Through the week I was bored of my blogger homepage having just information on blogger so I decided to add some RepRap blogs to my feed so they would show automatically. One of them was RepRap Pro and this had a multi colour (3 colours) extrusion setup. This worked was setup via a slave controller to control each individual extruder. This is great as it shows that this design with controllers is definitely viable.
Another post which was either from RepRap Pro or on the normal RepRap blog was about mbed set of experiential boards using ARM microcontrollers. I had a look at these and they could potentially be used as a main controller but reading some reviews, they are a bit quirky. This is because all the coding and compiling is done online and then copied over to the chip via USB using it as a virtual flash drive. I think I will just look into using a normal ARM chip, I just have to work out how to attach one to the breadboard for testing!
Now to some mechanical things I found and thought of this week. Firstly, I realised that I can buy the compounds for making polyurethane at a shop not too far away from where I live which will be great for making components. I (my dad does at least) own a milling machine and lathe so I can make parts in metal and then use those as a cast to make my mould from. I can ask if I can get the technicians at uni to make things on their machines for me.
Talking of polyurethane, I'm thinking I might use plastic pads on the carriages that slide on the aluminium profile. This is because, from what I have found on the web such as on engineering toolbox, aluminium on aluminium seems to have a fairly large friction coefficient. Plastic on aluminium would have a lower coefficient and would also no wear as much as aluminium on aluminium.
I have found a treating process that smooths the plastic (well eats the plastic to give the appearance of being smooth). This would be great for aesthetics and for aerodynamics. The post is on the reprap blog and has a great picture showing what can be achieved from this process.
Today I have started fixing up my inventor CAD model as mentioned last time. I'm having some trouble getting frame generator working so I may be going back to just using the frame as parts that I make the right length manually. With the redesign, I've started deciding on dimensions of parts that I hadn't yet done such as how wide to make the grounded bars used for the X axis slide. I've also started cataloguing parts and grouping them into sub-assemblies.
I've decided that I'm not going to calibrate the thermistor temperature sensor yet as that is a boring job and I see it being much more essential to get SPI working next. I can come back and calibrate later as it shouldn't be hard, just some small coding. This is actually the reason I want to do something else - coding means windows which means restarting and is harder to change to other tasks. SPI shouldn't be too bad, not sure when I'll get a chance to do it though as I can't work on it remotely very easily.
Finally, I've thought of some other projects to make once I have a working printer. I keep reading about UAVs and other drones at the moment so I think I will make one of these and due to the Australian laws on drones where you need a pilot to fly one, I will try and make it autonomous to get round this law (I technically won't be flying it!). Another thing I keep thinking of, is that if I need to make a large item, that won't fit, I can make some nice plastic joints that will allow everything to slot together.
That's everything for the moment. I thought I better post something as I didn't want the blog to become stale. Hopefully this week I'll get quite a bit of CAD done as I have to do some safety course from 8-9am every morning but the lecture theatre its in is great for using laptops so I'll try and do some work during that. Don't worry about me not paying so much attention, I've managed to get through two years of electrical units with plenty of times that the equipment could have killed one of us using it and I believe we are only doing the course due to the change of head of engineering at the uni. I'll also have time to do things at night this week as I won't be out drinking each night and hungover the next day though I am in Melbourne again next weekend.
