Wednesday, 20 April 2011

New Pulleys!

I haven't done much of late as I have been waiting for parts...

Thanks to LenBok I now have some different pulleys to try

I did a visual comparison between Lenbok's Pulleys and my own, apart from his being a much nicer colour and higher res, there is a significant shape difference in the teeth



The left pulley is my original, the right is the new one, the teeth in the left pulley are much pointier than the teeth on the right pulley, which are more square. Since the belt also has square teeth, i'm hopeful this will solve some of my slop issues in the Y-axis.

Thursday, 14 April 2011

Y axis issues and retuning to 0.36 Z axis resolution

I continue to have issues with my Y axis, I have exhausted all software options...
So now there are only hardware options. I have asked another NZ reprap person to print me a new set of pulleys as high a resolution as they can manage.  If this fails to improve things, I will look at investing in some commercially made pulleys.

In the mean time Ive been learning on how to tune skeinforge, I found this nice collection of test objects and instructions here  

I noticed a little while ago that the default Z axis resolution is 0.4mm in replicat.org using skeinforge 35. Reading up on this a lot of people tune their Z axis to less than this, the record is 0.1mm  most go for 0.36mm. The issue is volume, the volume extruded from a 0.5mm nozzle, the lower the Z value, the volume has to spill out into the  X and Y Axis. This is why you can get smaller nozzles. The common nozzle sizes seem to be 0.5, 0.4, 0.35 and 0.25

I have decided to re-tune for 0.36mm steps in the Z axis.

i started with the standard 20x20x10mm boxes, as per the article I used solid infill


The first test looked  like a toffee that has been in the sun to long.
The second looks nearly the same, but from the side angle...


The issue here is that the layers build up, fractionally over size, till the nozzle scrapes the plastic to the side.

The solution is to reduce the extrusion rate. After 5 attempts I have a standard solid test cube with a Z resolution of 0.36mm

I then made a 20x20x20mm solid cube and verified the issue wasn't still happening at a higher level, it was a little and few minor tweaks later and that that was also corrected.


For now the reprap is on hold till i get new pulleys, or sort something else out.

In the mean time, I have finally located pipe for the main frame of my CNC machine. 


I will replacing the spine of my CNC with this soon.

Why I mention it here in my reprap blog is that the aim of this CNC machine is to mill Reprap cct boards. And maybe even some of the parts from solid materials.

Monday, 11 April 2011

Issues with Y Axis

Im still having issues with my Y axis, I seem to have stopped the random size discrepancies, I pulled the axis apart and found that the board didn't run down the bearings very well, it was quite tight. I moved the right hand bearing right by about a 16th of a nut rotation and is now a lot loser.   Now I seem to have over and under shoot issue, where its doesnt seem to end up quite in the correct place. I have currently glued the nuts of the belt holders down so I can pull the belt tight and tighten the screws without a third arm!

In the mean time I printed this, as it doesnt need to be so dimentualy acurate





Back to The Y axis, I have never liked the way the Y asis bearings work. Apparently I am not alone in this.

I was looking at the Prusa kit from Makergear.com

I noticed that instead of the standard washer and bearing combination of a standard Prusa on the Y axis they have a Printed part. The standard part has a space of 9.6mm with a 5mm pulley in it, this wanders off the bearing all the time and im sure its not doing anything any good.

After a bit of hunting I the piece found it on thingiverse and have made two.


Unfortunately this is right in the heart of the machine, and it will require rebuilding nearly the entire machine... Im not that keen on that at the moment. Ill try all other options before installing these.

Thursday, 7 April 2011

Added my first thing, and size calibrations continued

I Just added my first thing to thingiverse. Hopefully this is the first of many things designed by myself.


Its a filament stand, it keeps the filament off of the stepper motor and its cables.
It was an interesting thing to design in openscad, as I wanted round parts, its not obvious how one does this at first.


Im still having some issues calibrating things so that they turn out the correct size. This should be linear, Q many degrees move the Y-axis R mm, but it doesnt seem to want to be that simple.

I have printed myself a test pattern to look at this further.


These boxes are 10 mm larger than the previous one.
Then I measured what I got vs what it should be...
Currently the larger sizes are more accurate than the smaller ones.
Eg the 20mm is 19.67 x 18.69
But the 80mm is 79.89 x 79.87
The Y-axis seems to vary a lot...

Wednesday, 6 April 2011

Z axis update and Purple!

The Glue on the last part of the replacement Z axis is dry.  The alignment is now much better, my repstrap probably needed a bit more tweaking before I printed the original parts, but I was to impatient!

The Z axis was still very stiff... on both sides, so I pulled it all apart again and had a play. Inside both the x-end-motor and the x-end-idler is a Dual nut arrangement with a spring in between them, The idea is to take up the slop in the drive thread. I Reassembled things and left this Dual nut arrangement as lose as I dared. This has loosened off both Z axis threads a lot and  I am now a lot happier with the Z axis.

I also started to play with the purple PLA today. So its back basics for now, more 20x20x10mm test cubes, and just as well to, I found that my X axis seems fine but my Y axis is out, by a full mm!

Here are various purple test parts

The test cube may all look the same but they aren't, they are various attempts to get the dimensions correct. The top left is the only 20x20x10mm.
I also printed a 40x40x20mm because I wanted to check the size error scaled.
There is also a test part, this shows other issues, things to look at tomorrow.

Tuesday, 5 April 2011

Z axis and hot ends

Today I replaced the final part of the original Z axis, it is currently being held together while glue bonds. Gorilla glue is interesting, its starts out a a fairly runny liquid, but is already sticky, you use it like normal glue, but after about 15 minutes it foams up fulling all gaps. It does take 24 hours to be fully dry etc though. Its not pretty, but is quite tough and easy to remove the dry excess.

When I migrated the parts from my Repstrap I found an issue with the PTFE in the hot end.


The thread has basically turned to charcoal!
I have seen other people with similar issues, especially those who work with ABS which has a higher melting point, the PTFE just cant handle it long term.
In my case this probably happened when my thermistor decided to take a little holiday and things got really hot for a while!

One other limitation of my current hot end is it is "hard coded" to 0.5 mm 
It works fine, but It needs to be completely replaced if I want to experiment with a smaller aperture. Replacement also involves a lot of dissassembly. 

Makergear have the solution for both these issues, they sell a very nice "V3 Hybrid GrooveMount for 3mm filament" Its modular in that you can change the "Big end"  and you change the extruder hole size. The main parts is PEEK and PTFE, providing more strength and heat resistance. It is also really easy to attach with their own grove mount system.

Mine arrived today :)


It also came with chocolate!!! I'm not sure what customs would think of this though, if they where to notice it.

Monday, 4 April 2011

Glowing PLA things

I managed to take a Photo of my glow in the dark X idler.


This is actually under a UV lamp, but it looks the same.

Also interestingly the purple glows a nice orange under UV


Doesnt show up the best, but... in real life its bright orange!!

Sunday, 3 April 2011

Yay, plastic!!

The plastic I had been waiting for arrived today

Yay!


Thanks Vik (My PLA supplier)

Z axis issues

I have been continuing to have Z axis issues, but not enough that I cant make it go with a bit a a poke and a prod. So this weekend Ive reprinted on the Prusa the Z motor holders and the X motor holder and idler parts (the other end of the Z Axis).

The new parts are much nicer than the old ones, as this machine is much smoother in its printing that the repstrap was. I am still blown away how much faster the Prusa is also.

Ive have installed the left hand side and it is noticeably better in the Z axis.

On printing out the X axis idler, I ran out of while PLA.  I saw this coming and decided I would try feeding in some of my Glow in the dark PLA as it was printing, just to complete the print.

Surprising this worked fine, the extruder didn't skip a beat.

So I now have a two tone X idler


The top half glows in the dark quite nicely. Sadly I cant seem to convince the camera to take a glow in the dark picture.

Now I have to wait for more white PLA to turn up, I ordered it over a week ago... but I suspect NZ couriers are using snails as beasts of burden.  Its only coming form the North Island. I get things from England faster than this...