Coming back together at last

One of the things that irritated me about the extruder was the time it took to open the pump and close it again. To make it slightly less fiddly I replaced the lock nuts with a pair of threaded steel plates :-



I used Forrest's recipe for cooling fluid while drilling these. It worked a treat, I had no idea you needed cooling when drilling steel to prevent the drill from being burnt.

The springs I used first time around that came from an old CD player weren't quite strong enough but I found some better ones in the hinges of an A3 scanner I dismantled recently. Six of these held the lid open.



Here they are installed on the machine :-



I should be extruding again tomorrow!

Well sprung

Some versions of the RepRap FDM extruder use four springs to press the filament against the threaded rod. The latest version uses compressed plastic piping but I read somewhere that it loses its tension over time. When I was dismantling the CD player out of my Jukebox the other day I came across five reasonably powerful springs :-



Unfortunately the two at the back are not as strong as the front three. However, Forrest Higgs has shown with his Tommelise machine that you can get away with just two springs at the top so I will put the weaker ones at the bottom.

Another problem is that the springs are too big in diameter so I made some stepped washers out of Perspex to fit in the ends. As eight were needed this was the biggest run of things I have milled so far. It was a good way of using up all the scraps of Perspex left in between things I have milled previously. The only problem was that a few disappeared up the vacuum cleaner and had to be retrieved from the bag!



I was worried about the friction in my extruder channel so I tried polishing it with metal polish. This worked very well and greatly reduced the friction. A friend just happened to give me a spray can of PTFE dry film spray today so I gave it some of that as well.

I put the pump together minus the barrel and checked that it can move HDPE filament. It remains to be seen if it can extrude it.