I've been playing round with the idea for the last year or so but previously haven't had time or the skill to put into designing one or understanding how the open source ones on the internet work. I have now and I've decided I would like to make my own for a number of reasons. These are, the price - the price of even the low cost designs are still quite expensive, and if I was to buy a kit or a commercial design this would end up being a lump sum. It would also be hard to fix if something went wrong as most of the parts seem to come as kits. The designs - the open source designs are all great and I'll most likely take some ideas from these but the engineering drawings seem to have been lost and so there are only templates or digital files for making the parts. This annoys me as engineering diagrams are obviously how someone in the know would make these so you should be able to easily find them but alas I can't (they might be hidden somewhere I guess). Same goes for the electrical side of things, I can find the board to buy to get it to work but there isn't a schematic or PCB diagram so to make your own. This would be quite likely far cheaper than buying the parts built up and would be easier to customise the circuit to different actuators (motors) at different power ratings, sensors for better determining where something is in the field to control mechanisms, where I would get it to run directly via USB or SD card but would love to improve this so to be able have it networked so can be elsewhere in the building and print to it or have multiple computers print to it and create a queue of projects to be made. Another feature I couldn't see on the open source models (I didn't check the commercial models as way over my budget) was the ability to have multiple jets, this would allow colour change on the fly for instance or different materials, such as plastics in two and different coloured chocolate in another two. My last feature I want but couldn't find was a large work field, most of the 3D printers I could find had a small workspace, normally less than a foot cubed (30cm^3) and if I'm going to do large robotics stuff, it would be much better if I could make it at least a foot and a half (half a meter) cubed, possibly even bigger as I have a project in mind which would be quite tall (I'll get to that in a second). So all up I think designing my own would be a good learning experience and challenge as well as improving upon designs. I'll try to post all my designs up on here too.
Just remembered a couple more things sorry. The first one being that the open source designs all seem to be in triangle shapes, which I don't understand, yes that might be strong but your only moving round a nozzle so a cubed shape would give more freedom and address the next issue. This is that these triangle shapes mean that the work is moved in one of the planes rather than the nozzle, this basically means the equipment has to be double the size of the work area in one direction which to me seems a waste of space. The other thing I remembered was that on none of the designs does the nozzle change angle, I'm not sure how useful this would be but I would have thought you could make slightly better designs, or at least add things to previous designs.
So that project I had in mind, well its a large item made out of coloured chocolate (not just white, brown and black but maybe yellow for instance). I would say more but it I want it to be a surprise at the end of the project for someone so I can't say anything more unfortunately.
Update: here's a picture of some ideas I scribbled down:
