Rapman Extruder Conduit Clamp

For a very long time now the Rapman's extruder conduit has been attached to the frame with a couple of velcro cable ties:

I decided finally that the cable ties were a bit too crude and set about designing something a little more elagent. Twenty minutes later I designed a clamp:

 Now it was only then I realised that the clamp needed an offset between the threaded rod and the conduit. So I had to throw away the nicely rounded clamp and start again.

Mark two was a little uglier - The part needs at least one flat face with no overhangs. That is, the face which will be laying down on the bed of the printer.

A couple of hours on the printer later and these were the result:

Still not perfect (I misread the protractor in my haste) but it clamps the conduit and the threaded rod OK. Mark three will be the correct angle :-)

If I say so myself this clamp goes pretty well with the first one made for this machine.

New Conduit Clamp for the Rapman

For about a year now the Rapman has had a clamp holding the plastic conduit. The clamp was inserted into the original 10073 conduit mount plate. The plate is laser cut acrylic and on a recent trip to a secondary school I managed to smash it getting into the car.

I decided to design a part that took place of both the clamp and the mounting plate in one piece... 30 mins in google sketchup later and I had this:

Into the printer and 50 minutes later I installed the new part :) 

Repairing the RapMan 3D printer:

So the RapMan started to misbehave a while ago... The parts being printed weren't very strong and the layers would separate with very little force.

With a bit of sleuthing I worked out the the 200k Ohm thermistor in the extruder nozzle was drifting out of tolerance in a big way.

A quick email off to BFB and Michael kindly sent me out four spare thermistors.

Let the rebuilding begin!

The extruder heater, nozzle and thermistor assembly are all held together by fire cement, this necessitated a little exhumation of the nozzle :)

I soaked the nozzle in hot water to soften the fire cement (I more than once very nearly took a swig of cementy water thinking it was coffee...)

After a little persuasion the cement was removed allowing the replacement of the thermistor :)

The printer has just this minute successfully completed a test print :D More to come.

Replacing the Magic Smoke

So I've been doing a lot of work with the Rapman Printer lately. The present mission is to print a set of spare parts for a complete machine. Said parts are going to be assembled into a replicating mashup of a machine, stay tuned on that one :)

The upshot of it is that running the printer for extended periods caused a very well documented manufacturing fault in the electronics to rear it's head... There is no real protection for the ADC of the microcontroller reading the thermistor in the extruder.

Now when you have:
A machine made of insulating plastic brackets supporting a metal frame.
Hot molten plastic flowing through a conductive extruder nozzle.
And a fan continuously blowing air over the nozzle and work piece.

The above is a very good recipe for static electricity :) Whenever the relative humidity droppled below about 50% the machine would start crashing randomly. Throwing away three or four hours worth of printing was starting to get a little frustrating so I went in search of answers.

The recommended fix in the BFB forums is to run a steam humidifier next to the machine. I did try this and yes it worked...

However I have some fundamental engineering, ethical and financial issues with this as a fix:
The machine as it is uses about 50W and the humidifier uses another 250W, Ethically I have an issue with increasing the power consumption of a machine by 6x just because of a design flaw. From an engineering point of view a lot of humidity around electronics and bearing surfaces is never good. And it makes the room damp in winter!

So I started poking the machine with  combination of zener diodes, capacitors and LEDs when something went pop. A wayward multimeter probe let the smoke out of the $25 extruder motor driver IC, bother. (feel free to insert non PC substitutions for bother which I may or may not have used at the time)

Above is the smoked 28pin T-SOP device sitting on my fingertip, it was removed with the judicious application of hot air from my SMD rework station.
The new IC was attached using solder paste, said rework station and a little swearing.

With the machine working again, my attention turned back to fixing the crashes.

On the right is a rather mediocre hand drawn circuit diagram on what I came up with to solve the problem.

The 220nF capacitor serves to soak up any high frequency noise and spikes while the 3.3V zener copes with overvoltages. The LED serves to increase the forward voltage and leakage resistance of the zener to a level that doesn't affect the temperature measurement accuracy. It also flashes whenever there is a decent static discharge to the thermistor :)

So far the machine has run for about 30 hours without any signs of crashing or glitches, long may it last.

Again on the right are the zener, capacitor and led soldered somewhat crudely to the extruder connector for now. Also of note in the picture, the extruder motor driver IC.

Driving the RapMan rapid prototyper

The following is a few pointers on driving the RapMan prototyper WelTec purchased in late 2009.

Destruction Manuals:

All the documentation is online in PDF format, the build manuals are 3d PDFs meaning they're best viewed with adobe reader. All manuals are on the Bits From Bytes download page. The version 3.0 manuals apply to our machine.

The build manuals should only be needed if something breaks.

Information on machine setup such as setting the Z axis height is all in the operations manual.

Skeinforge:  The application that slices STL files into layers and generates the gCode tool paths.

The Skeinforge Wiki has information on how to install and configure skeinforge.

Skeinforge announcement and trouble shooting blog

Skeinforge settings for different plastics:

Polyactic Acid (PLA)

ABS

More to follow...

Building a Part:

Start by generating an STL file from your 3d CAD package of choice.

Open Skeinforge and select the material profile you want to use.

Click the Skeinforge button to open the file you wish to process.

Skeinforge will appear to "lock up" until is has finished generating the tool paths.

Once Skeinforge has finished there will be a YourFileName.bfb file in the directory the STL file was opened from.

Copy the .bfb file into the root directory of a FAT32 formatted SD card.

Insert SD card into the machine and refer to operation manual on how to run the file.

RapMan's first creation :D

The plastic filament I ordered from Vik Olliver for the RapMan arrived today.

Sooooo tomorrow morning (Friday 15th of January) at 09:30 we're going to be doing the first build at work in Petone.

Let me know if anyone wants to drop in and take a look.

RapMan's Hello World!

Today the incredible machine printed it's first ever test part :-D (the white squiggles on the build table)

Apart from a bit of a feed issue that you can see in the centre of the build table the machine seems to work OK.

I'll be taking the machine into work on monday if anyone wants to see it.

Time to order some ABS filament so we can start making stuff :-D

It's Alive MWAHAHA

Yesterday I finished the construction of the extruder assembly.

I have now finished off the wiring and installed the extruder into the machine.

The machine is warming up for it's first test print :-D

Time to evict the spider and do some work :-D

I've been neglecting to work on the RapMan a bit lately. As the photo above (woohoo macro lens) shows a baby orb web spider who decided that the machine looked like a nice place to build a home.

Once the spider was safely relocated to the outside world I started on the wiring:

Both the X and Y axes are now connected to the controller PCB, It makes cool whirry noises now :-D

Belts and a Build Surface

Yesterday I fitted the drive belts that transmit the drive from the stepper motors to the X and Y axes.

Also fitted is the build table (clear plastic plate in the middle) which is moved by the Z axis. When the machine is running, parts are printed onto the build table layer by layer.

The Z axis lowers the build table by about 0.1mm after each layer of the part is completed.

Tomorrow: Starting on the wiring and the construction of the plastic extruder. Smoke testing is rapidly approaching :-D

Slidey Stuff

The RapMan kit is now fitted with both X and Y axes.

Other items of interest:
The Y axis motor and drive shaft.
The Carrier for the extruder, mounted on the X axis.

Signs of Movement

Yesterday (Yes WORK on Christmas day) I got the X and Y axis slides installed.

Installation of the bars that the linear bearings run on took much use of the eyechrometer. This is due to the bars needing to be perfectly parallel.

The beast is starting to get quite heavy... I may not be photographing it on the deck soon.

Due to the design of the clamping parts things keep slipping around from time to time. If the fastenings are tightened any more the magic CLICK comes out of the acrylic and I'm delayed by another 12 hours waiting for glue to dry. Hopefully it will stay square enough while building parts.

RapMan Squared :-D

Well I have all the cross braces installed and I "think" all the sides are now square as they will ever be...

Several hours spent on the Bits From Bytes forums revealed that the supplied assembly jig is 2mm longer or shorter than it's supposed to be...
Needless to say short of creating a temporary black hole in order to adjust the laws of physics. Pythagoras' theorem is always going to apply...

Applying TLAR (That Looks About Right) my eyechrometer and mostly ignoring the jigs seems to have worked.

Another New Toy to Build!

Firstly a little history:

A while ago the rapid prototyper at work let some of it's magical blue smoke out. While discussing the options around the round table, I suggested we look at the RepRap project.

About two weeks later I was emailed a shipping confirmation telling me that our shiny new RapMan kit from Bits from Bytes was on it's way.

Now that exams, pyrotechnics, a music video and visiting family are all over I've been able to get started on the build.

First Impressions:

My camera barfed while writing to it's memory card so I lost the unpacking pics :(

A lot of the laser cut acrylic parts have stress fractures in them :( I've only seen this happen after cleaning laser cut acrylic with xylene before.

After three days I now have a cubical structure assembled that is proving very difficult to get square.

Adding to the fun I managed to break a couple of the acrylic parts... Solvent welding the breaks with trichloroethelene works but it takes aaaaaaagggges to dry. Where did I hide that tube of super glue?