BNBSX Short Ears Extruder vs. Skelestruder  

RE: BNBSX Short Ears Extruder vs. Skelestruder

Interesting designs.  I have not installed one yet, but I have followed their development.  

RE: BNBSX Short Ears Extruder vs. Skelestruder

You won't get a definitive answer, each has its own pros to the design, so what's "best" for you depends what you're looking to get out of the upgrade.

(FWIW I have a skelestruder for serviceability, gearing, and reduced weight and am very happy with it.)

RE: BNBSX Short Ears Extruder vs. Skelestruder

Ok, which stepper motor you have installed? 0.9 or 1.8?

Wolfgang

RE: BNBSX Short Ears Extruder vs. Skelestruder

The recommended 1.8 OMC pancake. (0.9 on a geared extruder is just silly. 0.9 only makes sense on a direct drive for extruder uniformity. If you want more e-steps, save the cost of the motor and just print different sized gears)

RE: BNBSX Short Ears Extruder vs. Skelestruder

thanks for your input...

what is the advantage of the BNBSX extruder? Who has tested this type and could give some input?

RE: BNBSX Short Ears Extruder vs. Skelestruder

There's a list of features on the main assembly page:

https://bunnyscience.dozuki.com/Guide/Bunny+and+Bear+(BNBSX)+MKS3+Geared+Extruder+Assembly/2

Skelestruder has one too:

https://www.thingiverse.com/thing:2845416

RE: BNBSX Short Ears Extruder vs. Skelestruder

Posted by: w.a.schmid

what is the advantage of the BNBSX extruder? Who has tested this type and could give some input?

I can't speak to the Skelestruder, but I've been using the BNBSX since a super early version and I've been quite happy with it. Like other lightweight geared extruders, I feel like it improves print quality through more consistent extrusion and reduced ghosting.

I also feel like it makes tweaking and maintenance easier. It's super simple to swap a motor, hotend, or other bit. The first time I replaced the motor on my stock extruder, it took hours; now I can do it in about ten minutes on the BNBSX. The Slice Mosquito replacement was about half an hour. I also like the separate hot fins -- I've printed several different versions in several different materials, and it takes just a few minutes to replace a set. That really paid off when I was experimenting with different high-temp materials. It's the little things, and I appreciate the attention to detail.

On the soft side, the designer is active and responsive. For instance, when I asked about a modified motor block for larger motors, he had one up in a matter of hours. Besides that, he's still improving the design, recently improving the filament path for flexible filaments.

The documentation and assembly guide is also great, and I appreciate all the little tweaks that have accumulated that make it an easier build. I'm building a second one now, with a few updates and polycarbonate filament, and it's great seeing how far the design has come.

RE: BNBSX Short Ears Extruder vs. Skelestruder

thank you for your answare...

I will go with the BNBSX. What is the reason for using polycarbonate? Is there a problem with the PETG?

RE: BNBSX Short Ears Extruder vs. Skelestruder

Nothing is "wrong" with PETG. It's actually easier for your first build and suitable for everything except the fan shroud. Fan shroud should be ABS or polycarbonate or will warp after a few hours of printing. A PETG fan shroud will last long enough to print 1 or 2 high temp fan shrouds.

If you want to print routinely in higher temp materials, then having hot fins, fan shroud and main extruder body in polycarbonate is desirable. Those pieces in polycarbonate will let you print at 290C indefinitely. PETG will eventually sag if printing at 290C (polycarbonate printing temperature).

RE: BNBSX Short Ears Extruder vs. Skelestruder

thank you for your answare...

...I would like to print ABS and polycarbonate for mechanical parts.

That is why I am first printing parts for an enclosure. After that I will do some experimantal prints with polycarbonate and the original extruder.

Hopefully I can print fast your extruder - metal parts are allready orderd 🙂

RE: BNBSX Short Ears Extruder vs. Skelestruder

If you are going to print parts out of polycarbonate, then take a look at Rigid.Ink clear polycarbonate filament, it is a pure polycarbonate material not a blend like a lot of coloured polycarbonates are. This results in it having a higher glass transition temperature, but will also require printing at the maximum temperatures your standard Prusa I3 will print at.

I managed to print the critical high temperature parts for my skelestruder just before the PETG parts drooped / melted and replaced them with the new PC parts, and have had no further issues.

I find the Rigid.Ink clear PC is like PETG on steroids, stiffer than PETG and considerably stronger when trying to break it. I also have not found it to be brittle at all like some reports of PC, but I suspect these are the PC blends, they have to be mixed with things like talc to get the opacity for some colours right, this would lead to a weaker material, but can improve print-ability.

Also I found that bridging with PC is not good at all, so if you do decide to use this material, be aware it is not the best at everything.

RE: BNBSX Short Ears Extruder vs. Skelestruder

thanks for your hint and the link for the website!

I have already purchased one spool of PC Max (I thing this is a blend, as you mentioned?), which I would try first... ...so at the moment I am still printing enclosure parts :-/

Printing BNBSX in Polymax PC

Don't worry, the PCMax won't go to waste. It is an intermediate blend that has higher temperature resistance than a more blended polcarbonate like Priline. You are going to need a fair amount of the BNBSX printed in black (or at least an opaque color) anyways. All the components surrounding the optical filament sensor should be done in opaque. Those would be main extruder body, motorplate gearbox, top cover.

Here is my advice about printing in polycarb. Follow these for consistent results.

Complete your enclosure BEFORE printing in polycarbonate. You want the build environment free of drafts and able to rise in temperature.

ALWAYS dry polycarbonate immediately before using it. DO NOT ASSUME THAT FACTORY SEALED FILAMENT IS DRY. Wet polycarbonate is a miserably stringy, poor fusion, hole riddle waste of filament. Once fully dried, it prints much better.

If you don't have a filament dryer get https://www.amazon.com/gp/product/B01M6AZ863/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

You can also process PLA, TPU, PETG in that dehydrator. It's cheap and saves your from wasting a lot of expensive filament.

No, you cannot dry polycarbonate by simply putting it in a container with silica gel.

Dry polycarbonate at 158F x eight hours for full drying. You can get away with four hours, but you will have some residual pops. Drying is not merely heating the filament to temperature. It also must be held at that temperature and with enough air circulation for moisture to gradually diffuse out of the entire spool.

PETG you can actually also process at 158F. I do so without problem. That hotter than you see recommended, but is still below the glass transition temperature.

PLA you MUST do at lower temp. The key is to always stay below the filament glass transition temperature.

Back to Polycarb printing...

Use a good Live-Z calibration gcode file. I have included my polycarb version of the forum recommended Live Z gcode file in an attached archive. Live Z is hyper critical for polycarb. Too high and your brims and 1st layer will fall apart --> warping or spaghetti monster. Too low and you get elephant foot.

Use a layer of PVA glue to get enough adhesion. Elmers ULTRA glue stick works well for me. I apply a uniform layer to the print surface. Wet it with a water spray and then spread it to form a uniform layer of glue. If you do it right, the glue becomes a syrupy paste as you work it wet. Dry  plate at 100C for about 5-10 minutes. Cleaning between print jobs is with IPA, followed by a fresh coat of glue and re-spread with water.

If you are doing polycarb on a routine basis, consider using a phenolic print surface. You will still need PVA glue, but the results are more predictable than on PEI. I describe how I made my phenolic print plates in a separate topic. https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-user-mods-octoprint-enclosures-nozzles-.../phenolic-heat-bed-surface-diy-for-polycarbonate/

Always use a brim. It won't harm your prints, but definitely saves you the heartache of finding bottoms of parts have slightly warped.

Use a brass nozzle or an equally thermal conductive nozzle like tungsten carbide to achieve best inter-layer fusion.

I have include a 3mf of the major BNBSX B08i extruder parts pre-plated for PolyMax PC. This is to give you my Prusa slicer print, filament, and printer settings that are optimized for PCmax. For other PC filaments you will need different settings for nozzle temp, retraction distance & retraction speed.

Until you have polycarbonate printing well tuned, you may be wise to open my 3mf, but remove components to print smaller number of parts at a time.

RE: BNBSX Short Ears Extruder vs. Skelestruder

Posted by: guy.k2

[...] Here is my advice about printing in polycarb. Follow these for consistent results.

I've got my 1st spool of Polymaker PolyLite PC Transparent on order. That seems like a good starting point after watching Stefan's CNC Kitchen episode on polycarbonate. Thanks for the tips. I'm going to save those for reference getting started. I've got one of the garolite print surfaces off Etsy that was discussed a few months back. Is that a good print surface for PC?

Thanks for the tips. They should save me quite a bit of time getting started.

RE: BNBSX Short Ears Extruder vs. Skelestruder

Posted by: bobstro

Posted by: guy.k2

[...] Here is my advice about printing in polycarb. Follow these for consistent results.

I've got my 1st spool of Polymaker PolyLite PC Transparent on order. That seems like a good starting point after watching Stefan's CNC Kitchen episode on polycarbonate. Thanks for the tips. I'm going to save those for reference getting started. I've got one of the garolite print surfaces off Etsy that was discussed a few months back. Is that a good print surface for PC?

Thanks for the tips. They should save me quite a bit of time getting started.

Keep us up-to-date on how it goes.  I am eager to learn from your experience.  

RE: BNBSX Short Ears Extruder vs. Skelestruder

Posted by: charles.h13

Keep us up-to-date on how it goes.  I am eager to learn from your experience.  

I'm feeling a bit chuffed after getting Taulman nylon bridge to print without an enclosure on PEI, but this stuff looks like it'll be a bit more of a challenge. I'm most concerned about fumes as I print in my basement office. I'm hoping I can print with the door open and fan blasting the air outside. Otherwise, I... need to buy a garage printer. Hmm.

I'll post results once I get something going.

RE: BNBSX Short Ears Extruder vs. Skelestruder

Garolite is phenolic with embedded fiberglass. It's a good surface for polycarb and that saved you building your own.

I would expect to still need PVA glue. I can sometimes get away without glue, but the occasional failure makes me go back to using glue for predictable success.

When staring out with PC, one gotcha is during switching back to a low temp material like PETG. You must clean the hot end thoroughly with cleaning filament and atomic pull. Otherwise you WILL eventually get a clog printing in PETG. Also, any PEI surface that you printed upon with PC will need a through DAWN wash. You may even need to season the surface again with multiple IPA wipes while hot before PETG will stick again. My ultimate solution was to dedicate one printer as my high temp PC machine and never do mixed use of a print plate. That might not be practical for everyone, but saves time and hassle of switching back and forth.

BTW, Polymax isn't really obnoxious while printing. I don't think you will need your garage.

RE: BNBSX Short Ears Extruder vs. Skelestruder

Posted by: guy.k2

Garolite is phenolic with embedded fiberglass. It's a good surface for polycarb and that saved you building your own.

I would expect to still need PVA glue. I can sometimes get away without glue, but the occasional failure makes me go back to using glue for predictable success.

So just watered-down white glue? Not a stick, right?

When staring out with PC, one gotcha is during switching back to a low temp material like PETG. You must clean the hot end thoroughly with cleaning filament and atomic pull. Otherwise you WILL eventually get a clog printing in PETG. Also, any PEI surface that you printed upon with PC will need a through DAWN wash. You may even need to season the surface again with multiple IPA wipes while hot before PETG will stick again.

That's why I went for the garolite on it's own spring steel sheet. I'll definitely keep them separate. I've got eSun and rigid.ink cleaning filament that I use regularly when switching materials. The rigid.ink stuff is rated up to 285C I think. I'll definitely clean it out afterwards. Is a dedicated nozzle worth considering?

My ultimate solution was to dedicate one printer as my high temp PC machine and never do mixed use of a print plate. That might not be practical for everyone, but saves time and hassle of switching back and forth.

Hmm. If I could get a cheap printer to stick in the garage, I'd do the same. Unfortunately, the Mk3 is the one that can print the exotics, and I hate the idea of sticking that in a garage. How are you faring with PC in bowden setups? Would upgrading a cheap printer with an all-metal hotend be sufficient?

I'm not after a bigger printer in this case, but I'd like one I could screw up badly with without being out of business for repairs.

RE: BNBSX Short Ears Extruder vs. Skelestruder

Elmer's ULTRA glue stick actually. 

Garage + high temp requirement + winter? I don't think that's going to work out well unless you are in a super temperate region.

I ended up building another Prusa out of spare parts and a few more bits from Prusa. Definitely didn't save any money over another kit.