Centroid Community CNC Support Forum

A few years back I started building a CNC plasma table, I started out a Mach4/ESS combination for the controller, but after a very short time I decided that I needed a better system. The 5v board made wiring in the 24v sensors a challenge, and was subject to false triggers. partly due to not using shielded cable, but the 5v signal was to close to the noise floor. I also wanted a more modern user interface than something that was cutting edge for windows 3.11

I started to look around at different controllers, and settled on the Centroid Acorn with THC and Ether1616. I liked the amount of documentation that was available, and the User interface.

below is a build thread on another site where I documented the build from the start, and also keep it fairly up to date.
https://www.tacomaworld.com/threads/cnc ... ld.746103/



Early on I ran into an issue that had me stumped along, it took a few days to figure out the issue. It is unrelated to the acorn, but it gives an idea on how I go about troubleshooting and also a bit of historic reference for the build.

https://plasmaspider.com/viewtopic.php?t=36378

Also the thread where I discuss the air scribe attachment for the table. I have since picked up a new air slide with the end lock attachment so it will stay in the up position until needed.

https://plasmaspider.com/viewtopic.php?t=37075

The Original Control box in progress...
Random specs and data for future reference:

Stepper Motor 23HS45-4204S:

Manufacturer Part Number: 23HS45-4204S
Motor Type: Bipolar Stepper
Step Angle: 1.8 deg
Holding Torque: 3Nm(425oz.in)
Rated Current/phase: 4.2A
Voltage: 3.78V
Phase Resistance: 0.9ohms
Inductance: 3.8mH ± 20%(1KHz)
Frame Size: 57 x 57mm
Body Length: 113mm
Shaft Diameter: Φ10mm
Shaft Length: 24mm
Number of Leads: 4
Lead Length: 400mm
Weight: 1.8kg


Stepper Driver DM556T:

Anti-Resonance for optimal torque, extra smooth motion, low motor heating and noise
Motor auto-identification and parameter auto-configuration for optimal torque from wide- range motors
Step and direction (PUL/DIR) control
Multi-Stepping for smooth motor movement
TTL compatible and optically isolated inputsto 5.6A
Input voltage 20-50VDC
16 selectable micro-step resolutions of 400-25,600 via DIP switches
8 selectable output current settings of 1.8A to 5.6A via DIP switches
Soft-start with no "jump" when powered on
Pulse input frequency up to 200 KHz
Automatic idle-current reduction
Protections for over-voltage and over-current

Electrical Specifications:
Output Peak Current: 1.8~5.6A (4.0 RMS)
Input Voltage: +20~50VDC (Typical 24-48VDC)
Logic Signal Current: 7~16mA (Typical 10mA)
Pulse Input Frequency: 0~200kHz
Pulse Width: 2.5μS
Isolation Resistance: 500MΩ
Output Peak Current: 1.8~5.6A (4.0 RMS)
Input Voltage: +20~50VDC (Typical 24-48VDC)
Logic Signal Current: 7~16mA (Typical 10mA)
Pulse Input Frequency: 0~200kHz
Pulse Width: 2.5μS
Isolation Resistance: 500MΩ

Type: HGR20 Slide Rail
Material: Gcr15 steel
Rail Shaft Length: 1500mm/59inch
Nuts: BF12/BK12 nuts
Fixing Screw Hole Size: M4x16mm
Static Load Ratings: 25.31
Allowable Static Torque: 0.17kNm
Weight: Approx.300g (10.6oz)

A Google photo album full of hundreds of pictures and some video of the machine as it was being built an tested



A Google Drive folder with spec sheets and manuals for the hardware and software
and any other document I want to save for future reference.

https://drive.google.com/drive/folders/ ... drive_link

Mocking up the new panel layout, and looking for a opinions and thoughts.


Power supplies, and drives at top, there will be a 120v 110mm 62cfm fan in the upper right side of the cabinet to help pull the hot air out, there will be a second fan of the same type in the bottom left of the cabinet, to blow cool filtered air into the cabinet

There is an unswitched AC Bus for devices that need to stay on even with an E-stop condition. Fans, an the power supply feeding the acorn. The Switched AC bus will disconnect the drive power during an E-stop condition

plan is to have the AC input come in from the Bottom left with outputs for sensors and motors on the right side, either in the middle or bottom. there will be a brush plate for the cable entry

The DC bus work along with shield grounds are on the lower right side

Welcome to the forum Pyro

Awesome build thread and photos. Love seeing Table Builds from the very beginning.


The new panel layout looks pretty good.

Good to see your using a metal panel and metal cabinet for better interference protection.

All grounds going to the same point on the Cabinet or panel.

Is the Acorn board mounted with steel bolts to the Panel? I see the RX has some nifty mounts for space saving. Thats pretty sweet.

What's your Plans for the TX board?

Do you have the Centroid Primeweld THC kit? That will come ready to go with the Primeweld CNC cable.

everything will be mounted to the back plate with stainless steel hardware.

The stacked Ether1616 and relay board mounts are from Clough42, he talked about them during his video on heat inserts




I really liked his design so I used his files to print everything, added a 3rd set of the the offset spacers for the first relay board, and then designed the THC-RX piggyback mount to fit on top of the acorn.
https://www.printables.com/model/141008 ... back-mount

The THC-TX board will go into a separate small cabinet, along with its Power supply. Not sure if It can share a cabinet with the Air solenoids for the scribe, But I have a 3rd cabinet same that they will go in, I Like the idea of keeping it separate in case I ever decide to remove that feature, it would make it as simple as unbolt the scribe assembly, and pull the hoses back out the cable chain and remove the control box from where ever ends up mounted.

I do have the Primeweld version of the kit. the cable premade is very nice to have, that connector for the CNC port is a not a real fun part to solder the cable to

its starting to look like a control cabinet.

component's are mounted, the Safety Contactor is wired into the main E-stop which will be on the door of the cabinet, and it will kill power to the stepper motors, and the switched AC bus.

The Acorn is wired for power off the DC Bus, an will stay on along with the +5vDC to the stepper drives PUL+ and DIR+ pins

Almost made a big mistake, so it's time to put the tools down and step back for the night. Hopefully tomorrow I can get the stepper drives wired in and get a test stepper to spin, and maybe get the case holes punch and cut so I can get the back panel mounted back in the case, and start doing the software configuration.

Started wiring up the stepper drives today.

First things first, prepping the shielded cable. Started off by soldering a ground wire to a piece of copper foil tape.
once the outer jacket was carefully removed, I wrapped the copper foil around the exposed shield.
This will allow me to ground the shield to help drain off the EMI.

after the drain wire was installed, I pushed back the braid and trimmed it to just above the foil tape, snipping off the excess along with the two extra wires. I then heat shrink everything to protect the ends, and keep any frayed shield wire from getting loose later.

It's Aliiiivvveee... again.

I bench tested the THC today, at first I ran into issues with a 0.00v reading. So I rechecked the the hookup made sure I was following the bench test schematic, double check voltage at the power supply for simulated torch voltage. I check at the THC-TX board and verified good voltage, I check voltage at the THC-RX board, verified good voltage. Verified THC was enabled in the profile manager. Ran the test again, and still 0.00 reading.

So I took a bunch of pictures of the wiring and photos showing the good voltage, ran a configuration report and screen capture of all the config pages and was about to upload it an see if there was an issue I was overlooking.

Then... I had the brilliant idea to do a search an see if anyone else had a problem with no voltage reading at the THC during the bench test. Seems I am not the first one, and the issue was simple. the pesky little torch on output had to be define. before running the test. something that I did not see in the section on the THC bench test or on the bench test schematic.

Once I defined the "Torch On" output and reran the THC bench test, it worked flawlessly. I was able to adjust the voltage on the power supply and the THC tracked the voltage change.

As of right now, all 4 axis are are spinning, X, Y, Z,Y(Slave), and the THC is working. almost time to mount it in the case, but first I will bench test the proximity switches I will be using for home and the 3 sensor round mount.