Tuesday, 25 March 2014

-=( Powersupplies and Pwm )=-

One of my many problems with power supplies have been solved by the location of a decent supplier of bulk 180watt power bricks:

these things are advertised with overload protection and short circuit protection, and actually have it in there.

the downside to these power supplies is that it is relatively easy to  trigger the overload protection or hiccup mode as these powers supplies are designed to plug into very specific piece of equipment and usually there are capacitors built into the device.

so Marlins style of low frequency (7hz) pwm may as well be bang bang in this particular application, the solution is to make it do genuine pwm using the avr's pwm module.

after talking to Evdz on #reprap irc it turns out that it's rather simple to make use of the hardware pwm, the reason it's done with the bangbang style in software is because of compatability across the range of boards,

so inside temperature.cpp you will find this line (line number 1075):

if(soft_pwm_b > 0) WRITE(HEATER_BED_PIN,1); else WRITE(HEATER_BED_PIN,0);

 and replace it with this:

if(soft_pwm_b > 0) analogWrite(HEATER_BED_PIN,soft_pwm_b); else analogWrite(HEATER_BED_PIN,0);

what you should see now is pwm frequency around 500hz on your bed heater output, this will only work provided the output is pwm capable which for me it is on the rumba board , this could also be done on the other heateroutputs and on the fans as well if you really wanted to but i haven't quite gotten that far yet

Sunday, 23 March 2014

-=( up close and personal )=-

I have recently acquired for myself a reversing ring for the Nikon D3100, this little $3 contraption allows me to attach a lens on my DSLR the wrong way around and allow me to photograph a miniature world otherwise not possible using the lens in the traditional manner,

if you do this, do not do it with the newer plastic type lenses as there are only two threads supporting the weight of the lens , get an older lens to do this with preferably on of the many aluminium built ones that are available, it doesn't even really need to be the same brand as the camera...

Friday, 7 March 2014

-=( filament market thoughts and pla production )=-

As some of you know the filament market in Australia is somewhat interesting/weird

- On one hand we have various small companies imprting filament and reselling it and making a mere several dollars per spool.

- On another hand we have one or two big companies that dominate the import brands market for those who want cheap filament because they use a lot of it (like me).

- Then there is the one and only producer in Australia that produces PLA at $48 to $50/kg, the reason they are the only one is because NatureworksLLC's Australian distributor has an exclusive arrangement with this company to only sell them pla resin and no one else, aside from raising legal questions if anyone wonders down the track why Australian produced pla is more expensive than anywhere else in the world and priced so that importing yourself is not economically viable by comparison... you know why.

as a result the first question i ask is what does it cost by comparison to get Chinese produced pla the answer is around $10/kg or roughly double and a bit more the cost of natureworks pla we should have access to, so we are left with the only other option aside from buying it on the spool and that is to polymerize it ourselves and extrude it into our own filament,

as i see it there are basic rough 4 steps to it
1 - mix raw materials dextrose + water + bacteria to ferment lactic acid
2 - heat and apply vacuum to remove water to polymerise the lactic acid ( catalyst may be nessary )
3 - collect powdered remains and further dry
4 - run through extruder to get something hopefully resembling filament

there is a lot of detail to go into about each step and i will as i go through them currently i am going through the first bit, i am on my third test batch and so far there is what looks to be some sort of gooey jelly like substance suspended in the water which i suspect is the lactic acid but i'll know better int he morning (it's friday ngiht atm)