Tuesday, July 29, 2008

 

A design charette for a printed linear stepper motor, part 2


In which the narrator possibly figures out a few things... or not... read more


 

Making CAPA Filament

I've been having trouble finding a CAPA or PLA filament supply, so today I did some experiments today trying to make CAPA filament from granules.

I created this:


It's basically the high pressure screw driven syringe with changeable nozzles. A nut is soldered into one end of a piece of plumbing pipe, and a pipe connector to the other. The wood contains a captive nut, a washer is soldered to the threaded rod to form a plunger, and the handle at the top is turned to force the plunger down.

The pipe is then dipped in boiling water for a few minuites so the CAPA melts, then the handle can be turned and this happens:



The nozzle I'm using has a 3mm hole in it, which created a filament of 3.4-3.5mm (pretty good consistency). I'm going to try making a nozzle between 2mm and 2.5mm tomorrow and see if I can get a 3mm filament.

See more pics on flickr

Monday, July 28, 2008

 

A design charette for a printed linear stepper motor, part 1


In which your narrator tools up to design a printable linear stepper motor, however clumsily... read more

Sunday, July 27, 2008

 

First steps towards printing a stepper motor


Printing stepping motors, or parts of them at least, may be the next step to reducing the "vitamins" required to grow self-replicating 3D printers... read more

Saturday, July 26, 2008

 

Stepping with interrupts


The rough test model for running the xy positioning table is being evolved into firmware which will ultimately run Tommelise 2.0... read more




Friday, July 25, 2008

 

Off to the races


It appears that the the faster you run the Tommelise 2.0 xy table the quieter it is... read more


Thursday, July 24, 2008

 

Tommelise 2.0 x and y axes operating in concert


Both the x and y axis of Tommelise 2.0 are not running in concert with a stand alone firmware test program... read more


 

Using (or not) telephone coil wire


Save yourself some grief. Don't try to do connections with moving electronics on your positioning system with coiled telephone connectors... read more


Wednesday, July 23, 2008

 

Tommelise 2.0 x-axis operational


A used Haydon 26000 series linear stepper has been installed on the x-axis of Tommelise 2.0 and connected to the controller board and tested... read more


 

Runout Error!

Greetings All!

I found out that regular threaded rod doesn't have much of a straightness tolerance on it, the hard way. I'm using pre-made pulleys instead of making my own out of Polymorph, so they have a rim that doesn't allow me to use the belt tight minus one tooth method outlined in the instructions. I pulled the belt as tight as me and a friend could get it and glued it together. Things were looking pretty good until I tried turning the stepper motor by hand. As I turned the pulleys went from their "out" position to their "in" position and the belt slipped. Upon further inspection, I could visibly see each pulley's runout error. I'm going to search for more expensive threaded rod to replace the bent rods.

In the mean time, I'm going to finish the electrical assembly and continue work on the extruder head. I might just design a ball point pen holder, manually move the table in place and draw stuff just for the fun of it. I'm going to take a week or two off of the project, so you won't be hearing from me for a while.

Rick.

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Monday, July 21, 2008

 

Tommelise 2.0 y-axis operational


The new Haydon 36000 series linear stepper has been installed on the y-axis of Tommelise 2.0 and connected to the controller board and tested... read more

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OOPS!

Well, I was feeling pretty good about my build and then I tried to put on the Y-Axis servo motor. That's when I found out I used an extra long post in the datum corner. Sure enough, I went back to the instructions and I completely blew through that instruction. I need to poll the audience. Should I just leave the current rod in place an hack it shorter or should I remove the existing post and put in the one I have already cut to length. Material is not a a problem; I bought extra a long time ago. Currently, I favor cutting the existing rod to length in the assembly. That way I don't have to re-align absolutely everything. What do the other builders think?

I also forgot to buy superglue, so my Z-belt drive will have to wait until tomorrow.

I was trying to get finished by July 23rd. I will have to settle for a working Cartesian Robot by that date. There is no way I could get the Extruder done and installed by then. Thanks for any words of encouragement or advice!

Visit my current build at http://htc_engc_bpc.axiscam.net/view/index.shtml

By the way, I left the light on for your enjoyment.

Rick.

Sunday, July 20, 2008

 

Group-Think Stepper Motor Problem Fixed

Hello all. Just a quick update on the stepper-motor problem from last time. If you don't remember, here is my description:

When i sent a signal from the reprap-host program to run one stepper motor, two boards would light up and start trying to move their motors. At one point, when I told my extruder to move along the +x axis, I got a 45 degree +x and +y movement instead.

Vik Oliver saw the post and kindly commented on it, predicting spot-on that the problem was a faulty sync connection. Indeed it was. I had tried to use two jumpers (like the ones on a motherboard) to make a removable connection that would short the three blue sync wires together, and two more jumpers for the white/blue sync wires. Apparently, this isn't a very robust approach, because a couple of the wires pulled free. After soldering the wires together instead (if I need to take them apart, I'll just cut the wires... no biggie), all three axis did what they were told and each no longer caved to peer pressure.

Thanks, Vik! :)

Thanks to Wade too, who suggested that instead of turning all four of my z-axis pullies right-side-up, I should only do two. Not only is this less work for me, which makes me smile, but if I have every-other-one in a different orientation, they should keep the pulley from slipping up or down, and still allow quick removal of the belt. I will definitely try this. Thank you, Wade!

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Assembling T2's xy positioning stage


With the USB/EEPROM link working properly, final assembly of the repstrapped xy positioning table for Tommelise 2.0 begins... read more


Saturday, July 19, 2008

 

Stepper Controller Working

I'm not quite sure why the stepper controller was giving me unpredictable results in the no load testing phase, but it is working great now. Perhaps changing computers made a difference. Since this is a blog, I can't help but share my feelings. I was really pumped to see the thing work. There was adrenaline flowing and happy hormones released when I saw it move on command. I took a video with my digital camera and edited it with Windows Movie Maker for your enjoyment. (There is no sound.)


video

I also discovered I needed some more parts to continue assembly. Shown below are the parts I created on a Stratasys Dimension 3D Printer.



Below is a picture of my RepRap as of 2008-07-17.




If you would like to take a self-directed tour of my lab (including the current status of my RepRap build), here's a link to the Webcam in my room:

http://htc_engc_bpc.axiscam.net/view/index.shtml

Warning! The room is undergoing some changes and no classes are being offered until late August, so it is currently messy. Furthermore, the lights are off most of the time. If it is daylight in Minnesota, you should be able to see around the room.

Enjoy...

Rick.

Thursday, July 17, 2008

 

RepRap Built - Z axis is stubborn

Hello all. It's been a few weeks since I last posted, and I now have a fully assembled RepRap! .





The collapsible stand below it was made from an old laundry hamper frame (the flexible mesh bag used to drape over the top like a garbage bag folds over the lip of a garbage can). Drilling holes for the four steel rods to slip into was all it took, it's structurally sound, and easy to transport. I like it.

The RepRap is not yet functional, though. Problems must pop up to allow us to conquer them and feel superior, right? :)

Well, anyway, the main problem I had was getting the Z-axis to work. The stepper motor kept skipping, not having enough torque to turn the belt.

Troubleshooting:

I tried running the motor from a different driver board (the y axis one, which works fine for the y axis), and got the same result.

I took off the belt and checked how hard I had to hold the motor coupler before the motor skipped. I compared this to the y-axis motor and found that the z-axis skipped much more readily.

This suggested to me that the motor might be the problem... So, I disassembled one of the four posts that comprise the z-axis, a seemingly daunting task, but something that wasn't so bad, in order to remove the z-axis motor and coupling from the machine. I also removed the y-axis motor and coupling, and ran them both side by side, applying the same grip test. Now, the two motors were identical!

Then came my hand against my forehead. Of course they were different before, there was a different amount of friction in the z-axis posts and y-axis rod. Because the z-axis had more friction, it required less of my hand-grip to make it skip. Wow... I should have thought of that! :)

Ok... So it's not the motors, probably.

I then checked how hard it was to turn each z-post, and lubed everything I could. Two posts were still difficult to turn. One would easily turn 90 degrees or so, but on each side of that it was difficult to turn.

To make a long story short, I narrowed it down to washers and nuts at the bottom of the post. When these were loosened, the post rotated freely. When they were tight, it would rotate a certain angle (at first 90 degrees, later about 180 degrees?) and then become too difficult to turn. Rotating in the opposite direction produced the same symptoms.

Take a look at the following video (ignore the audio, though). It shows the bottom washer on the subject post as I turn it. It's hard to see, but it seems to bind at the extreme angles. At first, and when I made the video, I thought the washer was bent. It turns out the washer is sufficiently flat.

The bottom side of the corner bracket supplied to me by Bits from Bytes is not flat, however. It instead, has lower edges and a higher middle, presumably from the casting material shrinking as it cures/dries.

video

Thinking this angled surface was producing more friction during some parts of the nut's rotation relative to others, I decided to sand the high parts of the corner down with my Dremel.



Yeah... That Dremel's an efficient instrument on this plastic. As you can see, I ground about twice as much out as I wanted to. :)

After putting the washer and bolts back on, the post turned quite easily.

The other stubborn post happened to fix itself while I was doing all of these troubleshooting steps. It was probably the lube that helped.

In retrospect, I'm not exactly sure what fixed the first post. I could have just been squeezing the corner bracket too hard, or I could be right on about the angled-corner-bracket-edge thing.

After assembling everything again, I was able to successfully move my z-axis under computer control. Whoohoo! :) :) :)

Challenges ahead:
* Last night, some weired things were happening with my stepper driver boards. When i sent a signal from the reprap-host program to run one stepper motor, two boards would light up and start trying to move their motors. At one point, when I told my extruder to move along the +x axis, I got a 45 degree +x and +y movement instead. This happened after I accidentally unplugged one of the boards with my chair, but I've since double-checked the wiring. Did I short something with the flailing wires as they were pulled loose? Did one of the stepper motor board's driver ICs overheat (the one with the big heatsink gets really hot)? Maybe I'm getting electromagnetic interference with my bundled wires? Who knows?

* My z-axis pulleys were installed upside down, I believe. The lip that is supposed to prevent the belt from falling down due to gravity is on the top instead of the bottom. The belt falls off after about 15 seconds of use.

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Wednesday, July 16, 2008

 

PICkit 2 Cable

I created the cable for the PICKit 2 and it worked great! I followed the advice of the instructions and kept the wires short (about 8 inches long). For those interested, listed below are the pin connections that I used:

Why bother with the PICkit 2? It is a small USB device that is purchased complete. No assembly required. (Other than the in-circuit programming cable that I built above.) Why make the cable? I have a notebook computer and the USB port gives 4.75 volts not the reuired 5 volts, so I need to use my RepRap power supply. Furthermore, my notebook computer has no serial ports making a USB solution a necessity.

One more thing that I have to share with the community... Silver Sharpie markers are truely excellent for writing on PIC chips. I'm not going to recommend adding it to the miscellaneous list, but if you have one silver on black is really easy to read.

I can hear some diodes begging to be installed in some Universal Controller cards...


 

Greetings RepRap Builders!

I should have started this blog when I started the project last January. My interest in this project is twofold. First, I am a teacher at Hennepin Technical College in Brooklyn Park, Minnesota (USA), and I've decided to use the RepRap project as a class project. The class I will use this project for is Industrial CAD Project. The RepRap printer will represent the product created by our "company", so I would like to have a working version for the students to study, document, and innovate. Secondly, I like tinkering with electronics, computers, and programming. This project has provided me growth opportunities in all of these areas.

Since this is my first blog (ever!), I thought I should start with a summary of what has happened so far:
Here's where I stand today. I am unable to establish functional software using a Windows based machine. I can't crack the java classpath code to get all the components to work together. I have downloaded the Live CD and it works well. I've tested the PowerComms card and it seems to be functioning properly. I have verified that one Universal Controller is working. I have failed to verify the other four are working. (I'm guessing that manhandling a PIC processor is bad, as now the working Universal Controller is not working.) Lastly, I have started this blog.

This morning, I am going to create the in-circuit programming cable for my PICKit 2 programmer. I actually bought two programmers for this project and the Ramsey Electronics kit worked to program the first PIC processor, but I really want to know both programmers work. The accessories that I bought for the PICKit 2 have not worked and do not have pin 1 labeled. Therefore, I've tried programming a PIC right-side up and upside-down with no results. I at least had the foresight to buy way too many PICs. Wish me luck...

Rick.

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Sunday, July 13, 2008

 

Cheap and dirty data compression


A simple data compression scheme achieves as much as a 70% reduction in the size of print files moved across the USB link between Tommelise 2.0 and the PC... read more


 

PC/USB/EEPROM link fully operational


Print files in excess of 500 KBytes are being successfully transmitted from Tommelise 2.0's PC, written into its EEPROM print buffer and verified... read more




Thursday, July 10, 2008

 

RepRap protoseedling: toy 2D plotter

The situation seemed hopeless until I remembered a device built by my good friend Neil Fraser: a simple children's toy converted into a 2D Plotter ... read more


Wednesday, July 09, 2008

 

Verifying data quality in T2's EEPROM buffer


Data integrity on the Tommelise 2.0 EEPROM buffer is verified... read more



Monday, July 07, 2008

 

Loading real print files into Tommelise 2.0's EEPROM buffer

A large, real print file was successfully loaded into the EEPROM buffer on the T2 controller board... read more

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Thursday, July 03, 2008

 

Creating the USB data stream for Tommelise 2.0

Slice and Dice's XML output is converted to Tommelise 2.0's USB data stream... read more

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