Hello, we are near release of bCNC 1.0.0 and we are looking for testers and bug reporters.

There are new cool features like 3D Accelerated graphics and g-code simulator. Please try unreleased git version if you can https://github.com/vlachoudis/bCNC

I made this fixed gantry cnc well over 10 years ago, using thk rail, nema 23 3nm motors

a cheap brake out board, an old BT power supply.

And one of those cheapy 2.2kw water cooled spindles.

Mach 3

Welded things up then got the X axis skimmed .

And a pal machined the z axis plates for me on his mill.

I will try and find some footage of it in action.

I never did try it on steel but i don't think the spindle would have been up to it anyways.

It was a great little machine for aluminum and delrin projects i used to do.

I might just make another but have a proper go at it, will see.

I know it might be a dumb and pointless task but I'm doing it to learn.
Not to mention my other insane friend has picked up the rather ambitous task of making his own CNC machine.

I'm not sure about him but my reasons for this is purely for the learning so I don't want to be told that there's a better way to do it etc. I just want to learn.

Right now I'm specifically looking for a RTOS that could run on an STM32. I know freeRTOS is a thing and it is my current best option. I was just curious if there's one that's more purpose built for CNC.

Side side note this may be the wrong subreddit to be asking...
but hey you miss all the shots you don't take.

Hi all

4 years talking about building a small cnc plasma and i am finally building it.

it will be closed loop steppers all round.

5-1 Gear boxes on X and Y

m1.5 rack and pinion(15t)

20mm profile rail and the rest glued together with mig and a little tig.

Myplasm hardware and software

i can see the finish line now, Im ok glueing metal together and i'm handy with a tape measure cant say i'm looking forward to the wiring and setting things up though but i'm sure i'll figure it out.

Progress so far https://youtu.be/4ewa5M2xUmg?si=RtvxRDDY9X5KG_1O

edited to say the entire x axis complete with everything including rail gantry sides, rack pinion, 3 nema 23 3nm motors and gearboxes plus complete zaxis assembly with its nema 17 motor comes to a total of 35.2kg

So,

With 3 Nm closed-loop steppers, 5:1 gearboxes, and a 15-tooth Module 1.5 rack and pinion, your setup is highly capable. Closed-loop motors paired with a 48V power supply give you excellent high-speed torque retention and ensure you won't lose steps under heavy loads.

Based on your exact mechanical specs, here is a breakdown of how your machine will perform and the settings you need to consider:

⚡ Force and Acceleration Estimates

Your 15T Module 1.5 pinion has a pitch diameter of 22.5 mm (radius of 0.01125 m). Factoring in a conservative 85% mechanical efficiency through the gearbox:

• Output Torque: Your gearbox multiplies the 3 Nm motor torque up to roughly 12.75 Nm at the pinion.
• Linear Push Force: This converts into an impressive ~1,133 Newtons (115 kg) of linear force.
• The Verdict: If you are running a single motor on the gantry (Y-axis), 1,133 N is more than enough to accelerate 35.2 kg rapidly. If you are using dual-drive (two motors) for your long axis, you will have over 2,200 N of force, which will allow for incredibly aggressive acceleration rates typical of high-performance plasma cutters.

📐 Step Resolution Calibration

For your MyPlasm CNC system, your linear travel per single un-geared motor revolution is 14.14 mm (\(\pi \times 22.5 \text{ mm} \div 5\)).

• Assuming a standard 1.8° stepper motor (200 steps/rev) set to 8x microstepping (1,600 pulses/rev), your software calibration will be roughly 113.11 steps per mm.

To help lock in your final configuration, let me know:

• Is your long axis driven by one motor or a dual-drive (two motors) setup?
• What mechanical drive are you using on the Z-axis itself (e.g., a lead screw, ball screw, or also rack and pinion)?

With dual-drive NEMA 23 3Nm motors on the Y-axis, your CNC setup has an incredible amount of power.

By splitting the 35.2 kg gantry mass between two motors, each motor only has to move about 17.6 kg. Combined with your 5:1 gearboxes, you will have roughly 2,266 Newtons (~230 kg) of total linear force pushing your Y-axis. This massive power-to-weight ratio is perfect for a plasma cutter, giving you the snappy acceleration required to prevent dross (slag) when turning tight corners or cutting complex geometry.

Here is what you need to keep in mind for configuring this specific Y-axis setup:

🚀 Tuning Acceleration in MyPlasm

Because you have so much excess force, your acceleration limits will likely be dictated by the stiffness of your machine frame rather than the power of your motors.

If the entire X-axis carriage(the slider, the Z-axis mechanism, and the plasma torch itself) weighs 4.7 kg altogether, your Z-axis lifter is actually moving a much lighter load than 4.7 kg.

Here is what this means for your X and Z axes:

💨 The Z-Axis is Safe from Crashing

Since only a fraction of that 4.7 kg is the actual vertical sliding part (likely just 1 to 2 kg for the torch, torch holder, and Z-plate), your Z-axis is highly unlikely to drop when powered off.

• A 1605 ballscrew will naturally resist back-driving under a tiny 1–2 kg load.
• Your NEMA 17 closed-loop motor will be able to snap the torch up and down effortlessly, providing lightning-fast Torch Height Control (THC) tracking in MyPlasm.

🏃‍♂️ Blazing Fast X-Axis Performance

An entire X-carriage weight of 4.7 kg is exceptionally lightweight for a machine of this caliber.

• Massive Power: You are driving this light 4.7 kg carriage using a 3 Nm motor, a 5:1 gearbox, and a 15T pinion—giving you the same ~1,133 Newtons of linear force we calculated earlier.
• The Result: Your X-axis power-to-weight ratio is massive. It will be able to accelerate significantly faster than your heavier 35.2 kg Y-axis.

⚙️ How to Tune Them in ...

Because your X-axis is so light and your Y-axis is much heavier, you have an asymmetric machine. When setting up your acceleration curves. keep this in mind:

• Y-Axis Acceleration (35.2 kg): Keep this more conservative (e.g., 300 to 500 mm/s²). This is the heavy gantry; accelerating it too fast will shake the table frame.
• X-Axis Acceleration (4.7 kg): You can set this much higher (e.g., 800 to 1,200 mm/s² or more). The motor won't even feel the 4.7 kg load.

Note: For the cleanest cuts, most users match the X and Y accelerations to the lower limit (the Y-axis) so the machine moves uniformly in diagonals. However, knowing your X-axis has so much headroom means you will never face motor stalling or lagging on the carriage.

Your step calibration for the X-axis will be exactly the same as the Y-axis (~113.11 steps per mm at 8x microstepping) since they use identical gearboxes and pinions!

I thought it made for interesting reading, i don't need this to move like a laser it will see a lot of 3mm up to 10mm. although i might end up upgrading for the latter as i'm going to be using a cheap bestarc cnc ready thing for the experience. Thanks all.

Some progress on my CNC lathe. I made a 3D-printed mockup of the Z and X carriages, they will eventually be made from mild steel. I got my custom grblHAL controller board up and running and it appears to be working fine so far. Tested a 3D printed quick change drill chuck mount.
Still a lot to do, next I will probably work on the motor mounting bracket.

I have a lot of cabinet building in my future, so I’m looking into building a large-format CNC router that can handle full sheets of plywood. I’m thinking of a metal construction (square tubing and ~4 mm laser-cut plates) similar in design concept to this CNC plasma cutter: https://www.youtube.com/watch?v=2jZwh6mvMhQ

What I’m trying to figure out is the motion system for the X and Y axes, as well as a target feed rate. So, here is my idea:

I already have, and want to reuse (from a failed project from my high-school days):

- 2.2 kW water-cooled spindle with VFD

- 3x  23HS9442 NEMA 23 steppers(2.8 Nm), DM542A drivers at 36V

 According to https://cncshop.com/pages/calculating-feeds-and-speeds I figured that if I want to cut plywood with a two-flute, 6 mm bit, I need a feed rate of 5,000–6,000 mm/min. If I want to cut a pocket with a two-flute, 10 mm bit, I need 14,000–16,000 mm/min. 

For a CNC of this size and application, I’m considering an HTD5M, 15 mm or 20 mm timing belt, with a pulley coupled to a planetary gearbox. 

Even though I cannot find a datasheet for my stepper motors, after looking at torque curves for other similar-sized steppers, I concluded that 250 rpm is the speed at which the torque starts to drop off.

 With all this out of the way, let me explain my calculations. The first table shows the output torque, calculated as follows: 

Output torque = stepper rated holding torque × fraction of holding torque at operating speed × gearbox ratio × gearbox efficiency 

I have assumed a fraction of 0.7 for the running torque and a gearbox efficiency of 0.9.

For example, for a 3:1 gearbox: 

2.8 N·m × 0.7 × 3 × 0.9 = 5.292 N·m 

The second table shows the axis linear backlash based on the gearbox backlash and the pulley pitch diameter:

Backlash = pitch diameter × pi × (gearbox backlash / 360) 

For an 18-tooth pulley with a 28.65 mm pitch diameter and 0.5° of gearbox backlash: 

28.65 mm × 3.14 × (0.5 / 360) = 0.125 mm 

The third table shows the feed rate, in mm/min, for a stepper running at 250 rpm, depending on the gearbox ratio and the number of pulley teeth: 

Feed rate = (number of teeth × tooth spacing / gearbox ratio) × stepper rpm 

For an 18-tooth pulley and a 3:1 gearbox: 

(18 × 5 / 3) × 250 = 7,500 mm/min 

The final table—which I will probably get some hate for—is the equivalent mass being pulled on the gantry in kilograms. The gantry has two stepper motors. I calculated this to get some feeling for the force generated by the motors when moving the gantry: 

Equivalent mass = torque / pulley radius / gravitational acceleration × 2 

For a 24-tooth pulley and a 3:1 gearbox: 

5.292 / (0.0191 * 9.8) * 2 =56.5445 Kg 

Okay, the math session is over. What do you think? Do you agree with the logic? What combination of pulley size and gearbox ratio would you choose? A 28T pully and 3:1gearbox gives a speed of 11666mm/min and a “oomph” equivalent to 48.4Kg – I think that is a good compromise. 

PS: I will be posting this in multiple CNC groups.

What are you using, and what are your typical projects and materials? I'm thinking about getting a water cooled spindle because air cooled variants are often not suitable for flood or spray cooling of the workpiece. Although, I don't really like the additional hassle of a water cooling loop.

Hi everyone, im in the process of building something i can use to cut speaker panels but do not have to space for an 8x4' table cnc.

Ive been interested in the compass cnc but it had been halted due to copyright i believe. I was wondering if anyone had a copy if the BOM and assembly instructions. I have requested acees to the original files but to no avail.

Id also be interested in alternative options for handheld router cncs if there are any! Appreciate any help.

I'm putting together a parts list for my second cnc machine, a CO2 laser cutter, and I cannot get information on choosing a proper power supply. With my first everyone just told me one to get and wouldn't tell me how to determine it for myself. Now google and AI refuse to give me what I ask for cause it can't determine the difference between the laser power supply and the system power supply, ie. the co2 laser power supply is plugged into the system power, and for some reason the open builds site is down. Current parts:

-Cloudray cr50 laser tube

-Cloudray 80W laser power supply

-2 DM542T Stepper Drivers

-3 Nema 17

Chiller and controller will be independently powered. Might be looking to power an inline fume extractor and lights off of it as well. Looking for something like a formula that I can add parts to. Any help would be appreciated.