Results 1 to 10 of 50
Hybrid View
-
08-15-2014, 12:23 PM #1
- Join Date
- Dec 2013
- Location
- Georgia
- Posts
- 934
Considering that the very first 3D printer back in the 1970s was a top surface SLA that used the natural leveling properties of the liquid and changed the surface level to move up the layers rather than lowering a platform, it's more accurate to call the designs 'cousins' than anything.
No I mean that only that part of the wave goes directly up and then directly back down without propagating out over the surface of the fluid. Indexes of refraction are almost entirely a property of a material's permissivity, or the resistance the material has to the energy passing through it. Mechanical waves propagate based on a material's viscosity. While the two are sometimes related, the two properties are independent, there are very very refractive fluids that are very low viscosity. (Mercury is an example, though the refractivity of Mercury is generally a moot point since it is opaque to light, but it's refractive properties come into play with very lower frequency radio waves.)
The problem with using light analogy to this is that with light, the permissivity of water is lower than air, allowing there to be a point where the light passes through without being reflected. If you were to shine the laser down from the air and into the water, even at an exact 90o angle, you would get some amount of reflection back up toward the laser.
Further, in order to make a proper analogy between water and light, you would have to find an interface that has similar differences in permissivity that water and air have in viscosity. Air is about as viscous to mechanical waves as say, milk is permissive to light, and water is about as viscous as air is permissive (roughly). If you were to shine the laser downward on the interface between air and milk, you would get a more accurate indication of what kind of behavior you would get back from mechanical waves.
... I hope I was able to get that to make sense. Physics is hard to explain sometimes.Last edited by Feign; 08-15-2014 at 12:55 PM. Reason: Changed my example to more directly fit the problem.
-
08-17-2014, 04:51 PM #2
- Join Date
- Mar 2014
- Posts
- 94
Ah I didn't know that, I should learn about the history. So cousins it is!
No I mean that only that part of the wave goes directly up and then directly back down without propagating out over the surface of the fluid. Indexes of refraction are almost entirely a property of a material'spermissivity, or the resistance the material has to the energy passing through it. Mechanical waves propagate based on a material's viscosity. While the two are sometimes related, the two properties are independent, there are very very refractive fluids that are very low viscosity. (Mercury is an example, though the refractivity of Mercury is generally a moot point since it is opaque to light, but it's refractive properties come into play with very lower frequency radio waves.)
So anyway as I was saying I think surface waves can form when you have waves hit a higher lower index of refraction (high speed) at a high enough angle and then from surface interactions can't reflect much so they form surface waves. When I say refractive index I mean the index for mechanical waves. Again this may not be correct use of the term, but mechanical (and all) waves can refract in the same sort of way as light does. It is just a matter of entering a new medium where the speed of the wave will be different.
The problem with using light analogy to this is that with light, the permissivity of water is lower than air, allowing there to be a point where the light passes through without being reflected. If you were to shine the laser down from the air and into the water, even at an exact 90o angle, you would get some amount of reflection back up toward the laser.
Further, in order to make a proper analogy between water and light, you would have to find an interface that has similar differences in permissivity that water and air have inviscosity. Air is about as viscous to mechanical waves as say, milk is permissive to light, and water is about as viscous as air is permissive (roughly). If you were to shine the laser downward on the interface between air and milk, you would get a more accurate indication of what kind of behavior you would get back from mechanical waves.
... I hope I was able to get that to make sense. Physics is hard to explain sometimes.
Anyway I just added the laser analogy to make things more clear, but obviously miserably failed here! haha Also this topic is supposed to be on holes in the prints, this has gotten way off topic.
-
08-17-2014, 05:05 PM #3
- Join Date
- Mar 2014
- Posts
- 94
Yeah I am pretty sure that the refractive index is only for light (since it is a number relating the speed of light to the speed radiation passes through a medium). Sorry for the confusion this caused. The way I was incorrectly using it I just meant how much a mechanical wave will refract when going from different mediums that have waves travel at different speeds. Man I really sent this discussion off topic!
Qidi X Plus 3 Paper thin first...
05-27-2024, 01:15 AM in General 3D Printing Discussion