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  A benchmark of extruder

Extruders bechmark slow

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鈥檚 done secretly or not. 

Yes, I鈥檓 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鈥檚 a hobby not a business I have to admit it was fun 馃槉, 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

       Drive gears machining quality

       Maximum print speed

       Surface artefacts

       Thermal evaluation

       The 3D Benchy

The Benchmark Setup

A benchmark gives valuable information if it鈥檚 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.

MachCube_25_v461

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.

1 Backlash

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.

Z dial CNC
BacklashTable 2

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. 

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2 Extrusion Force

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.

Mini-Portable-Digital-Scale-Handheld-Luggage-Scale-for-Travel
AverageForce

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).

Forceweight
3 Filament Acceleration

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.

acceleartion table

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.

4 Retraction Speed

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.

5 Extruder Grip and Extrusion Consistency

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).

228200010_10165442016190557_6154503353315010770_n

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掳C

       PETG, ABS and ASA -> 250掳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鈥檝e 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 鈥 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) 鈥 without a rubber cover over the lever it breaks my fingers鈥rom 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.

repeatability

The test was performed using ESUN ASA filament @ 250掳C. I commanded extrusion of 300mm of filament @8mm/s speed. Repeated the measurement for 30 times. Next table presents the summarized result. 

Repetability table

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.

6 Drive Gears Machining Quality

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.

image

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.

image
7 Surface Artefacts

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 鈥渦nsymmetric鈥 planetary gear reduction design.

8 Maximum Print Speed

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掳C

      Extrusion width: 0.5mm

      Layer Height: 0.25mm

Volumetric flow1
SpeedTest

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:

9 Thermal evaluation

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掳C for the Delrin Dupont gears and 180掳C for the housing and the latch. Where SLS and ASA printed part can be used up to ~85掳C

SM-A520F, Android 8.0.0

Orbiter v2.0

SM-A520F, Android 8.0.0

Sherpa Mini

SM-A520F, Android 8.0.0

LGX Lite

SM-A520F, Android 8.0.0

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掳C). Using them in an enclosed chamber the stepper temperature will increase together with chamber temperature (In an chamber temperature of 50掳C the motor temperature will increase by additional 50-25 = 25掳C).

10 The 3D Benchy

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.

20220305_125619

Next pictures shows a Benchy printed out of Devil Design ASA, @ 250掳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.