KwartzLab Makerspace » robotics

3D Printed Robot Gripper

karlw — Tue, 01 May 2012 20:00:09 +0000

A lifelong dream has been to have the ability to design a robot using a CAD program and then easily produce a prototype or finished product from that design right on my desktop. After a few months of tweaking my Reprap Mendel 3D printer, that dream has finally come true. I’ve always been interested in designing, modifying and refining robotic grippers. Last week I used Solidworks to create and test a new design that would lower the complexity and number of parts. The great thing about Solidworks is the motion study capability. It lets you simulate the movement or your assembly before creating a physical object. This tool saves a lot of time when figuring out if the assembly is functioning as desired. When the simulated design was working properly, I exported the parts as sterolithography files (.STL). Another program named Skeinforge was used to create g-code that the control software uses to direct the 3D printers movements. The grippers were printed using a strong biodegradable plastic called PLA. I really like the white plastic because it reminds me of the Star Wars storm trooper body armor suits.

3D printed standard servo robot grippers

Robot gripper printed with white PLA plastic.

Karl P. Williams

Creating 3 dimensional objects on a Taig mill with a Rotary Axis

karlw — Wed, 10 Aug 2011 03:47:04 +0000

In my last blog I detailed the conversion of a manual rotary axis into a CNC rotary axis. I finally got some time to mount the rotary axis on the mill, configure the stepper in Mach3 and run it through some tests. The parameter for the g-code command to position the rotary axis is a positive or negative number ranging from 0 to 360 degrees. Positive numbers rotate clockwise and negative numbers rotate counter clockwise.
I started by creating a 3 dimensional object using Solidworks and designed a projectile that will eventually be milled in metal for a coil gun project that I’m working on. I decided to do the cut in wood since this was the first project using the rotary axis and I wasn’t sure how it would work out.

The next step was to export the solidworks object as a sterolithography file (STL). The STL file was imported into MeshCam, choosing the 4-axis option with 8 index positions. MeshCAM lets you create toolpaths from your 3D files quickly and easily. Meshcam generated G-code that would instruct the CNC machine to cut the entire object by indexing the rotary axis and using the regular X,Y and Z axis’ to position the endmill attached to the spindle. For my next experiment I’m going to try increasing the number of index positions by a much larger number.

Three Dimensional projectile created in Solidworks. Its size is .50 caliber and 1.5 inches in length.

In this MeshCam screenshot, the yellow lines indicate the 8 rotary axis positions between which the material is removed to create the object.

For my next rotary axis experiment I will try to optimize the cutting path by selecting a much larger number of indexes and cutting an object in aluminum.

Karl P. Williams

Balancing Robot at KwartzLab TON

Eric Gerlach — Wed, 13 Jul 2011 16:10:00 +0000

At July 12th’s KwartzLab Tuesday Open Night there was a Balancing Robot made by Phil and Nick, two UW mechatronics students, for their 4th year project. It’s designed to eventually allow telepresence, but the fact that it stands on its own is awesome!

Original Post

Taig Milling Machine Stepper Motor and Controller Upgrade

karlw — Sat, 25 Jun 2011 03:12:31 +0000

A friend was selling some 200 ounce/inch, 3.5 Amp stepper motors for a great price so I thought it was time to upgrade the taig cnc milling machine. With the old steppers installed, the machine was accurate but slow. Since the old controller couldn’t handle 3.5 amps I decided to upgrade that too. I found a 5 axis controller on ebay for a great price. This controller uses the Toshiba TB6560 stepper driver that can handle up to 36 VDC at 3.5 Amps. I wanted a board with at least 4 axis’ so that I could add a rotary axis to the mill but more about that in another post. I went to the local electronics supplier (Sayal elelctronics) and Parm set me up with a Hammond electronics 24 VAC, 10 Amp transformer (a local manufaturer). I picked up a bridge rectifier, large capacitor, switch, fuse, computer power cord socket and indicator light to complete the power supply. The entire conroller and power suppy were mounted in a computer case.

Transformer, bridge rectifier and capacitor.

Switch, fuse and power socket.

Mounted indicator light and switch.

TB6560 stepper controller board and 200 oz/inch stepper motor.

Power supply and controller mounted in a computer case.

Close-up of computer case.

After getting all of the stepper motors wired to the controller board it was time to start testing. I noticed that the motors started losing steps and stalling out at speeds greater than 20 inches per minutes. I hooked the oscilloscope up to the step line on one of the axis to see what was going on. Instead of a nice square wave it looked more like a sawtooth because of the slow rise time. This is what was causing all the missed steps at higher speeds. The culprit was slow rise times of the optocouplers situated in the circuit between the parallel port and the drivers. An easy fix was to take the optocouplers out and jumper them with a wire. The parallel port is no longer isolated from the driver chips but that has never been an issue with my other drivers on different machines. The machine can now run easily at 40 inches per minute.

In this photograph, on the left, you can see the waveform of the slow rise time of the optocoupler. The waveform on the right shows nice square waves generated after the optoisolators were jumpered. This makes a big difference considering that there are 8000 steps in one inch.

Karl P. Williams

CNC Art Experiments – Part 2

karlw — Tue, 27 Jul 2010 19:06:20 +0000

The CNC router machine has been busy cutting more CNC art experiments. The larger face above is 3-1/2 inches wide and the smaller faces are 1-1/2 inches wide.
I wanted to see how small I could make the faces and still be recognizable.

The faces were all done with a staight .045 inch cutting bit.

Click through to see more cnc art fun…

Help, I’m stuck inside a tree!

A seahorse cut into foam (the kind used to stick flowers in).

Seahorse swimming in a box.

A basswood fridge magnet seahorse.

Susan Arnold, photographer, graphics artist, and friend of Kwartzlab, painted the cnc tree!

Karl Williams
The robots are here.

CNC DIY FUN – Part 3 – Router mounting bracket

karlw — Tue, 26 Jan 2010 05:37:57 +0000

I’m jumping ahead with a blog posting about the router mounting bracket. But, since I only have a few minutes tonight, here’s the mount fabricated out of aluminum with a hacksaw, grinder and a small drill press.
I have completed the X-axis and most of the z-axis of my my CNC machine and will be posting about that soon. The router I decided to use is the RotoZip RZ2000. The mount will allow me to attach the rotozip to the z-axis.

Excalibur Robot Arm Position Controller Device

karlw — Tue, 29 Dec 2009 17:39:15 +0000

During one of my robotics adventures this week I was given what appears to be the controller for a robot arm named Excalibur. It was manufactured by a Canadian company known as Robotics Systems International. According to the serial number tag, the company was located at 9865 W. Saanich, Sidney, B.C. Canada. Each degree of freedom on the device actuates a potentiometer that is connected to a controller board with a parallel port output.

It looks like the original PCB was probably replaced with a custom board. The circuit is made up of a 74LS00 quad two-input NAND gate chip and two LM342 Quad Operational Amplifiers.

A quick search on the net came back with a paper that references the Excalibur arm, also by RSI.

http://dspace1.acs.ucalgary.ca/bitstream/1880/45573/2/1988-324-36.pdf

Karl Williams

CNC Router DIY Build Details Part 1

karlw — Sat, 05 Dec 2009 23:50:53 +0000

Part 1

The CNC machine is considered by many to be the Holy Grail of the maker. This sacred object figures into the literature of maker technology, most often identified with the guru and said to possess miraculous powers. There comes a time in every makers life when he quests for such a thing. But if he is to prove himself worthy he must build it himself. Building such a device will challenge the builder to call upon all of his previous experience culled from the toil of midnight engineering and creative problem solving.

Okay, maybe that’s a little dramatic but this project is exciting because it involves many of my main interests: automated control systems, electronics, mechanics, software, design and building. To paraphrase our friend Darin White and fellow maker commenting on his own cnc machine, “When you see it running for the first time it’s like magic!”

A couple of months ago I decided that it was time to build a CNC router to cut light aluminum, acrylic, and wood. I was designing a new robot that will include some more intricate parts than usual. The thought of using a CNC router in place of the band saw and drill press crossed my mind and a new project was begun.

Now it’s time to create some magic. The following blog posts will update the progress in my search for the Holy Grail.

Karl Williams