Frame Design

Over the last few days, I've been having a go in Inventor and doing a mock-up of my designs. (I say mock-up as explained later.) This has helped solved some of the problems I've had and provoked ideas on what needs to be done and changed. None of the pictures have the x slide/axis carriage shown as that is a more detailed feature and so I haven't designed even a basic version yet for the design.


So firstly here is a picture of what I mean by aluminium profile.

I thought this material would be the best for the frame as its quite rigid, light and easy to handle. It also has slots that can be used to bolt things too or use as slides. Yesterday I had a quick thought that maybe it was a bit over the top after looking at the different reprap designs, including Prusa and MendelMax. I then decided that it was almost the same weight, as what was used on these as its aluminium rather than steel, it can be used for slides and most importantly, I could actually get hold of it easily compared to other shapes, so I'll stick with it.

This next picture is the CAD version of the what I had sketched out in the last post. Seeing it like this I think I will need to change the height or make the base bigger but for now I will keep it like this and can later do some calculations on strength and the like.

 This picture shows the my currently proposed motor locations. These are likely to move as I change my views on practicalities such as balance and moment of the moving frame. The other thing which this image shows is that I'm going to go for grounded steel bars as the rails/slide for the x axis. I'm currently thinking, I will try and use the same spacing as those used on RepRap based models so its easier to convert parts over if I ever needed. It also would work in reverse. There is obviously one major difference though in that I'm not going to use a belt drive and instead will use threaded rod and later a ball screw. This allows higher precision and accuracy.

The final image shows the next few things I will do basic mock-ups of.  The red lines show some extra support which will help support the upright frame. I'm leaning towards equal angle for this as should be quite strong. The blue lines are simply the other drive shafts which I haven't added yet and the carriage.

A few last notes to add. The brackets that attach the slides to the drive shafts is made of a simple V shape with some flats at either end to mount. This is a very strong bracket, its downside though is it is harder to manufacture over the simple use of mounting a threaded nut. I would prefer the V bracket as being stronger can cope with moving heavier masses plus it attaches to the drive shafts in two locations.

I'm going to indefinitely suspend development work on other mounts and uses for the printer such as a CNC drill and chocolate printer. This is because I can then use the plastic printer to create mounts for these other tools.

And finally, as I said in the intro, being mock-ups, they will have to be redone. This is because the constraints are partially wrong which means occasionally parts end up in the wrong place and do weird things. Parts also need to be catalogued correctly and given part names and the entire work needs to be rotated as currently Inventor has the model upside down!