Bondtech BMG upgrade for the N series

Topics around mechanical design, controller and electronics. Mods & hacks welcome.
firesped
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Re: Bondtech BMG upgrade for the N series

Postby firesped » Fri May 05, 2017 2:10 pm

what is the steps per axis on the BMG?
RL name: Michael Nolen
printers:
raise3D N2 kickstarter Early Bird
Trinus Deluxe (running smoothieware on Azteeg X5 GT board)
Monoprice Maker Select v2

Jetguy
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Re: Bondtech BMG upgrade for the N series

Postby Jetguy » Fri May 05, 2017 2:19 pm

Sorry this is taking so long, I spent last night getting my nozzles aligned and offset tuned. Remember, that has nothing to do with this Bondtech, that's just me upgrading this printer from a single to dual extruder for the first time getting the hotends right so I can compare the various dual extruder options. Also, going to build Erin Lien's force testing rig so I can directly tell you in chart form, you can compare the maximum force each version and variant provides.

Again, sorry, just calibration blocks to set the nozzles and offsets, but now ready for some serious testing!!
Hoping to run Dual Ninjaflex and other materials through them this weekend.

Printed parts are this http://www.thingiverse.com/thing:1353231
Dual Extruder Calibration Square by SuperBearFur

Before you ask, the numbers and the arrow on top were so I knew what direction the cube was printed on the bed (arrow points to front face) and number written was the toolhead offset value in mm. I liked this test because it's easy to look at the sides and see which way I needed shifted. My final number was 24.8mm but that is specific to my printer. Y offset was 0 meaning my printer is perfectly squared up and nozzles are in a perfect line in X.
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IMG_0560[1].JPG
Last edited by Jetguy on Fri May 05, 2017 2:51 pm, edited 1 time in total.

Jetguy
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Re: Bondtech BMG upgrade for the N series

Postby Jetguy » Fri May 05, 2017 2:20 pm

BMG is 415 steps per mm. (assumes 1/16th stepping and 1.8 degree stepper motor) That's what the N series is, A4988 stepper driver @1/16th stepping driving 1.8 degree motors.

Stock Raise 3D from the factory = 94 steps/mm
Current Bondtech mini upgrade = 140 steps/mm Current version for sale that reuses your stock motor
Bondtech QR remote Bowden = 476.5 steps/mm Remote bowden as an option for the second extruder
Bondtech BMG extruders = 415 steps/mm Newest version being tested in this thread (lightest possible option of all)

firesped
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Re: Bondtech BMG upgrade for the N series

Postby firesped » Fri May 05, 2017 4:31 pm

was working on a marlin 1.1.0 firmware release, so I wanted to reference the numbers. unfortunately marlin 1.1.0 is not stable atm.
RL name: Michael Nolen
printers:
raise3D N2 kickstarter Early Bird
Trinus Deluxe (running smoothieware on Azteeg X5 GT board)
Monoprice Maker Select v2

Jetguy
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Re: Bondtech BMG upgrade for the N series

Postby Jetguy » Fri May 05, 2017 4:51 pm

So here are the notes on install so far.
You unload the filament on both sides from your old extruder, let the printer cool down leaving the fans running until it's back at room temp for safety. Then power down.
You unplug the 3 pin heater power cable and ribbon cable from the extruder breakout board. You may have to cut a ziptie that helps lock the ribbon cable into the breakout board (newer models shipping with this extra ziptie around the board and thus the cable). Finally unplug the stepper cables but make sure you label them with tape for left and right motors to not get them mixed up.
Now, remove the 2 screws holding the entire cable chain on the N2 and N2Plus models to the extruder block. Since all cables are now unplugged it can be swung out of the way.
Next is the 2 M3 screws that hold the breakout PCB to the head. Just remove them and the entire housing + board, heater wiring, thermocouples, and fan wiring all swings out of the way.
The entire extruder block is held with 2 screws from the sides and 2 screws in the middle of the back to the central crossing block. They will be tight because the factory used thread locking compound on the screws to prevent them from falling out from vibration. At this point, the entire original extruder feeder and motors will pull straight up and off the central crossing block.
The new BMG dual extruder module just sits back down over the PTFE guide tubes and attaches with the same 4 screws to the central crossing block. Do not overtighten and crack the plastic housing. Do not add threadlock as unless you are 100% sure it's plastic safe, some threadlock can damage the plastic. Not worth the risk.
The breakout board can be attached to the new extruder feeder body using the new housing as supplied with the new extruder. This rotates the board from horizontal to vertical orientation. Note, there is an M3 and M2.5 screw that will be supplied with the kit. The breakout board has smaller mounting holes at the large heater screw terminal end. Just saying, be aware of screw sizes here. Bondtech is aware and is supplying the correct screws.
Again, attach the electronic breakout board first, then attach the metal bracket for the cable chain. Trust me, it aligns easier this way as they are very close.
Now, on the wiring for the stepper motors. On newer printers, the new short stack NEMA17 plugs match your existing cable set with the BOHONG black motors. If you have the previous version of motors (aluminum ends) supplied during the kickstarter campaign and or shortly after, then you will use adapter cables. The front facing motor is the LEFT side extruder, and the rear motor is the right. Note, the left will be correct polarity and is plug and play. The right motor cable (the rear motor on the new extruder) needs the cable pins reversed in your cable. This is easy to do and I'll try to provide a more detailed instruction. You just use a small thin bale like a knife to pry the tiny plastic tabs on the connector to unlock the pins, pull them out, and then reverse the pin order by 180 degrees. Really easy. Again, left motor is plug and play, right just needs a minor reversal of direction.
Attach the cable chain and the ribbon cable and 3 wire heater connector to the breakout, ensure the steppers are plugged in and correct left and right.
Finally, adjust the stepper motor current by adjusting Vref to 0.5V to prevent overheating the motors by sending too much current.
The last step is going into your machine definition in Ideamaker and changing steps per mm.

Exported gcode.jpg

Printer settings2.jpg

Printer settings.jpg

Jetguy
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Re: Bondtech BMG upgrade for the N series

Postby Jetguy » Fri May 05, 2017 5:37 pm

Also a tip for usage. Create a simple gcode print file to run on first printer startup. In other words, with stock firmware, when booted, the printer defaults to the stock 94 steps per mm. If you attempt to load filament using the load filament menu items, it will do it, but the rate of feed is 4X slower than normal (94 VS 415). By printing a simple gcode that sets steps per mm to 415 at startup, as long as the printer is not rebooted or the mainboard resets for some reason, then load and unload scripts use the updated steps per mm. You just unzip the attached file upload so it's in your onboard memory and print when you first turn on the printer. (Note, I have not tested this file since mine is running a print at the moment).
Attachments
StartupN2Plus.zip
(551 Bytes) Downloaded 28 times

Jetguy
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Re: Bondtech BMG upgrade for the N series

Postby Jetguy » Fri May 05, 2017 6:17 pm

And, first NinjaFlex test print using the BMG. Now this is only a single extrusion print, next up, dual Ninjaflex. Note, I also used those super slick guide tubed I had linked earlier from MRRF. http://captubes.com/

That's a huge difference in that those tubes add almost no drag to filament where every other tube I have tried with Ninjaflex adds considerable drag.
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IMG_0564.JPG
IMG_0565.JPG

firesped
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Re: Bondtech BMG upgrade for the N series

Postby firesped » Fri May 05, 2017 6:20 pm

any chance you can get me a contact email, jetguy? I got the firmware working for marlin 1.1.0 and I can send it your way for testing. I already sent off a copy to Derek. hopefully they can review it and put it out officially.
RL name: Michael Nolen
printers:
raise3D N2 kickstarter Early Bird
Trinus Deluxe (running smoothieware on Azteeg X5 GT board)
Monoprice Maker Select v2

Jetguy
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Re: Bondtech BMG upgrade for the N series

Postby Jetguy » Fri May 05, 2017 8:19 pm

PM'd you.

frjez
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Re: Bondtech BMG upgrade for the N series

Postby frjez » Fri May 05, 2017 8:30 pm

HOLLY CAW!!!
Congratulation to Martin and the team. I've got exactly the same idea! Though I'm happy Bondtech did realize it. I never had time to materialize my own idea. So one dual-extrusion-pancake-kit for me. In case you are making a list of buyers :D
WELL DONE!!! Because the original extruders are worth big pile of BS.

Ohhh I'm soooooooo happy!

frjez
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Re: Bondtech BMG upgrade for the N series

Postby frjez » Fri May 05, 2017 9:03 pm

@jetguy
..one tiny question, though. Is this BMG the same BMG (single extruder) already available on Bondtech site? Because I have a 2nd tought about the plastic gear. Eventually I'll replace it with a metalic. Because If my engineering degree still holds, when two gears are in contact only 3-tooth are touching at best. Acording to Push Force Test (http://www.bondtech.se/en/products/extr ... -extruder/) that's almost 9kg on those three tiny plastic tooth!

Jetguy
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Re: Bondtech BMG upgrade for the N series

Postby Jetguy » Fri May 05, 2017 9:28 pm

I think you got the math wrong there.

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Re: Bondtech BMG upgrade for the N series

Postby Jetguy » Fri May 05, 2017 10:43 pm

The first thing is the NEMA 17 motor is not exactly the brute force king here. It's a 25mm pancake motor. http://shop.bondtech.se/ec/steppermotor ... 25-mm.html
The next problem is that data sheet, nor the OEM data sheet http://www.omc-stepperonline.com/downlo ... -0704S.pdf
Provides the "Pull out" torque rating, which is the value you use. The holding torque is the force to make a locked motor skip a step. The actual maximum force the motor can push before skipping steps is not even 1.8kg/cm
If the shaft is 5mm in diameter. The pinion is larger than the shaft at 9.45mm OD at the teeth edge and a root diameter of 8.2mm making the middle of the tooth 8.825mm diameter or 4.41mm radius.
So, maximum value here is 1.8kg/cm (1.8kg at 10mm radius using holding torque value) and we are less than 10mm at 4.41mm radius we end up multiplying the torque by 2.27 to get a maximum tooth force of 4KG for holding torque. Running torque or Pull out torque is not equal to holding torque, so then the actual value is less, and then that assumes and overloaded jammed extruder and running the motor at less than rated current to reduce temperature rise and that means even less torque. Bottom line is that people have been running these for months without wear.
E3D sells theirs with the same basic spur gear arrangement and they are not failing, nor are users claiming that metal spur gear is needed and that's with folks using big honking full length NEMA17s capable of much more torque.

I just think you are off when you try to imply there is a problem "almost 9kg on those three tiny plastic tooth" and math and real world tests don't come up with the numbers you described.

frjez
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Re: Bondtech BMG upgrade for the N series

Postby frjez » Fri May 05, 2017 11:44 pm

@jetguy
Hmm, you got me here! Not to push this too much further, but... on the Bondtech site (the link above) they said, well the diagram, that the Pushing Force is (actually) around 100N - cca 10kg, right? Not to go deeper in the testing procedure (http://www.bondtech.se/en/products/extr ... e-testing/) but knowing that the gear ratio is 3:1 (since I don't know the "gearbox design"), I asume that the tooth has to withstand 10kg : 3 =3,333kg. Also knowing that, theoretically and only if there are more than certain number of tooth on the gear, only 3 or less, in practice is more like 2 or even 1 are in contact... Well that means that this involute gear tooth are pretty much stressed.
(as an amusement: http://geargenerator.com/)
But, yeah...you are right is not 9kg it's more like 3kg...still a lot :o

Jetguy
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Re: Bondtech BMG upgrade for the N series

Postby Jetguy » Fri May 05, 2017 11:57 pm

FWIW, Martin from Bondtech has sent me this teaser picture of a gear he machined in house for testing. Maybe, for special customers, he will make you a set.

For me, I definitely do not want metal. The reason is metal pinion and metal spur on a stepper? That would be definitely louder and metal on metal wear is much different than plastic on metal. But, Martin tries to make every customer happy, so if you insist, he probably can deliver.
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frjez
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Re: Bondtech BMG upgrade for the N series

Postby frjez » Sat May 06, 2017 12:39 am

hahahhaha, you guys are greate, no matter what!
RESPECT!

I'm a buyer anyways... I might be a beta tester for a metalic gear :D

eclsnowman
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Re: Bondtech BMG upgrade for the N series

Postby eclsnowman » Sat May 06, 2017 7:12 am

Since I did the tests I know a little about how they were performed :)

The Nylon gears will not be the failure point. Before ever going to the compression test (to better simulate actual printing conditions) I did it with pull testing against a scale. Given enough input motor torque, the filament will fail far before nylon gear. I only say this because I put up to a 60mm stepper on the BMG when playing around when coming up with the test conditions. And between pull testing and push testing I probably brought the BMG to full motor stall, or filament tensile failure 500+ times. In fact I did a full suite of tests on the Beta version of the BMG and it had a PLA printed gear before Martin sourced the nylon ones. Even the PLA gear showed no signs of wear.

Start from the maximum recorded load, and work backwards. The maximum recorded value in any run on the BMG into the strain gauge was 25.8lbs (aka 11.7kg, aka 114.7N). Working backwards you have to look at the effective radius (aka lever arm) on the filament drive gear that 25.7lbs is acting on... which is approximately 3.76mm. Then working further backwards that filament drive gear is on a common shaft with the nylon gear. The teeth on the nylon gear are at an effective radius (aka lever arm) of around 13mm. So essentially it is a simple lever arm force balance equation: http://www.engineeringtoolbox.com/levers-d_1304.html

Image of the dimensions: http://imgur.com/IPb22DA

Fl = 25.8lbs , dl = 3.76mm , de = 13mm , Fe = force at the nylon gear teeth

Fe = (25.8lbs*3.76mm)/13mm = 7.46lbs (aka 33.2N, aka 3.38kg)

Now this might sound like a lot of force... but it really isn't. Think about this. How much force does it take you to rip a zip tie. Really. It is made of nylon, has a similar cross section to that of the gear teeth. Now grab one end and pull. You can apply far more that 7.5lbs of force. Can you even come close to stretching it. Put it in both hands and try and shear it. You can't... and with substantially more force than 7.5lbs. And remember 7.5lbs was the works case scenario I could produce, and when I got to those numbers the filament was almost always what failed. Nylon has added benefits of being quiet and self lubricating. If you look inside many tools (drills, kitchen mixers, etc) you will find these nylon gears, and with substantially higher loads. For example I took apart a broken kitchen mixer when I was a kid to try and fix the motor. It was 1/4hp I think. And the gearing inside... Nylon :)

Sorry about the long rant. Just thought I would lend a little context since I know more than most about the load cell testing done so Martin could optimized the product performance in order to give his customers the best thing out there, and by a healthy margin. And I put the BMG into countless worst case scenario tests. The gears look like new. So even if you full on jam your hot end 500+ times you should have gears that look just like mine, good as new. The only thing I think you could do to mess up the gear is get a bad mesh with the metal gear on the motor (positioning the nylon gear travel over the grub screw on the metal drive gear would do the trick :), but short of that I don't think you have anything to worry about.

frjez
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Re: Bondtech BMG upgrade for the N series

Postby frjez » Sat May 06, 2017 1:29 pm

As we sorted this out...now the most intriguing question of all... :o
When will we be able to empty our wallet? ... just a time frame (days, weeks,... don't want to pronounce the next step :-) )

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Bondtech
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Re: Bondtech BMG upgrade for the N series

Postby Bondtech » Sat May 13, 2017 6:17 am

frjez wrote:As we sorted this out...now the most intriguing question of all... :o
When will we be able to empty our wallet? ... just a time frame (days, weeks,... don't want to pronounce the next step :-) )


The new DualDirectDrive will be available in about 1.5-2 weeks.

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JohnSays
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Re: Bondtech BMG upgrade for the N series

Postby JohnSays » Sat May 13, 2017 1:04 pm

Will you be offering any discount for the people who bought the earlier N2 extruders? I bought one a few weeks ago and another a while back, but I think this one is going to be an awesome upgrade and I want it.
- John
2 Raise3D N2 Duals, V2 nozzles, Bondtech BMGs, and adjustable table


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