Controlling five to six different printer heads with same axis

[cnctom]

Hello
I'm wanting to install five to six different 3d printer heads on my cnc each to have a different color, I want to use my gecko g540 A axis witch is no problem but i need to have a switch to switch between the five to six different steppers all controlled by axis A. So can anyone point me in the right direction. I should be able to figure out the Mach4 side of it but the actual switch is stumping me.

Thanks for your time

[Mjolinor]

You need to explain more, it is unclear what you are doing. These 6 heads will probably (unless you have some greater plan) all be in different places so switching extruder heads mid print will lead to lots of air printing.

[cnctom]

My plan is to use offsets for each color meaning if each head is 2.500 between each nozzle black could be set to g54.1p1 red could be g54.1p2 blue could be g54.1p3 and so on so instead of setting up additional axis for each stepper i would switch my A axis between all five to six stepper's but i need to figure out a switch.

[truly_bent]

A switch? I think you need 5 or 6 four pole relays, which would connect the windings of each individual stepper motor to your 'A' axis outputs - preferably using bifurcated contacts for low resistance. Avoid switching relays while running.

Edit: Forget the bifurcated contacts. Those are for low current, low voltage signals.

[Mjolinor]

OK. Well you need a whole lot more than a switch for a whole rake fo reasons starting with:

Powering off the extruder stepper will allow the filament to relax back from the head.
The steppers use microstepping so for 12 out of the 16 positions the stepper is held in a position that it will not maintain without power so you can't restart where you left off even if you stop the filament affecting the head at power off.
All of the arithmetic that goes on inside the printer firmware (PC software) regarding used filament would need a significant bit of rewriting. For you to be able to do that you would have to let the control software / firmware know which head is selected.

It is a lot less work and a lot less hardware to just have a stepper driver for each stepper motor.

If you have two stepper drivers you can do as many filaments as you want using a drum selector.

[truly_bent]

Could you elaborate on the "drum selector" option? Googling "3d printer drum selector" turned up nothing useful, except this thread. Thanks.

[Mjolinor]

Well I don't suppose it would.I only made one.

It's in bits now. I sold the printer it was on.

Essentially one stepper has a drum on with the pinch wheels, the other has the drive spline, a long one.

There are pictures of it in a thread on here somewhere. I will dig the bits out and take pictures of the bits I can find.

[Mjolinor]

OK. I can't find the hot end right now but here is the pusher. It has to be a bowden pusher.

You can see the drum with only one pushing wheel in, I used the other for something else. In the other picture you can see the brass bit that rotates to push the filament. It will only push the filament that has the pushing wheel behind it, all the others stay where they are. To change colour you just rotate the drum until another wheel lines up. At the hot end I had a stainless pipe with the nozzle on attached to the end of the PTFE tube and the actual hot bit had a hole that the nozzle fitted into so that changing colours involved removing one nozzle/ptfe pipe and replacing it with another one so that the extruder nozzle stayed in the same place.

I had it working with 2 different filaments but lost interest at that point. I never automated the nozzle change because it is a pretty trivial thing to do so never bothered.

For whatever reason, I am unable to upload any pictures so I have stuck them here:

http://homepage.ntlworld.com/dknpowe...225_150548.jpg
http://homepage.ntlworld.com/dknpowe...225_150614.jpg

[truly_bent]

Think i get it. Looks like a well thought out plan.

...At the hot end I had a stainless pipe with the nozzle on attached to the end of the PTFE tube and the actual hot bit had a hole that the nozzle fitted into so that changing colours involved removing one nozzle/ptfe pipe and replacing it with another one so that the extruder nozzle stayed in the same place.

I can see that automating the filament selection wheels would be relatively easy, but swapping the nozzle/ptfe pipe for each filament might be a little more mechanically involved.

From a programmer's point of view, i'd be more inclined to have a go at the software option. It's already set up to handle at least two extruders from the get go. How difficult would it be to extend that to 5 or 6?

[Mjolinor]

Changing the nozzle is exactly the same as a million CNC machines with a tool changer.