1 Topic by pirvan

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Topic: Dual Input Switching hot end

Has anyone considered, or have any information on the Dual input Switching hot ends?

Sounds very interesting, kinda like the best of both worlds.  The question is what kind of changes do we need to make in the firmware.  I'm currently running a RAMPS board, so dual extruders are a definite option.

To print or, 3D print, that is the question...
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2 Reply by wardjr

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Re: Dual Input Switching hot end

Are you talking about the Cyclops?  The hardest thing is to decide how to handle only using one heater and one thermistor.  You should have no issues figuring out how to manipulate the firmware.  You just need to decide how you want convince it that there is two heat cartridges and two thermistors since that is what it is expecting.  I covered this on the multi-extrusion section but if you have more questions just let me know.

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3 Reply by pirvan

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Re: Dual Input Switching hot end

So I looked at your post on the Cyclops and I have a few questions:

Instead of using that firmware "redirection" couldn't you simply wire the thermistor to both the pads (E0 & E1)?  Also you could leave the heater pads empty.  I don't think the firmware can detect the lack of resistance, so it would think it's working as long as it gets a signal from the thermistor.

Alternately, you could drill holes into the opposite side of the heater block for the heater cartridge and the thermistor, effectively creating a "redundant" system.

I noticed you were printing a skirt as a means to waste the blended color filament.  The problem I see with that, is that on a small model you might not waste enough mixed color filament out, whereas on a larger model you might waste too much.  Why not figure out how much filament extrusion is needed to get rid of the mix and get a pure color, then create a "waste tower", a hollow cylinder or rectangular pillar that prints enough perimeters to account for the needed extrusion length.  You could add that tower to all your prints and simply scale it vertically to match the height of whatever model you're printing.

Another question.  in a given layer, does it print everything in one color then switches to the other, or does it alternate back and forth between the colors?  The waste tower does NOT make sense if it does the latter.

Anyway, I do like the idea of the single output and alternating feeds, no wasted build area.  Primarily I'd like to get it so I can print PVA, but I'm sure I would print in dual colors as well.

To print or, 3D print, that is the question...
SD3 printer w/too many mods,  Printrbot Simple Maker Ed.,  FormLabs Form 1+
AnyCubic Photon, Shining 3D EinScan-S & Atlas 3D scanners...
...and too much time on my hands.

4 Reply by wardjr

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Re: Dual Input Switching hot end

A quick answer to the thermistor/heater question is,,,, it either didn't work or I didn't like how it worked.  That doesn't mean you shouldn't try it and see.  As far as the skirt, that is just how I did it at that time.  Purge tower works well once you get the correct size figured out.  You can design in when each extruder prints or you can switch it manually mid print.  The only thing you need to be careful of is too much retraction, allowing filament to push through from the other side.

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5 Reply by elmoret

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Re: Dual Input Switching hot end

pirvan wrote:

Instead of using that firmware "redirection" couldn't you simply wire the thermistor to both the pads (E0 & E1)?  Also you could leave the heater pads empty.  I don't think the firmware can detect the lack of resistance, so it would think it's working as long as it gets a signal from the thermistor.

No, bcause then you'd effectively have two balancing resistors in parallel. You'd need to come up with a new thermistor table.

pirvan wrote:

I noticed you were printing a skirt as a means to waste the blended color filament.  The problem I see with that, is that on a small model you might not waste enough mixed color filament out, whereas on a larger model you might waste too much.  Why not figure out how much filament extrusion is needed to get rid of the mix and get a pure color, then create a "waste tower", a hollow cylinder or rectangular pillar that prints enough perimeters to account for the needed extrusion length.  You could add that tower to all your prints and simply scale it vertically to match the height of whatever model you're printing.

A purge tower is what E3D does in their blog post introducing the Cyclops.

pirvan wrote:

Another question.  in a given layer, does it print everything in one color then switches to the other, or does it alternate back and forth between the colors?  The waste tower does NOT make sense if it does the latter.

That's up to the slicer, the hotend doesn't care.

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6 Reply by IronMan

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Re: Dual Input Switching hot end

elmoret wrote:

That's up to the slicer, the hotend doesn't care.

Yes, ultimately it is up to the gcode generated; with a designator for each extruder motor (T0 or T1) on either a particular layer or portion of a layer.  When I say "portion", the switch could occur within a layer if you selected Ext 1 for Perimeters and Ext 2 for Infill.  If you combine multiple STL files within Slic3r and then slice, then each of those could be assigned Ext 1 and 2...again depends on your slicer settings.

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7 Reply by pirvan (edited by pirvan 2015-09-22 18:49:40)

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Re: Dual Input Switching hot end

I need to do a few simulations and see what the output looks like.

I'm really considering this for my next printer build, which has been sitting in a box ready for assembly for over a year.

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To print or, 3D print, that is the question...
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8 Reply by IronMan

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Re: Dual Input Switching hot end

Pretty sweet!  What is the build area?

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9 Reply by pirvan

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Re: Dual Input Switching hot end

You know what... I couldn't even remember myself, I had to go back and look.   The print area is 10" x 10".  Total vertical lift will depend on the printhead design, but about 10", maybe a bit more.

To print or, 3D print, that is the question...
SD3 printer w/too many mods,  Printrbot Simple Maker Ed.,  FormLabs Form 1+
AnyCubic Photon, Shining 3D EinScan-S & Atlas 3D scanners...
...and too much time on my hands.

10 Reply by jagowilson (edited by jagowilson 2015-09-22 16:59:22)

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Re: Dual Input Switching hot end

How fast can you print with ballscrew axes like that? Seems like you'd need more rotations than you can provide for speeds like 200mm/s, assuming those are >1000 steps/mm.

11 Reply by pirvan

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Re: Dual Input Switching hot end

jagowilson wrote:

How fast can you print with ballscrew axes like that? Seems like you'd need more rotations than you can provide for speeds like 200mm/s, assuming those are >1000 steps/mm.

I don't really remember, but I think this was covered at one time or another in the original thread.

Anyway, I don't plan on printing at 200mm/sec, more like 70-80m/sec.  The ball screws have a 5mm/rotation travel, so that makes it about 6-8 times slower than a belt, but the motors should still be able to drive these at 80-100mm/s

To print or, 3D print, that is the question...
SD3 printer w/too many mods,  Printrbot Simple Maker Ed.,  FormLabs Form 1+
AnyCubic Photon, Shining 3D EinScan-S & Atlas 3D scanners...
...and too much time on my hands.

12 Reply by grob (edited by grob 2015-09-22 22:36:17)

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Re: Dual Input Switching hot end

My calculation says Pirvan's ballscrew system will be capable of applying more force to the carriage than a typical belt driven printer at 100mm/s, taking into account the torque reduction of a typical motor. About 2-3x more force. smile

But you *have* to use at least 24V (preferably 36V), or the motors won't make it to this speed. Typically a NEMA17 tops out at 900-1000RPM on 12V, and for a 5mm pitch screw 100mm/s = 1200RPM.

Top speed could be anything upwards of 150mm, this would depend significantly on the exact motors and friction so not going to call it until he's built it. smile

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13 Reply by osmanharac

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Re: Dual Input Switching hot end

pirvan wrote:
jagowilson wrote:

How fast can you print with ballscrew axes like that? Seems like you'd need more rotations than you can provide for speeds like 200mm/s, assuming those are >1000 steps/mm.

I don't really remember, but I think this was covered at one time or another in the original thread.

Anyway, I don't plan on printing at 200mm/sec, more like 70-80m/sec.  The ball screws have a 5mm/rotation travel, so that makes it about 6-8 times slower than a belt, but the motors should still be able to drive these at 80-100mm/s

Anytime I see this printer , I get excited. Please let us know about the status of the project.
I may also start a project like that but my limited budget might be a problem.