Thursday, 30 June 2011

and so it begins...

Oh for it was a happy day when that glorious package from did arrive.  Nestled within its corrugated womb was a Prusa hardware kit and 5 high-torque NEMA 17 stepper motors.  Being an impatient kind of fellow, I impressed myself by not starting to actually build my first reprap until 22:45!  From there, the addiction set in and held out through to 00:30, at which point I really needed the use of a circular saw... and that would definitely be frowned upon by my wife and kids.

Nonetheless, the last couple of hours have been very productive and have seen the basic frame assembled.  I've been round and carefully adjusted all critical measurements and it's looking pretty good (if I do say so myself).  Next up is fabricating the bottom plate for the Y carriage -  that'll be tomorrow evening if I can get away with it :)

All told, it's been great to get started at last and I'm very impressed with the quality/speed of my thingfarm order - will definitely use them again (although just noticed they've put the Prusa hardware kit on sale and it's now £10 cheaper :( ).  Rock on tomorrow...

Sunday, 26 June 2011

Nursery, presents and orders

Like preparing for our first child, I'm feeling the pressure of an imminent arrival, so spent several hours over the weekend adding some finishing touches to the nursery (office).... namely some discrete slatwall (destined to hold component bins, tools, etc) and a mini-lathe (inherited):

I'm also the lucky recipient of my final birthday presents - a Seeduino Mega and a pair of Pololu drivers :)  Fortuitously, an ebay auction has also gone very well, so I've ordered a Prusa vitamin kit plus a set of 5 stepper motors from - hopefully they'll arrive next week and then the build can get underway!

To pass the time, I will be continuing to experiment with OpenSCAD and partake in the most excellent Thingiverse community - currently I'm working on a parametric loc-line-esque library and some kitchen fittings

Monday, 20 June 2011

STL validation (design rule checks)

I've seen a few comments around the reprap forum regarding some sort of tool to do design rule checks before printing an object.  It sounds like a very sensible development and I stumbled across this good example earlier today:

It would be great to incorporate this into Skeinforge, perhaps initially as log data and then later with some sort of visualisation...  another one to add to the (rapidly growing) list

Friday, 17 June 2011

Printed Parts

Couldn't resist getting all the bits out and checking them off against the BOM:

Good news - they're all there!  On closer inspection, I also noticed that nophead included nuts/grub-screws in the two pulleys - nice touch :)

Opto EndStops

So... having explored many of the options, I've settled on using 6 of the Gen7 EndStops (v1.2) by Traumflug:

I started out looking for kits, and other lazy/cheap ways of obtaining equivalent parts, but can't find anything with reasonable shipping costs (there is quite a bit available in mainland Europe, but the shipping is more than the parts cost!).

If I go it alone, getting the parts from Farnell will cost £12.73 + shipping, but Farnell have a minimum order of £20 - so would have to order the rest of the electronics at the same time to make it economical.

Before I commit to that, I've emailed Traumflug to see if he has any kits available at a reasonable price - fingers crossed.

Wednesday, 15 June 2011

First parts

My family has done me proud and to ease the pain of another year, I'm now in possession of:
  • A set of printed Prusa Mendel parts, inc Wade extruder - ordered from nophead via ebay, arrived in less than 48 hours and are superb quality - very impressed!
  • 2x Pololu drivers
  • £50 towards other bits (I'm thinking a bundle of steppers)
Just need a hardware kit from thingfarm and I'm good to go....

Tuesday, 7 June 2011

Slicing NURBS: surface intersection with a plane

I'd like to create a skeinforge equivalent that takes a pure NURBS model as input and creates a set of NURBS toolpaths, the fundamental challenge in this approach is how to efficiently/accurately slice the model into printable layers.  Graphics literature contains some promising leads for suitable algorithms, this is the most directly applicable I've found so far:

Ignoring it's use of the GPU, my summary of the technique is as follows:

Find the intersections of two NURBS surfaces by building an octree that progressively identifies child nodes that contain an intersection of surface bounding boxes.  The octree is expanded until the desired precision is reached.  A new curve(s) can then be fitted to the identified intersection points (defined by the octree leaf nodes), using MLS, etc. 

I was hoping for a more direct method, but a search based technique will do although maintaining sufficient accuracy on complex models may involve a large computation overhead.  I doubt this would be a practical limitation - especially as the host could be generating slices as the model is being printed, so the delay before printing can start would be negligible.

Referring to my earlier post regarding tool path optimisation, the "smoothing" process would be incorporated into the curve fitting stage of the slice algorithm - intuitively I suspect this could be optimised, such that the fitting algorithm simultaneously solves for an accurate and sufficiently smooth curve.

More to follow...  once I've read this paper properly:

Bezier tool path optimisation

I'm intrigued by the idea of generating tool paths as bezier splines in the host software with the reprap firmware natively operating on the splines, rather than G-Code.  Researching that idea, I came across this excellent paper on optimising bezier tool paths:

Another potential supplier

Found another useful supplier in the UK at - looks like a good value supply of ABS and some Kopton tape:

Monday, 6 June 2011

Research and inspiration

Aside from cruising, a lot of my research has come from some very well written blogs....In particular, nophead's HydraRaptor blog is crammed with insight, best practises and ideas.  Given the number of repraps in the wild, I'm surprised by the very small number of people that are advancing the field with good quality documentation and innovation.  I'm sure there are many small contributions, but many of the major advancements seem to come from just a handful of pioneers.

From my point of view, this is a major motivation - I can't wait to get into a community where it may be possible to make a big difference, especially one with as much future potential as this!

A RepRap is born (or at least specified)

So... after months, perhaps years, of reading about RepRap the time has finally come for me to try and build one.  Nicely catalysed by placing reprap parts as the only items on my birthday list :)

This of course entails producing a very family friendly list of reprap parts, carefully itemised, from reputable suppliers, such that my family stand a chance of ordering the right bits!  All in, I think the total cost will be around £350 (exc filament), which seems very competitive compared to buying a full kit.

What to build?
  • Settled on a Prusa Mendel as the perfect "first fabber" project, Huxley is too small and I'd rather not go via the repstrap route (keen to get to the good stuff )
  • Seeduino Mega for the controller (with a bunch of Pololu A4983 drivers) - seems to be the best value and simplest electronics combo - will use to build the stripboard version of Adrian's Pololu electronics
  • I like really like the look of the new v6 hot end from - reviews well and should be easy to maintain/extend
  • A heated bed seems a no brainer, and the resistor-based heating elements look the way to go
  • Power will probably come from an old ATX supply (if I can find one lying around) or perhaps a laptop power brick

Who to buy it from?
  • First up, I'm more than happy to pass business in the direction of Mr Bowyer, so Pololu's and possibly filament will be coming from his spin-off business:
  • Printed parts would have gone to Adrian as well, however, nophead's parts are in ABS rather than PLA, so given I'm keen to work at higher temperatures, nophead wins:
  • Vitamins will be from, great price and a single package contains all main hardware inc. the bits for the extruder
  • The Seeduino is somewhat easier to source, with several good options.  My shortlist is either or
  • have some great parts, good prices and good UK shipping, so will use them to mop-up on motors (loving the long leads), hot-end (great kit) and heated bed.  They also have good value filament, so my 2nd choice for PLA.
  • Anything left over (e.g. miscellaneous electronics) I'll probably get from Farnell, Maplin or RS once I'm actually into the build.

I spent last week making those "hard" decisions and compiling a parts list into google docs for the family, assuming they go for it (not like I gave them any other options), I should be able to start assembly by late June - fingers crossed :)

World of 100


I feel the need to print these out and stick them round the office :)