Things that still suck about the V1 printer - according to the founder

[User_Defined]

"It could simply be a question with laser power, spot size, layer numbers, and print time. If you print it slow and take your time it may come out better?"

yes longer print times small spot sizes and slower laser seems to help, but more than 100 layers per mm dosent seem to make any difference.
No matter what settings I use there is often some subtle oscillation leaving rings on a print, it seems to happen with a period of about 50 layers.
You can see it in this rocket, pronounced near the tip.

Attachment 6564

more layers per mm probably would eliminate the patters you can see on the tops of each stair here( altho you cant see these with just the human eye) :
Attachment 6565

my latest Theory's are things to do with the way resin flows during the print, as well as how air may be affecting the surface of the resin.
Im coming up with test prints that can help support or disprove what I think is happening. I feel like we are very close to really nailing perfectly glossy prints( as far as the human eye is concerned).

If it truly was surface tension on the print layer, one would need to explain why a straight column prints so well.

It has to be something, especially if it is evenly distributed along the print. I'm thinking software or physical/mechanical. I would see if you can line up those errors with a video of the print and see if you can spot them as they are being made.

I would also check for linearity over the print surface. Maybe the column has no variations over its height and doesn't suffer from nonlinear effects as much.

Also see if you can print different shaped columns and see where the boundary is between glassy smooth and beginning to get rough.


-UD

[mike_biddell]

If it truly was surface tension on the print layer, one would need to explain why a straight column prints so well.

It has to be something, especially if it is evenly distributed along the print. I'm thinking software or physical/mechanical. I would see if you can line up those errors with a video of the print and see if you can spot them as they are being made.

I would also check for linearity over the print surface. Maybe the column has no variations over its height and doesn't suffer from nonlinear effects as much.

Also see if you can print different shaped columns and see where the boundary is between glassy smooth and beginning to get rough.


-UD

I think it does explain exactly that. This is quite difficult to explainpeachy.jpg
I hope my cr*p sketch explains it. And you must understand this is only a theory. But it does explain why it does not affect even columns. The effect of the surface tension is to delay Z. The printer is printing Z, but as there is no resin layer on the object, therefore this printing has no effect and these Z values are 'lost'. When wetting occurs, the old Z values are not re-printed and if the object is tapering, the new X,Y values are smaller than the x,y for lost Z values, thus creating a step.
With a cylindrical object, it doesn't matter about the lost Z values, because post wetting, the x, y values are the same and the resin is hardened without a step. I hope that makes sense, it is quite difficult to visualise.

[mike_biddell]

This problem is difficult to resolve apart from printing through the bottom of the tank. But there may be a potential improvement in delaying Z. That is you print nothing for 50 layers of Z and then start printing. Then experiment with Z delay until you get the best print.

On reflection, this wont make any difference, there will always be a point where you are printing with a bulging meniscus and no resin on top of the print and hence you are printing into 'thin air'

I'm rambling on ..... LOL........... heating the resin could significantly reduce the surface tension of the resin and could be worth a try

I've just thought of a serious contender for a solution. As you will know, surface tension is the uneven pull of the molecules into the surface of the fluid, because there are no molecules above to pull equally. Well why not float say 1 cm of ordinary tap water on top of resin, to equalise the pull and neutralise the surface tension. Firing the laser through the water. The water should float on the resin easily.

My theory is that this should neutralise the surface tension in the resin layer and print the missing Z values.

Angles must not be too steep or reflection/refraction could occur in the water layer.

[iplayfast]

I wonder if having ultrasonic vibrations in the water would remove surface tension issues.

[mike_biddell]

I wonder if having ultrasonic vibrations in the water would remove surface tension issues.

iplayfast, according to the Physics textbooks, a thin layer of water will remove the surface tension in the photo resin and produce glassy smooth prints..... but since I dont have a Peachy, I am not in a position to put the theory to the test !!!!!

[amoose136]

If it is a surface tension issue and if you had a way of also removing saline you could, between layers, add more saline than needed and then remove it to the proper level. This would probably fix the surface tension issues relatively easily but would also increase print times significantly as the laser would spend a lot more time off waiting for the resin to come to the right level. In theory you could then print with molasses or another high surface tension liquid using this method. The easiest way to test if it is surface tension though is make two identical prints with the same printer in the same room-- once with the room temperature high and once with the temperature low. The ridges should get smaller in the high temperature case.

[quertz]

Hey guys,

I think the best way still is to just use less power.
The resin won't cure completely and there will always be a wet layer.

Lowering the layers will be pretty much impossible with the current Peachy setup.

But let's wait first for Rylan to tell us about the true source of those riffles!

quertz

[iplayfast]

iplayfast, according to the Physics textbooks, a thin layer of water will remove the surface tension in the photo resin and produce glassy smooth prints..... but since I dont have a Peachy, I am not in a position to put the theory to the test !!!!!

That might work. The reason I was thinking ultrasonic was other sla printers print a layer, then the object moves down and up before the next layer is printed. I was guessing that this is to insure the model is coated, and break any surface tension. Ultrasonic would keep a constant ripple at a high frequency where the average wave would be the print area.

However, I like your idea better. So much simpler!

[android78]

How about if you had a speaker (audio, not ultrasonic) that would vibrate the tank between layers. So have the laser trace the pattern then turn off while the tank is shaken, wait a short time for settling (avoiding ripples) and then do the next layer?

[oninoshiko]

How about if you had a speaker (audio, not ultrasonic) that would vibrate the tank between layers. So have the laser trace the pattern then turn off while the tank is shaken, wait a short time for settling (avoiding ripples) and then do the next layer?

I'm not saying it's not worth trying, but I would think the sound would also shake the mirror.