Mount and Reservoir Discussion

[jontelling]

Aha, didn't know about peristaltic pumps. One of those would work great and be much cheaper than I was thinking.

I may make a syringe pump one day

[Toasterboy]

Reading the peachy beta kit instructions, it looks like the calibration step is smart enough to scale the Z per "drip" based on the height provided. Is that correct?

If so, and we replace the basic dripper with a peristaltic pump, it seems like the drip contact detection mechanism should still work about the same. If the volume of the pulses from the peristaltic pump is small enough that the z-level rise in the container per pulse is appropriate for the target layer height (i.e. operates at a similar scale to dripping in a small container does), I would think it would be OK. Looks like I can get an appropriate 12V pump (one which pushes 20-100ml per minute) for about $10 plus power supply (I have a 12v dc controller for a train that should work for testing). May be a very easy mod?

So....that still leaves the question of what the maximum deflection angles the printer can support are, so it doesn't have to be mounted 30' in the air to get larger build volumes.

[jontelling]

Reading the peachy beta kit instructions, it looks like the calibration step is smart enough to scale the Z per "drip" based on the height provided. Is that correct?

If so, and we replace the basic dripper with a peristaltic pump, it seems like the drip contact detection mechanism should still work about the same. If the volume of the pulses from the peristaltic pump is small enough that the z-level rise in the container per pulse is appropriate for the target layer height (i.e. operates at a similar scale to dripping in a small container does), I would think it would be OK. Looks like I can get an appropriate 12V pump (one which pushes 20-100ml per minute) for about $10 plus power supply (I have a 12v dc controller for a train that should work for testing). May be a very easy mod?

So....that still leaves the question of what the maximum deflection angles the printer can support are, so it doesn't have to be mounted 30' in the air to get larger build volumes.

From the other thread Rylan said the drips as the z-axis can be out by 5%, but a peristaltic pump is 1%. As you say the drip detector should be be the same so it should work great and better than a passive dripper.

I can see speed printing becoming a thing,

[rylangrayston]

Hey Tosterboy
The peachy printer is very easy to modified and it was built with that in mind, including the way we write the software.
You can definitely signal the drip detection pins with other things like photo interrupters or reed switches, what ever you like.

As for deflection
We typically print with deflections of up to 20 degrees ether side of zero. ( so 40 deg total swingl)
But even the peachys max deflection is very easy for you to change by changeing the spring force ( moving a few magnets)
By lowering the spring force you can get the mirror to go a full 180 deg (not that the laser will hit the mirro at this point, but you cant do it.

We have yet to Write a feature where you get N calibration points. ( Right now you just get 8.)
and because higher deflections require dealing with many none linear we ares We plan to avoid them for the time being.

[oninoshiko]

hopefully the community will help with a lot of these kinds of mods and experiments once we start seeing more peachys out there!

[Toasterboy]

Awesome. 40 degrees of deflection is great. With those angles, 10' of height (e.g. a ceiling mount) gives you 7.2' square of surface below the top of your build area, so this seems like it's already operating at a good scale for doing very large prints.

How long does the laser need to cure each layer? Say, if you are targeting 1 micron layers or so. This is important for understanding how much acceleration of the dripping actually makes sense to attempt. Does the software compensate (or need to compensate) for longer cure times at the larger outside angles ?

Oh, what is the interface for the 2-way digital communication? Is it going to be possible to signal a drip command and/or other parameters? Would be sweet to digitally control the dripping. I have also been thinking about using a used automotive fuel injector; they typically have open/close times in the neighborhood of 2ms, so an injector would provide excellent digitally controllable variable drip size and frequency, though it would also require a pump.

Thanks again for the great work on this printer project. I can't wait to get my hands on one.

[oninoshiko]

Awesome. 40 degrees of deflection is great. With those angles, 10' of height (e.g. a ceiling mount) gives you 7.2' square of surface below the top of your build area, so this seems like it's already operating at a good scale for doing very large prints.

How long does the laser need to cure each layer? Say, if you are targeting 1 micron layers or so. This is important for understanding how much acceleration of the dripping actually makes sense to attempt. Does the software compensate (or need to compensate) for longer cure times at the larger outside angles ?

Oh, what is the interface for the 2-way digital communication? Is it going to be possible to signal a drip command and/or other parameters? Would be sweet to digitally control the dripping. I have also been thinking about using a used automotive fuel injector; they typically have open/close times in the neighborhood of 2ms, so an injector would provide excellent digitally controllable variable drip size and frequency, though it would also require a pump.

Thanks again for the great work on this printer project. I can't wait to get my hands on one.

If memory serves, one of the project goals was to try and print a full-sized canoe, so large prints was always something that needed to be possible.

[rylangrayston]

Awesome. 40 degrees of deflection is great. With those angles, 10' of height (e.g. a ceiling mount) gives you 7.2' square of surface below the top of your build area, so this seems like it's already operating at a good scale for doing very large prints.

How long does the laser need to cure each layer? Say, if you are targeting 1 micron layers or so. This is important for understanding how much acceleration of the dripping actually makes sense to attempt. Does the software compensate (or need to compensate) for longer cure times at the larger outside angles ?

Oh, what is the interface for the 2-way digital communication? Is it going to be possible to signal a drip command and/or other parameters? Would be sweet to digitally control the dripping. I have also been thinking about using a used automotive fuel injector; they typically have open/close times in the neighborhood of 2ms, so an injector would provide excellent digitally controllable variable drip size and frequency, though it would also require a pump.

Thanks again for the great work on this printer project. I can't wait to get my hands on one.

The software dose no yet do exposure compensation for the laser spot becoming elongated at higher deflections, but this is planed.
Since the laser spot isnt round It draws like a calligraphy pen ( its a very suttle effect) but that hasnt been accounted for in exposure ether.

how long would it take to cure a 7.2 ft long layer (say were printing a 7.2 foot long wall) from a celing mount....
The peachy printer software dosent use accelaration yet, instead we just go the speed at which we can turn a sharp corner and still have it look sharp.
Which is about 1 second per 40 degrees of deflection. But by the time we ship acceleration will very likely be working so the printer will be much faster than it is now.
ok so we know that we can go about 7.2 ft per second in this masive setup what is that in mm per second
7.2 * 12 * 25.4 = 2194 mm per second is the speed the laser spot would be travleing.
To expose the resin at that speed we will need lots more laser power.
typicaly in a small printer we go at 100 mm/s so now we need 22 times the laser power of a standard setup ( 2194 / 100)
I cant quote exactly how many mw a standard printer emits just yet.

now here i need to be careful I dont want anyone to think that a normal peachy printer emits an extremely powerful laser beam, that can burn the flesh on your arm...
We have put various measures in place limit the laser power to safer levels, so that you only need laser saftly glasses, and or a good enclosure around your printer, to be safe.
We also dont want the diodes to burn out so we are shipping diodes that are over rated for the job, technically they could handle emitting 50 mw with no aperture and a heat sink.
Which would be very dangerous to the eye! For liability reasons im sure its a bad idea for me to explain how to make the laser more powerful but I trust the community of expert hackers here has all the skills necessary to thwart our safety measures and get a printer to emit more laser power.
So I will just end with a warning, Lasers can be really dangerous, make sure your taking the necessary precautions, alwase where laser safety glasses, not just normal safely glasses and build a completely enclosed printer, so that when others walk in to the room unexpectedly, they are safe too.


As for a hack to tell the peachy that you have just Put water in the printer.. There will be lots of ways to do this but here is one I did just yesterday it works like this :

paristaltic pump shaft > IR inturpt sensor > arduino( with debounce script) ----voltage divider----> peachy printer circuit ----USB---> peachy printer software

Peachy circuit is 3.3 volt hence the voltage divider between it and the arduino and the 10k resistor between the peachy circuit and ground makes me feel safe if i happen to create a ground loop between it and the arduino. So when pin 13 goes high the peachy gets 2.5 volts, which is over the 1.8 volt on threshold for its 3 volt circuit.

IMG_3793.jpg


and here is the debounce code for the arduino:

int ledPin = 13;
int sensorPin = 8;
int debounceTime = 1000 / 20 ;

void setup() {                
  pinMode(ledPin, OUTPUT); 
  
}

void loop() 
{
  
  if (digitalRead(sensorPin) == HIGH )
  {
  
    digitalWrite(ledPin, HIGH);   
    delay(debounceTime);
    
  }
   
  
  
  else if( digitalRead(sensorPin) == LOW ) 
  {
    
    digitalWrite(ledPin, LOW);
    delay(debounceTime);
  }
  
}

I love the injector + pump Idea , I dont know how injectors will like salt water but i know there are some injectors that put water into diesel engines ( making steam that makes extra power from the heat in the engine)
I hope you will post all about some it day.

[jontelling]

Nice informative reply Rylan. But as always I have more questions.

Do you plan (I'm sure you do) allow serial input to the peachy board? I ask as this would allow an arduino (are in my case as I had a bad habbit of blowing them an atmega chip) to bridge the gap between a PC (via wifi) or an SD card or even just tell the peachy that you added XXml to the build area of salt water.

[Toasterboy]

Yes, thanks for the great response. I'm really excited about the printer.

Are there any other I/O pins for output on the peachy board? It sounds like there is a drip sensor pin on the board ; wondering if there's another pin for output besides USB, or if the expectation for this hardware version is that the Peachy software would signal other (separate) devices (like a drip assembly) through other I/O mechanisms on the computer.

It seems like long term, the printer (or its successor) should have the capability to signal the zlevel rise directly rather than relying only on external passive decoupled drip + detection. Since the travel path of the laser for each layer is variable, to get optimal print speed it would benefit from being controlled by signal rather than depending on an external sensed rate. But I can certainly see where it makes sense to focus engineering on a whole list of other areas, like laser speed and accuracy, and variable laser focus and power output that need to be tackled first. It might be a bit silly to build a super accurate, super fast Z level control mechanism to support larger build areas if the laser speed / power needed requires minutes to cure each layer. =) Still, accurate, controlled z-level on smaller volume build areas is still useful and important.

>We have yet to Write a feature where you get N calibration points. ( Right now you just get 8.)
Can you comment on this further? 8 points for which calibration? for Z or for XY?

I picked up a used 300cc fuel injector on Ebay for really cheap. The math suggests that for the ~2'x2' container, @~40psi the injector should be held open about 80ms per pulse to get 0.33ML, the amount needed to raise 1 micron in this container. (roughly) Assuming that salt water flows similarly to gasoline, and the used injector is in more or less good condition, and the thing is actually accurate. That's a lot of assumptions. Will need to experiment and see if it's in the ballpark.

I also picked up a peristaltic pump. It's a bit hard to tell from the specs what the pulse size will be. Anyway, I can play with both ideas. What size pump are you playing with above?

I'm not going to attempt to run anything bigger than 2'x2' for now. That size is still manageable to build UV cage around for safety (not to mention it will be a while yet before you guys are ready to ship). And anyway, even if the injector can do the z-level rise at ~12.5 pulses per second as the napkin math suggests, the laser speed has a long way to go before it can cure that many layers per second (if it's even possible to go that fast).

What is the layer height you are using on your test prints? With surface tension and other effects, how would you say the printer is performing with respect to z-layer height?