CNC to 3D Printer

New to the forum, so hello everyone!

I have currently built a few reprap machines in the past few years, and was given an opportunity to create one for my employer. I was given an old custom CNC as a motion platform (should be around 500mm x 600mm x 500mm build area). It has ball screws on each axis for motion which is awesome and built like a tank. The current motors and drivers are not suitable for a 3D project, so I am reaching out to you all to see what I should start with in terms of controller and motor sizes. I have experience with the RAMPS1,4, melzi, but thats about it.

I do know that NEMA17 is TOO small. Maybe NEMA23 would work? NEMA34?

I understand that the higher the voltage, the better. Preferably work with 24V?

Can I use a RAMPS1.4 to drive a NEMA23 with the standard DRV8825 driver, or will I need something beefier? I have not bought any motors. Which ones would be ideal? Im able to navigate Marlin firmware, so that would be ideal as well.

I am no expert, but learn quickly. Any help you can provide would be excellent. I have scavenged through the forums in regards to similar projects, but could use some personalized help. Thanks a bunch.

... the equipped motors seems to be servos with encoders?

If yes, then the best would be to find servo-drivers with STEP/DIR input, so they will behave like ordinary steppers from the controller view - then any of the RepRap-electronics will do.

I've reactivated two servo-driven CNC-mills for laser-engraving or paste-dispensing with UHU servo-drivers and common CNC-controllers, meant for stepper driver+motors ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Lucky bastard! Stick with the servos, if that's what they are, they'll give much better results than steppers. It looks like you could add a heated chamber as well.

How do I know what I actually have for motors? The original paperwork says nothing and there is no identification actually on them. What kind of pictures will you need to be able to help me out? Also, heated chamber is definitely happening.

How are you going to get that build volume from this machine? You are going to be limited on the Z axis by the Z rod assembly.

At the current time, we are only going to go for 6" in height as it will capture our primary use for it. To increase this in the future, we would pull the x axis out with a frame of sorts. First things first, get it moving and printing.

Hi guys,

I dunno what kind of servomotor this is, and if you will be able to use them.
Do you have any electronics which comes with the machine ?
If not, using that servos can be a nightmare (custom wiring, encoder status/steps, AC or DC powering, and so on...).

Anyways, ballscrews does not fit 3d printing speed requirements on the X and y axis.
Fast servomotors can run at last at 3000 rpm which makes them usefull if you want speed.
Through, with ballscrews, acceleration must be low. So direction changes might be slow.
A CNC mill and a 3D printer don't have the same expectations.
Otherhand, your mecanical base is probably pretty good if there's no play in the screws.

If the machine overall quality was the first goal, I would buy 3 Leadshine Servos and drivers, controled by a Smoothieboard.
Then your printer worth will be at last $5000, and it will perform pretty well.

++JM

... I'm using a CNC-mill equipped with servo-motors, 500-encoders (2000 clicks per rev.) and spindles with 5mm per turn with the UHU controllers which can run the steppers with max. 100kHz, what will give 250mm/s max. moving speed when fully powered and 'step'-resolution of 2.5microns (0.0025mm).

Actually I'm driving the UHU drivers with only 48Volts @2A (they can be powered with up to 150V and up to 50A) - this gives me usable speeds with up to 150mm/s without stalling.

But for laser-engraving I'm running only with max. 80mm/s to avoid mechanical oszillations when changing direction, as this is visible in the fine laser-lines (20 or 50 microns line-widths, depending on used laser)

For 3D-printing 120mm/s will be good enough, but I have other machines, built for 3D-printing, so use the servo-CNC-mill only for laser-engraving/cutting.

So the possible and usable speeds are two different values, but much better with servos than wit steppers -- so if possible, stay with them!

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Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Hi guys,

I use 200w servos @ 230v AC. As we can't identify what type of servos this is, we can't power them properly.
I desagree about the 120mm.s
A fast printer is very comfortable. Some can print pretty well over 120mm.s, why can't this one ?
My i3 prints good @ 180mm.s, a Taz5 @ 200mm.s

++JM

Edited 2 time(s). Last edit at 02/05/2016 03:31AM by J-Max.

Hi JM,

... is your i3 driven with belts?

I have no problems to run my other belt-driven machines with up to 500mm/s and accelerations of up to 3000mm/s^2 - but to avoid resonancies and wobbling because of the belts elasticity I can't drive them faster than 100mm/s with accs of 500mm/s^2 for inkjet-printing or even slower for laser-engraving -- what's not better/faster than the servo-machine with spindles.

So it depends on your setup and wished accuracies, what's defining the practical/usable speeds ...

Edited 1 time(s). Last edit at 02/05/2016 04:58AM by VDX.

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Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]