disciple
I'm new to this, but does anyone know what medium I would use to make a mold from a stone. In other words, There is an old building with a beautiful design sculpted in to it. I want to copy this design. I know there is a material out there that I can press against the original design and make a mold of it and then cast the design in plaster. I just don't know what material I would use to do this without hurting the stone.... Help!!!
Answer
I think the sculpey or any clay will work. If you use normal clay, any residue left will dissolve in the next rain, just don't use brown clay on light stone... if you use water based clay you would have to cast your plaster into the mold while the clay is still wet.
As the clay won't be very stable just on its own, you should consider making a mother mold on top of that. That is a hard shell, which just gives support to the soft part of your mold so it doesn't deform. It depends on the size of what you want to copy if you need it. You could make the mothermold from plaster bandages, but don't put plaster directly on the stone.
Before you start, consider carefully the shape of what you want to copy and where undercuts are and where you have to put in parting lines. What technique you use for mold making really depends on the exact shape of what you want to copy. If the structure is something complicated, you may want to practice how to make molds from more simple structures first so you are aware what causes problems and get some experience in how to solve them.
Another completely contact free method is if you happen to be at a university where they have a 3D laser scanning camera you can borrow, you could use the 3D laser scanner then make a model of your structure in the computer from the scans. That you could print out using a 3D printer. that way you can scale the model to any size (though anything large will be expensive to print)
Help with building RGB LASER Scanner?
Matt
Hi there previously I have build some laser spyro projects but I have absolutely no idea about RGB LASER Scanners can someone please help.I have tried to find every possible information on the internet but I guess I need to start from the basics.
Thanks : )
Answer
there are several ways to do this, each involving different amounts of electro-optics in digital and analog forms.
you'll have to decide what you're scanning. is it 2D? 3D? still? or live-action?
in the easiest of cases, you can probably find an old photocopy machine and see how that works.
in the hardest case, your scanning data might become real-time input to a vehicle that must navigate through its environment.
so you will have a scanning beam, and a detector.
the scanning beam is a laser; you're interested in tri-colour, so this is either three lasers of different wavelengths, or it is a white-light laser that you will later filter. true white-light lasers are pulsed. if the pulse rate is really high (eg: in the millions of pulses/second), then each pulse could represent a pixel, and still have a mean free path of several meters.
the detector is a CCD photoreceptor, (or a whole lot of them), filtered to pass the desired wavelength(s). you can choose to capture:
a) a stream of individual bounces without regard to the focus;
b) a whole scan line into a buffer at once; or
c) a whole 2D frame into a buffer at once.
each method implies different mechano-optics, with a) being the simplest, mechanically. additionally, it may be possible to convert some digital cameras to use for this purpose.
to scan, you'll draw a point of light across a remote object, detecting the intensity of what bounces back. if this is not a range-finding device, then the outbound signal may be constant-intensity; but to detect distance, velocity, or absorption spectra, you will have to do some optical and/or high-speed tricks (sub-nanosecond processing is hard) involving correlating the outbound signal to the returned signal, to build a profile.
photon time-of-flight would indicate distance, (1 ns is about 30cm), and doppler shift would indicate speed.
to detect time of flight implies very high sensitivity and probably high frame rate, too.
to detect doppler shift and spectral lines would require that the returned beam travel through a prism, to give angular separation to the photon stream by wavelength. in this case, you'll always be scanning into a buffer, whose width covers the returned wavelengths.
each scan line would be drawn using a mirror that can tilt and swivel on two orthogonal axes. (or a pair of mirrors, arranged to swivel on orthogonal axes). controlling the mirror(s) will be subtle and delicate, because vibration may cause some fuzz in where the point gets drawn.
(think of a mechanism very similar to a DVD reader, for instance.)
for noise control, you'll want to distinguish between ambient light and returned signal.
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