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tim.w
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Re: Ninjaflex and the Extruders

Sun Sep 10, 2017 7:09 am

Okay - because I want to print ninjaflex again, I really don't want to buy another 3d printer, and I don't want to give up the multi-material option, I decided another approach was to design a new direct drive extruder. I don't want to convert the printer back to its pre-MM days, I just want to quickly switch it to a direct drive extruder when I need it. So my new extruder is shaped to fit into the same gap as the y-splitter and bolt to the frame in the same way. To install you simply remove the y-splitter and attach the direct driver extruder. I have it wired as extruder 4.

Here's the first prototype:
IMG_2104.jpg
IMG_2104.jpg (200.86 KiB) Viewed 118 times

It's based on the same design I tried for the other extruder, but here its used to directly drive the filament straight into the hotend.

And here's my first print using NinjaFlex:
IMG_2106.JPG
IMG_2106.JPG (161.52 KiB) Viewed 118 times

I printed the NinjaFlex at 240C, 40C bed and ... accidentally ... printed it at the default speed (40mm/s). But it came out rather well I thought.

mavu
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Re: Ninjaflex and the Extruders

Tue Sep 12, 2017 7:24 am

Thanks for the onshape link!

Also, I love the extruder switch idea. could you post that too?
An easy way to switch between MMU and standard mk2s would be the perfect world for me.

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tim.w
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Re: Ninjaflex and the Extruders

Wed Sep 13, 2017 7:23 am

Here's the Onshape link for the direct extruder. I'm still tinkering with sizes and clearances on this and on the previous extruder. Also, on this new one, I accidentally created it as a mirror of what I really wanted (you have to plug the stepper in backwards!) so you'll find the mirror version (*not* the one to use) and the non-mirror (use this one) on Onshape. When you install this extruder in place of the splitter, there's a gap between the top of the ptfe sticking out of the hotend, and the drivegear inside the extruder - I think it's about 10mm. You need to push a bit of ptfe tubing into the extruder to give the filament a smooth path down to the hotend.

Link: https://cad.onshape.com/documents/f4b15 ... 3a2680bae9

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tim.w
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Re: Ninjaflex and the Extruders

Wed Sep 13, 2017 7:56 am

Also - because this is fun - I decided to build a hybrid bowden/direct multi-material extruder. This attached the splitter to the top of the direct extruder:
IMG_2108.jpg
IMG_2108.jpg (106.05 KiB) Viewed 100 times
The goal here is to allow me to print with multi-materials, including ninjaflex. The direct drive stepper takes care of making sure the softer stuff extrudes correctly, while the splitter and bowden steppers take care of moving material into the splitter. In theory at least, I can switch materials just like the original MM design, but have the advantages of a direct extruder.

A couple of interesting things to note while testing this. First, I realize I'm going to have to mess with the Slic3r code because the distance to unload/load when switching materials has increased (maybe its easily configurable somewhere?). Second, The original MM electronics came with a spare 4-pin socket which lets you plug a stepper directly into the stepper signal coming in from the Rambo board. That means, in theory, its easy to run the direct stepper whenever any other extruder stepper is running (since that stepper signal is common to all); and that's what we want. I notice the new MM electronics don't have spare socket anymore. Third, I realize I'm running two steppers in parallel off the stepper drive. Since this is what the Rambo does for the y-axis I figure this isn't a problem. However, I can only get the new Prusa steppers (the ones that came with the MM upgrade) to play well together. If I try to use the original extruder stepper, or another random stepper I have, then they start skipping. Not sure why yet.

Here's the ninjaflex test, again at full speed:
IMG_2114.JPG
IMG_2114.JPG (219.9 KiB) Viewed 100 times

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PJR
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Re: Ninjaflex and the Extruders

Wed Sep 13, 2017 8:19 am

tim.w wrote:
Wed Sep 13, 2017 7:56 am
I realize I'm going to have to mess with the Slic3r code because the distance to unload/load when switching materials has increased (maybe its easily configurable somewhere?).
The only thing that's configurable is the length of the Bowden tubes (firmware reset to set this) but that won't help, because the additional length is after that point.

You do have the option of using KISS and my post-processor, where you can configure the load/unload distances, or you could edit all the output G-code files.

Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage or loss.

daniel.k7
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Re: Ninjaflex and the Extruders

Thu Sep 14, 2017 1:56 pm

That seems to be very interesting. How do you adjust the Setting when you change from multi Extrusion to single? I am thinking about to use the third extrusion motor for your single Extrusion Setup. Because I do not really see the need in printing multicolor.

anthony.c9
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Re: Ninjaflex and the Extruders

Thu Sep 14, 2017 3:24 pm

I'm really interested in the MM upgrade, but mostly to be able to integrate hard+flex+scaffolding into a print - as opposed to colors. Adding a direct extruder pretty much makes this the "perfect" MM printer for any combination of materials, to the point of competing w/idex.

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tim.w
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Re: Ninjaflex and the Extruders

Sat Sep 16, 2017 5:53 am

daniel.k7 wrote:
Thu Sep 14, 2017 1:56 pm
That seems to be very interesting. How do you adjust the Setting when you change from multi Extrusion to single? I am thinking about to use the third extrusion motor for your single Extrusion Setup. Because I do not really see the need in printing multicolor.
For the single extruder I'm basically loading the filament into it by hand; or more specifically by pushing button in an OctoPrint window to gradually load the filament into the extruder. Then I just print as a single using gcode generated with a single extruder profile with a little but of gcode added to select my single extruder at the beginning of the print.

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tim.w
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Re: Ninjaflex and the Extruders

Sat Sep 16, 2017 5:56 am

anthony.c9 wrote:
Thu Sep 14, 2017 3:24 pm
I'm really interested in the MM upgrade, but mostly to be able to integrate hard+flex+scaffolding into a print - as opposed to colors. Adding a direct extruder pretty much makes this the "perfect" MM printer for any combination of materials, to the point of competing w/idex.
I started down this path, at least in part, because I wanted to print flexible and support at the same time. The combination of direct drive and multiple filament is probably the most flexible setup but requires the most changes to software and firmware to get working.

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tim.w
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Re: Ninjaflex and the Extruders

Wed Sep 20, 2017 1:15 am

Had chance to tweak some gcode today to try to run a multi-material print with the hybrid arrangement ... and it's going go need some more work. What happens (and I worried it would) is that during retraction to change filaments, the soft retracting filament gets squeezed by the direct drive gears and blocks the extruder. Obviously its still too soft to extract at that point. I've been fairly simplistic in how I'm handling this so far but it looks like I need to consider letting the filament cool in the cold part of the hot end a little longer; and maybe there are side effects with doing that.

The current unload retraction is split into several bits, looking like this:

G1 E-15.0000
G1 E-50.0000 F5400
G1 E-15.0000 F3000
G1 E-12.0000 F2000

I wondered if anyone (looking at you PJR) could break down exactly what each distance and speed corresponded to and why. I'm sure this was extensively tweaked during beta.

Thanks
tim.w wrote:
Sat Sep 16, 2017 5:56 am
anthony.c9 wrote:
Thu Sep 14, 2017 3:24 pm
I'm really interested in the MM upgrade, but mostly to be able to integrate hard+flex+scaffolding into a print - as opposed to colors. Adding a direct extruder pretty much makes this the "perfect" MM printer for any combination of materials, to the point of competing w/idex.
I started down this path, at least in part, because I wanted to print flexible and support at the same time. The combination of direct drive and multiple filament is probably the most flexible setup but requires the most changes to software and firmware to get working.

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