Maximum Overhang?

[tinloaf]

I watched the assembly video a while back, and to me it looked like some heated rubber thing was wrapped around the dripping tube in the dripper. I figured that the printer can heat that thing to slow the dripping...

Can anyone with a printer confirm this?

[rylangrayston]

Hey guys,

I'm pretty sure, Peachy's default dripper system is uncontrolled, at least not by electronics.

Using extreme numbers:
If the water takes 20min to rise 10cm (I guess, that's a fast, but realistic print), you get .5cm per minute and during those 10sec per Layer (see videos) the water will rise about 1mm per Layer.
The Platform being maybe 5cm wide, this gives you 88.5°.
Seems pretty close to 90° to me (As I said before, I think, these are really extreme numbers).
Making the dripper slower (I guess, .2cm per minute is a realistic value) you can get angles as close to 90° as you want.

Greetings,
quertz

Ohh napking math time ...
here is how I would do it.

we have 100 layers per mm so each layer we move up 0.01 mm, and standard .7mm laser spot size ... lets say we need to over lap the spot by 75 percent each layer to make sure the layers connect( this is very untested)
so every 4 layers we move .7 mm over and .04 mm up and Im feeling lazy so ill go here http://www.cleavebooks.co.uk/scol/calrtri.htm
I get 86.7 deg

wow our napkin math answers are very close quertz!

here is a pick of a rook printed with the standard v1 kit printer:
aa.jpg
The rook has stairs that have rather flat tops:
aaa.jpg
With the flat tops lit just right from behind, and a macro lens we can see what appear to be layers!
seeing individual layers is very rare... sometimes we see artifacts that look like layers but are some other effect like break over. In most situations our layers are to small for the human eye to see:
a.jpg

PS that last pic is my favourite peachy ever

[Slatye]

Umm you sure about that.
I understood the even on the original model the dripper was controlled.
Either that or the laser has to cover the entire surface of the print vessel for every single layer. Which would set a specific print time per layer that would allow any part of the surface to be printed.
Otherwise it would be impossible to print different things on each layer - the very definition of 3d printing.
Either way you can print the entire surface per layer.
And the resin must be less dense than the water otherwise the whole thing just would not work.

The dripper is only "controlled" by a manual valve - the printer itself can't change the drip rate. As Synchron has said, if you replace the dripper with a pump then you can print a perfect 90 degree overhang, or maybe even more (in that you can run the pump backwards and effectively re-print earlier layers, as long as the parts you need to access aren't shadowed by parts already printed).

To be able to create absolutely any part (with overhangs to 90 degrees, but no more than that) with the whole surface being touched at every layer, you would indeed need to set the drip rate to a very low level so that the laser would have time to cover the whole print area. This is not practical. Instead, you make an estimate at how much of the area the laser will actually need to cover (probably something like 1%, since you'd normally just print a shell rather than a solid object) and set the dripper to allow that much time.

Because the layer height is so small, the laser can probably cure a couple of layers at a time - so if it takes three layers to get to every part of the job then it'll probably still be fine (although possibly not as smooth).


The challenge is when you do want a very large amount of stuff done on one layer, like a big flat surface. If you want to print fast, you need active water level control so it can slow down for this part and then speed up for others. With the dripper, you'll just have to turn down the speed until the result is acceptable.

[Morten]

So overall print speed can be optimized if we augment our Peachy with a micropump of some kind, and for some prints this can be a dramatic increase? Has anyone started trying to use a motorised pump yet?

[CescoAiel]

I'm just new to the Peachy (learned of it from a friend), but AFAICT negative overhangs can also be done in theory, as long as you tether them with a (very thin) tether from the base (or a suitable part of the object)... As long as they're not completely free floating from the point they start at, it should work...

I'd love to see an option for a controlled pump in the peachy, and some kind of measurement device so it can keep track of the factual level, and not just the estimated level. Supersonic echo-location (distance measurement by high frequency sound wave) has become pretty accurate, and could be part of the setup in this.
It would allow the Peachy to control the rate of rise as well as reasonably accurately (not in single layers, but close enough) measure the actual levels. (If only to be able to assess the pump/drip rates as it prints...)

[harpo99999]

quick question re the accuracy of the measuring, is it able to repeatedly measure to the 0.001mm level or is it a LOT coarser than this?as with the drop meathod it is possible depending upon the container dimensions to get near to the 0.00001mm resolution

[CescoAiel]

quick question re the accuracy of the measuring, is it able to repeatedly measure to the 0.001mm level or is it a LOT coarser than this?as with the drop meathod it is possible depending upon the container dimensions to get near to the 0.00001mm resolution

No, it is much coarser than that IIRC, which is why I mentioned using it as a way to maintain a continuous active calibration (And possibly use it for initial calibration too). It may not be able to measure 0.0001m, but it can average out that 50.000 drips is still 10cm (for instance)...
Standard laser would be more accurate (up to 1mm approx, IIRC), but there are 2 issues with that: 1) possible unintended resin hardening (if there is a UV component) and 2) the resin may be too translucent for it to reflect reliably.
And of course, the more precise the measurement instrument, the more expensive it is...

I don't have all the answers, obviously, or I'd have made the printer myself!
Just trying to think how we could improve reliability without breaking the bank!
(As a matter of fact I have plenty questions myself, and will start asking once I have read through the topic lists, so I know what has or has not been answered yet)

Hmmm... Interesting read I found when I started googling: http://www.olympus-ims.com/en/applic...ckness-gaging/

[harpo99999]

that was an interesting read regarding the thickness gaugeing but the article implied that it was mostly for testing solids, not delta distance in atmosphere to a liquid that would be usefull for the peachy

[CescoAiel]

True, but it does seem a reliable measurement can be gotten that way. Possibly by submerging the sensor in the fluid, we could get better results (measuring delta is more important than the absolute level here. We can give it a one-time offset to compensate for the measurement difference too, so the absolute is corrected)

[harpo99999]

the main catch as I see it is the interfaces between differing materials ie salt water to resin to air and each having differing speed of propigation of ultrasonic sound, and assuming you are placing the sensor in the salt water to get the 'z' height then there is the corrosion issue for the sensor, and if my understanding is correct the higher frequencies are used for the higher accuracies/smaller distances