Estimated Print Time Relationship To Print Weight

[KimLindaberry 0]

Hello All,

 

My first question in this forum But I'm sure I'll have more.

 

I'm using Cura 15.04.6 to prepare my files to print with 1.75mm Hatchbox PLA on my ONI Kage Tall. I'm trying to keep detailed records about estimated print times as well as estimated weight of each print. And when each print is done I also record the actual print time so I can compare it with the estimated time.

 

I know this is pretty standard operating procedure but I'll say it anyway. The reason for recording the est. time and real time is so I know when to go remove a print and start a new one if I need to. the reason for recording the estimate weight is I can figure out if there will be enough on any given reel of filament for the next print, or to see if maybe it's time to put on a different reel sp I don't run out of filament mid print and waste time and material.

 

So what my question is, are the estimated time and estimated print weight directly related to each other in a reliable and constant manner. Here is what I've encountered. CURA 15.04.6 has consistently over estimated my print time and not by just a minute or two on my longer prints. Here is an example of a recent print: Estimated Time - 35 Hours 28 Minnutes --- Real Time - 30 Hours 37 Minutes. So in this instance my actual print time is 86.32% of the time estimated by CURA. Could this time ratio be applied to more accurately figure out how much filament was actually used? The estimated weight of this print was 517 Grams. Would it be reasonably accurate to calculate this to be 517 x .8632 = 446.3 Grams?

 

I know the simple way to figure out how much has been used off a reel is to physically weight each print, but I don't have a gram scale and was hoping this maybe a reasonable alternative?

 

Thank you,

 

Kim

[gr5 2,170]

Time estimates - The original author of Cura 15.X, for a while, had trouble predicting how long a print would take until he finally included the jerk and acceleration values of the printer.  At that moment the predictions got impressively accurate.  To this day I think cura still uses Ultimaker values of 5000 mm/sec/sec for the acceleration and 20mm/sec for the "jerk" (it's not truly jerk but that is what Marlin calls that setting).

 

Probably they updated Cura to know the actual default settings for Ultimaker printers but probably never did that for other printers like your ONI.

 

Those values might be somewhere in the settings of your printer profile which is probably in some .json file for the ONI.  Or they might be in a default json file that the ONI inherits but doesn't modify?

 

You might be able to enable jerk and accel settings and just set them to the actual values of your particular printer.  Such that they wouldn't modify the ONI but that might be enough to get Cura to make accurate time estimates.

[gr5 2,170]

grams - Well the gcode specifies exactly how far to move the extruder.  In millimeters.  So cura knows how much filament is supposed to go through the extruder (if you are underextruding it will be less - for example if you are printing a bit too fast for your printer).

 

Then Cura uses the known density for PLA to calculate the weight.  It should be pretty close to the weight of your part.

 

Actually checking the weight of your part is a good way to measure underextrusion.  10% low is typically fine.  20% low is pretty crappy.  I've seen parts that were 50% underextruded - they kind of have holes all the way through them.

[KimLindaberry 0]

18 minutes ago, gr5 said:

grams - Well the gcode specifies exactly how far to move the extruder.  In millimeters.  So cura knows how much filament is supposed to go through the extruder (if you are underextruding it will be less - for example if you are printing a bit too fast for your printer).

 

Then Cura uses the known density for PLA to calculate the weight.  It should be pretty close to the weight of your part.

 

Actually checking the weight of your part is a good way to measure underextrusion.  10% low is typically fine.  20% low is pretty crappy.  I've seen parts that were 50% underextruded - they kind of have holes all the way through them.

 

Okay thanks. the extra long time estimate doesn't bother me too much. Since I record estimated time and real print time I have  decent idea what to expect. Plus I have a remote webcam setup on the printer bed so I can keep an eye on the progress of any print and anticipate when it's going to end. 

 

The actual weight being printed and what will be left on a reel is what I really want/need to keep track of. Maybe it's just time to buy a gram scale so I'll have a truly accurate account of what's on a reel.

 

Thanks!!!