managing 4-8 hotends

I would like to configure my printer with at least 4, maybe 6 or 8 hotends, I think I have figured out a way to drive all with a single stepper and use another stepper to switch between them. What I am unfamiliar (ignorant) with is how to control the hotends individually and what additional electronics would be needed. My printer uses Arduino Mega and Ramps. Where do I start?

I don't know of any ready-made electronics and firmware that can handle 8 hot ends, but a Duet 0.8.5 and DueX4 combo (see [www.think3dprint3d.com]) can handle 6 using standard firmware. It's designed to use a separate stepper motor for each hot end. If you want to use just two steppers, you would need to modify the firmware, and work out a mechanical way of holding all the filaments in place except for the one you are advancing or retracting.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I had a hard time to get two nozzles level. The risk of ripping off the 1.st layer is much higher and frustrating.
Adjusting four or more nozzles to the same height would be a nightmare.
If you´ve developed a tilting mechanism to drop only the nozzle in duty, it would be a winner.
-Olaf

@dc42
It wouldn´t be too difficult to bridge six ( faked ) stepper signals to feed only one stepper. A DueX4 wouldn´t even be necessary, he could use the expansion port.
-Olaf

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o_lampe
@dc42
It wouldn´t be too difficult to bridge six ( faked ) stepper signals to feed only one stepper. A DueX4 wouldn´t even be necessary, he could use the expansion port.
-Olaf

You would need some electronics to detect a pulse from one of the step pins and send a delayed version of the pulse to the stepper driver, giving you time to set the direction pin to the correct level first. Not difficult, but by no means trivial. Easier to do it in software.

However, this still leaves the issue of temperature-controlling the hot ends, assuming it isn't a single-nozzle switching arrangement.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks for the feedback guys. Seems as though Edvardas and I coincidentally are dealing with a similar issue today [forums.reprap.org] .DC42, This will have individual heaters and thermistors. O_lampe, I am hoping the fact that, in a 4 hotend arrangement, the designs 4 nozzle centers fit in an 11mm square limit the issues with height variations. The Extrudrboard also looks like an option if its compatible with my current setup or the Duet/DueX4 with some sort of a work around for the lack of individual steppers.

Bill, I am checking my thread as much as yours
Extrudrboard is compatible with ramps and would get you 4 extruders: [reprap.org]
Radds v1.5 seems to be able to run 4 nozzles if you do not have a heatbed.
Rumba should be able to run up to 5 nozzles.
And duet is the ultimate board in this regard.

Edited 1 time(s). Last edit at 09/25/2015 09:14PM by Edvardas.

Thanks Edvardas. A quick search didnt lead me to a supplier for Extrudrboard and Printrbot doesnt show it on their site.

I will stick with 4 hotends to start using 2 steppers, one to drive the 4 filaments a 1 to select the appropriate one.
If I can find the Extrudrboard (or utilize one of the other boards) I am definetly going to need some help with the work around using less steppers via software or an additional device.. Any help in that regard would be greatly appreciated. I would even be willing to pay someone for their help with this,

Edited 1 time(s). Last edit at 09/27/2015 05:54AM by Bill Clark.

There is an extrudrboard for sale at reprap.me
So are you planning to use ramps? I am affraid there are only outputs for 3 hotends on it.

Ahh, I thought it supported more than 2. Wondering if I could use this [reprap.me] for the bed then I could have 4 hotends utilizing the Extrdrboard and ramps?

HPX4 MAX from Dglass 3D is another quad extruder using two steppers for driving the filaments and 2 servos to switch filaments. I plan to use Radds board with repetier firmware (still in development stage). Initially about two years ago I started with Duet Duex4 with bowden setup but could not recieve a decent/acceptable print quality. Only a light weight direct drive can give a good quality print in my experience. For this reason I selected the D3D quad extruder (kickstarter backer) along with auto lift nozzle retraction systém from D3D as well.

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alfredanil
HPX4 MAX from Dglass 3D is another quad extruder using two steppers for driving the filaments and 2 servos to switch filaments. I plan to use Radds board with repetier firmware (still in development stage). Initially about two years ago I started with Duet Duex4 with bowden setup but could not recieve a decent/acceptable print quality. Only a light weight direct drive can give a good quality print in my experience. For this reason I selected the D3D quad extruder (kickstarter backer) along with auto lift nozzle retraction systém from D3D as well.

I don't know what you regard as "acceptable print quality", but here is a print I did using a dual Bowden setup, with the printer driven by a Duet 0.6 + DueX4:



Bowden extruders need more effort on getting the retraction settings right, but can give good results. Auto lift of the inactive nozzle(s) would certainly help, but I don't have that. I understand that Stratasys has a patent on auto lift nozzles, which is likely to make it difficult for anyone without a good patent lawyer to sell them.

Is the reason you are switching to RADDS purely that someone is developing firmware for it to support the D3D extruder with its servos?

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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dc42
I understand that Stratasys has a patent on auto lift nozzles, which is likely to make it difficult for anyone without a good patent lawyer to sell them.

Probably not that difficult. Just sell the parts required for a design as a "kit", or read the patent and find a workaround/loophole. Patents are often a game of words, and expensive game at that!

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dc42

Is the reason you are switching to RADDS purely that someone is developing firmware for it to support the D3D extruder with its servos?

D3D extruders came with marlin support but was for dual extruder only, since marlin is limited to just three extruders. I found Reprap firmware bit complicated to modify and build support for servo, eventually gave up (due to my inability but the firmware is excellent). Switching to Radds with repetier firmware was more easier and cost effective (Due clone+Radds V1.5). Although it is still work in progress, working with repetier firmware makes quad direct extrusion more possible/workable. Reptier online configurator is a piece of cake for an amatuer programmer like me, it is felexible and easy to work with. Using Silent StepSticks further gave added advantage with 256 micro steps and sleath chopper which reduced noise levels drastically. Auto lift nozzle from D3D is a very simple mechanical construction, I managed to tweak the design many folds.

Edited 6 time(s). Last edit at 09/30/2015 04:16AM by alfredanil.