque than Reprap recommended one, but also higher resistance/rated voltage (8V) which makes me wonder whether the stepper board (either v1.x or v2.x) will have enough power to drive this stepper. Usually steppers are driven at significant overvoltage - for example Contraptor steppers are rated for 2.3V while PC power supply puts out 12V.

If you're looking at the above 80/20 sketch, my wild guess is that torque rating around 150-200 oz*in would be needed to move the gantry with more or less decent speed. This would require more powerful stepper board. Please don't hold me to this number though :)
Y and Z motors on the contrary would not need to be as powerful, so if you needed to upgrade, it would likely be for one motor/board set.

My preference in an unknown situation is to start with something cheaper and upgrade as needed, but that's me.
Alternatively, you could estimate the power you'd need based on the estimated weight of the gantry and your desired speeds and accelerations.