gcode for quieter printing

[Nargg]

Is there a definitive list of all commands for the Dreamer out there somewhere? And, what settings do you recommend for the M907 command?

[Graham]

Yes, but it looks like attachments are not permitted here.
Go to the FF Google Group and search for "Dreamer G Codes"

This link might work: https://groups.google.com/forum/#!searchin/flashforge/dreamer$20g$20codes%7Csort:relevance/flashforge/8A7TinFnDMQ/3khz4iLzBQAJ
or here is the group: https://groups.google.com/forum/#!forum/flashforge

Find the message from Lisa Zheng-Flashforge on 8/11/2014 where she attached them.

Graham

[Nargg]

Thanks Graham. Interesting that Lisa provided an example on that command and not any others. The example appears to be a lower value too. Hmmm...

[Graham]

I just realized that I missed answering another part of your question.

Not sure that I particularly recommend them but I use the default value that FF uses in Flashprint and have never had reason to alter them. I used these same values in the startup section of other slicers.

M907 X100 Y100 Z40 Axx Bxx where xx = 80 for an active extruder and xx = 20 for a standby extruder.

If I were to attempt to optimize these, I would reduce them until I started getting skipped steps and then bump them back up 5 or 10 to give some safety margin.
Due to the nature (poor design) of the standard Dreamer thermocouple wiring, I would be tempted to get the A and B values as low as possible to let the motors add as little heat as possible. I have modified my thermocouple wiring so it is not a real concern in my case.

Graham

[Nargg]

Graham,

Thanks for that info, that helped a lot. I'll test those settings and see if it makes any difference or not.

I wish I could agree on the "poor design" of the wiring on thermocouples but I've not found that to be the case. I tested that theory and found zero evidence that there was any problems. My external thermometers all read the same temp within 1 degree of what my Dreamer was showing. I think someone was just overthinking an issue they personally had with a defective machine when they came up with that theory.

[Graham]

I wish you were correct about the "poor design" but the facts show otherwise.
To clarify, unless FF has changed the Dreamer (It would be a simple change and there have been several revisions to the core board) the "potential"problem is real and certainly not over thinking. The "theory" is a physical characteristic of thermocouples and cannot be questioned. The voltage generated in the thermocouple wire is almost directly proportional to the difference between the temperature at the thermocouple junction (hot junction) and the temperature at the end of the TC wires (cold junction) or where the TC wires connect to copper wires or traces. For more detail sees:
http://www.acromag.com/sites/default...tters_926A.pdf
In the Dreamer, the thermocouple connections to copper are in the wiring box above the extruders. The cold junction is measured by the TC Amp (Texas Instruments ADS1118) on the core board in the bottom of the printer.
For the TC amp data sheet see: http://www.ti.com/lit/gpn/ads1118

The practical application is, of course, subject to other variables.... especially how the firmware uses the TC data but unless the actual temperature of the cold junction (interface between the thermocouple and the copper wiring is measured), it is not possible to obtain an accurate temperature. I do believe that FF has some kind of fudge factor in their firmware that uses an arbitrary cold junction offset that is higher than that measured by the TC amp located on the core board which has built in cold junction compensation. They could even be using the chamber temperature as measured by the existing thermistor and while I would still consider this a poor design, it would certainly be better than not having any reliable measure of cold junction temperature.

However, I also would agree that if you use the Dreamer within its published recommended temperatures i.e. <=230°C, it is unlikely that you will ever have a problem.

I have done extensive temperature tracking using a second FF thermocouple in the front hole in the extruder and a third monitoring the cold junction temperature in the wiring box above the extruder and the under reporting of the extruder temperature has always <=10°C so no real problem with extruder temperatures set to 235°C or below. The error increased significantly (up to 15°C ) on the rare occasions that I used higher temperatures but I still found no evidence of the potential for thermal runaway. I believe this is because the temperature of the area above the extruder at the location of the actual cold junction does not increase as fast some have theorized due to its location at the top and the fact that the fans will come on when the chamber temperature reaches 50°C. The risk is definitely real, but unlikely within reasonable operating temperature ranges.

It should be noted that I no longer have the top on the Dreamer when printing. Before I was aware of this design issue, I followed the conventional wisdom at the time and closed up the Dreamer for ABS printing. On my first multi hour print, I melted the extruder carriage. It was replaced under warranty, and this is what led me to research this issue.

Graham

p.s BTW the easy field fix is to replace the copper wires that run from the wiring box to the core board with Type K thermocouple wire. http://www.omega.com/search/esearch....ch=gg-k-24s-25

[Nargg]

However, I also would agree that if you use the Dreamer within its published recommended temperatures i.e. <=230°C, it is unlikely that you will ever have a problem.

So, by that one sentence, I think you verified that this was "overthought" And, basically a non-problem unless you are printing at much higher temps, which are not recommended for the machine. Thanks again for the help on the codes.