Monday, June 30, 2008

 

Dusting off Slice and Dice

Slice and Dice is resuscitated for use with Tommelise 2.0... read more

Sunday, June 29, 2008

 

Making the Extruder Extrude - followup

An update on my extruder:

With a bit of hot-melt glue, I've filled in the extra space around the rectangular void in the "molded part that interfaces with the motor's drive shaft." Now, it does not wiggle on the drive shaft as it turns, and I believe it is more centered.

As for the silicon tubing, I found that part of my problem was that I wasn't extruding at a good temperature for HDPE. After previously carbonizing my JB Weld, I was a little skittish about high extruder temperatures. Since the melting point of HDPE is around 130C, I thought 150C should be plenty hot. Only this weekend did I find a "Guide for Newbies" that specifies some temperatures that the wise and skilled nophead has been using:

HDPE.raft_temp = 200
HDPE.first_layer_temp = 240
HDPE.layer_temp = 220

PCL.raft_temp = 0 // no raft
PCL.first_layer_temp = 130
PCL.layer_temp = 120

ABS.raft_temp = 200
ABS.first_layer_temp = 215
ABS.layer_temp = 230

PLA.raft_temp = 0
PLA.first_layer_temp = 180
PLA.layer_temp = 160
Alas, when I cranked the temperature up to 200C (I'm using HDPE), the extruder extruded just like it was supposed to. Piece of cake. :)

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Headaches

Electronics and firmware development proves to be much easier than software... read more

Monday, June 23, 2008

 

Alternative alignment

The Darwin build instructions recommend squaring up the frames by adjusting the corner blocks to get the correct length stubs sticking out, as the excerpt below shows: -

20.JPG

This assumes that the rods are exactly the same length. I think what is actually important is that the gap between the rods is exactly 400mm. To achieve that I made a temporary jig from a couple of diagonal tie brackets and a piece of the 8mm rod and adjusted it so that the outside of the brackets was 400mm. I then used that to space all the rods of the lower frame. I also set the short stubs to 20mm using the first method above. Any variation in rod length then ends up on the the 28mm stub.

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Mapping print data onto the EEPROM buffer bank

A few simple functions allow for mapping of print data onto a bank of EEPROMS... read more

Sunday, June 22, 2008

 

Making the Extruder Extrude

I am now working on getting my rebuilt extruder to extrude, and there seem to be a couple obstacles to perfect extrusion.

On first assembly, it seemed that no amount of tightness (way beyond the "hand tight" suggested) on the silicon tubing produced enough "grip" to push down the filament without slippage.


I plan to take out the silicon tubing as I have seen on another RepRap blog somewhere (I don't remember where), and see if that helps.

Also, the drive shaft does not seem to be rotating with a constant velocity. Instead, certain parts of the rotation are faster, and others are slower. I suspect it has to do with the fact that the rectangular hole in the moulded part that interfaces with the motor's drive shaft is too big. Therefore, certain angles of rotation cause the part to shift on the motor and the resulting rotation to be uneven. Another possiblity is that the axis of the flexible shaft and the axis of the motor are offset (also because of the interfacing piece), causing different amounts of "slack" in the flexible shaft, and therefore different amounts of friction. What do you think? Here's a video of the situation. Try cranking up the sound to hear the differences in the motor wine. Also, any clicking you hear is not the camera, but is that "interfacing part" shifting on the motor's drive shaft.

video

I plan to test both of these thoughts when I continue. Right now, real-life beckons me. Alas, I must go grocery shopping...

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Up in Smoke

Let me recount a little episode involving my fledgling RepRap extruder and its self destruction last weekend.

I had just finished assembling my extruder and was ready to test it. I followed the Thermoplast Extruder instructions, slowly increasing the set temperature to the melting point of HDPE.


( I found that changing the Desired temperature didn't have an effect on the "current temperature" until the heater was deactivated and reactivated. That was a little confusing at first, and could maybe be improved upon. Ideally, the set temperature would take effect after changing focus out of that field or after a delay of a second or two.)

With a set point of 50C, my 'current temperature' wouldn't budge above 38C. My extruder started smoking, and by the time I had shut it down (a minute or so later), all of my JB weld was charred and my 8 ohm winding of nichrome wire had transformed into 32 ohms, rendering it useless. What happened? Apparently, the temperature of the extruder barrel was not interpreted correctly by the reprap-host software. When it thought the barrel was at 38C, it was actually around 260C, the point at which both JB weld and the PTFE (Teflon) used in the extruder break down. I figured out the 260C figure by looking at the displayed temperature when submersed in ice water and (near) boiling water and extrapolating.

Here is a picture of my extruder (with insulation removed).

My barrel's charred remains (sad. :-[ ).


With help from the kind and generous Ian Eagland in the RepRap forums, the culprit was found.

These three settings in reprap_host were my problem:
Extruder0_Beta(K) 550.0
Extruder0_Capacitor(F) 0.000003
Extruder0_Rz(ohms) 4837

I had set these to the actual values used in my hardware, which was a mistake. These constants are left-over from the pic-based electronics, and in the Arduino-based systems no longer represent real physical entities. Setting these values to what I was explicitly told to do in the Setup Host Software part of the Generation2Electronics instructions fixed my temperature readings.

I have since tore off all of the weakened JB weld and nichrome wire and replaced it with new stuff, using both a thermocouple and thermistor in case I ever want a second opinion on the temperature.

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Friday, June 20, 2008

 

Opto Isolator v1.0 Build Video

Here is a timelapse video of me building the new Opto Isolator v1.0 board.


Opto Isolator v1.0 Timelapse from Zach 'Iowa' Hoeken on Vimeo.

Wednesday, June 11, 2008

 

Walking CNC Router Robot


Hello All, My name is Matt Denton, I'm very new to RepRap, and only really discovered it after building this robot which was spotted by a RepRap member. I've been building hexapod robots for about 8 years, and most recently converted one of my hexapods into a walking CNC router.

This idea has been bouncing around in my head for some years now, but I only just got the time and a hexapod with enough payload capacity to pull it off. I'm not sure how far I will take this project, currently I have only cut polystyrene and high density foam, but I'm sure with some tweaks I could cut soft plastics.

Video of hexapod machining 3D face You may want to turn your sound down.. or wear ear defenders, the router is pretty loud!

More details of this project can be found on my forum here:
hexapodrobot.com

I hope you like the project,

Matt.

Tuesday, June 10, 2008

 

A RepRap sprouting in the midwest - Intro

Hello world. My name is Andy, and I'm a huge RepRap fan.

This is the beginning of my blog contributions, whose goal will be to document the building, using, maintenance, and improving of my RepRap machine. Hopefully, doing so will be cathartic for me, help build community around the RepRap project, and enhance the flow of feedback necessary to continually improve the design.

I first heard about the RepRap project from a Slashdot article in the beginning of April, 2007. I was hooked. I've always wanted a rapid prototyping machine, I am a huge fan of open-source initiatives and the service they do for the world, and the thought of such a useful machine subject to a potentially exponential growth inspires awe in me. Furthermore, a well-designed future version of the RepRap has the potential to bring to much of the have-nots (at least 90% of the world) the production capability now reserved for the wealthy. If this project even slightly narrows the gap in "wealth" between the rich and those less fortunate, it will be a huge success.

Shortly after catching the RepRap bug, I looked at securing the parts for my own machine. While the RepRap parts lister is a great tool, I found it difficult to determine which combination of suppliers would provide the needed parts at the lowest cost. I spent about a week trying to figure this out before concluding that the Bronze Mechanical Kit from Bits from Bytes was about the same price as if I got all of the mechanical parts individually, and therefore would be a better value. Part of the reason for this is that many of the hardware (like bolts) need to be bought in quantities of 100, even if only 3 are used, significantly increasing the cost. About $1100 later, I had all of the mechanical and electrical parts for a RepRap. This is significantly above the $500 price point quoted all over the place, so I must have made some poor purchasing decisions somewhere. Either that, or the extra parts I have are worth a lot of money. :)

I shared my excitement with a few friends and got a small team together to build a RepRap together (8 of us, 3-4 of which are available on any given weekend. Some bribery in the form of food and at-cost printing of parts was offered. :) ). So far, we've had five six-hour builds. The first two were spent teaching people how to solder and soldering up the electronics, and the last three were spent building most of the cartesian robot and thermoplastic extruder. Much of that time was spent decyphering the directions (which were actually quite good) and trying to iron out discrepancies between the parts referred to in the instructions and the molded parts supplied by Bits from Bytes, which were in some cases different. It's probably quite difficult to keep production in sync with an ever-changing design.

I look forward to posting about futher developments tomorrow. Please leave comments about all or any of these postings. I'd love to hear what you have to say. :)

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Sunday, June 08, 2008

 

Talking to the EEPROM buffer through the USB link

After a great deal of difficulty, I got the PC-USB-18F4550-EEPROM link working smoothly... read more

Tuesday, June 03, 2008

 

512 Kbyte EEPROM buffer operational on T2 big board

Circuit chasing and firmware testing of the 512 Kbyte EEPROM buffer from the Tommelise 2.0 controller board is complete... read more

Monday, June 02, 2008

 

T2 USB transfer speed takes a big jump

The comms rate for the USB connection between the PC and the 18F4550 took an 8-fold jump... read more

 

A 512 KByte data buffer for T2

Having proved the practicality of using EEPROM for a print instruction buffer a full-sized one is built for T2... read more

Sunday, June 01, 2008

 

Writing fast to the EEPROM

Writing data to the 24FC1025 EEPROM by the page... read more

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