Tuesday 19 July 2011

1st Prusa Child & issues with ABS printing

I have been printing with the Bath Prusa Mendel for 2 weeks now. It’s been a good learning process along with discovering more things about Skeinforge, high speed printing, hot-ends, and using ABS.
I now feel comfortable about the tool-chain and using the Prusa Mendel along with some of its limits, so I can now try a few more adventurous things in the coming weeks.

Below are some of things I have printed so far, and the issues I had along the way.

PLA works well, I have used 4 different types from 3 different suppliers, and they all have a slightly different extruding temperature and flow differently.

Just as I was getting to the end of the White PLA I had a hot-end failure jam, the nozzle was flexing down and catching on objects, on closer inspection the PTFE had split around the top and the PLA was jamming in the barrel.

I replaced the split PTFE and also the Hobbed bolt as I was getting slipping and inconsistent feed
 No change in spring tension or cleaning of the teeth seemed to fix it.

The White PLA from Adrian was used up printing upgrades, spares and experimenting with speed.
First upgrade was the Prusa Z Rod Constraint by ScribbleJ shown above.
And a few of my own 8mm T-slot mounting blocks as I needed some for my other machine.

I then switched to Gold PLA and started to print a full set of upgraded Prusa parts.

This included the new Prusa Z Axis using LM8UU Linear bearings.

And Greg frost’s LM8UU X Axis and Y Holders for Linear bearings.

So after the first week I had managed to get it working well and print these.

I decided on Andrew dent’s MV6 frame and foot vertex pieces as I like the look of them and they are a little fatter than the official Prusa ones.

I was getting confident at this point and even did my first print using multiply in Skeinforge to get me 9 x M8 bar mounts printed in one go.

I printed a few fun things to keep my princess happy –
This is one of the exceptional Heart bracelets by MakeALot

And a 1.8 X scaled version of the Princess Heart Crown by syvwlch

So a few days later I had the first child set of Prusa Mendel parts I decided to name ‘Mendel-Bling’ for building up my next machine. 

At the weekend I decided to experiment with ABS. It’s the material I first started with on my original repstrap back last September and I was expecting it to be easier than PLA… it was not, but maybe that was my unfortunate choice of colour.
Sunglasses on, it really is that PINK.

As it was looking quite hard to get this ABS extruding I decided that my first ABS print should be another extruder, that was a good choice as shortly after printing this the PLA extruder melted.
It’s good that I had an ABS X carriage or that would have melted also.

Extruder replaced. Still using PLA gears for good wear resistance.

When printing with the Pink ABS it needs 263 degrees C to extrude, I’m running it at 270 because of the following issue. - At 80mm/sec and 30% infill the Hot-end power is on 95% of the time and that quickly goes to 100% when doing solid infill layers while the temperature also drops 8-10 degrees, that’s right on the limit of the power I can get into the material with this particular hot-end, any faster and the extruder will jam and grind through the filament as the temperature drops too much.

Take a look at this short video of a Pink print below, the hot ABS comes out looking slightly Purple and as it cools turns back to Pink, it’s really cool watching it print especially doing solid infill, this is my first coloured ABS so I don’t know if they all do that?

With Natural ABS I still see a temperature drop at 80mm/sec but not as much while the extruding at a lower (230) temperature.

So really I should slow down the ABS speed to be safe and then build a better hot-end that can deliver more power quickly into the filament so I can speed things up again.

I don’t see this temperature problem with PLA, but I have only gone upto 100mm/sec at the moment, I’ll wait until I have my Linear Bearing Prusa (Mendel-Bling) before going any faster.

I have a puzzle to build up tonight, the Heart Gears by emmett

Thanks for reading,


Monday 4 July 2011

eMaker Reprap Master Class event in Bath (UK) 1st-3rd July 2011

The build weekend started on Friday night around 6:00PM with a great introduction by Adrian Bowyer to RepRap and the highly impressive community team that Jean-Marc had managed to bring together for us. –
Dr Adrian Bowyer, Dr Andrew Dent, Josef Prusa, Kliment Yanev, Ruben Lubbes, Rhys Jones and Sally Bowyer.

People had travelled from all over the UK and Europe to be at the event with everyone having an interesting reason to own a Reprap. Among these included the desperate need to print a Moustache ring and the desire to experiment with automatic PCB wiring; some just wanted a cool 3D printer or to meet up with the RepRap team.

We all started with the mechanical frame build using the Wiki and visual instructions, marching ahead with excitement and enthusiasm all the way till 11:30pm with only a quick break for lots of great Pizza and beer. 

Most of the frame construction was now finished. Jean-Marc and a few others stayed up until the early hours preparing parts for the next day (thank you all for doing that).

As Ruben has organized many of these events around Europe the Master Class was a very slick setup but I was very pleased to see it also evolved and adapted to live design improvements as we built the machines and found better ways to do things, the Wiki was live updated as we went along to reflect this.

Ruben and others brought many interesting printed objects including the amazing
Geared Heart by Emmett
Inspired by the  Broken heart by Greg frost (Geared)

And a lovely printed ceramic pot from Unfold even a working printed spinning wheel by Kliment (sorry I didn’t get a photo, but it was really nice). See it and read about it on Kliment's website here

We had a streaming live video of us to add to the excitement along with various comments on IRC keeping us all amused, many of them early on were about ‘girls’ actually being at the event.

Adrian gave an informative and amusing demonstration of successful pulley casting with resin using a silicon block and a jig that allowed trapped captive nuts to be placed inside the cast pulleys.

End of Friday night.
Saturday was electronics build-up and machine wiring, for many this sounded the most daunting but the Sanguinololu (V1.2) electronics although a little fiddly as the PCB is small and packed together it all built-up quickly and worked really well (I’m totally convinced now by this little setup), anyone who has used RAMPS and thinks this is a lesser design, think again.

We had drop-in visits during the day from other Reprappers and suppliers of the components we had used over the weekend, this again was great to discuss ideas and design improvements with them first hand.

After a very good night out on Saturday we all started slightly later on the Sunday for the heated bed build and electronics commissioning, this all went well. Kliment setup the firmware and tested all our electronics.

We slowed down slightly with wiring, especially all the wire crimping but stayed on-track of the build plan.
Jo helping this printer - print.
All the team provided constant help and advice to anyone not quite sure what to do next. It does not take long to realise that all the advice you absorb at one of these get-togethers would take months to get online. 

Participation takes thought and concentration making for a very intense, exciting and satisfying weekend, I can’t speak for anyone else but I was shattered at the end of it but elated to have an ‘official’ and working machine to take home with me. I believe building and servicing a Prusa Mendel is well within the means of most people and immediate good results were not hard to achieve thanks to the effort Josef & Kliment put into setting up Skeinforge, printrun (pronterface) and the Sprinter firmware for us.

Not my machine, but a nice looking pig print.

By Sunday afternoon all the machines got to the point where they could print (most opted for a nice pig cookie cutter
I printed my favourite calibration object – the Hollow pyramid Originally I had sticky X and Y axis causing some slipping on the axis while printing, I turned up the motor drive currents to compensate and it was better but still skipping.
This turned out to be oxide or unclean rods, a quick clean and silicon lube made the much better. I added heatsinks to the Pololu boards (very kindly supplied by Ruben).
The Pololu’s were still running too hot and sometimes thermal-tripping so causing skipping and miss printing.

Adrian measured my driver chips at over 85 degrees C with an IR thermometer (this was too hot) so we turned it back down and due to the now clean X and Y smooth rods it now made a pretty good print of the hollow Pyramid.

It’s clear from the many conversations we all shared that great and interesting things are set to happen in the RepRap community in the coming months, stay tuned, and get involved and if you ever get the chance to meet up with other Reprappers or go on a Reprap Master Class anywhere in the world make sure you DO IT!

Many thanks to Jean-Marc, all the RepRap team and everyone who attended and visited us over the weekend, we all made new friends and I think we managed to push RepRap even further forwards.

And a special thank you to Clare and Andrew for helping transport all my stuff and nice new printer back to my car at the end.

I'm sorry if I have forgotten anyone or anything, if I don’t write something right now about the Master Class I’ll never be able to pull myself away from my new printer J It’s already printing it’s first upgrade – Printable Ball Bearing Upgrade by GregFrost

And finally if you have not yet tried out Kliment’s printrun, check it out, it’s really great.


Friday 1 July 2011

Layer selective colour 3D printing

After printing coloured and multicoloured things, I wanted to experiment using my Filament joiner to make prints that had different coloured finishing layers (at different heights) on an object.
A business card seemed a suitable object to start with as I could place things and text onto it and vary the height of each object.
This is what I ended up with, below is how it was done - 

First I actually needed to learn Sketchup so I could design it. I had quick go as hacking other peoples parts a few days back but as I wanted the open hardware logo on the card I needed to work out how to do that first.

Download a picture
Import it into Sketchup and turn on Xray
then trace around the image to form a closed path you can extrude

Extrude that to whatever height you like
Then I added text using Sketchup font tool.

The model should turn out like this.

Design the rest of the card
Each text block finishes at a different height from 0.8mm to 3mm

Export and re-scale in Netfabb if required
this is 85 x 55mm

I did a quick test of fonts to see if they would actually print – 
This just showed me that you need it to be an outline without any infill or it will end up messy.
I could have made a better selection of font and size, but not bad for a first print.
I need to work on the font size so Skeinforge produces a tool path that does not try to fill little gaps in the letters.

Then after slicing in Skeinforge you can use the output Gcode and a program like Grep to isolate out the extruded movements for each layer.
Then you can join the sections of filament together the correct length and print !

At each point you decided should have a different colour the layers change and slowly build-up a multicoloured object.
The red text is only two layers high and a little smudged.

It looks good enough to eat!

A few other multicoloured things printed for fun yesterday.

close up, the changes are quite sharp, I initially imagined it would take many layers to change colour.

I had a go at also doing horizontal selective colouring on the base, but it's not easy to see in this picture.

The inside of both bases lines of different colour so with correct filament lengths you can select  both horizontal and vertical colouring.
If you were printing a cylinder for example, with the correct lengths of filament you could colour half of the object in the vertical plane as it was being built up (quite hard to do though).

Fitted together perfectly.

Many thanks to AgeingHippy for sending me some white PLA to try.
And thanks again to Greg Frost for suggesting using Grep for working out lengths of input filament.

I need to get ready for the RepRap weekend now, so thanks for reading (quite a long one this time).