After a long absence with no posting I have been busy designing and printing a reprap. I nearly went for a Darwin but having tried to build the original it was fiddly to set up and had a lot of complicated parts which I struggles to separate from the source forge AOI file.
At the same time I discovered that school had a site licence for Solidworks so I thought give it a go build a simple threaded rod 3 axis machine the same as I have at the moment.
I also decided to minimise the different parts. Currently it has
Nema 23 motor holder
threaded rod bearing block
threaded nut holder
And other parts
8mm threaded rod (stainless)
rubber pipe(motor to rod coupling)
Plus various nuts and bolts
In the picture you can see the Z and Y axis. The Y axis is a little big and is not MDF but an old shelf that was lying around.
I have stolen eD's idea about using the skate bearings as bearings for the slides. That works well- (Thanks eD if you read this)
Both the axes move smoothly and I have run the Z axis for 2 hours backwards and forwards to see what fell off (and nothing did)
I tried to make a printed motor to rod coupling but nothing I made had as good a characteristics as the rubber pipe.
I have been improving the quality of the printing in the manufacture of all the components. The Biggest is the Nema 23 motor mount at 8cm X10cm X 4cm. I found that if you make it too thick (1cm) then it tends to delaminate so I redesigned to to 5mm thick and added webs to it and it is now really sturdy. Warping was not a major issue- I am now extruding onto a glass chopping board(Robert Dyas 5 pounds) coated in evostick.
I also found that the accuracy was pretty good. I designed the bearing holes at 22mm diameter and then all I had to do was tap the bearings in with a rubber mallet with no preparation at all. The same for ineserting the long nut (studding connector) that runs on the threaded rod - just tap in .
My major issue was with some ABS I bought which varied in diameter causing many jams. I gave up in the end and bought some from Bits from Bytes and had no trouble at all, but it is very expensive. I would hope to pay 20 pounds for a reel soon.
Anyway next steps make the x axis, the extruder and double my production capability.