Thursday, January 20, 2011

Prusa upgrades installed

it took some tinkering after installed but everything is together and moving again. It looks like I have some backlash on the new x-axis, how unexpected... so I have to turn lash on, and I'm turning the feedrate up to 10 from 5.7, trying a proportional flowrate of 8.7. trying that out in Skeinforge, oh and lash set at default of 0.2mm.

A problem to fix first, for some reason the z axis is stopping about 5mm up, makes a grinding like noise... both motors stop.

I changed it to 1/16 stepping, whisper silent, works, but still stopping in the same place. I'm going to check the captive springs, they might be jamming somewhere. It appears that the hexagonal holes the 'captive' nuts on the threaded rods are too big.

17.(optional) Insert a spring into the top of the hexagonal channel
oh, apparently it's optional I guess I could try without the springs.  In taking it apart I found the ends of the springs were jammed into the top nut on one side, and the threaded rod hole on the other.

Yup, the springs were the problem.
Pictures to come...

guh, more jamming PLA

I've decided I might have been wrong before, I'm trying 190 as the temperature again, maybe I can get the extruder idler block to work.

Out of frustration and impatience I started the print, and pushed the unattached bowden cable into the extruder after it was up to temperature... strangely that is working...

It came out, but there's a lot of strings, and seemingly too much plastic.  I'm increasing feedrate to 5.7, trying to print 39 tooth gear. I'm doing the same thing to start the print, hopefully this will not be a longer term solution... well it's jammed again... another unfinished print.

PLA working... ish

I'm trying out a difference in settings I found here. I'm hoping by also lowering my "Infill Perimeter Overlap" ratio while raising the "Infill Interior Density over Exterior Density" ratio to 1.0 I can get slightly better prints. I've had a few successful prints in 4043D PLA, and I'm continuing with that.

It appears after further attempting to print, that at present I cannot reliably print with PLA. I either need be able to print with a higher flow rate or not have a bowden cable in the middle of the extruder assembly. the heat from the hot end is travelling up the pla filament into the bowden cable where it softens and creates blockages. quicker prints would forgo this, but best would be quick prints without the cable assembly.

Catalyst meet PLA

Trying to get PLA to print, I'm working at printing wade's extruder, it's jamming on occasion. I'm turning up the the temperature 5 degrees from 190 hoping this will prevent jamming.  I was considering an oily sponge connected through my bowden cable But I'm trying out just turning up the heat a bit.  I found there was a blockage, a large blob above the thermal barrier and below the nut holding the bowden cable to the hot end.  This might be a reason to remove the bowden cable.
*disassemble extruder*

That was the jam that stopped the extruder... how to fix this...
trying to print again...

I think the problem is a result of metal conducting heat up to the nut holding the hot end of the bowden cable in place, PLA expands or simply melts enough into a blob and bob's your uncle.

I don't think it's likely that using a bowden cable with PLA is workable.

Monday, January 10, 2011

posted on eBay

I posted the ABS parts from a Wade's Extruder. Here's the listing...
 I finally have some really decent prints coming out of my repstrap. I managed to make a couple of wade extruders, I wanted to replace some parts on my extruder. Instead of saving them until I can assemble my first child reprap I'm selling them. These are the parts that turned out the best, I took the second best ones for my use.

As you can see in the pictures the motor block warped furthest from the bearing block.  There a couple dark spots in the block also. These parts are printed in uncolored ABS.  I started cleaning these up, but some of the holes will still have to be reamed or drilled.  Only what's pictured is included.  If you have any questions, please ask or check my blog.

Wade's Geared NEMA extruder
Beefed up idle bracket for Wade's extruder by nophead
Gear with Setscrew for Wade's extruder by nophead

Friday, January 7, 2011

Mendel Axis Pulleys

Telling the Truth / Lying to machines

It's likely that most of my thought processes, no matter what I'm doing, are colored by my conception that I'm an artist.  As such I'm most often interested in how to use a reprap.  To me this new tool isn't just something where I can find the best settings in Skeinforge, and click print with each new object. There are varying scales and best ways, little hacks to get best prints. I think at this point I understand enough about the process and settings in Skeinforge that I can start exploring the many ways to print. An artist is not defined by what medium they use, but how the medium is used.

I'm starting small, while within the scope of printing other repraps and reprap parts. Yesterday I was fully focused on an Axis Pulley. I have printed about 10 of these in the last couple months, never happy with the results. They come out, they're usable but it always seemed It was possible to make them better, but I couldn't articulate to the computer how.  Starting with the assumption that the hardware machine is limited, but nothing could be done to get about these limitations, I started looking to firmware and software.

top usable, but ... bottom aesthetically pleasing
From hardware up; the firmware is still a work in progress of hacking from an older standard reprap code. There were a few things I thought I could get working that would make my prints higher quality. Namely; 1. a working heated bed, 2. better extruder control 3. fewer pauses 4. quicker prints.

1. a working heated bed, I know how this works and had a low temperature heated bed working previously, but not cost effective for finishing in a day.

2.The extruder works, but for some reason... likely because I'm using old code intended for a DC motor, the stepper motor will not reverse.

3. fewer pauses... This could be fixable in just code, but the code possibilities are limited by the hardware, so this is out.

4. quicker prints. This is really dependant on hardware and the two previous points working

SOoo... the extruder firmware code; I managed to get some of the functions from a more recent reprap firmware intended for an Arduino Mega with a stepper extruder.  I cannot run all the code intended for a Mega on the much smaller and weaker Arduino 328p, but the algorithms and a couple functions could be adapted and in the end I managed to get the extruder to go in both directions. WOO HOO!

But still my pulleys looked unfortunate. So software. What can i do in Skeinforge? I played with this all yesterday, really 90% of the day went to adjusting things in skeinforge, trying different infill ratios and patterns. No matter what I did the pulleys still came out about the same, with gaps in the gears. So then I tried lying, which comes just before sledgehammer solutions. I told skeinforge the plastic coming out of the nozzle was less than it actually was. the setting originally was .48mm for a .50 nozzle, I dropped this to .45 then .42 and I started lowering the flowrate in speed from 5.6 to 5.4 and 5.3 I finally end up at a layer height of .36 and a flowrate of 5.0 an 11% reduction in flow and 25% lie in layer height. But it worked you can see the difference in the pictures above.

Sate of the Machine 2011

State of my repstrap:
It works, it works consistently, but there was much changed and adapted to get to this point. For myself and for anyone else on so perilous a path I thought I should document what finally worked to get this PITA to work.  I'm going to spend 2011 working to produce as many repraps as I can, many of the problems I've had over the last year could have been solved much quicker by having a second machine.  I have to figure out where I'll be selling the ones I don't keep, for the time being it's likely to be eBay.
the heap that finally worked

Things added;

heater board (PWM Driver 1.1)

Dc driver board

Plastruder Mk4

arduino proto shield, sorry don't remember from where

Thermistor board

Old computer Power Supply, to replace the 18v PS

washer flywheels, I needed a fly wheel on either end of the X axis threaded rod. This though I'm finding is making the X-axis inaccurate because the threaded rod overturns.

Blue Painter's tape on wood base, the original plexiglass build plate warped terribly.  But presently I'm printing on a plexiglas plate on top of my heated bed, which is off... as it doesn't get warm enough for ABS

IDE Cable; I found splitting some old ide cables where needed made for cleaner wiring

5W-30 motor oil, I needed oil... I had it on hand, probably not the BEST idea

Things lost:

2 - 3 thermistors, yea I broke a few when making and remaking extruder nozzles

Feet of nichrome wire, well I kept it and ended up using it to make a heated bed

many feet of Kapton tape, but I still have more

patience... I totally lost it a few times

pounds of ABS... it's all in a box, hopefully I can recycle it some how in the future. Or I'll throw it out when the box is full

I managed to print Wade's Extruder and have been using that with much MUCH success.  The Makerbot MK4 / Dc Driver board have been relegated to backup status.

The path forward:

I've been working on printing a Prusa Mendel out of ABS, most of the printed parts are done.  Some of the parts are being adapted right now to replace the Z and X axis on my present machine.  I want to replace the threaded rod X-axis, which means I have to replace the Z-axis. That is coming in the next couple days and weeks.  I bought some black PLA from Ultimachine a week or so ago, I'm going to try switching to PLA for a while starting later today.

I've been thinking about a modified Makerbot I might make make in the course of the year... more about this at another time.

I had been keeping extensive notes on my computer before Christmas, I'll post those as soon as I edit them for readability.  Going foward I'll be keeping my daily notes on this blog, seems like a good use of this space.