Monday, August 24, 2009

Lots o Boards


The stepper controller boards arrived today.

Sunday, August 23, 2009

Back Added



I added a back to this to increase the side-to-side stability. It helped but not as much as I would have liked. Next up is adding motor controller board. The back can also serve as a mounting place to keep the PCBs out of reach when you are handling the bot.

Saturday, August 8, 2009

Electronics Melted

I have the motherboard working. I had 1 motor controller working. It melted. I saw silicon glowing red hot, and one of the pins melt. There was a lot of stinky black smoke in my bedroom. Not sure if the device was bad, the soldering job was bad or the motherboard was bad. It was the 12V supply that melted down. I need mother motor controller boards.
Here are some improvements that could be applied to the electronics:
-a fuse or some over current protection mechanism

Well this gave me a chance to improve upon the Green Monster's body; I am adding a back wall. The electronics will be safely hidden behind the wall.

Wednesday, July 29, 2009

Mechanical Parts Completed



WOW! That's about all I can say now. I threw together the Zstage and it looks great. It even holds up better than I expected. I was originally planning on putting two supports on the ends of the X rails to keep this from falling over but it doesn't look necessary now. As it is now this thing will have a range of 20" in the X direction, 16" in the Y direction and maybe 6" in the Z. The treaded rods are hanging down now, I need to translate those up to the top so I can access them with the motor. Also I've got some more room on the Z carriage if I go back to the laser.

In other news I got my motor controller working but only slightly, using the motors I "harvested" from a printer the controller only works with a supply from 6 to 8V. The power supply should be giving this 12V. I am going to try the controller tomorrow with some more "standard" motors. The motherboard is nearing completion.
http://www.cnczone.com has a lot of good information.

well documented boards



Soldered up all of stepper motor controller. Used toaster oven reflow for the controller IC, not necessary spacing on pads very comfortable. Have not tested yet. Will test after oatmeal.
The motherboard I was getting ready to solder and The Dangler stepped in and asked me if he could do it. He wanted to show off for the lady in the room. (He stated that out loud.) The pictures shown here are his workshop and the finished product of the ICs on the motherboard. Very, very, very good work. THe final product of his soldering is pictured here also.

These boards are super well documented. I would like to make that clear. The circuit is easy to understand, and easy to assemble. I never looked at the documentation to solder up the stepper controller. I think that is a testament to the great documentation done by the RepRap team.

Tuesday, July 28, 2009

Z stage completed


Well almost, I need to attach the motor yet. I have not addressed where I'm going to attach the motor and what I will use for gears to spin the threaded rod. Perhaps acrylic?

Reaping the rewards of painful learning


"An expert is a person who has made all the mistakes that can be made in a very narrow field." -Niels Bohr
I made a lot of mistakes on the laser, and now I've got a pretty good handle on it. Yesterday I made a lot of progress on the laser and my acrylic Z axis, where do I begin?
Well first I quit my job on Friday, so I've had a lot of time to work on this project. It's still feel a strange feeling to not be busy doing something I don't like. I like this personal fabricator.
My parts from Makerbot came yesterday also after 4 weeks. I asked one of the founders to throw in two boards to make up for the mistake by throwing in two bare PCBs for the stepper motor controllers. They threw in two free PCBs, but they threw in the wrong PCBs!
Back to my Acrylic, I made this "capture nut" and press fit assembly to attach vertical and horizontal pieces. I made the gap to attach these 2mm larger than the material thickness; that was loose as a goose. I later made the gap the same dimensions as the material thickness and that works beautifully. It is a very tight fit, I had to do a little filing but once the pieces went in they were not going anywhere. I had a fear of the capture nut weakening the material, but 1/4" acrylic is very strong.

The picture here is the Z base with two press-fit supports attached using no capture nut, there is a nut in one piece but no bolt.

Saturday, July 25, 2009

Heavy Nut


Part of the new Z stage I designed was the capture nut. This method of attaching two 2D pieces to make a 3D assembly relies on a nut being captured and not turning. This is accomplished by keeping the slot cut out for the nut too small. When my parts came out of the laser the slot was larger than expected. I found a solution to this by going to the hardware store (OSH in NorCal) and buying a new nut. The new nut needed the same threads 5/16" but a larger outer diameter. They carry this at the hardware store and it's called "Heavy Nut".

My new novel Z axis is not done yet, and will need another set of captured nut assemblies. I will reduce the tolerances so a standard nut will work.

Results from the Friday's Laser Session


Pictured here are the results from my laser session on Friday night. I did not get all the parts I designed printed out. I learned a few things.
1. Saving a pdf from Solidworks directly is 1/10 of the actual size when I import the pdf to Adobe Illustrator.
2. Pdf's imported using this method get printed 3 times. DXF files get printed 21 times.

The 3x lasering made some dimensions on my parts larger than expected.

Friday, July 24, 2009

New Z stage, from the ground up


I spent some time redesigning the Z stage. To the right is a screenshot from SolidWorks of the components I have used. I used a technique new to me, called capture nut. I will add more details on how this works later, I will bring it to the laser tonight. The small square is a 1" by 1", this is used for calibration as the dimensions get altered when I import this into Adobe Illustrator before printing.

Well I just did some cleaning in my life and got a lot more time to devote to this project. I decided to totally deviate from the McWire Z state, I think it could be done better. So I designed one using acrylic plastic instead of steel. To the left are the main supports for the Z stage and whatever tool will be attached. I really like this color, but locally they only had it in 1/8" so I special ordered it in 1/4". The price was great. I have kept the protective paper on there to avoid any scratches while I'm sawing and drilling.
The thing will work like a classical microscope, instead of an eyepiece going up and down I will have a tool going up and down.

Wednesday, July 22, 2009

Alpha Geek


I decided to experiment with using a 45W laser to pattern the resist on a PCB, I coated a copper clad PCB with flat black paint then etched my pattern in the circuit. (Image to the left.) When it came time to etch the board would not etch very well, what was happening was the laser was not removing all of the paint, and that was enough paint to resist the etchant.

One Step Closer to Self Replication



The image to the left is the output of a laser printer on some photo paper. I am making my own PCB. I am making a motor controller for my personal fabricator. The design of the motor controller is not much, they get 12V in and take in a logic signal in the 5V range, and output the necessary voltage levels for driving a stepper motor. I took the existing design from RepRap and laid it out in 1 layer instead of a 2 layer PCB. This opens the door for me to make the PCB at home. I am doing this because the company that sells the board has not shipped my order yet and it's been close to four weeks since I ordered the stuff that was "in stock" at the time of my order. In the larger scheme of things you can use a CNC mill to mill your own PCB designs. This is pretty big. Doing this to a RepStrap would make it closer to being a RepRap. Although I think people who worry about such definitions are internet trolls. Milling a PCB for surface mount has been done before, and it will be done again. The board pictured on the left is not yet ready for milling, instead I'm using a technique that involves ironing the pattern on to a PCB and then etching this off. I'm not the originator of such a method, but I have successfully done it before.

Up To Speed


I've been making this personal fabricator for a month or so now, but I just decided to write about it. I really needed an independent place to host this. I think personal fabrication is a really exciting technology, there is a lot to be done yet in this field.
I started from the RepRap McWire 1.2, and made a few changes. Right now I have the X & Y stages completed. In the picture here there are no motors or springs. I have both of those. In the end I am deviating from the McWire design, as the guy who posted most of the work did also. It's good to get started on and for learning, but there is a lot of waste in it as well.
The blue platform for the two stages is acrylic plastic 1/4". I used the patterns from the McWire 1.2 and cut it out on an Epilog 45W laser. 1/4" stretches the limits of the 45W Epilog; I had to do 1 pass on the highest power setting and one pass on a slightly lower setting to make sure everything was cut properly. The was a little bit off on the Teflon bearings, so I drew a set of new .dxf files. I will post those files later. The McWire 1.2 calls for 16 skate bearings. I had some leftovers from changing my rollerblade bearings. Skate bearings was a brilliant idea. You can get 8 for $6 here in San Jose from the skate shop. If you buy bearings elsewhere they are 10x the cost. The rest of the stuff I got from OSH here in San Jose. The Teflon bearings I ordered from McMaster-Carr. I want to say it was a pleasure ordering from McMaster-Carr, they had my order on my doorstep in 2 days and it only cost me $6 in shipping. (I live 5 hours North of their West Coast distribution center. )