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Discussion Starter · #1 ·
Hi All,

Great to be here. Really looking forward to learning a bit more.

I am not new to woodworking, but I am looking to branch out to CNC work. By virtue of pulling apart a scrapped 3D printer, I have a number of bits of high-quality rails, bearing mounts, steppers, screw drives etc. The control of these was via proprietary boards, so nothing to save there.

It seems to me that there are a number of ways forward to make a CNC:
1. A raspberry pi with a screen, driving stepper motor controllers,
2. A computer driving an Arduino, driving stepper motor controllers,
3. A proprietary board, often including the drivers,
4. Some combination of 1,2 or 3.

My question: is there a sensible process that anyone knows of that might determine the best way forward. I suspect 1 and 2 require some programming skills, which I have, whilst 3 is more expensive (someone else has done the work).

I am open to any and all suggestions on this. I would not say money is no object, but I am not averse to paying for quality equipment. I am also not averse to installing and programming an Arduino or RasPi.

Your help is appreciated.
 

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G'day @StuffaK , welcome to the forum..

You may receive more/better responses if you post your query in the CNC section of the forum.
 

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It is hard to point you in a direction not knowing the specs on the components you want to reuse from the 3D printer. That really depends on how big the motors are.

The stepper motors from the printer might be too weak to feed a very big bit in a small spindle.

It might be alright to carve small v-carved signs and things like that but you need to remember that the motors were not made to push heavy loads like a router or medium size spindle around. You might be able to use a rotary tool as your spindle or maybe a small spindle.

I know prices have at least doubled on a lot of parts to build a CNC in the last 2 years so another thing to consider, is it worth the time and effort?
 

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just about any parts from a 3D printer will be too flimsy for anything but a toy CNC router. Now, if you want to build a laser cutter, those parts might be ok.

For control, I'd look at an arduino running Grbl or perhaps an esp32 or teensy running a 32 bit version of Grbl.
 

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Sorry for the long response, but I think the information below will help you with your research. There are 3 primary ways to connect a CNC control board to a computer. USB, Ethernet, and Parallel port

I am not a fan of the GRBL/Arduino (and a couple Raspberry PI options) which covers most (but not all) USB options. I feel that GRBL it is a bit of a limiting platform. It is good for a very basic 3 Axis setup, but you will find limiting as you try to expand the capabilities of your machine.

I went with an Ethernet option for my build, and I am using Raspberry PI as the controller computer. The software I am running on it is LinuxCNC, which is free, well developed, and has a strong community behind it. The control board I am using is a MESA 7i96 board, that connects to the PI via Ethernet. MESA does make boards that attach directly to the GPIO of the PI. I chose to not go with one of those boards as I wanted to be able to move to a more robust computer if needed. Because it used TCP/IP over Ethernet, no special drivers are needed at the OS level, and LinuxCNC supports the board I used natively. So far, I do like the software/controller combination for my CNC.

LinuxCNC is typically used on Intel based PCs running Linux, using a real time kernel. A few years ago the option to compile a real time kernel for the Raspberry PI became available, so that is why it works on that platform. When I started my CNC build 4 years ago (long story, see my MikeMa's CNC thread on that) that was not an option!

There is a PC option for Ethernet as well. This is the Ethernet Smooth Stepper, and runs with Mach 3 and Mach 4. There is also a USB Smooth Stepper, but the company recommends the Ethernet option over the USB. This is a more expensive option, as both versions of Mach have licensing fees. The biggest reason I did not go with this is Mach 3 is no longer being updated, and Mach 4 doesn't support all the hardware that Mach 3 (like MPCs) does. This made me feel like Mach 4 is still a work in progress. That said, both Mach 3 and 4 are widely used.

Parallel port is the original method for running a CNC. For a little background, to make the stopper move on unit, a pulse is sent to it. A real parallel port is able to send pulses in real time. You connect a break out board (or BOB) to the parallel port that allows you to wire in the stepper drivers, as well as inputs for limit switches and e-stops. The computer itself IS the controller for the CNC, the BOB just breaks out the signals and wiring. Both LinuxCNC and Mach 3 support using a BOB via a parallel port. A single parallel port can cover most functions of a 3 or 4 Axis CNC, but you can use multiple parallel ports to add more Axis or input/outputs. The main issue is getting a computer that has a real parallel port is getting more and more difficult to find, and those that do are older machines that do not support current versions of Windows. That said the smooth steppers and some MESA boards actually give you up to 3 or 4 parallel ports, you attach the BOB directly to them. the MESA board I have has the connectors on board for the equivalent of two BOBs but has a parallel port on it as well that I can connect an external BOB.

My preference, and recommendation, is a using an Ethernet based controller card with an OS that is currently maintained (Windows or Linux).

I did choose the Linux option over Windows, not so much with cost, but I felt like LinuxCNC was better maintained than Mach 3 or 4, with a stronger user community. That said, it is a matter of preference, as I said before, there are folks who are very happy with their Mach 3/4 setups.
 

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Discussion Starter · #8 ·
just about any parts from a 3D printer will be too flimsy for anything but a toy CNC router. Now, if you want to build a laser cutter, those parts might be ok.

For control, I'd look at an arduino running Grbl or perhaps an esp32 or teensy running a 32 bit version of Grbl.
This was quite a large machine. The two motors I have are 3A and 4A with torques of 2.1Nm (297ozin) and 2.7Nm (388ozin). Only one of them is a NEMA standard though.

Having said that it looks like I will need the drivers and the best value seems to be to get them in sets of 4 with the motors. I can keep these as spares.
 

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Discussion Starter · #9 ·
Thanks MikeMa for that response. Your conclusion around arduino v raspi was pretty much what I had come to as well.

If I could ask a few questions about your setup:
1. When you say the RasPi is the controller computer I assume you have a screen attached to it (off the HDMI)?
2. I assume the ethernet port is used between the Raspi and the 7i96 ?
3. Then the 7i96 is wired directly to the 4 stepper motors?
 

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Thanks MikeMa for that response. Your conclusion around arduino v raspi was pretty much what I had come to as well.

If I could ask a few questions about your setup:
1. When you say the RasPi is the controller computer I assume you have a screen attached to it (off the HDMI)?
2. I assume the ethernet port is used between the Raspi and the 7i96 ?
3. Then the 7i96 is wired directly to the 4 stepper motors?
1. Correct, the RasPi is actually mounted on the back of the monitor, and then a wireless keyboard and mouse is used to use it. The first photo shows this setup.
2. Correct, it is a normal TCP/IP connection.
3. Sorta. The 7i96 wires to the drivers which both powers the steppers and converts and transmits the pulses from the 7i96 to the steppers. The second photo shows the controller while i was still building it. The circuit board is the 7i96, and the 4 black boxes are the drivers, one for each stepper. You can see there are two power supplies, the small one is a 5v that powers the circuit board. The large one is a 36V one that powers the drivers and steppers. The steppers are 3.5amp 381oz/in Nema 23. These are much bigger and much stronger than the ones that would come on a 3D printer and easily move a large Bosch 1617 router through any cut.

Raspberry PI mounted on the back of the monitor. SSD Zip tied to the RPI Case.
Peripheral Computer Output device Gadget Audio equipment


Controller:
Circuit component Passive circuit component Hardware programmer Electronic component Audio equipment
 
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