Making Mendel90

Printing the Shy Light

Mon, 26 Nov 2012 21:50:00 +0000

This beautiful curved model by virtox had proved extremely tricky to print for various reasons. My best attempt had been in black ABS and although the print completed successfully (unlike several earlier attempts) it cracked in several places whilst it was still printing. This, more than any other, was the model that prompted me to build a heated chamber for the Mendel90.

Here is the print, lying on its side, showing the cracks that appeared as the plastic cooled and shrank causing delamination.

This copy was printed in natural ABS inside the heated chamber at 35 C and, as you can see in the picture, the surface is smooth and blemish free.

And here are the two prints side by side.

And here is the first model to come out of the Mendel90 inside...

Mon, 26 Nov 2012 21:10:55 +0000

And here is the first model to come out of the Mendel90 inside its new heated build chamber. Admittedly, I shouldn’t really compare an ABS print with a PLA one since they have very different characteristics, but nevertheless, I was very pleased with the quality.

This weekend I finally got around to completing a project that I...

Sun, 25 Nov 2012 18:45:00 +0000

This weekend I finally got around to completing a project that I had been planning for some time. Some of my large ABS prints have been splitting (called delamination) due to excessive shrinkage as the model cools whilst printing. This has steadily worsened as Winter approaches and the temperature in my garage has dropped to around 10 degrees C. The best way to avoid this is to print in a controlled warm environment, ideally at about 35C. This means putting the printer inside an insulated box. I bought some lightweight polycarbonate sheet and pine strip wood from B&Q, designed a simple box shape, cut the pieces to size and then glued and screwed everything together. I picked up a cheap digital thermometer from Clas Ohlsen to monitor the temperature inside the chamber. The heat comes only from the heated build platform, but at a regulated 110C, this seems ideal for maintaining the air temperature at close to the 35C I was hoping for. Now I can start trying to print some of those large thin-walled items that have previously failed.

Rodin’s ‘The Thinker’ via PhotoToaster, using...

Wed, 14 Nov 2012 09:08:26 +0000

Rodin’s ‘The Thinker’

via PhotoToaster, using these settings.

Successfully printed the tricky Fabric test by Pretty Small...

Tue, 16 Oct 2012 22:00:27 +0100

Successfully printed the tricky Fabric test by Pretty Small Things in brown PLA. It’s like 3D printed chain mail.
http://www.thingiverse.com/thing:31234

Richard,Can you tell me more on PID control calibration? I have build a Mendel90 and want to calibrate the PID control. What software are you using? I don't recognize the screenshots? Your prints look great! Thanks,Maurits Brock

Mon, 24 Sep 2012 23:19:00 +0100

Hi Maurits

There are basically two approaches - the easy way and the hard way. The easy way is to use firmware that supports auto-tuning of PID control, such as Marlin. I bought a 1284p Atmega chip for my Sanguinololu board so that I could run Marlin. Then you can just use the M303 command described here to let the printer find its own values.

The harder method is to read up about PID control theory (Wikipedia is a good place to start) and learn how to do the tuning manually, iteratively tweaking the numbers until your hot end rises quickly and smoothly to the correct temperature with minimum overshoot.

The software is not really important for this process but I am using Repetier Host for all my printing now. I like its temperature graphing more than Pronterface’s because the resolution seems better. It also has a much better 3D preview of the Gcode, which I regularly used to check Slic3r’s output.

Using a 3D printer to spruce up a board game

Sat, 08 Sep 2012 09:49:00 +0100

Last weekend, one of my sons gave me an unusual board game for my birthday (thanks, Luke!). The game comes from Germany and is called ‘Das Waldschattenspiel’, or ‘Shadows in the Woods’.

The contents include a large ‘forest floor’ mat, 10 wooden trees in various sizes, a die, a tea-light and 7 wooden pegs to represent dwarves. The simple rules involve the dwarves playing hide and seek in the woods by the light of the candle which is moved around the board by one of the players. I was intrigued by the concept but somewhat less excited by the suggestion of using a felt pen to draw faces on the men and then gluing on cotton wool and felt cones (included) to represent beards and hats.

It took only milli-seconds for me to realise that I could improve the game by exchanging the wooden pegs for proper dwarf models made on my 3D printer.

A quick search on Thingiverse revealed that several models had already been uploaded but one stood out as being perfect for the job. He is a lovely little fellow called Gnome baldbeardington. It was a simple matter to resize the model down to 3 cm tall, the same size as the game pieces.

I haven’t played the game yet but already I can see future possibilities for adding levels of difficulty by printing dwarves in different sizes to make hiding easier or more difficult - and why should all the characters be the same size? The potential for game modifications is just mind-boggling.

Another two fantastic prints on the Mendel90. The standing model...

Thu, 23 Aug 2012 17:09:00 +0100

Another two fantastic prints on the Mendel90. The standing model was printed at 0.2 mm layer height (the stripey legs were not intentional but the result of some residual black ABS that kept seeping into the buttercream PLA). The seated model was printed with 0.1 mm layers and is stunningly detailed with almost no visible texture.

My entry for the latest RepRap printing competition.This 10cm...

Wed, 22 Aug 2012 14:08:00 +0100

My entry for the latest RepRap printing competition.
This 10cm voronoi vase was printed at 0.2 mm layer height in yellow 3mm PLA from Faberdashery on the Mendel90.
I would really like to reduce the fine strings and small blobs but probably need some advice about tweaking the settings to achieve that.

… I have finally succeeded in fitting a proper, ducted...

Sun, 05 Aug 2012 23:44:58 +0100

… I have finally succeeded in fitting a proper, ducted cooling fan to the Mendel90.
And it really works!

After a succession of failed prototype fan ducts …

Sun, 05 Aug 2012 23:43:19 +0100

After a succession of failed prototype fan ducts …

Trying again and this time I’m using ‘the...

Sat, 04 Aug 2012 15:06:32 +0100

Trying again and this time I’m using ‘the brim’ (thanks Idolcrasher!) to stick the print down more firmly, and a fan to stop the edges from curling up.

My new design for a cooling fan duct for the Mendel90 just...

Sat, 04 Aug 2012 13:33:24 +0100

My new design for a cooling fan duct for the Mendel90 just turned to a pile of spaghetti.
Steep angles and curling edges caused the print head to knock it over while I was out.

Best print quality ever!My Mendel90 finally found its sweet...

Fri, 20 Jul 2012 19:45:05 +0100

Best print quality ever!
My Mendel90 finally found its sweet spot, so I just had to capture the settings I used to make this bottom half of the Raspberry Pi case.

Firmware: Marlin
Flow dialled down from the default setting of 42.3 to 36.0

Software: Slic3r 0.8.3
Layer height = 0.25 mm
Extrusion width = 0.45 mm
Filament diameter = 3.0 mm
Extrusion multiplier = 0.9
Print speed = 30 mm/s

Come and see us at the Manchester Mini Maker Faire Live 3D...

Fri, 13 Jul 2012 16:52:21 +0100

Come and see us at the Manchester Mini Maker Faire

Live 3D printing demonstrations on the eMaker Huxley and two Mendel90s (mine and nophead’s).

http://www.youtube.com/watch?v=77GC3I0hXls

Panelolu - printing without a PC

Thu, 12 Jul 2012 01:21:00 +0100

Most RepRaps are capable of printing whilst disconnected from the host computer as long as they have an SD memory card attached. But usually this means that the printer just carries on regardless until either it finishes the print or you pull the plug.

Not any more.

This clever little accessory is a real bargain at £30 as it includes an SD card reader, a click controller and a backlit LCD display panel. The display can show 4 lines of 20 characters and the click controller, in combination with the Marlin firmware that I’m already using, operates a menu system that provides extensive control over most of the printer’s functions.

You have to make your own case and control knob but , hey, that’s what 3D printers do best!

Printer problems

Fri, 06 Jul 2012 21:47:02 +0100

Two weeks ago, the heated printed bed on the Mendel90 suddenly stopped working. The cause was pretty obvious on closer inspection. The power connector had overheated and melted the plug.

Nophead had warned in his build instructions that it was better to bypass the plug and attach the wires directly to the metal body of the power controller but I didn’t bother to make the change and the plug failed :(

Worse still, when I tried to repair the connection using nophead’s method it still didn’t work, leading me to conclude that I had damaged the circuit board as well.

And then, in my sorry, tired state, I committed an even bigger blunder whilst testing the circuit, accidentally shorting two pins together and sending 12 volts down the 5 volt line which destroyed the processor and all four motor controllers.

Fortunately, I was able to afford a replacement board, swiftly supplied by Think3DPrint3D, and a set of spare chips to repair the old one. So now, two weeks later, I have a complete spare set of electronics which I intend to keep at hand for the Mini-Maker Faire in Manchester at the end of the month.

And then after that, maybe they’ll find their way into my next 3D printer! Who knows?

Finally got back to doing some printing after a holiday and a...

Fri, 06 Jul 2012 21:29:01 +0100

Finally got back to doing some printing after a holiday and a string of printer problems. I liked the shape of this Siamese Orchid Vase and also the challenge of printing it without support structures.

Last week I entered the RepRap 3D printing competition (purely for fun) and came first in the...

Sat, 23 Jun 2012 15:41:25 +0100

Last week I entered the RepRap 3D printing competition (purely for fun) and came first in the judging. This was my entry.

My prize for winning was to choose the subject for the next competition so, naturally enough, I chose a puzzle.

There were several excellent entries but this was Greg Frost’s winning print.

His great suggestions for successfully printing at low layer heights have inspired me to have another go myself. Here’s a print I’m doing at 0.15 mm layer height using a honeycomb fill every 2 layers. So far it seems to be working very well.

PID Control Problem Cracked!

Sun, 10 Jun 2012 17:29:00 +0100

Last night I finally solved a problem that has been dogging my Huxley printer for weeks. I previously wrote about how I had managed to find the correct PID settings for the Mendel90 and how this was now benefiting from very stable temperature control.

Well, I’ve been trying to achieve the same thing with the Huxley and failing miserably. All of my recent prints have had to endure ridiculous swings of +/- 20 degrees C and the quality has been suffering as a result.

I’ve read more and more articles and forum posts about the art of PID tuning and failed to understand why I couldn’t fix my problem. Finally, I stumbled across one line that proved to be the key to finding a solution - “sort out any hardware problems before attempting PID tuning”.

I took the hot end off the printer and inspected it carefully. Sure enough, there was a completely dry, loose connection between the thermistor and the heater block. No wonder the controller was having a hard time getting the temperature right - the readings must have been changing every time the head moved!

Squirting a little heat sink compound down the thermistor socket and replacing it cured all the temperature swings and now I’m looking forward to seeing a real improvement in surface quality of my prints.