Sunday, September 9, 2012

Rostock 3D with improved extruder

I made yet another change the the Rostock. I have been using a wades extruder but the high ratio between the gears had been causing some issues. Although it had a lot of torque, it is a bit slow to respond to the big retracts needed for retractions through the bowden tube. Because it need such long retractions and such a hi ratio, retractions would take over 1 second causing pauses as the head waited for the retract.
So I created a new set of gears that have a much closer ratio (almost 1:1).
The response is much much fast now and it has improved print quality too.
here is a little video. Nothing too special but its printing a complicated print and the extrudes start and stop exactly where required even the little drops:
The camera really seems to be sensitive to the noises from the printer. this video makes it sound like its making a racket but its actually nowhere near as harsh as it sounds here.

Thursday, September 6, 2012

New Rostock Firmware installed and working

No new images today but I just wanted to report that the Rostock is working well with the new firmware.
I did initially have a teething problem where my extruder was not working after the upgrade.. but I found the magic setting I needed to adjust. Interestingly the parameter was set the same in both versions of the firmware :Default Retract Acceleration. Its possible that it may not have been properly implemented in the first version of the firmware. I am not sure why the value had to be different but it is working again.

One of the biggest changes in the firmware (amongst many) is the removal of the bottom end stops. These are no longer required for leveling the effector or finding the home position. Although this means the Rostock no longer does its little dance when you home all axis, it simplifies the how process and is more straight forward. This also means you may be able to use other controller boards that do not support both min and max end stops (like the Gen6 for example). Although I have not tried any of these.

I am still working on getting the best out of the bowden extruder. It still occassionally fails to deposit small amounts after a retract, but it is getting better with each tuning.

Also I manages to print several complex objects using Pronterface.exe. The issues where this used to cause pauses during prints seems to no longer occur.  I printed from pronterface for about 3 hours straight without a hitch.

The print quality of the layers is really good to my eye, except for the occassional miss with the extruder. If I can nail these issues, it will be almost flawless.


Sunday, September 2, 2012

Another Improve in Rostock print quality

I think i have solved the lumpiness issue now. I was correct in that I think it was being caused by a big difference in speed between standard perimeters and Small perimeters. This would result in little blobs as it slow down and the extra flow of the bowden would deposit a bit too much plastic. I changed the slice settings so they both print at the same speed (90mm/s) and this seems to have eliminated the "warts" I was getting on the outside of the objects (See Yoda below).
I had to post process this picture to remove some of the colour. The camera was having a hard time with transparent red again.  This is Spoctopuss a .2mm layer height.


Saturday, September 1, 2012

A Yoda I have printed hmmm?

Well After many failed attempts to complete the print job of Yoda. I finally succeeded.
With previous attempts one axis would miss a step somewhere along the way throwing the whole print out. On rostock it is hard to tell which one was the culprit so I went back to basics and checked the reference voltages on the stepsticks and found one was lower than the other two. I set them all the same and managed to complete the whole print at .2mm layer height with a .5mm hot end.
Its a long way from perfect but at least it printed.
The image on the left shows him with the support structures still in place.
The main issue that will affect all prints are the small blobs... it is extruding inconsistently. Its possible that with the bowden extruder it is having trouble if I have too much of a speed differential between the speed of the small perimeters and large perimeters. Flow control could be an issue there. I will try to make the speeds more consistent and see if that helps.

The holes in the ears I think are cause by them simply being too thin in the model so I am not too worried about that.