Pronterface caps on/off oddity

Quentin mentioned an oddity about Pronterface, which I have now experienced myself, at least under Linux. When typing in commands in Pronterface, e.g. G1 X100 Y100 Z10 F5000, it is important to stick to all upper case or all lower case. Once you start mixing cases, the result is NOT what you expect.

 I typed in the example above, except I used a lowercase "y", and Morgan again tried to wring its own neck (at least, tried to move the print head right through the drive shaft).

This is just another thing to be aware of, this can seriously (and probably did, for me) hamper your calibration efforts.

Happy with results

I completed the final calibration of the Theta and Psi steps per degree today. Fine tuning, just printing another calibration phantom and updating the steps. The Morgan is printing very nicely, except for small parts. I have no fan and I have not experimented with Slic3rs cooling settings. Large parts are sticking well and printing nicely. Small parts are sometimes "smearing" as if the previous layer is still soft (which it probably is). Time to move on to PLA, which from what I've heard, is easier to work with. The PLA is on its way, from ABS-Filament (online store). Everyone in Centurion is sold out.

Update on bare bed

The clean plate glass bed (no Kapton tape) works well for small parts, but as soon as the part gets larger, it seems to come off the bed rather easily.  So, for the time being, it will be Kapton tape always.

I have three plate glass sheets 200x200, I will keep at least one bed taped up and ready to go for if the working one should tear or bubble. 

I now wish I had purchased the 200mm wide tape I saw on e-bay!  Lining up the 50mm wide strips of tape is a lot of work.  Not too difficult, but work.  But then again, 200mm tape might be more difficult to keep bubble free.

Bed without Kapton tape

The Kapton tape on the bed started looking a bit tatty, and as an experiment I tried printing ABS directly on the plate glass. Initial prints show that the workpiece does not stick as well as to the Kapton tape, but it does stick and does not warp.  For the moment I will keep the glass bare and at 110 degrees, and see how that goes.

Acceleration of 100 mm/s/s gives good results, as well. Slow but smooth.

J-head thermistor died!

For some reason, the thermistor in Morgan's J-head died last night.  The print I set going was completed, and upon startup today I could get no hot-end temperature reading.  The thermistor measures open circuit.

Luckily, I had ordered a pack of 10 thermistors for the heated bed, so I replaced the thermistor without much trouble.

At the same time, I also fixed the toolhead square to the Psi arm (it was ever so slightly tilted, the embossed shape that fits into the arm interfered, and I fixed it with the small grinding head on the Dremel).  The hollow for the J-head was also cleaned up, and for the first time the hot-end sat square in the toolhead.

I had to re-do the z-axis calibration, as the J-head now sits a few millimeters deeper into the toolhead.

When I was at H4H, Schalk (Heunis) asked whether the slight tilt on the J-head on my printer would make a difference. I answered in the negative, but after thinking about it, I have changed my mind.  On a Cartesian printer a slight offset will make no difference, the print would just be offset by that amount, but on a SCARA printer misalignment will show up in lines not being straight (slightly, but the problem will be there).  Having a hot-end that is properly aligned (with the centre of the B-arm ends) will make prints better.
  

Acceleration figures

The Slic3r default is not to limit acceleration, i.e. movement in any direction does not have a "soft start" but creates a jerk, causing unwanted movement of the bed (in fact, all parts of the printer). Last night I printed the base of the bolt hobber with acceleration limited to 10 mm/s/s, it is SLOW. 7 hours printing time!

The next print used 25 mm/s/s, that was slow as well.  Next I will try 100 and see how that goes, but for now we have no power, so I wait...

Slic3r settings

After a few days of experimentation, and reading up on Slic3r settings, some prints are coming off the Morgan that are useful.

I have been printing some large-ish, square items (the spool holder, a bolt hobber, and others), most of which have warped to some extent.  I have printed a few tree frogs and they seem to be less prone to lifting. 

One part (bolt hobber base) have come off the bed entirely, and the printer being unattended, continued to build for two hours.  An interesting mess.  Cleaning the Kapton taped bed religiously helps but does not prevent warping.

This was experienced with Quentin's default 90 degree bed temperature and ABS filament (from Filament Factory).  To try and fix the problem, I increased the bed temperature to 110 degrees, and that seems to have sorted out THAT problem.  The plate glass bed shows no signs of strain yet.

The glass is just a 200 x 200 square of 3mm plate glass, no cut-outs that can cause high stress points.

I have also started using Slic3r in "advanced" mode, where I can specify the extrusion width as well as layer height.  In "simple" mode Slic3r selects the extrusion width based on the nozzle size, and uses a figure which is bigger than what I have seen suggested on the web.  I use 0.2mm height with 0.5mm width on my 0.4mm nozzle.