Volumetric Stage Two

This seemingly innocuous calibration part was produced with a rather interesting set of numbers.

When extruding, the volume extruded (V) in mm³ is equal to πR²E, where R is radius of the filament, and E is distance passed from skeinforge/sfact via gcode.

For gcode to be printer-agnostic, we need a universal unit for filament extruded.

If we choose mm³ units, then we must solve D for D=2R, V=E, V=πR²E and feed this to skeinforge/sfact. The result is D=2.√(1/π), or about 1.128mm. Filament of this diameter would have the curious property that 1mm (length) has a volume of exactly 1mm³.

We must then alter our firmware to accept E in units of mm³, and adjust all the corresponding speeds appropriately. I had my sfact tuned for a filament diameter of 3.0mm. π(3/2)² is almost exactly 7, so all speeds must be multiplied by 7, and retract distance must also be multiplied by 7.

So, with diameter = 1.128 (orig. 3.0), E_steps=90 (orig. 635), retract distance = 12 (orig. 1.7) and retract speed=400 I produced the pictured calibration part.

Next step: move retraction into firmware! It's unlikely that we're all going to have printers that need to suck back 12mm³ of filament!

ps: my extrusion width is set to 0.5mm rather than the default 0.6, so the pictured reading shows a fairly well calibrated set of numbers :)

And the Printing continues

I've printed, broken and adjusted lots of things since my last post. I've taken my frankenmendel to a science expo and had a lot of people very interested. I've submitted a few things to thingiverse. I've snapped my Z belt a few times, I've had pulleys spinning on motor shafts despite set screws on all four axes at different times. I've added springs under my bed, reshaped the bed clamps, replaced parts with ones I've printed, ripped up my tape with the nozzle countless times, had wires falling out of my electronics... It all seems to be settling down though, anything that comes loose gets blasted with the hot glue these days!

Here's a quick photo tour:

Herringbone Extruder Gears Cube Gears Lash Maze modified Y bracket Heart Crown Spool Holders Butterfly, two colour Frame Vertex Frame Vertex Complete Electronics Mechanics

My things are on thingiverse if you're wondering.

First Print!

Just finished my first print!

Material: 3mm Orange PLA
Layer height: 0.35mm
Nozzle diam: 0.5mm

Something happened here, printer randomly decided to slow down to about 10 steps per second and start driving out into space. I paused it, cut off the blob with my dremel and hit resume. It seemed to go okay from there, but there's a noticeably bad layer through the middle of the object. I hope it won't affect it too much.

Here's the object still stuck to the bed

And here's the other side so you can see the bridges. They're a bit stringy, but good enough to print over the top of. Not bad for a first print :D

I calculated my E_steps_per_mm instead of measuring it, seems like my calculations were good! :D

Calculation was 3200 [steps/rev] * 39/11 [wade gear ratio] / 6.75 [hob effective diameter] / 3.1415926535 [pi] = 535.0

For those curious, that's cheap cloth tape on the bed, probably PVC or something. I just couldn't get this PLA to stick to the bare glass.

Extruder failure!

After my success with MakerGear's new SS barrels and thoroughly enjoying my heatsink mounting system, I tried printing some PLA. This involved switching barrels for a brass one with a 3mm bore that I had lying around. I decided to try reusing my heatsink mount to see how it would go with the brass barrel, and also because I didn't want to have to take my entire wade's apart again to put on the groovemount that came with this barrel. A few short minutes after getting it all warmed up and squirting hot PLA at 200°C, I noticed the following:

Extruder failure Extruder failure Extruder failure

Considering that this same wade's and carriage had been perfectly fine printing nylon at 290°C, it becomes evident that the stainless steel barrel and its thermal break had far more to do with that success than my heatsink!

The heat really likes travelling up that brass:

How am I gonna clean this?

Now I know why everyone's adding fans!

One of Greg's Accessible Wade's has been earmarked as the first thing to print for quite a long time due to how much of a hassle it is getting around this classic wade's. It seems my hand is being forced.

I think this is salvageable...

And It Begins!

Here's my first print!

Something happened to the comms after that little bit, and I was so excited that I pulled it off the bed and ran off to show people before taking photos which is why you can see that it's not stuck to the bed.

First Print

First Print

First Print

That's the 1.65mm nylon weed trimmer line I showed yesterday at 290°C nozzle, 110°C bed- printing nylon apparently requires an excellent hot end!

Calibration, here we come!

Hot end mounted
Mounting detail

With a new X carriage that actually has room for the heatsink (courtesy of Auzze), it's now time to start calibration!

It's been a long road getting here, and would have been quite a bit longer without the generosity of the reprap community. My first post in this blog was November 3, 2009! So, almost 21 months later, I'm just about to start :D

Hobbed Bolts

Here's the bolt I've been using in my latest round of experiments:

Home-made Bolt
Home-made Bolt

As you can see, the teeth are crudely effective. This bolt was made with a hand-held cordless drill and an M6 tap, and it shows! Also, due to the short shank, I had to insert them backwards, with the nylock in my wade's gear and the bolt head on the back- a less than ideal arrangement. If I had a lathe I could perhaps have cut the teeth straight into the threads, but that's almost impossible with a hand drill.

Auzze generously decided to send me a preview of some hobbed bolts he's going to sell via his online shop (still under construction), pictured below:

Auzze's Bolt
Auzze's Bolt

I think these will be far more effective, and at the very least more uniform! Unlike my dishevelled creation, these actually have a groove for the filament to ride in. The position of the hob is slightly different to mine, but some washer swapping had it lined up perfectly

Between Auzze, GregFrost and the various RUGs, it looks like Australia is really starting to get its reprap on!

Experimental MakerGear Hot End

The amazing and lovely folk at MakerGear sent me an experimental 1.75mm barrel (2mm bore) for my experiments with nylon.

WARNING: when heated, nylon can emit hydrogen cyanide, a gas that's deadly even in low concentrations. osha.gov lists MAXIMUM EXPOSURE to a mere 10ppm over 8 hours! Nylon also emits a number of other noxious gases such as Carbon Monoxide. Please see a MSDS before switching your printer to nylon, and install adequate ventilation!

Having said that, this barrel should work beautifully for anyone needing higher temperatures to print at speed, or experiencing jamming issues. Read on!

Experimental SS Barrel

It's stainless steel, which has 7.5x lower thermal conductivity than brass. The notch in the middle is a thermal break, to give us a very short thermal transition from <T_glass to >T_melt, which should help massively with the jamming I've been experiencing with the regular brass barrel conducting heat far up into the insulator, as well as my hot-end having difficult achieving target temperature.

I have also added some felt insulation to my heater to help it reach target temperatures of 260°C and above:

With Insulated Heater

Even with this excellent barrel material and carefully cut thermal break, we can help sharpen the thermal transition even more by adding a heatsink just above the break.

Heatsink All put together

And does it work?

New Possibilities

So far my experiments have simply been pushing some filament through, then leaving it for a while, coming back and pushing more through. This was impossible with the brass barrel, the heat travelling up would cause the nylon to swell, and jam in the barrel without melting. With some wider testing, this barrel could be a contender for the title of "jam-proof"!

Here I am holding the heatsink while the nozzle is at 260°C! That's over 200°C dropped across a distance of about 2.5mm!

Thermal Break Is Effective

My only complaint is that it's not long enough at the top- there's no room between mounting plate and heatsink for M4 nuts, let alone a carriage. Rick informs me that they will be made longer before appearing in the shop.

As soon as my new X carriage (with room for the heatsink) arrives, I could be printing!

---

Update: After almost exactly an hour, the felt turned black and started smoking. Apparently it's great at 110°C but can't take 260°C, or maybe my felt isn't pure wool felt. I may just keep heating it until it's all carbonised and see if it settles down or falls apart.

PCB Heated Bed

Overview Thermistor

Here's my homegrown heated bed. I decided to make my own because prusa's needed a bigger board than I had available.

Resistance measures at 0.9 ohms although my multimeter isn't exactly accurate with stuff like that. Eagle's length-freq-ri ULP also pegs resistance at about 0.9 ohms.

It reaches about 116°C with ambient of 10°C, a felt underlay, and my power supply's 12v rail drooping to about 11.3v despite two 12v 50w lights loading the 5v line.

Here's the eagle BRD file for those interested: Heated Print Bed.brd.

Straightening my wade's idler

Just need to add a proper surface now, and see how it goes!

First Extrusion! Working Axes!

First Extrusion! Very Exciting!

I haven't posted in a while, been waiting for parts, money, ideas to come. Over the past couple of weeks I've made significant progress though. As you can see below, my printer is no longer all wood, and so this blog is probably now rather poorly named, however I'll keep it here until I can think of a better name.

Here's the current state of my frankenprinter:

Output Side
Top View
Electronics
Z Belt Tensioner

All the axes are working, if a shade stiff. Now I need to construct a bed somehow, and I can get printing!

I have bought a piece of blank PCB which I'll etch a heater pattern onto. Here's my current design:

Heater Pattern
Please comment if you think this won't work, or will work well!

Big thanks to Mark Lagana and Greg Frost for printed parts, MrAlvin for the mega (and a ramps board not pictured- I'll use it when I get around to removing my pololus from my current board, or have to replace them), and MakerGear for a lovely hot-end

FiveD on Arduino Firmware: First confirmed print with photo!

First confirmed print

FiveD on Arduino firmware reached an important milestone today- first confirmed print with photo, reported by Markus Amsler here in the forums.

Big thanks to Jake Poznanski, Markus Amsler, Markus Hitter and Stephen Walter who have all provided heaps of patches, to those who have provided just a couple of patches to scratch their personal itch, and also to all those who have simply tried this out and reported how they went :)

For those of you just viewing this now, forum, source, wiki and I can occasionally be caught on the reprap IRC channel too.