Speed tests with a single 0.5mm wall cube

I did some more speed tests with the same 0.5mm cube:
The cubes were pulled off the bed while still hot, so they deformed a little.

The 250mm/s one took 0:54" @250mm/s to complete but I think the speed was limited by the acceleration being 2000mm/s^2 and the side of the cube being 20mm. I tried again @350mm/s with acceleration 3000mm/s^2 and it took 0:47" to complete.

I forced the parts off the bed while still hot and they deformed a little. The wall is indeed 0.5mm thick as in the STL. ABS at that thickness is quite flexible.

The maximum feedrate I can safely achieve with the Hadron is 22000mm/min = 366mm/s for a 210mm travel, after that the motors start skipping.

EDIT:
As I suspected, the acceleration is limiting the speed for small travel. I designed a similar shape but this time with a longer side of 100mm so that the head can achieve the requested speed and this is the result:
The bed is covered with ABS juice so that the parts stick firmly to it.

The 150mm/s part printed fine. This proves my DIY extruder's limit lies somewhere between 150mm/s and 200mm/s.

It seems that to claim high speed records one should have to print objects that allow the print head to reach the claimed speed, otherwise the record would be false.

EDIT 2:
Doing a little math, a 20mm travel can only allow a final speed of :
Code: Select all
`v = sqrt( (20mm/s)^2 + 2*3000mm/s^2*10mm = 245.7 mm/swhere:initial velocity = 20mm/sacceleration = 3000mm/s^2travel = 20mm/2 = 10mm`

while a 100mm travel allows a final speed of:
Code: Select all
`v = sqrt( (20mm/s)^2 + 2*3000mm/s^2*50mm = 548.0 mm/s`

We take half of the length available as travel because the head needs to equally decelerate before it reaches the end.

At 3000mm/s^2 the 350mm/s speed is reached after 20.35mm of travel, which means that a minimum length of 40.7mm is needed if we include the necessary deceleration travel. To be sure, an additional length of travel should be added so that the extruder extrudes at that speed for some more time. The best possible test object would span the whole bed; 210mm would allow the head to accelerate, reach 350mm/s final velocity and extrude 169.3mm of plastic @350mm/s feedrate.

Or, a 210mm side will allow a final speed of 794mm/s to be momentarily reached.

Hopefully the above make sence. Here is the STL file, in case someone else wants to measure the performance of his extruder.
Attachments
0.5mmx100x20-thin-wall.stl.zip
Last edited by dzach on Sat Jun 23, 2012 11:30 am, edited 1 time in total.
dzach

Posts: 180
Joined: Sun Feb 19, 2012 12:47 am
Location: Athens, Greece

Did you increase your temperature as you increased the speed? Sometimes you have to increase it dramatically to handle sustained high feedrates. The downside is the increased tendency to string.
mxk

Posts: 123
Joined: Wed Jun 08, 2011 11:02 pm

mxk wrote:Did you increase your temperature as you increased the speed?

Yes, I forgot to mention it. I increased the temperature to 220°C in all tests, because the extruder was skipping heavily at 185°C. It stopped skipping around 220°C but even at a higher temperature, e.g. at a "boiling" 250°C, it couldn't go higher than 200mm/s without skipping. As it can be seen in the pictures above, even at 350mm/s, the sort sides of the parallelepiped print much better than the long ones because the head doesn't have the time to reach max speed.

So the real limiting factor in my case seems to be the extruder. I wish I could find some comparison data, but it seems that many people claiming high print speeds make the same mistake: set the speed to a number and print a random object, ignoring the fact that the actual speed achieved is not even close to that number.

It would be interesting to see how other extruders perform under the same conditions.
dzach

Posts: 180
Joined: Sun Feb 19, 2012 12:47 am
Location: Athens, Greece

The tests with my Extruder looks similar.

Parameters:

Extruder: MakerGear Stepper Plastruder
Nozzle: 0.35 mm
Filament: PLA
Slicer Software: Slic3r, Version 0.8.3
Temperature [°C]: 195 (185)
Layer height: 0.25 mm
Print Speed (all settings, Perimeters .. Bridges) [mm/s]: 150, 200, 250

flurin

Posts: 203
Joined: Mon Feb 27, 2012 12:09 pm
Location: Switzerland

Thanks for the report Flurin!
It looks like despite the ORDbot's speed, the extruder is literally and metaphorically a bottleneck

What was the acceleration used for these prints?

I've posted about the extruder performance measurements in the RepRap forum. There may be some more people interesting in this kind of measurements.
dzach

Posts: 180
Joined: Sun Feb 19, 2012 12:47 am
Location: Athens, Greece

The acceleration is the default value: 3000 mm/s^2.

Note:

The results are better if I use an additional cooling fan and increase the temperature to 230 °C. But obviously the limit is the extruder capacity.

flurin

Posts: 203
Joined: Mon Feb 27, 2012 12:09 pm
Location: Switzerland

After a week or more of testing with Skeinforge and Hadron, I finally managed to print an improved test object at true speeds, I believe, around 300mm/s before hitting another limit, that the calculations above do not anticipate. The extruder does not miss any steps and the limit seems to be mechanical. The time to print the test object @300mm/s was 1:08 with the nozzle hot.

I reiterate my conclusion from above that, unless the object to print is big enough in size, increasing speed (feed rate) doesn't make any difference because the printer does not have the time to accelerate to the requested (high) speed. I've found that my Hadron's max XY speed is about 21500mm/min = 358mm/s, down ~500mm/min from previous max of 22000mm/min since I added a 5mm aluminum bed.

Here are some pictures from the test print (layers 0.25mm, object height 5mm):

Apologies for the dirty print bed, it is ABS juice that wasn't cleaned between the tests.

The duration for a test print at 250mm/s was 1:17" and the duration for the same test at 300mms/ and at 350mm/s was 1:08", as timed with Pronterface. The prints were timed with the nozzle hot.

The test data:

Code: Select all
`2.1   Filament      2.1.1   Material   ABS   [PLA, ABS, other]2.1.2   Filament average diameter   1.7   mm2.1.3   Die swell (mid air extrusion diameter)   0.85   mm         2.2   Thermal      2.2.1   Melt zone temperature   ~240   °C (thermistor not trusted any more)2.2.2   Temperature fluctuation   <1   %2.2.3   Ambient temperature   28   °C2.2.4   Ambient humidity   50   %         2.3   Mechanical      2.3.1   X,Y,Z acceleration   2500   mm/s^2         2.4   Nozzle data      2.4.1   Nozzle orifice diameter   0.4   mm2.4.2   Nozzle orifice length   0.2   mm         3   Test results      3.1   Quality      3.1.1   Quality grade   average   [low, average, high]         3.2   Speed      3.2.1   Minimum Usable Feed Rate, FRMN      mm/s3.2.2   Maximum Usable Feed Rate , FRMX   250   mm/s`

If you are up to a challenge, then have a look at the test material in github. A more detailed description of my tests is given in the RepRap forum.

So far only @flurin has performed this test with a Hadron, besides myself. Thank you Flurin !
Last edited by dzach on Tue Jul 03, 2012 2:40 pm, edited 1 time in total.
dzach

Posts: 180
Joined: Sun Feb 19, 2012 12:47 am
Location: Athens, Greece

Hi dzach

I've installed Skeinforge in order to print the tests with Skeinforge. However on my Mac (OS 10.7.4) Skeinforge doesn't display the fields and the field descriptions correctly. I'm searching for the reason.

Has Skeinforge a similar INI-File as Slic3r? If yes, could you please post your Skeinforge-settings.

flurin

Posts: 203
Joined: Mon Feb 27, 2012 12:09 pm
Location: Switzerland

Unfortunately it has 51 config files, one for each tool, but here is a zip file with them as I used them for the test:

ABS-150.zip

I haven't yet used Skeinforge for PLA.

The breakthrough in my understanding Skeinforge was finding the "magic" ratio of feed rate to flow rate. This gets just the right amount of plastic through the nozzle and one can then fiddle with other settings like oozing, stringing etc. knowing that the basic flow calculations will not change. The instructions usually say to use the same numbers for feed rate and flow rate, but doing so put just too much plastic though my CuHotE extruder.

My "magic" ratio is 50/39, feed_rate / flow_rate. For e.g. 150mm/s the settings will be 3*50mm/s and 3*39 or 150mm/s and 117.

Although Slic3r is a user friendly and fast piece of software, I find the fact that it hides most of the details not helping me understand the extrusion parameters and process. I just couldn't get it to print accurately and consistently. Skeinforge, though user unfriendly, allows greater control over the extrusion parameters and gives me confidence that I can make it do what's necessary for a good print.
dzach

Posts: 180
Joined: Sun Feb 19, 2012 12:47 am
Location: Athens, Greece

Thank you dzach!

I've still troubles with Skeinforge on my MAC. I'll try your settings ASAP.

flurin

Posts: 203
Joined: Mon Feb 27, 2012 12:09 pm
Location: Switzerland

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