A benchmark of extruder
One of the most important step
of a development process is understanding the existing state of the art
technology in the field of the product you want to develop. Nobody wants to
reinvent the wheel or design something which is has no advantage over existing products.
A common practice of many companies is benchmarking competitor products.
Buy and tear down competitor products with the aim of understanding their
performance and technology thus establishing your state-of-the-art knowledge
and your technology position in the market.
Some might considers this practice
cheating or coping or stealing intellectual property especially in the 3D
community. Certainly, buying a product with the aim of replicating and
commercializing it is unethical and can be considered stealing. But using
competitor products to learn and establish your own state of the art knowledge
based on which you make strategic decision of what to develop and where to
improve is called innovation process, regardless if it’s done secretly or not.
Yes, I’m the designer of the
Orbiter extruder and you might consider this evaluation is biased towards it,
but what would I gain if I fool myself?
My main goal with this
benchmark was not to prove which extruder is better or worse with the aim of gaining
some commercial advantage over competitor products. I wanted to understand
their performance, good / bad ideas they have implemented to enlarge my
state-of-the-art knowledge.
It is not meant to be a
guide to buy an extruder!
I've done this evaluation over the past few months, since for me it’s a hobby not a business I have to
admit it was fun 😊,
therefore I decided to share openly what I have observed.
Benchmarked performances:
· Extruder
backlash
· Extrusion force
· Filament acceleration
·
Retraction speed
· Extruder grip and extrusion consistency for several commonly used materials, PLA+, PETG, ABS and ASA
·
Maximum print speed
· Surface artefacts
·
Thermal evaluation
·
The 3D Benchy
A benchmark gives valuable
information if it’s done in the same condition as much as possible.
For this benchmark I used my MachCube v2.0 printer equipped with Dragon HF hotend + Bondtech CHT 0.4mm nozzle.
Designed adapters for each
of the extruders and tested them using the same conditions, same filament same
gcode etc. The only difference between the tests where the extruder specific
configuration like stepper current and rotation distance.
So far, I have included in
my benchmark one of the best extruder designs out there, Including Orbiter
v2.0, LGX, LGX Lite, Sherpa mini (made by LDO with Bondtech gears) and
Hextrudort with Trianglelab drive gears.
For each extruder I adjusted the settings according the manufacturer /
designer recommendations. Steps/mm was calibrated for each
extruder separately as follows:
Orbiter v2.0
rotation_distance: 4.637 # orbiter v2
run_current: 0.85 # with LDO 36-STH20-1004AHG
#run_current: 1.2 # Orbiter v2.0 with Turbiter
add-on
LGX:
rotation_distance:
7.8 # BT LGX
run_current: 0.65
LGX Lite
rotation_distance: 5.55 # BT LGX Lite
run_current: 0.65 # with LDO 36-STH20-1004AHG
Sherpa mini
rotation_distance: 22.0 #for sherpa mini 8t
motor
gear_ratio: 50:8 #for sherpa mini 8t motor
run_current: 0.35
# with LDO motor 36STH20-0504AHG with T8 spur gear
Hextrudort
gear_ratio: 50:10 #for hextrudort
rotation_distance: 22.0 # Hetrudort
run_current: 0.8 # with LDO motor 36STH20-0504AHG
with T10 spur gear
I focused on performing test
which gives relevant information about the extruder performance not the printer or hotend
performance.
Backlash of an extruder influences its retraction performance. The
amount of backlash is added to the retraction distance needed to for the hotend
to avoid stringing.
As example if you have a
hotend which requires 1mm retraction to avoid stringing and the extruder
backlash is 0.5mm, the retraction you need to set in the slicer will have to be
1.5mm, therefore lower backlash is better.
Edit based on community feedback: Backpressure of the hotend helps canceling out the backlash effect. As long as the retraction distance is low enough (~0.5mm) to still keep some pressure in the hotend the backlash effect is mostly canceled out.
Measurement of backlash:
Backlash of an extruder it
manifests through a free up and down movement (play) of the filament.
I measured the backlash
using a Z offset calibrator tool used for CNC machines. I placed the extruder
over the gauge with filament inserted and I moved the filament up and down by hand.
The gauge will show a maximum and minimum value, the delta difference is the backlash.
Next graph and picture present
the measured values.
For the LGX lite I have repeated the measurement on L2 tension lever position as well. Because the tension lever moves both drive-gears, the distance between the main drive gear toward the fixed spur gear changes thus the backlash changes to.
Lorem ipsum dolor sit amet
Extrusion force is important
to be able to exploit the whole melting capacity of your hotend and get a
consistent extrusion even during fast nozzle pressure changes.
There is a balance between
maximum extrusion force and filament grinding. Too much extrusion force will
end up grinding the filament which is worse than having the extruder skipping
steps. Ideally the maximum extrusion force should be lower than the force needed to grind the filament. A better filament grip helps since the force
required to grind the filament is increased.
Measurement of the extrusion
force
I measured a force by
pulling a nylon PA12 filament tied to an analog weight gauge. Commanded extrusion at different speeds and noted the maximum weight indicated
by the gauge before the extruder started to skip steps. I used a portable
analog weight gauge (with max scale of 12Kg) to have a springier load for the
extruder.
For the LGX lite I have
measured on both tension positions L1 and L2 since on L1 I noticed the extruder
was losing grip instead of skipping steps.
The force measurement result
of the Hextrudort is valid for many similar extruders using the same internal
Bondtech components & 36mm stepper motor LDO36STH20-1004AGHG with T10 spur
gear like the Sherpa mini v1, Saifin, NF Sunrise, Mini Afterburner etc.
Knowing the weight and force
of these extruders we can rank them according to their extrusion force / weight ratio (expressed in Kg / 100 grams of weight, higher is better).
Defining the maximum
acceleration of an extruder which can be used in real printing scenarios is not a
simple task. There are lots of variables, therefore just for the sake of
benchmarking I decided to do this evaluation with the extruder alone and just filament
inserted inside, no hotend attached.
I defined a gcode macro which
commanded 15mm of extrusion followed by 10mm of retraction. This code was
repeated three times for each acceleration level after which the sequence is repeated with increased
acceleration. I have noted down the point at which the extruder was not
able to keep up with the acceleration and started skipping steps.
Now, as mentioned in the beginning this performance represents what the
extruder can handle alone not in connection with a hotend or drag of a PTFE
tube and weight of a filament spool. Therefore, in practice it is advised to
set a much lower limit. In case of the Orbiter (equipped with LDO36STH20-1004AGHG
@ 0.85A) I found a good
compromise is to set acceleration to maximum 3000mm/s2. Higher
acceleration does not really improve printing quality but do increase clicking
noise of the extruder due to jerky filament movement.
Please note that the maximum acceleration is defined by stepper torque
and weight it moves. The stepper torque is dependent on the motor current. If
you reduce the stepper drive current the maximum acceleration is reduced by the
same amount.
A low stringing behavior of the printer requires fast retraction and
insertion performance, meaning fast speed and acceleration.
The maximum retraction speed of an extruder is defined by the stepper electrical characteristics, the stepper driver supply voltage and the overall steps/mm of the extruder. This evaluation is based on pure theoretical calculation considering the stepper motors and extruder gearing specification.
The picture from the right represents a comparison point @ 4 kg of extrusion force (chose 4Kg just to be able to compare the extruders - it has no special meaning). The graphs are calculated having 24V stepper driver supply voltage. With 12V supply voltage the maximum retraction speed is reduced to 50%.
As basis for the calculations,
I used the tool developed by Eddie which you can find here.
One of the most important performance indicator of an extruder is its filament grip and how it can keep a
low extrusion error for different nozzle pressures.
To test this, I have chosen
four commonly used materials, PLA+, PETG, ABS and ASA.
First lets establish the ground basics. An ideal extruder with a perfect grip would have zero extrusion error up to the point the stepper starts skipping (ideal curve) at which point the extrusion error should increase with extrusion speed. Next picture shows an example measurement I've done during the Orbiter development compared with an ideal behavior.
When the extruder pushes with high force the filament plastically deforms under the high pressure. This leads to under extrusion at higher print speeds (requiring higher flow rates). Eventually if the backpressure is high enough the filament is grinded or the stepper skips steps. The amount of plastic deformation depends on the tooths shape and how many tooths are into contact with the filament in the same time.
The end effect is that the actual flow will change with print speed. As a surface artefact can appear between layers printed at different speeds as shown in the next picture (of course this is not the only issue which can lead to such artefacts).
The test procedure:
I have made a sign on the filament with 310mm distance from the extruder
filament entry point. From Klipper I commanded extrusion of 300mm of filament
and using a caliper I measured the remaining filament. I repeated the test for
several extrusion rates up to the point at which the extrusion error increased
drastically, either due stepper skipping or loss of grip and filament grinding.
Nozzle temperature:
·
PLA+ -> 210°C
·
PETG, ABS and ASA -> 250°C
The Tested Sherpa Mini was
an LDO manufactured sample using LDO-36STH17-1004AHG stepper with T8 spur gear,
original 8mm Bondtech drive gears.
The Tested Hextrudort sample
was printed out of ASA and equipped with LDO-36STH20-1004AHG stepper with T10
spur gear, 8mm Drive gears purchased from Trianglelab.
Next pictures presents the extrusion performance of each extruder for the chosen filament types:
Next pictures presents a comparison of the extruders performance over different materials:
The results of the Sherpa mini and Hextrudort depends a lot on the machining quality of the drive gears and the stepper motor type. Extruders sharing the same internal components would have similar behavior (as examples the Mini Afterburner, Saifin, NF Sunrise etc.).
I’ve done my best to ensure consistent measurements, sometimes repeated
the measurement of each point several times to make sure I have a plausible
result (point on the graph representing average value of measurements).
For the Hextrudort is very
hard to insert the tensioning screw, at the point the Screw has some grip over
the nut the tension is already at maximum level, no possibility to reduce
tension.
I have to say mostly I struggled with the LGX and LGX Lite. Was really
hard to get consistent measurement especially for the LGX Lite on L1.
Several measurements in the same conditions give a difference of up to
5mm in extruded filament. This was the reason I decided to repeat the test on
L1 and L2 position as well, even if I felt I might break something while
engaging L2 – was really difficult to engage the lever to that position,
requires significant amount of force, especially on the LGX lite (L2 is
intended for flexibles) – without a rubber cover over the lever it breaks my
fingers…From what I can conclude this is due to the rigid way the tensioning
mechanism is designed which is unable to keep a constant grip or auto adjust
itself to variation of the filament diameter during printing which is never an
issue for spring based tensioning mechanism.
Next graph shows the extrusion repeatability comparison.
The test was performed using ESUN ASA filament @ 250
I performed this test only with the Orbiter v2.0and LGX lite since this repeatability issue I have mostly seen with the LGX and LGX lite, the LGX lite being most affected. The repeatability error increases with the volumetric flow.
Grip performance is affected by the shape of the filament biting tooths and the
number of teeth coming into contact with the filament.
As we already know bigger
drive gear diameter give better grip, theoretically. I have already shown in the
story of Orbiter v2.0 how the filament contact surface is influenced by the drive gear diameter. In the next pictures you can see close-up pictures of the gears from the different extruders I have evaluated.
Next picture shows the contact area versus pinching depth of the driver gears for 8mm diameter used in the standard BMG style extruders, 12mm diameter used in the Orbiter (also Bondtech QR) and the 18mm diameter used in the Bondtech LGX.
Note the effective diameter of the filament path is smaller by ~0.6mm.
The data is summarized in the next table, out of the calculations the contact area increase is roughly ~25% for each drive gear diameter increase.
One crucial performance indicator of an extruder is its extrusion speed stability. In other words, how constant is the filament extrusion speed. This
can be observed as surface artefacts like wooden patterns or salmon effect etc.
There are many factors which
can contribute to this surface artefacts but overall, they are all caused by
the same basic phenomena, which is extrusion speed variation, vibration.
All main parts of the
extruder can contribute to such pattern like, gears mashing, tooths profile, stepper
motor, mount and extruder rigidity.
For this test I have used
the test procedure suggested by MihailDesigns, description you can find here:
Next pictures present the results:
Best in class here seems to be the Orbiter and Sherpa mini, for the Sherpa mini the pattern is slightly visible, in case of the Orbiter is less visible, its very hard to spot I was not able to make a proper picture to show, but with naked eye a very very slight pattern can be observed.
For the Sherpa mini the
distance between the gears is adjustable thus this effect can be significantly reduced.
In case of the Orbiter this effect is almost not visible due to the “unsymmetric” planetary gear reduction design.
Filament extrusion force and
grip are the most important factors influencing the maximum print speed it can
be reached from the extruder point of view.
Of course, main player here
is the melting capacity of the hotend, as the hotend reaches its maximum flow
the nozzle pressure increases exponentially and does not really matter if the
filament pushing force is even doubled the real flow will have just a minor
improvement.
However, until the maximum
melting capacity is reached a high extrusion force is still beneficial since we
want to squeeze out large amount of melted plastic through a tiny hole, like
0.4mm the standard nozzle size I use.
To test this, I designed a
simple model, printed in vase mode. Configured the slicer to
increase the print speed by 50mm/s every 5mm height with starting speed of 100mm/s, last layers speed is 400mm/s. Printer XY acceleration was configured to 3000mm/s2 (not
higher to better replicate a real printing scenario).
Print setup:
· Hotend: Dragon HF with 0.4mm Bondtech CHT
nozzle
· Filament: ESUN PLA @210°C
· Extrusion width: 0.5mm
· Layer Height: 0.25mm
Test results for Orbiter v2.0
extruder:
Test results for Orbiter v2.0
extruder with Turbiter add-on, stepper current set to 1,2A RMS:
Test results for LGX extruder
tension L1:
Test results for LGX extruder
tension L2:
Test results for LGX Lite extruder
tension L1:
Test results for LGX Lite extruder
tension L2:
Test results for Sherpa mini
v2 extruder:
Test results for Hextrudort
extruder:
Stepper motor temperature is important factor. By design stepper motors should run hot, but not too hot to melt the extruder plastic components.
Compared to the other extruders tested here the Orbiter v2.0 stepper motor can be allowed to run hotter since the temperature deflection of the used plastics is higher, 120
Orbiter v2.0
Sherpa Mini
LGX Lite
LGX
Remember that the stepper temperature is in direct relation with the stepper current. Higher current means higher extrusion force and filament acceleration but higher stepper temperature as well. The best is to run the stepper hottest possible but below the maximum operating temperature of the extruder parts with a safe margin.
In addition please consider enclosed chamber temperature if its the case. The above measurements has been taken at room temperature (~25°C). Using them in an enclosed chamber the stepper temperature will increase together with chamber temperature (In an chamber temperature of 50°C the motor temperature will increase by additional 50-25 = 25°C).
I have performed several test prints with each of the evaluated extruders. First printed at a moderate speed of 100mm/s with 3000mm/s2 acceleration. As you can see all extruders performs great there is no visible difference between the print results. In this setting they delivered a close to perfect Benchy and calibration cube.
Next pictures shows a Benchy printed out of Devil Design ASA, @ 250°C, 300mm/s speed with 10.000mm/s2. The LGX lever was set to L1 position.
Benchy details: 0.25mm layer height, with 0.4mm width, four top and bottom layers, two walls and 10% infill.
LGX Lite
Orbiter v2.0
More to come soon,
Best places to look for differences are the areas where layers are printed speeds at different speeds. Like above the door opening arches. The different speeds requires different flow where extrusion errors will lead to under-extrusion artefacts.
Final thoughts and personal conclusions
All results are based on my
personal observation.
Myself being the designer of
the Orbiter extruder some might consider these results are biased and made to advertise
the Orbiter extruder. Everybody is free to try to replicate my tests, and judge
on their own observations.
During these few months of benchmark
testing, I learned a lot about the effectiveness of certain features and which ideas
are better or worse. Overall, even if the test results show great differences,
these are among the best extruders you can employ today.
Let me share some of my personal
impressions.
I was truly impressed by the
compactness of the LGX extruder, Initially I imagined it bigger than it is in
reality. The LGX lite have a very innovative filament tensioning mechanism, the
tension lever moves both driver gears in the same time, thus keeping the
filament path centered. Personally, I did not like the rigid tension mechanism.
The adjustment is somewhat clumsy very rude, and especially handling the LGX Lite lever was hurting my fingers. On the LGX was surprised that out of the six levels only the first two are useful for rigid filaments. The way the mounting features are designed in are
also not on my preference list. Most hotends are bolted in place from the front
or top side, the LGX extruders mainly from the bottom. You could use in theory the side
bolts of the extruders but this complicates the design and ads more flexing
possibilities, overall from my perspective is not an optimum solution. I personally prefer a design in which everything is bolted
together from the top side.
Before I tested the Sherpa
mini I always had some doubt about the rigidity of its skeleton design. I thought
the skeleton design might be too flexible. Well, I was wrong, during my tests I have not observed any flexing, the skeleton design is stiff enough for the
forces the sherpa mini can deliver. Using 8mm standard Bondtech gears its
extrusion performance is strongly influenced by the gears quality.
Initially I really liked the
Hextrudort design, it looks very cool and rigid. After printing and assembling my
enthusiasm went down due to the sweat involved in the process. I would really wish
that printing tolerances and shrink effects (especially for holes and nut slots)
are considered in the design. With standard BMG tensioning mechanism the
filament tension is over what the maximum level it should be.
A big thank to my friend
Petrus from www.reprapmania.ro for lending
me some of the extruders tested here.