Archive for the ‘Uncategorized’ Category

Holo Projector Motivator

Posted: August 5, 2017 in Uncategorized

The holo projector is the thing in the 1st Star Wars (Episode IV) that projects Princess Leia’s message. It is located on the front of R2’s dome, right next to the radar eye. For my R2 build I wanted it to move. This will add a little bit of life and motion to an otherwise rather static droid. I want to the holo projector to move around randomly, as if it were scanning or looking at different things.

I saw a mechanism on Edwardo’s builder log over on the Astromech.net forum and that gave me an idea. Having become a huge believer in 3D printing, I thought “I could do that” and set out to build my own holo motivator (My own name for it). What I came up with works pretty well and slides right over the back of the holo projector. I imagine I will end up gluing it in place eventually, but for now it press fits decently enough to test it out:

I believe in part reuse and trying to get as much functionality out of a single piece as possible. With that in mind, the linkages and control arms are identical. To build it required only three different stl files, with two of the files run twice. These three parts were the Base, Control Arms and Linkages:

Figure 1-Base

Figure 2-Control Arm

Figure 3-Linkage

All that was required to complete the assembly was to drill out the holes (3D printing results in holes shrinking a little) and bolting everything together. In all, you will need:

Part

Quantity

File

Base

1

Base

Control Arm

2

ControlArm

Linkage

2

Linkage

Standard Servo

2

 

#6-1/2in Bolt

8-12

 

Small servo arm screw (Came with servo)

2

 

 

I choose to only bolt the servos down with two bolts each, but you can do 4 if you feel it is necessary. The control arms will rest on top of each other with one upside down. Finally, the control arm file (Not seen in the pictures below) has two holes for mounting to the servo. These holes are 1/4in apart and allow for a little bit of adjustment in the way the control arms are moved.

With everything installed I wrote a quick Arduino Sketch based on the provided servo example to test it out:

#include <Servo.h>

 

Servo Servo1;

Servo Servo2;

 

int S1Min = 25;

int S2Min = 25;

int S1Max = 165;

int S2Max = 165;

int DMin = 500;

int DMax = 3000;

int pos1 = 0;

int pos2 = 0;

 

void setup()

{

Servo1.attach(5); // attaches the servo on pin 5 to the servo object

Servo2.attach(6); // attaches the servo on pin 6 to the servo object

}

 

 

void loop()

{

pos1 = random(S1Max-S1Min)+S1Min;

pos2 = random(S2Max-S2Min)+S1Min;

Servo1.write(pos1);

Servo2.write(pos2);

delay(random(DMax-DMin)+DMin);

}

 

The results were pretty good. Here are two videos of the holo eye moving from the inside and outside of the dome:

Inside:

http://www.youtube.com/watch?v=-Yh0xzSn_bU&feature=youtu.be

Outside:

http://www.youtube.com/watch?v=iZrs3FqsL04&feature=youtu.be

 

I will probably refine the code a little. As you can see the two servos move completely independently. I will probably change the code to allow force the movement to be linear.

That’s it for now.

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If you have followed, I tried adding a plastic extruder to my CNC Router. The results were less than desirable. Not horrible all of the time but terribly unreliable. So, I finally decided to build my own 3D printer. Having studied RepRap and many other printers I settled on something that I could build with the tools I had, a CNC router. I started out with the items I had:

  • 650watt PSU (Computer power supply)
  • Printrbot Geared Extruder and hotend
  • Heated Bed
  • 2 x T2.5 10 tooth sprocket
  • 1m of T2.5 reinforced belt
  • Ramps 1.4 board (Bought as a kit and assembled… That was hard, not for the faint of heart)

I had to gather a few other items:

I tried to get everything I could from Printrbot. This ensured compatibility as well as giving some money to the person who designed it to begin with. I also had to order a bunch of bolts to assemble the thing. I got these from boltdepot. I am not going to post that BOM as I was off on a few things. Follow the one on Printrbot’s website. It is “Mostly” right. I would recommend you get a few more #6-0.75 bolts and you will need some collars for roller bearings on the Y-Axis (More on that later).

The next step was to produce the wood parts. I downloaded the inventor files from printrbot.com and took the time to create DXF files of each part and loaded them into my CAM software:

The next challenge was trying to find the right wood. I never did… I ended up using the closed thing I could, 0.23in thick BC grade plywood (Yuck). I figured thickness was more important than quality. This decision would lead to voids the plywood causing some structural issues in some area. If I were to do this again I think I would special order. I optimized the CAM files for a 1/32in bit and added dog bones everywhere I needed to.

About 1 hour later I had a pile of parts:

I was ready to start. Except, my bolts still hadn’t come in. They would take another week to arrive, the Fedex ground that boltdepot.com uses is just too slow. Drop that stuff in a flat rate priority mail box and get it in a couple days.

Finally everything arrived and I got to building. You will notice that I spent the week waiting painting as much as I could. A nice satin white. I mentioned that you will need spacers that are not mentioned anywhere on the official BOM. This little 5/16in collars did the job great for me. I don’t remember where I got them, I have a whole pack from a project long ago. Another option would be to just use a 5/16in bolt. It is a little big though the wood, but it would work.

It took me two evening to assemble everything, but I am really happy with how it turned out.

Wiring was a bit of a pain. The RAMPS board can be a challenge. When you are setting the motor current and have all of the drivers plugged in, the ground for the current sense is right next to the VMOT pin. Well, I accidently shorted the two pins and blew a board. A quick Amazon order and the next day I had a replacement, time to get printing:

I printed a few pieces and quickly realized that the 1/4in thick aluminum plate was just not getting hot enough. With an IR thermometer I read it as reaching 80oC. I removed the plate and am printing now on kapton directly on top of my heated bed PCB. I am now able to get 110oC which has allowed the pieces to stick much better.

If you remember me talking about how the voids in the plywood were causing issues, my Z nut on the right side was working loose due to one of these voids. I decided that before things broke down too much I would print replacement Z nut traps.

It is not the prettiest piece ever, but remember the printer was only working in the Z axis on one side. I think given that, there aren’t too bad. I printed two, one for each side. These had another benefit that they decoupled the X-axis from the Z axis. I now have no Z-Wobble, while before it was pretty bad. The next immediate upgrade was to replace the plywood shaft couplings on the Z-axis with printed ones. I found a decent coupe on thingiverse and customized it to the 5/16in diameter threaded rod:

Elf Helmet

Posted: August 5, 2017 in Uncategorized

This is a very old prop for me. I built this back in 2002, I was 19 at the time. I got a head cast to sculpt on and sculpted the helmet out of clay. I built the helmet before the Lord of the Rings (The two towers) movie was released and carved it from the few reference photos I could find (Mostly very dark photos) so I didn’t get it quite right and had to fill in the gaps. I created a mold out of plaster and let it set. After removing the clay I cast the piece with fiberglass. At the time I was unaware of gel coating or how to do it so the finish was actually straight fiberglass resin. This was not optimum and did create a few problems later on. I then did a two tone finish, using gold leaf (Another first) on the lower portion and gold paint on the crest. This is not one of my finest pieces but one of my first, so I show it for posterity.

In 2007 I was approached to produce two life clocks from the movie Escape from New York. In the movie, the main character is given 24hrs to live and a watch to show how much time he had left. From reference photos and constraints of the required electronics I was able to generate some design files. The final piece was to be machined from brass, have a translucent screen and contain all of the electronics.

I first designed and built the electronics. At the time I could not find super thin 7 segment LEDs and did the best with what I could. Finding a batter with enough current was also hard. Where were cheap LiPo batteries? The final design was pretty small but still used mostly through-hole parts, something that is no longer a limitation to me.

The case was then machined on my first CNC mill. It took a few tries as my machine kept loosing steps (There is a reason it was my first, not my last). I inserted a thin piece of smoked plexiglass and closed up the case. You can see the two black buttons on the left (Not present in the movie version but required to control the state of the circuit)

The unit was shipped to the customer who then finished the prop with a nice leather band. I have unfortunately lost his email and cannot cite him at this time but the photos he provided to me are shown below. If you are reading this and these are your photos, please email me and I will be very happy to cite.

Halo AR

Posted: August 5, 2017 in Uncategorized

I have to be honest upfront that I am not a big video game player and have only played Halo enough to do research on the gun. Seems like a cool game, just too many other hobbies to take up my time. I found the AR interesting as it is similar to the pulse rifle from Aliens in function and capabilities. I used the game to grab a few reference photos. I think the ones below were from a web search. If they are your photos, thank you and sorry for not citing you, it was 6 years ago and I had never intended to post.

Using a casting from “Adam of the 405th” who trade some electronics for a rough cast I was able to build an AR relatively quickly. The piece came as one solid casting. There were some decent seam lines that had to be filled and sanded out. This was especially annoying on the forward grip. I then cut several piece off. The first was the area depicted below by the orange dotted line. I removed this piece to facilitate the addition of the electronics. I also cut out the magazine area so that I could remove it.

In the magazine well I added a micro switch to detect when the magazine is present. I also added a close pin to the magazine to grap hold of a pin in the well.

I also added screw posts into the battery well on the top so that batteries can be removed and replaced easily.

The electronic in the screen housing were the most difficult component. Internally all of the electronics were arranged as:

 

I should note that I did custom electronics on my own for this project. Based on a 16 bit PIC microcontroller I was able to display the ammo, read all of the inputs and output 2 channels of audio. The screen was setup to be backlit. I cut a stencil out of vinyl and glued the 7 segment led display into place. I then backlit the whole thing with a pair of blue LEDs.

Adding a small power LED on the side, I closed it up and gave it a test run:

Then it was on to a lot of paint work. It is mostly spray paint with some weather with acrylic paints. It is worth noting that all of the black outlines were actually done using a permanent marker. In addition, the grip was finished spray vinyl to give it a little rubberized texture.

1911 Grips

Posted: August 5, 2017 in Uncategorized

I don’t currently own a 1911 but that doesn’t mean I don’t appreciate what can be done to customize them. A friend and fellow aviator came to me looking for a set of grips with aviator wings carved in. I was happy to help.

The grip texture proved to be the most difficult part. I tried setting up a grid of lines and having a v-bit follow those lines but the results were horrible. In the end, I was able to create a shaded height map of the grip that was able to be cut using a 1/32in tapered ball nose bit. The results are amazing and the points ended up being quite sharp.

Unfortunately I did not have a 1/32in bit. I hoped over to www.precisebits.com. I cannot say enough great things about this company. I have even had an hour conversation with them on how to optimize my cutting, free of charge. This one hour conversation about the capabilities of their bits and how to optimize my machine has saved me hours of cutting time and tool life. About the only down side to them is the $50 USD minimum order which often means you have to buy more than you need. I loaded the bit into the machine and blank of rosewood. 3 hours later I had a set of grips hot off the CNC. Even with my speeds set pretty high I was never able to get over 30ipm on my cuts due to the 3D profile and acceleration values of my machine. The grips were then finished with an oil.

After other saw the grips, a retired Master Nav (Airforce) contacted me and request a similar set of grips with his warfare insignia. I followed the same procedures as above and successfully created the following:

These turned out beautifully. The grips have really tested my machines ability to go small. As a result I found some lost steps in the z-axis, which through hours of trials were found to be being caused by a wireless keyboard and mouse latency issue. The lesson learned, again, is do not use wireless keyboards and mice, I really don’t know why they cause so many issues but they are just bad news.