Dual parking extruder design requires 2 X -axis steppers

I'm thinking of putting together a Dual headed Prusa Mendel so that I can print PVA support material with PLA. I have an idea that, if the heads position on the X axis could be independently controlled rather than being mounted on the same carriage, I could park the head not being used with a strip of thin metal pressing against the head to prevent ooze. To do this, I will need two X - axis motors mounted so that the whole X axis assembly had two belts, one at the front and one at the back. I intend each motor to have its own Poulo driver but I was thinking of using an analogue switch (like a 4066) to switch the Speed and direction pulses between the two X-axis Poulo drivers. I don't intend ever running the two steppers at the same time. I want to work with the Ramps board because it can already run two extruders. Does anyone else have experience of doing what I want to do?
I am also guessing that I will have to re-configure one of the Ends stop switch so I have two home position indicators, one for each X carriage rather than one set of limit switched.

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Using ABSPrusa Mendel Zaphod with Pronterface and slic3r 1.3.0. Printing well with 3mm PLA and ABS through 2 x J Head Mk IV b and Wade Geared Exruders. Controlled using RAMPS1.4 board running Marlin_v1.1.9

try here

[forums.reprap.org]

its full parallel application, but may give you some ideas


carel

Frustrated with the dual extruder ooze problem ... or the standby warm up and down time to avoid it - so I am thinking of doing exactly the same.

Did you get any further on yours?

My Bukobot Duo (Dual Head) already consists of two single extruder x-carriages which are held together with a link, so all I need to do pull out the linking plate and design new X-axis ends to mount & route the second motor & drive cable.

I don't have a spare stepper driver slot so I was thinking of just buying a 4-way 5V controlled relay such as: [www.uxcell.com] ($10-14) which is almost as cheap as Polulo anyway and a lot easier to hook up. I only need to drive one x-carriage at a time and the relays should handle the current (and my Azteeg X3 has a switched output with enough drive current to handle all 4 relays from one pin). Thoughts?

I'll add another end-stop switch at the other end of the X-axis as well so that both carriages can be homed. The tool change command in the firmware will need to be changed to park the old head, rehome the new head (since the motors weren't energised they may have moved very slightly), update the new tool position and continue when the tool change occurs. Interestingly, there doesn't need to be a second extruder offset specified now - you just need to accurately determine the co-ordinate of the second extruder park position.

Edited 3 time(s). Last edit at 04/28/2013 11:24AM by buildrob.

Thinking about this approach more, you would need to ensure that you disable the FET outputs (by pulling the ENABLE input high) before switching the relays to the other motor.

I guess in the worst case this would happen simultaneously if you reset the Arduino when the second stepper was powered. Not sure if this is a problem but you are disconnecting both sides near-simultaneously which means that a large induced voltage shouldn't be put across the output terminals for any length of time.

Anyone see any problems with this?

I finally finished my dual parking extruder project. Getting some good results.

I eventually decided just to build a separate stepper driver board and connect the enable/direction/step signals to 3 of the digital expansion pin headers rather than mess around with relays.

I did a write up here:
[www.thingiverse.com]

I can only guess that this isn't getting much attention because it is buried in the RAMPS forum. But I wanted to let you know I think your design is great and executed very well.

Is your Azteeg's 5th stepper driver controlling the additional X stepper or the additional E stepper?

Fl0yd

The new 6th stepper controls the second X-axis stepper. This kept the pin allocations on all the other stepper unchanged (so the Azteeg's 5th stepper is on the second extruder).

Robert.

i like that duel parking idea. its got me thinking now.

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[mike-mack.blogspot.com]

Im working on the Printrbot dual direct drive extruder beta release. There is 10 of them being released in the wild. Im interested in this and looks like a great little project. If you would like to see the build log and how we do it feel free to check out my WordPress site linked below. I will be updating it regularly, keep up the good work.

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This is beautiful.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

I didn't realise that others were contributing to this thread! Well, anyway, I've just completed the build and now have a dual head (dual X motor). I'm using the current version of Marlin from GitHub and have configured it for Dual X in the Configuration_Adv.h file. I have some other issues at the moment but I see that there is no native support for the second Extruder and X motor in the LCD menu? I built up a second stepper controller and have connected it to pins 44, 42 and 40 on the Aux 2 header on the Ramps Shield. I couldn't use the ones specified in the Marlin code as I have an LCD and those pins are used for driving that. Am I likely to have problems with my choise of pins? Is the only way to test this second X and extruder by using G and M codes?

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Using ABSPrusa Mendel Zaphod with Pronterface and slic3r 1.3.0. Printing well with 3mm PLA and ABS through 2 x J Head Mk IV b and Wade Geared Exruders. Controlled using RAMPS1.4 board running Marlin_v1.1.9

Bad choice of pins. Stops the serial working. Will try and find some others.

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Using ABSPrusa Mendel Zaphod with Pronterface and slic3r 1.3.0. Printing well with 3mm PLA and ABS through 2 x J Head Mk IV b and Wade Geared Exruders. Controlled using RAMPS1.4 board running Marlin_v1.1.9

Hi mate,
You should pretty much be able to use any pins as long as they don't conflict with other pins in use. They don't need to support PWM or PININT.

Set DEFAULT_DUAL_X_CARRIAGE_MODE to 1. Then you should be able to change between the x-carriages on the LCD just by changing your active toolhead. The new toolhead will move into position once you adjust the position of the head. [And printing from an SD card should be seamless.]

Edited 1 time(s). Last edit at 04/29/2014 06:32AM by buildrob.

It's alive!!!!!
Got it working last night! Managed to connect power up wrong to my Vero-board mounted Pololu. So, one small fire and blown LCD module later, I then discovered my replacement Pololu was also faulty! That now fixed, I'm all up and running. I need to calibrate everything, which I will do this weekend.
One question though...
Before, my X,Y and Z endstops were essentually at (0,0,0) in the bottom left hand corner of the print bed. Now, with a new mounting of the Y endstop and the fact that the X1 and X2 heads home well away from the print bed, how do I tell Marlin, Slic3r, Pronterface and Repetier that the print origin is not at the end stops? The comments in the code are ambiguous to say the least!

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Using ABSPrusa Mendel Zaphod with Pronterface and slic3r 1.3.0. Printing well with 3mm PLA and ABS through 2 x J Head Mk IV b and Wade Geared Exruders. Controlled using RAMPS1.4 board running Marlin_v1.1.9

Excellent.

It is usually simplest to keep the co-ordinate systems indexed from the end-stop (i.e., 0) in the firmware.

Every slicer I have seen allows you to configure where the print bed is located with respect to the origin (i.e., by specifying the bed center and size, or bed left/right/top/bottom).

Hope that helps.

I'm have some trouble. I am find that when I do a tool swap, the firmware is trying to park the head by moving it extremley quickly. It is so fast that one time in three, it stalls and doesnt get moved all the way back to the home position. As far as I can see in the code, it should only do this at max feed rate but, in reality, its much faster than this. Buildrob, have you seen this?

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Using ABSPrusa Mendel Zaphod with Pronterface and slic3r 1.3.0. Printing well with 3mm PLA and ABS through 2 x J Head Mk IV b and Wade Geared Exruders. Controlled using RAMPS1.4 board running Marlin_v1.1.9

It attempts to accelerate up to DEFAULT_MAX_FEEDRATE when changing tool heads - so make sure they are set to sensible values in Configuration.h

BuildRob, I was wondering if you could help? My two extruders are slighly different lengths with ext1, the right-hand or second extruder being about 0.6mm longer and, consequently, closer to the bed than ext0.

To adjust for this, I assumed that I should set up my Z endstop, which is on the right nearest the ext1, so that the left hand, ext0, when on the right hand side of the bed just touches the bed. I then move ext0 to the left and then adjust for just toching by turning the left hand z thread. This should ensure that my x axis an bed are parallel.

I then set #define EXTRUDER1_Z_OFFSET -0.62, telling Marlin that my ext1 is 0.62mm lower than ext0. I then Build and load this onto Marlin.

I check that ext0 homes on z and find that it does. I then select T1 and check ext1. However, my change appears to have had no effect on ext1.

What am I doing wrong?

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Using ABSPrusa Mendel Zaphod with Pronterface and slic3r 1.3.0. Printing well with 3mm PLA and ABS through 2 x J Head Mk IV b and Wade Geared Exruders. Controlled using RAMPS1.4 board running Marlin_v1.1.9

Ha Ha EXTRUDER1_Z_OFFSET is defined alright but is not referenced any where in the code! I'm using a pretty current copy of the Marlin_v1 branch. Is this the correct branch to be using?

So, I can set it to what ever I want and it won't make the blindest bit of difference!

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Using ABSPrusa Mendel Zaphod with Pronterface and slic3r 1.3.0. Printing well with 3mm PLA and ABS through 2 x J Head Mk IV b and Wade Geared Exruders. Controlled using RAMPS1.4 board running Marlin_v1.1.9

Ah yeah - apologies. It was something I was planning on implementing but decided to pull it out (too many places that I would have needed to change to properly implement it). I obviously forgot to remove the values from Configuration_adv.h

Also, really I think you would be better to get the two extruders to be at the same height. Consider using small washers or shims (e.g., circles of thin aluminium like they use for gardens) above or below your mounting plate bolts to get the two extruders equal.