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the scribe-bot: a machine to create scratch holograms

by:QY Precision      2019-12-02
When most people think of making holographic photos, they think of a complex device that includes film, laser and complex optical platforms.
It turned out to be a holographic image.
A two-dimensional image that looks Three dimensions
Size object-
It can be made using a crossed compass and a piece of plastic.
These hand-made 3D images are called Scratch hologram.
Scratch hologram is created when there is a thin scratch on the plane.
When you change the angle of view, point the light source (
Like a Sunny Sun)
A single part of the reflection curve.
By changing the angle of view, this reflection point moves along the curve.
When you put a lot of these scratches together, you can create one or three
Size images that can be viewed offline in reflected light.
There are many great notes on how to make scratch holographic photos by hand on this website and elsewhere: If you want to know the science of these images, william Betty wrote a very good paper in the electronic imaging program about why this method works.
The problem with making scratch holographic photos is the effort needed to make them.
In order for the reflection pattern to match the object, you have to make a series of concentric scratches by hand.
Each point in the image must have a corresponding scratch arc.
It\'s tricky to automate these scratches.
For the reasons we will discuss in the next section, you cannot make these using standard CNC machines or laser etcher.
It turns out that you have to build a special tool.
In this project, I will show you how to modify the CNC machine to automatically make the scratch type required for complex scratch holographic photos!
Even if you are not interested in making scratch holographic photos, this project will show you how to add additional tools to the CNC machine.
It will take you through the physical design of the system, the electronic equipment needed to trigger the scratch, the interface of the CNC controller and the G-
The code required to run the machine.
Of course, you are free to modify the code for your own project to use your own dedicated tools.
When I first discovered that you could make a scratch holographic photo, I grabbed a piece of plastic from my shop and a crossed compass to make one.
I am very happy with the result, but it is too tedious to create this image.
To make a simple pattern, I made one scratch after another after the scratch.
The final layout is not as uniform as I thought it would take a long time to complete.
I quickly realized that I wanted to automate the process.
Of course, I look around my store and the local manufacturer space to see if I can do the work for me using the existing machines.
The most obvious tool to create scratch hologram is laser etcher.
You can use the laser cutting machine to make very fine laser etching lines with acrylic resin almost effortlessly.
I quickly wrote some python scripts to locate the center of the arc and then generate an arc for simple letters.
I took the generated eps file to my production space and etched the pattern on a piece of acrylic resin.
The results were a bit surprising.
The picture above is the result.
Basically, I found that there are two problems: Although the CNC machine with stylus does not have the same problem as a laser when vaporizing the plastic, pixelated in the circle caused by the step still creates problems with the type of reflection we need to make the holographic work.
Since we can\'t use the XY stepping motor to create the arcs needed for scratch holographic photography, I realize that we have to create a new machine to make smooth arcs.
This is the driving force behind this project and this new tool.
Overall, there are two basic parts to this machine: the cnc I use in the project is X-carve.
Any project where a CNC machine tool will work, as long as you have a frame to connect the Servo System z. axis.
The core of the project is the servo system and supporting software.
There are a lot of interrelated elements in this project: I will take you through these stepsby-one.
In order to add additional features to your CNC machine, you will need: You will also need to purchase some long stitches and get a 3d printer for the parts.
In order to make a holographic photo, you will need to buy some thin acrylic tablets at the local building supply store.
I just used 0.
093 inch thick acrylic resin for Windows.
To connect the servo to the router, you need to print the STL file at the top of this step.
There are four parts: all of them are designed for this project using Fusion 360.
After printing these parts, it is simple to assemble them: Once these steps are completed, the physical assembly of the scribe-bot is done.
The electronic equipment of this project is relatively simple.
There is basically only one digital input.
When the input becomes high, the servo scans clockwise from the start position to the final position.
When the input goes back to the low state, the scan goes back to the starting position.
I used a mini to assemble the system
Prototype board connected to Arduino Uno r3.
I found this Holder\'s plan on things. A-Verse. (
The board and the permanent Arduino shield would be better, but the project was designed as a prototype.
This should also be placed in the box to protect the electrical connection.
The input of the circuit is taken from the M8 \"flood\" output of the CNC controller.
This input part of the circuit is powered through a resistor through a 4N35 photoelectric coupler to prevent any possible electrical feedback between CNC controllers.
This may not be absolutely necessary, but I want to make sure the controller is protected and isolated from the servo and external power supply.
I parallel the green LED and resistor to the 4N35 so I can see when the controller is between high and low.
The Arduino sketch converts the pulse of the control servo to a state.
When the input changes, each stroke that the servo travels to adjust the scanning speed has a delay of 7 ms.
The sketch of the project is included above.
You can easily modify the scan angle and scan rate by modifying the constants defined at the top of the sketch.
Two power supplies are needed to make this all work properly.
First, you need to power the Arduino itself.
I did this with a simple 5 V USB charger and USB cable.
A second 5 volt power supply is required to power the servo.
Make sure there is enough current to power the servo system.
High torque servo system can get 3 amps of power.
The final step of the Electronics is to connect it to the M8 connector on the CNC controller.
Since this trigger is a low current connection, I used two leads for a line 20 around the store.
Make sure the wire is fed into the optical coupler before connecting to any power supply or turning on any power supply.
Once you connect the device to the controller, we can generate some G-
Code and start making holographic images!
To generate a scratch hologram, you need to start with the pattern of the points, which are the center point of the arc drawn with the action compass.
When you look at the hologram, you will see that these points are reflected on the arc.
You can do the layout of the dots by hand, but it\'s been a while --consuming.
There are 159 points in this project.
You can see the layout in the picture above.
I decided to write a python script that converts simple strings into point patterns for making holographic images.
Basically, the script takes a string and converts them into vector graphics using the old style Hershey font.
From these vectors, our code, and then the position of the sample points along these curves.
To access this code, download make dots_code.
Open from the tgz file above. (
This is the gzipped tar file on the Mac, but it should work fine in Linux and even Windows. ).
Go to the directory created during unpacking and edit make dots. py code.
You can change the string from the default \"MTSU\" to something else.
Before you have experience using the machine, I would suggest keeping this simple.
You can also change the size of the layout.
There are some instructions in the code on how this works.
I have included the full Hershey fonts and the code to read them.
Hershey code is using a lot of on-
Line resources and sample code, so I have not declared the author identity of this code or related data file.
They are distributed without a license, so they can be used in your project.
My Python code is only for strings, but it\'s quite easy to write a code for doing this for any vector graphics file.
I want to add this but I want to take this project out so that others can play.
For testing purposes, you can bypass this step completely, using the example \"mtsudos \". Txt \"file above.
This is just a collection of x.
Y pair for next step.
As I mentioned, any with x-Y\'s right. Making the G-
The code is also easy.
All you need to do is run make gcode.
A py file with a point text file as input.
There are more detailed instructions in the code listed as comments.
Basically, the code just generates a set of simple moves for each point in the dots file.
Code for each point: 1)Moves to the x-
The y position above the center of the point. 2)
Reduce the stylus to plastic. 3)
Trigger the servo clockwise scan using the \"M8\" mist command. 4)Pauses for 1.
Let the servo continue to sweep for 5 seconds. 5)
Lift the scrawled from the plastic. 6)
Clear the \"M8\" fog command and trigger the servo to return to its starting position. 7)Pauses for 1.
For 5 seconds, give the servo the time to sweep back to its default position.
This is an example of G -.
The code pattern repeated in the code.
For each point, everything in this snippet is repeated over and over again.
The only change is the X and Y positions associated with each point.
Delay programmed to G
Code currently set to 1. 5 seconds.
This is a bit longer than required, but it seems prudent to be conservative in the beta version of the code.
There is also a startup and finalize section of the code that follows me for X-carve.
You may need to modify this code for other CNC machines, but the code seems quite generic.
To get started, you can look at the example G-
Code used to generate the above MTSU holographic image.
The file that made this is mtsu. gcode file.
Maybe my favorite part of this project is to write this simple g-code generator.
It helps clarify how the CNC machine works.
Feel free to analyze the code for your own project.
Once you have G-
Created code files, connected electronics, and scriber physically connected to a CNC machine, you can try the first holographic photography.
For this I used the Easel software of ventables to send the command to my machine, but for any type of g-
Code sending software. And away we go!
In the next hour or so, the machine will repeat the same basic mode, lower the spindle, scratch, lift the spindle, and move to the new position.
If the servo is not scanned, please check the LED carefully and make sure the Arduino program triggers correctly.
Hope you start with the aircarve (
Suggested in the previous step)
Help debug possible hardware issues.
If things don\'t go well, you may need to check if there is a loose connection on the prototype board.
You should see this boost mode if everything is OKreset-move-drop-
The scribe repeated over and over again.
The video above captures this very well.
If you find that the scribbles are not actually scratched to acrylic, you may need to abort the engraving and reposition the z-axis offset in order to be closer.
In the engraving process, you will not see much on the machine except for a series of scratched circles.
When the engraving is finally completed, remove the plastic piece from the CNC machine and bring it to the sun. (Or. . .
Find a place on the other side of the room with a bright light. ).
You need to have a highlight to watch the holographic image --Light source.
The sun is ideal, but having a bright light bulb at the far end of the room will work well.
First, remove the protective plastic on the back of the acrylic resin and attach a piece of black paper on the back.
This is not absolutely necessary, but it will help you to see the pattern more clearly from the reflection.
Place the plastic sheet on a flat surface and adjust the position you use to see the light reflected by the plastic scratches.
You don\'t want to see the sunlight reflected directly from the acrylic resin, just the sunlight reflected from the thin scratches. OBVIOUSLY -
Don\'t stare at the sun or its direct reflection!
It will blind you!
The light reflected by tiny scratches should be good, so just reposition yourself to avoid direct sunlight reflection from acrylic.
When you move the head back and forth above the scratch, you should see the letter pattern moving on the arc.
The video above can help you see this.
Basically, because of the way the reflections are mapped on these arcs, you look at the letters from different angles.
There is no single angle to make this work.
You should be able to see reflections from many different angles.
You can also use acrylic as a transport holographic to watch the same effect.
You let the light pass through the acrylic and watch the light reflect from the back of the scratch.
Once you \'ve made the first holographic photo successfully, you can start trying to improve the machine.
If you change the arc radius of the scratch, change the apparent depth of the letters seen in the reflection.
This can be done easily by mechanically moving the scriber needle further from the servo system.
You can also change the angle range of the arc (
By modifying the Arduino program)
You can see it from a different perspective.
You can also create software to generate other types of point patterns.
Ultimately, it would be cool to have both the scribe radius and the scribes corner range controlled by the software.
Generate G-through these modifications and adding some software-
Code, you can create real 3D objects and overrides that appear and disappear when you change the perspective.
It can be a bit difficult to make these changes when your CNC controller has only two
Control line (
M8 \"fog\" and M9 \"flood \")
But it may be possible to pass some clever programming.
Please let me know what you came up!
I would love to know how this project is used for future projects.
I would like to thank Ben Becker and Neal McClain of the MTSU Walker library for their helpful discussions in building this project.
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