Month: September 2013

The recent modifications to my printer have made a huge difference.  Not only is it printing much more accurately, but I can print item after item without recalibrating.  There are further improvements to be made (aren’t there always?), but I’m now at a point where I can be reasonably confident of being able to print the parts I need to make modifications.  Here’s an example:

These two clamps are created so that I can mount a scavenged motor securely for my next project.  I modelled these in OpenSCAD, sliced them in Slic3er and printed them using Repetier-Host control software.  Everything just worked.  I haven’t mentioned Repetier-Host before, because I’ve only just become aware of it.  It’s a very nice front end for the printer, and manages Slic3r.  You can load and view a .STL file, slice it and print it from the same interface.  It’s slicker than Pronterface, which I had been using.  It’s definitely my software of choice now.  It makes it really easy to adjust the printing speed during printing – meaning that you can slow down the head for fiddly areas, and speed it right up for less important bits.

Flushed with success printing useful things, I thought it was time to try some frivolity.  Here’s a “Skull with pointed teeth”, from a model I found on thingiverse:

It’s about 5cm tall.  It would look better printed in white plastic, but I’ve only got blue.  I’m really pleased with this print.  Next time, I’ll make it hollow and mount a couple of red LEDs in the eye sockets…

Finally, I decided to try something more complex.  Printing objects with overhangs is not simple for this style of printer, because there is no surface deposit material on.  So I have not tried it before.  Slic3r has a setting you can use which will help to print overhangs by printing columns of expendable support material underneath.  These can then be cut away when the print is complete.  The example I tried is a minion from thingiverse (if you don’t know what a minion is, you should watch the film Despicable Me at once).  Here’s a picture of it mid-print:

It’s hard to see the shape, because of all the support material (the vertical columns at the front), but you can see the honeycomb-shaped fill of the main part.  When the print is finished, the poor minion looks like this:

Ten minutes with a scalpel, cutting away the scaffolding, and he looks like this:

He’s a long way from perfect, but given the size (about 6cm tall), it’s not too bad.  His arms are only about 3mm thick, and they could not have been printed as part of the main figure without support.   Again, it doesn’t help that he is translucent blue rather than yellow.  Perhaps a paint job will improve him.  A light sanding certainly would.

You will become like us.  Yes, I like Doctor Who (as if that was unlikely).  This isn’t about Cybermen, though, it’s about a significant upgrade to my 3D printer.  As initially designed and constructed, many of the pivots in the printer are simply screws passing through holes in the PLA printed parts.  Over usage, these holes have become enlarged, so that the screws are loose.  This means that apart from the danger of them falling out, there is unwanted movement in the printing mechanism.  This leads to inaccuracy in printing.  So, as part of my plan to gradually improve the accuracy of the printer one step at a time, the next step is to replace the pivots with proper bearings.  Naturally, my initial designs, printed by Rob, do not allow for the insertion of bearings.  That would be far too easy.  No, the pivots are part of the carriages which move up and down the columns, and are each printed in one piece.  I have to design new parts which will fit on to the old carriages.  Why can’t I just print new carriages?  Because the printer’s not accurate enough yet.

I discover that I can now print small items (and in particular, things which are not very tall) with quite good results.  This means that I can finally use the printer to print some parts for itself to upgrade it:

Those are bearing mounts.  I’ve sourced a load of tiny ball bearing races off eBay (7mm od, 2mm id) for the ridiculous price of 20p each, and I’m going to replace each of the pivot screws on my carriages with them.  They are really tiny.  Really, really tiny.  I’ve already lost one.

The bearings will be located in the parts in the first picture, which in turn are mounted on the carriages using the original pivot holes.  I’m also replacing the pivot bars with newly printed ones.  If all goes well, my prints will be better.  It all fits together like this:

 

I’ll have to go through the whole calibration routine again once I’ve fitted the new parts (which is a bit annoying, as it’s actually working quite well at the moment), but I’m confident it will be worth the effort.