HowToMakeaRobot.us robot contest winner

We just had the drawing to win a simple line following robot, many of you had entered the drawing during the 2012 Atlanta Mini-makers’ faire.  And without further ado, the winner is:

James Martin

James has 7 days to claim his prize.  If we don’t hear back from James, we’ll draw another name and try again until there’s a winner!

Solidoodle 2 Review — September 2012

Introduction

We’re had a Solidoodle v2 3d printer for over 3 weeks now and I just wanted to write about its strengths and weaknesses.  In preparation for the Mini-Maker’s faire in Atlanta we had to print out 15 of our simple line following robot plans, so we really put the Solidoodle through its paces.  Each simple line following robot kit consisted of 5.5 hours of printed parts, so it took awhile!

Construction

Overall the Solidoodle is well constructed and it arrived in a large box with lots of bubble wrap.  We have found one small issue with the z-axis homing switch.  First off, if you’re not familiar with 3D printers, particularly DIY 3D printers, the printer homes each axis prior to each print.  The homing of the z-axis is critical, because it sets the distance between the nozzle and build platform.  This distance kind of smears the first layer down, so it sticks to the build platform.  If you have this distance too big, the parts won’t stick and the second layers will pull up the first layer and you’ll definitely not get a good print.  If the distance is too small, the nozzle will collide with the build platform and perhaps tear up your kapton tape.  The solidoodle build platform is constructed of aluminum with kapton tape on top.  The kapton tape also helps adhere the first layer, since its a high temperature polyimide film.  I noticed during printing all those simple line following parts, that z-axis homing distance was getting smaller and smaller.  At the time, the solidoodle was very new to me and I didn’t think much of it, the prints were coming out fine, just the raft was getting thinner and thinner. Raft is a 3d printing term for the support lattice.   The raft or support lattice is also there to help adhere the first layer of the part.  OK, back to my story, the rat was getting thinner and thinner, but why?  Upon inspection it appeared the z-axis homing switch positioning screw was moving.

Simple Line Following robot v2

I would first like to thank everyone who attended our Atlanta Maker Faire workshop. You were all great and I hope you enjoyed the workshop as much as I did. During the workshop many of you noticed a few mistakes in the wiring schematic, so as promised below is the updated electrical schematic:

Here’s my brother and I standing behind our booth at the Atlanta Mini-Makers’ Faire.

       

For those of you missed the Maker Faire workshop, the robot is completely open source and the design has a Creative Commons Attribution 3.0 license.  Here’s are the files and drawings needed to reproduce the robot.

And here are the stereolithography (.STL) files to use in your 3D printer:
48004v4 3″ dia. wheel (qty-2)
48008v2 peg
48009v2 sensor light shield
48011v3 motor mounts (qty-2)
48012v2 base

In addition to the above 3D printed parts, you’ll also need the following purchased parts

Part No. Description Price Qty Extended Price Supplier
TCRT5000 Optical sensor / reflective switch $0.994 4 $3.98 http://www.newark.com
9452K351 Buna-n O-ring, As568a Dash Number 241 (pack of 50) $11.21 1 $11.21 http://www.mcmaster.com
Nano v3.0 Arduino Nano micro-controller $13.80 1 $13.80 http://www.kennymarket.com/index.php/vmchk/ADAPTERS_CONNECTORS/Arduino_Nano_v3.0/flypage.tpl.html
253471 120rpm 12vdc gearmotor 6mm shaft $14.95 2 $29.90 http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_253471_-1
2159411 Dual H-bridge $19.95 1 $19.95 http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2159411_-1
 24gauge wires & jumpers  Motor wire, jumpers, etc.  $3.00  1  $3.00  Various suppliers

And finally you also need to make the sensor array PCB, here’s the PCB layout constructed using our Taig CNC machine.

$499 3D printer, SLFv2 and future edger bot

We’ve recently added a 3D printer to our bot building arsenal:

 

We really wanted a RepRap, but we just don’t have the time to build one from scratch and fully built models are usually well over $1000.  So far the solid doodle is a great 3D printer, especially for the price of only $499.  Here’s our first print,  a wheel for our upcoming version 2 of our simple line following robot:

 

And here’s the solid model of our upcoming version 2 simple line following robot:

The new simple line following robot uses a arduino nano micro-controller and the same dual axis h-bridge driver as the first version.   We replaced the swiveling wheel with a simple peg that will now drag instead of rotate and the sensor bar array as been updated as well, to be more simple to assemble.  We’re going to feature this new bot at the upcoming mini-makers faire at Georgia Tech next month, so stay tuned.

Also in the works is a more advanced robot codenamed Mitchel.  Here’s a sneak preview of the advanced edger bot’s drive train:

Mitchel the edger robot’s drive train uses two Hitachi DC servo motors with encoder feedback.  One servo motor drives the rear wheels with two timing belt pulleys and the steering is controller through a ball screw assembly.  The robot will ultimately have a machine vision camera to follow the lawn edge and a motorized edger head to perform the actual edging function.  We hope to roll out this robot sometime in the upcoming months.

 

Mini-Maker Faire — Oct 6 Atlanta GA

We’re going to be at the Atlanta Mini-Maker’s Faire on October 6th in Atlanta.  The Faire is on the GA Tech campus and will feature hundreds of makers and best of all it’s free!

Howtomakearobot.us will be presenting a workshop on our version 2 of our simple line following robot.  The robot is an upgrade from our version one and we’re going to show you step-by-step how to construct and program you’re own line follower.  I know line-following robots are a real newbie type bot, but I think that’s actually a good thing for a workshop at the maker’s faire!

I hope to see you all at the faire!  It’s going to be a blast!!

First CNC mini-mill part

CNC mini-mill first part solid modelSetting up the mini-mill went fairly smoothly but it took awhile to get the all the settings in EMC2 correct.  For our first CNC part, I took the hometomakearobot.us logo and extruded it onto a block to create the 3D solid model shown to the left.  I figured this part would be a good one to test our milling capabilities.  Even though the part doesn’t provide any function, it’s complex enough to require a working cnc mill.

I tried numerous CAM (computer aided manufacturing) programs without success.  My brother finally stumbled upon a program called EstlCAM 3D at download.com.  The CAM program is in German, but the version you download from download.com is in mostly english. EstlCAM is very easy to use and creates clean G-Code. It’s shareware and only mills 80% of the part until registered but the registration is only $22 dollars!

Here’s the g-code that EstlCAM provided for the above solid model:

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%

Since EstlCAM only works in metric units and I work in english units, we had to run the g-code thru a program that converts it called “NC code scaler”.  We also had to manually modify the feed rates, but you could adjust them accordingly in EstlCAM beforehand.  Here’s our first CNC machined part:

Mini-mill first part of HowToMakeaRobot.us logo

As you can see the engraving didn’t produce the robot visor details.  This is due to the fact the end mill we used was too large to get into those details and EstlCAM knew this fact and didn’t put in the g-code to produce it.  There is a lot of information to know in order to machine good parts, that’s where a 3D printer would have been easier.  However, 3d subtractive milling is still the best way to make robot parts and you can work in metal too.  Future work includes understanding feed rates, depth of cuts, engraving versus milling, the list goes on and on, but we’ve demonstrated for the moment that future robot building will be much easier and a hell of a lot more precise too!

CNC Mini-mill for Under $1350 dollars

Taig CNC mini mill set-upMaking robot parts can be tough without the right tools, this post will show you how to procure a great CNC mill for under $1350 dollars!  Now, I considered many different options for making robot parts, but I decided that a CNC mill using subtractive milling would be the best bang for the buck.  I came very close to building a reprap 3D printer, but after reading many reviews I came to the conclusion that DIY 3D printers are not ready for prime time yet. The reasons I make this statement are resolution and raw material cost. The DIY 3D printers work great, but they still need improvement in the area of resolution and don’t make commercial products, yet. Also, the reprap printers use what they call plastic filament for the raw material.  Basically this filament looks like weed wacker plastic wire and is just extruded plastic wire.  This is not a problem but the pricing on the 3D printer filament is outrageous!  The cheapest available 3D printer material filament is around $8 dollars per pound.  I work as a plant engineer in a plastics injection molding plant, so I know roughly the raw material cost of plastics and most plastics sell for less than $1.30 per pound.  So, why is 3D printer material filament so expensive, I’ve seen the filament for sale for $30 dollars per pound!  Recycled plastic pellets are even cheaper and should work just fine in a DIY 3D printer, so why the outrageous pricing for the raw material filament?

Anyway, that’s why I settled on a CNC mill instead of a 3D printer, of course in the future we might be using both technologies.  The above photo shows our CNC mini-mill.  The mill was supplied CNC ready from Taig Tools.  They make a great product and are highly recommended.  I then purchased three NEMA 23 stepper motors from Kelinginc.net. They seem to have a new website Automation Technologies Inc. The NEMA 23 stepper motors I ordered are 355 oz-in models and cost just $140 dollars plus shipping.  I next ordered a 4-axis Toshiba TB6560 cnc driver and 24vdc 15amp power supply for $64 and $37 dollars, respectively.  Here’s the final BOM:

Part No. Description Qty Price Extended Price Sources
2019CR-ER Taig CNC ready Mini-mill 1 $1100.00 $1100.00 Taig Mini-Mill
TB6560 4 Axis TB6560 CNC Driver For NEMA17/23/34 Motor 3A 1 $63.99 $63.99 TB6560 on Ebay
RYD-350-24 24V 15A 360W DC Regulated Switching Power Supply CNC 1 $36.98 $36.98 24VDC P.S. on Ebay
KL23H284 NEMA23 355oz/in 3.5A 1/4” Dual Shaft Stepper Motor (KL23H284-35-4B) 3 $45.00 $135.00 automationtechnologies

 

The grand total for the CNC mini-mill was $1336 dollars and it’s a great machine.  I know I went with the el-cheap-o driver, but it seems to work fine.  The only issue with it is the fact you have to leave it off until you run EMC2.  Oh, yeah, I decided on an open source solution for the CNC mill software and it’s called EMC2.  You can read about it at linuxCNC.org and, of course, you need a personal computer to run the software.

Here are some additional photos of the CNC mini-mill we built for less than $1350 dollars:

4-axis TB6560 Stepper motor driver

Taig CNC mini-mill close-up

CNC mini-mill computer with 24vdc p.s. and stepper controller

I just used an old PC I had lying around.  In the old days (1991-2001), I would upgrade my PC every twenty-four months or so when processors were constantly changing.  Now, you don’t have to upgrade nearly as often, but I still have 2-3 old computers lying around that I hadn’t given away.  I believe this computer is an AMD athlon which would be equivalent to a Pentium 4 running about 3 ghz.  You’ll need an older computer with a parallel port and I’ve seen similar machines in garages sales for $10-20 dollars or you can buy one from price watch or Ebay for around $200.

In the next post, I’ll show you how to set-up EMC2 and our first cuts.

How to Calculate Your Robot’s Speed or Velocity

Calculating the speed of your robot creations is a basic skill for good robot building.  I hope the below tutorial helps you to pick out the correct gear ratio for your motor and wheel size for your robots.

Step 1)

In order calculate the speed of your wheel driven robot, we first need to review some basic geometry.

Using the circumference of a circle for robot building

As you keep the larger diameter you choose for robot, the further the robot will travel in one rotation of its wheels.  For instance, if you pick 3″ diameter wheels, the circumference is 3.14159 times 3 which equates to 9.42 inches.  With each rotation (assuming no wheel slippage) of the wheel your robot would travel 9.42 inches using 3 inch diameter wheels.  OK, let’s do the calculation one more time and this time choose 4″ diameter wheels.  The circumference would equate to 3.14159 * 4 or 12.57 inches.  As you see, choosing large wheels should equate to higher speeds since each rotation propels your robot further.

So how do we use this simple geometry to calculate the theoretical speed of our robots?

The answer comes from a simple formulas to calculate the speed:

FPM = Cf * WRPM (wheel RPM * circumference in feet = feet per minute)
FPM * 60 = FPH (feet per minute * 60 minutes = feet per hour)
FPH / 5280 = MPH (feet per hour / 5280 feet = miles per hour)

Dirt Cheap Hexapod robot — Part 1 Mechanical Build

Dirt cheap hexapod free robot plans & blueprintsHowToMakeARobot.us is proud to present the following free blueprints and robot plans to make a very cool dirt cheap hexapod robot. We designed this hexapod robot to be as cheap and simple as possible. There are only two parts to be made besides the 18 RC servo motors and the microcontrollers plus sensors. With three RC servo motors per leg, if you build this robot, you’ll have a 18 DOF robot for under 100 dollars!! I’ve seen similar hexapod robots using slightly larger R.C. servos selling for $399 dollars, so this robot is a bargain to build.

Here are the blueprints for the two parts:

Dirt Cheap Hexapod robot base plate blueprint

Dirt cheap hexapod robot leg blueprint

And here are the free robot blueprints in PDF format:

Dirt Cheap Hexapod robot base plate blueprint in PDF format

Dirt Cheap Hexapod robot leg blueprint in PDF format

We’ve created a youtube video on how to make this parts, the robot base plate and the robot legs.


  Here’s the completed dirt cheap hexapod robot:

Dirt Cheap Hexapod robot