Friday, April 13, 2012

Much Progress, Some Issues.

It has been a while since I posted, mostly because I have been meaning to take some pictures of various things to show what I have been doing.  Since I still haven't taken those photos I decided to just go ahead and post an update anyway.  Maybe I can get the pictures taken this weekend.

Things were going fairly well for a while.  I finished making a circuit board clamp that I found on Thingiverse and it works fine (my first multi-part object).  In the process I used up the last of my grey PLA and switched to the 5lb roll of Green that I had purchased.  I found that the green filament melted at a lower temp and would turn black occasionally at the temps I was using previously.  After some experimentation I found that printing at a set temp of 187 worked fine but I still have to do some tests on the actual vs reported temp to see whether it is reporting accurately.  Also, it appears that all PLA is not created equal and I may have to make adjustments every time I change a roll.

I removed the spool from my electrical cord reel, sawed it in half, and dropped my green filament in.  I managed to remove the winding handle without breaking it so I can use it to lock the halves of the spool together whenever I drop a new roll of filament in.  I had tried to print a Thingiverse object that was intended for that purpose but found an interesting issue instead:  The large body of the plug printed fine but the fill (set at 60%) began to sag in the middle so that after about 2" of height there was a dip of about 2mm in the center of the object and when the extruder attempted to print the prongs in that spot it was too high above the existing layer to bond.  I believe this is caused by the plastic being too soft and spreading out too much horizontally after it is laid down.

I also started to encounter some missing steps in my prints.  Since my first prints did not encounter this I know that it is not caused by electronics or firmware.  It is happening consistently now but only in one direction on the X-axis, so my prints slowly lean over as successive layers are laid down.  I have increased the current to the X-axis as well as adding heat sinks to all my stepper controllers (in case I need to increase current to others).  I also loosened up the bolts holding the X-axis bearings.  They were quite tight when I checked them so they may be my problem if they were restricting the bearings rotation.

My biggest problem is that I have large blobs of plastic oozing out of the extruder somewhere hidden by the X-carriage.  It started slowly but got progressively worse over time.  I am sure that the original problem was caused by an extruder crash into the print bed.  Since I did not have my endstops working I was manually zeroing the print head and then removing the home instruction from the G-code.  Of course, the inevitable happened and I forgot to remove the instruction once.  That resulted in a full speed crash on all the axis.  I wanted to print instead of taking the time to resolve the endstop issue and so I must pay for my impatience.

So, before I try printing again to see if my adjustments to the x-axis solve the missing steps problem I am removing the extruder to rebuild it.  I have additional brass tips, PEEK sleeves and a couple of removable heaters from Techzone that I never used so I should be able to get it back in service fairly quickly.  At the same time I will install microswitches to replace the opto-endstops that I have never managed to get working.  I tested the mechanical switches with the sanguinololu and they worked fine so I just need to remove the optos and get them mounted.

Hopefully these changes will give me a stable platform so I can proceed with some of the backlog of print objects that I want to produce.  At the very least I can say that I am having a great time after such a long time building the machine itself.  Fine tuning and repairing are a lot more fun.

And I promise, pictures soon!