Last week i have been experimenting with lots of different things, maybe even too many. Actually i felt lost a few times in between so many new variables and thing to control at the same time. But i had extract a few interesting conclusions.
First i tried to cook eggs using a typical pcb hot bed. First i tried to cook to the proper unfold-proteins-cooking temperature for and egg around 63 degrees. Soon i realize that if i wanted to achieve a faster cooking i must need to hardcorely increase the temperature. In the next video you can see some syringe-handmade eggs. Ikea thermometer said it was around 130ºC.
My goal was printing an omelette. But i realized that beaten eggs contains too many suspended particles that easily blocked my needle-nozzle.
Having a bigger id nozzle partially ”solved” the blocking issue, highlighting as well some peristaltic pump design issues (more later).
Half a dozen eggs later i decided to quit (for now) my “dream” of printing an open hardware omelette. Mainly because there was too many variables uncontrolled at the same time. Liquid (beaten eggs), solidification temperature and peristaltic pump issues.
I switched printing material to Jelly. The Jelly show time! Jelly is and awesome printing material. Cheap, perfectly extrudable (no obstruction) and with enough consistency to support several layers.
Also i froze one sample for around 30 minutes.
Last but not least, i wanna explain some of my conclusion about the new PLYUMP version 0.4. The one its been used for the last week experiments.
Some pics first.
I am gonna commit all the files to the repository (branch v0.4).
Comparing to version 0.35b it is way smaller and easier to print. Has less rollers and consequently less bearings.
The rotor shaft position can not be adjusted, its fixed. This fixes the pinched tube force. Being able to adjust it, reduces the the motor torque required what would be a nice feature (for next version).
Motor position is awful. The motor gear giraffe neck makes no sense. Increasing the gears diameters will allow to flip the motor upside-down and reduce the total bulkiness.
Probably the most difficult issue to explain is the interior pump wall design proooblem. I try.
It has two parts.
The first one is a curve which radius matches the rollers position plus the pinched tube. It has a angle dimension a little bit bigger than the angle between rollers.
Its duty is to guarantee that at any rotor-spinning-time its going to be at least one roller pinching the tube “forcing” the pump effect. The shorter the curve is, smaller will be the friction, then less torque is needed.
The second part its just used as a support for the pump and its actually where the pinched tube is released. I designed version 0.4 just paying attention to the first part. But in fact, i do believe now, the second part has a bigger role! Because controlling this part we can control the released of the tube, which has a direct impact on the pulsation effect. Faster the tube is released faster will be the pressure variations between the pump and the nozzle-needle. If this pressure changes are too fast our “pressure tank” can not “eat” the pulsation.
When i say pressure tank i am talking about the effect used to linearize the peristaltic pulsed output by using a silicone tube between the peristaltic output and the nozzle, containing enough pressure to even the flow. The pressure is build up because the nozzle interior diameter is smaller than the peristaltic output peristaltic.
Well i think for today its more than enough, as always i might be wrong about my theories, but wont know until the next version ;)
If you read the whole text block you deserve a beer if we ever meet! so write a comment and claim your prize!
My awesome girlfriend teach me about having fun at Carrefour. At first i was quite skeptical. But with time i have discovered what an awesome place for ideas and resources Carrefour it is.
Today’s experiments consistsss of using a whipped cream can as a extruder for my 3d printer.
Here you have the first test.
jajaja i was fool enough to think that just like that was going to work! jajaja The issue was that i tried to reduce the tube inside diameter too much, without fasten them properly! so boooooom, the pressure inside was enough to “ruin” my first try!
its was a sweet explosion ;)
I was not going to stop until i try it on my printer. So i did…
At the end I find out that whipped cream so far isn’t the most reliable source to pursue a compressed gas type of extrusion. And its not because i said so, MY MUM DID!
Was a nice, sweet and fun Sunday experiment! Anyway i am sure one day i will try again maybe with some new ideas!!
Lots of things happened lately but instead of explaining them let’s focus on whats going on now!
Thanks to some awesome FEEDBACK i decided to go back to my previous peristaltic extrude without caring about pulsation.
So this weekend i have been doing some test printing different viscous liquid. To probe that the first version (0.2) was able to “print” without pulsation thanks to the silicone tube between the pump and the needle. The tube worked as a pressure tank that once is full “eats” or reduces the peristaltic pump pulsation.
First i tried cuajada. Cuajada is kind of a yogurt not as runny as water, but thicker than peanutbutter.
This first attempt showed the main “pressure tank” issue. Whenever the extruder stops, the existing pressure within the tube tends to keep the flow on, dropping some unwanted liquid tears. A few tests later i could “overcome” it with some hardcore and proper retraction.
The problem with cuajada and other kind of similar viscous liquid is that by itself can not hold 3d structers (lower layers can not support the upper ones).
So i had the cute idea of using a thicker material. Here is where peanut butter came to my mind. I had no idea what i was doing, but i decide to give me some credit and just try it!
First problem, peanut butter is waaaaaaay thicker, its so thick that the extruder could hardly pump it without collapsing, might help a bigger tube, but i was already into it. i did lower the flow rate to 1mm/sec. Might not be the fastest printer out there, but as probe of concept i am more than happy :)
Also i am not sure if its the first 3d printed peanut butter open hardware logo in the world. But i bet its in my neighborhood, not 100% sure though ;)
The printing its taking over an hour. So i just post a short video.
Taste quality control.
At the end of the day, I just can affirm printing food smells much much better than ABS!
Yesterday i did my first “whatsover” peristaltic print.
Today i am gonna do some more trials or attempts. I had decide to mix yogurt with some powder in orde to do a thicker liguid. Also i am planning on start playing with some Skeinforge settings to “improve” my print.
After some random new skeinforge setting, removing one bearing and cutting one centimeter of the peristaltic inside tube i manage to print this:
The funny part about this is that i can still appreciate pulsed effect, stilll i am quite “pleased” with this attempt!
At very low speed the pulsated-flow is quite obvious. Increasing the speed obviously reduces the pulsation, but around 1100mm/min the pump doesnt “seem” strong enough. The tubes at fast speeds cames out, or gets stucked between the bearings and the plastic gear.
Maybe running a really fast peristaltic pump kind hide the pulsations problems, in somehow doing a liquid PWM where the modulation is controlled by the peristaltic pump “pilow” distances.
Nozzle: sillicone tube interior diameter 5mm
My feeling is that has less pulsed effect, but is a feeling not a fact so i dont know ~~~~
Nozzle: syringe needle
Wow! interesting effect! Using a thin nozzle, reduces the flow, but creating a pressure cabinet inside of the tube thtat goes from the noozle to the pump, this pressure seems to even the flow ~~~i keep saying seems.
who knows maybe using some hardcore retractions i can solve this or using some valves, anyway! today is new years eve and is time to celebrate!!!
Today i am printing a new version with tube diameter 3.5. Also i fix some distances in the files.
Making the tube diameter bigger makes the pump stop working, not enough pressure. Actually i can breath through the tube! not soooooooooooooo good ~~~
Now i am trying to reduce the output tube angle to get more more “even” position of the peristaltic gear. Maybe in the future i can try some planetary gear to use the motor as a gear shaft ~~~ but meanwhile i take it easy! ok i better go!