The definitive solution, which mimics form1

[mike_biddell]

I have started a new thread because the other one was getting rather long.

1) We use ordinary water, so that the resin sinks (this would allow the use of heavy fillers which is what I was after).

2) The laser fires through the bottom of the tank (where the resin is)

3) we drip in water from the upper tank using the existing calibration and valve

4) A floating platform (loose interference fit to the tank walls), sitting on the resin rises up on the water and pulls the print upwards

Voila, no O ring and heavy resin fillers possible. One extra part, the floating platform. We know this works amazingly well from seeing the Form1 prints and the peachy team need only make one extra part, the floating platform. Plus you dont have the bother of making brine.

[Compro01]

Interesting idea.

Though one potential issue I can see is making sure the platform is light/buoyant enough that it doesn't sink/fail to rise consistently under the weight of the print.

[mike_biddell]

the print is virtually weight neutral because of archimedes. decent floats in the platform, will carry a lot of weight anyway

[Keldor]

I would be worried about the print sticking to the bottom of the container. The Form 1 uses a special tank with optically clear silicone in the bottom. It's an expensive part.

[mike_biddell]

you could stick piece of cling film (stretched tight) to the base, before the printing starts.

[Anuvin]

Which problem are we trying to solve again? Because if it's just a laser focus problem then SpellJammer beat us all to it.

[mike_biddell]

Which problem are we trying to solve again? Because if it's just a laser focus problem then SpellJammer beat us all to it.

This has problems:-
1) wobble due to mirror movement communicating to the raft
2) unable to use heavy resin (with filler)

[Slatye]

Not sure about everyone else, but there are two options that appeal to me.

(1) Just fit an autofocus system on the laser. Adjustable-focus lasers are trivial to find, and you could control the focus with a $2 HobbyKing servo. No need for super-high precision on the focus or a lot of travel, so a hobby servo will do just fine.

(2) Have a mechanically servoed plate that the print job sits on, inside the water bath (obviously the electronics that drive it will be outside the tank). That way you just leave the water level alone and lower the job into the bath at whatever speed you feel is appropriate. This would require a high-precision mechanism (similar to the lead-screws that FDM printers use for the Z axis) but it means that you have a reliable measurement of Z axis movement (I still don't really trust the droplet-microphone integration method).


Hopefully, of course, it'll all be irrelevant because the Peachy in standard form will be able to print anything that you'd realistically want to print (large objects are obviously very expensive, so you probably won't be printing those anyway).

[mike_biddell]

Not sure about everyone else, but there are two options that appeal to me.

(1) Just fit an autofocus system on the laser. Adjustable-focus lasers are trivial to find, and you could control the focus with a $2 HobbyKing servo. No need for super-high precision on the focus or a lot of travel, so a hobby servo will do just fine.

(2) Have a mechanically servoed plate that the print job sits on, inside the water bath (obviously the electronics that drive it will be outside the tank). That way you just leave the water level alone and lower the job into the bath at whatever speed you feel is appropriate. This would require a high-precision mechanism (similar to the lead-screws that FDM printers use for the Z axis) but it means that you have a reliable measurement of Z axis movement (I still don't really trust the droplet-microphone integration method).


Hopefully, of course, it'll all be irrelevant because the Peachy in standard form will be able to print anything that you'd realistically want to print (large objects are obviously very expensive, so you probably won't be printing those anyway).

Slatye

I like the uncomplicated drip method and should provide amazing Z resolution, but I would like to be able to print with heavy resin (e.g. copper or brass filled). I think the method proposed here will work.

The devil is in the detail and a product may be a much greater success if it marries together disparate needs. Since we have not had any experience of Peachy, we dont know how much of a problem focus is !!!!

More concerning for me is that all the sample prints so far have been long and thin i.e. not very large X and/or Y. Is there a problem with large X or Y? Presumably the linearity of the mirror deflection may be very non-linear for large deflections. After all springs only have linear deflections over a smallish range (Hook's Law).

[rylangrayston]

@mike_biddell

After reading this thread just wanted do drop in and say that I love this idea... cant wait to see it in action
like any implementation it probably has some hurdles to get it working great. We are constantly designing the peachy printer with modularity and hackabuility in mind to make
trying great ideas like this as easy as it can be.


now for my own 2 cents.


I think that the print will adhere to the bottom strongly enough to prevent
the print from rising every layer. In other words it may take more than one layer
of water to pressure the float to break the print off the bottom window.

But I still love the simplicity of the float, so what if this was solved by adding a pump, the pump could constantly do 50 layers forward 49 layers back, alwase causing the float to displace enough water to break away.

I also think this float would need some really great linear guides and a large mass to help overcome any static friction, alowing it to slide back down into position reliably. If the build platform was feather light it might go 50 steps up but then just stay stuck up there, adding mass would really help it back down.

Really looking forward to seeing this hack of the peachy!