Wednesday, 6 February 2013

Two years of 3D printing

Almost two years ago my good friend Phil Hands invited me to attend a workshop at bath university to build a 3D printer. I had previously looked at the Reprap project and considered building the Darwin model, alas lack of time and funds had prevented me form proceeding.

Jo Prusa and Phil Hands watching a heart print.
The workshop was to build a new, much simpler, design called the Prusa. Of course the workshop was booked and paid for well in advance which left me looking forwards to the event with anticipation. Of course I would not betaking the results of the workshop home as Phil had paid for it, so I started investigating what I would need for my own machine. 

Of course at this point I muttered the age old phrase of "how hard can it be" and started acquiring parts for my own printer. By the time the workshop happened I already had my machine working as a plotter. I learned a lot from the Bath masterclass and a few days afterwards my own machine was complete.

First print
The results were underwhelming to say the least. There then came months and months of trial and error to fix various issues:
  • The filament feed bolt had to be replaced with a better one with sharper teeth. 
  • The thermistor which reads the extruder temperature needed replacing (it still reads completely the wrong temperature even now).
  • The Y axis was completely inverted and needed re-wiring and the limit switches moving.
  • Endlessly replacing the printer firmware with new versions because every setting change requires a complete recompile and re-flash.
  • The bushings on the Y axis were simply not up to the job and the entire assembly needed replacing with ball bearings and a heated bed otherwise prints would be completely warped.
  • The Z axis couplings kept failing until I printed some alternates that worked much better
Once these issues had been fixed I started getting acceptable levels of output though the software in the workflow used to produce toolpaths (skeinforge) was exceptionally difficult to use and prone to producing poor results.

Alas the fundamental design issues of the Prusa remain. The A frame design provides exceptional rigidity in one plane...the other two? not so much. This coupled with an exceptionally challenging calibration to get the frame parallel and square means the printer is almost never true.

Prototype iMX53 dev board eurocard carrier printed on my printer
In operation the lack of rigidity in the x axis means the whole frame vibrates badly even with extra struts to try and improve its rigidity. I am not the first to notice these design flaws and indeed Chris has done something about it by creating a much superior design.

I do however have a working printer and have developed a workflow and understanding of what I can expect to work.

Improvements in the software means that slic3r has replaced skeinforge and gives superior results and the CAD software is continuously improving.

Currently I mainly use the printer to generate prototypes and simple profiles and then send the resulting designs to shapeways for final production though simpler designs are usable directly from the machine.

Because I am away from home a lot and moving the machine is simply not a workable option the printer does not get used for "fun" anywhere near as much as I had hoped and the workflow limitations mean I have not been able to make it available to my friends to use as a communal device.

Recommending a 3D printer

In a previous entry I wrote about the technology of additive manufacture and the use in printing three dimensional objects.

My Prusa Reprap printer, not recommended for new builds
It is now almost two years since I built my own 3D printer and I keep getting asked by colleagues and friends about the technology and often what printer to buy.

I will answer the purchase question first and then describe my experiences which have lead to the conclusion in another post. This may seem a bit backwards but the explanation is long and is not necessary if you are happy to learn from my mistakes.

Of all the options available right now, and there are many, I would choose a Mendal90 kit from Chris Palmer. The complete kit including everything to build the machine is £499 plus shipping. If I could afford it this is what I would buy myself to replace my current machine.

This is a Fused deposition modelling (FDM) printer similar to my Prusa Reprap but better engineered to produce repeatable results without the numerous issues of the other models. In Europe I would also recommend faberdashery as a materials source as their product is first rate every time.

Yes the kit requires some assembly but the commonly available commercial printers either cost many times more to deliver equivalent results, use an SLS or other print strategy requiring very expensive consumables or are from a company with dubious track record with the community.

If forced to recommend one, the 3DTouch from Bits From Bytes is not awful, but really do not be afraid of the kit, you will learn more about how it all fits together and save lots of money for your materials.

A 20mm high pink dump truck toy
One thing anyone buying a 3D printer right now should understand is that this technology is nowhere near as polished as the 2D equivalent. With the exception of the SLS systems like shapeways and the like use (and have price tags to match) The output will have clear "layering" and some objects simply cannot be created using the FDM process.

I guess what I am saying is do not expect a thousand pound machine to produce output that looks like that of a hundred thousand pound printer. To be clear you will not be printing complex moving machines on an FDM process more simple things that need assembly.

Having said that I have some pretty good results my favourite has to be the working recorder though, I might have said the whistles except my sons have them and they are way too loud.

You will spend a lot of time designing your things in 3D CAD packages and fair warning they all SUCK and I mean really, really badly. Add to that all the rest of the tools in the workflow are also iffy and I do wonder how anyone every gets anything printed.

My (open source) workflow is:

Which is probably a case of "least bad" tool selection though I warn you now that OpenSCAD is effectively a bad editor (I wish I could use emacs) for a 3D solid macro language with visualisation attached and definitely not a graphical tool.