Hello everyone

Greetings!

My name is Chuck and I live in Austin, Texas. I am currently making Irish pennywhistles and shipping them all over the world. (It's a labor of love, not a business) I am also learning how to use a metal foundry as another hobby. I have a couple of web sites:
[whistlemaker.com]
[chucktilbury.com]

I am seriously considering building a reprap. I want to make sand molds for aluminum and bronze. I have taken a look at things like extruders, which I thought would be the hardest part. I am thinking air powered with a solenoid to stop the flow. I will probably use sodium silicate (aka water glass) as the binder and inject it into layers of dry sand.

It looks like I could get away with very little development. I was not very clear on the different types of machines. I will want one where the stage moves up and down. I would like to have a space of about a 30cm cube. That is about 25kg of sand. Does anyone have suggestions as to where I can go to get an idea of the cost of such a machine?

I also need to get a clue about what software people are using. I am looking at FreeCAD as the design software. There seems to be quite a bit of open source CAM applications available as well. I would like to know what people are actually using.

I am very interested in reprap and in moving this project along. I will at the very least document the build on my web site along with my other projects.

Thanks!
Chuck Tilbury

Hello Chuck, welcome to RepRap!

Usually it's a good idea to start with something which is known to work already. Doing so one can collect all the knowledge already available. Going in small steps towards your ultimate goal is much simpler, then.

The first choice you have to do is to pick a type of machine. The RepRap wiki has plenty of designs. All wooden designs, designs with printed parts, designs using industrial stock like aluminium extrusions or a welded steel frame. The most often built design is probably the Prusa Mendel, the most simple design is a Wallace/PrintrBot, the cheapest design a WolfStrap, a rigid design the MendelMax or EventorBot, ...

After doing this coice you need four groups of parts:

- printed parts
- "vitamins" like threaded rods, bolts, nuts, belts
- parts and vitamins for an extruder, these are usually handled seperately
- electronics and stepper motors.

What exactly you need depends on the type of machine, of course. Software chimes in when you get to the electronics stage.


Have fun!

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

I think my design is going to look something like RepMan. I am confident that I can build something usable. I also have a mill and a lathe which allows me to make parts. I will probably use gauge steel and all-thread to build the frame and all. I am planning to use drill rod and all-thread for the active parts. I will use 2 nuts separated by a small spring to minimize backlash. The stage will be a box with a movable bottom (Z only). As each layer is deposited, the bottom will move down a bit until the part is built up. It has to hold at least 50lbs (25kg) of material for a 12" (30.6cm) cube work space. The steppers that move the stage are going to have to be rather strong. I am thinking of using a different driver. Maybe this one: [www.aaroncake.net] (really simple; I would have to modify it to do microstepping, but that's no problem.) or maybe this one: [www.st.com] (L298H). I have not done the math yet for the stage motor. If it is really rough, I could use one of these: [www.geckodrive.com]

After taking a look at the schematics, it looks like the uC outputs step pulses a direction signal and inputs end stops. (among other signals) That's correct isn't it? It looks as though I will have to modify the firmware to change the semantics for a heater into a pneumatic head and the steps in between layers so that they screed the sand and drops the stage. I have been doing that kind of thing for a living for a while, so I think it should be OK. How do people submit changes to firmware for the community?

Here are my proprieties in the order of importance for the prototype:
1. I need to get something working quickly that can do at least 5 or 6 layers so that I can begin experimenting with sand and binders.
2. Not to build something that I cannot take apart and rearrange.
3. Minimum expense, as in no waste. I do not want to spend money on parts that I cannot use. (except for spares)
4. No intrinsic flaws that prevent using it for something. For example, poor control over the amount of binder layed down.
5. Self-replicating. (probably in aluminum)

Traumflug,
I like your signature. There is a wealth of information there.
Thanks!

Quote

Maybe this one: [www.aaroncake.net] (really simple; I would have to modify it to do microstepping, but that's no problem.)

One of the most important features of stepper drivers is current limiting. Without it you loose tourque at higher speeds quickly.

Quote

After taking a look at the schematics, it looks like the uC outputs step pulses a direction signal and inputs end stops. (among other signals) That's correct isn't it?

That's correct.

Quote

How do people submit changes to firmware for the community?

Most firmwares are hosted on Github. There you can do a fork and notify the author about it or open an "issue". Sometimes I even pick up patches from this forum.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

This is mostly off-topic, sorry for that. Your goals reminded me of this project: [www.youtube.com]

Will you update this space (or a blog?) with your progress? I'm very interested in your extruder ideas and what you find for binders.

Nice link, thanks for posting it. I will definitely post all documentation for my machine at least here: [chucktilbury.com]. I will post it all elsewhere if there is any demand.

I am still exploring the ideas at this point. I will certainly get it done, though. I will make the corners and carriage parts out of aluminum bar. I found sources for the motors and controllers that I want to use. I will most likely use modified Gen 7 electronics and modified teacup firmware. I expect to start spending money around the beginning of January.

Cheers!
-=chuck=-

Hi Chuck,

In addition to the link above for Markus Kayser's solar sinter, there are some other projects that you might be interested in.

There is a SLS wax printer on the Reprap wiki. If you want to print a binder into layers of sand, the design of the powder distribution mechanism used in this one might be informative.

Open3DP does a lot of work with direct-printed ceramics and molds, and they post their recipes too.

The Unfold group has also done a lot of work on ceramics printing.

The Stone Spray project uses an interesting extruder that mixes binder and sand together in a spray.

And lastly, many people use standard plastic parts printed on a standard 3D printer to do "lost plastic" casting, for example here and here.

MattMoses Wrote:
-------------------------------------------------------
> Hi Chuck,
>
> In addition to the link above for Markus Kayser's
> solar sinter, there are some other projects that
> you might be interested in.

Great links! Thanks for posting them!