I wanted to post a quick review of my experiences with centroid acorn. I purchased centroid for my first mini lathe cnc conversion.

Some background: I am fairly new to CNC. I have built 4 CNC machines from scratch in a distinctly hobby grade process rife with mistakes. The first 3 machines used GRBL though I have dabbled with G2Core. My first lathe was a 8x16 import that had a ridiculous quantity of problems. Fixing it up taught me quite a lot about the machine and it's limitations but i am in no way a professional machinist. One big issue I had with this lathe was that the change gears did not match the manual and the banjo did not actually work for many of the thread pitches. This prevented me from any practical threading. I did quite a lot of research and initially settled on trying to make an electronic lead screw. I made some progress with the design by reading through the Russian ELS project forums and I had a semi working prototype. Unfortunately I had to move and I was unable to continue to have the space to work on the 8x16 lathe. Some months later I found a deal on a 7x10 lathe which was small enough for me to use in my new place. I decided to buy an acorn so I could spend less time tinkering and more time making. The acorn is marketed as hobby friendly and I am in no way building a manufacturing capability. My goals were to learn basics about CNC lathe, do threading, and to save the time figuring out how the spindle sync ports of GRBL worked.

I purchased the acorn on amazon which made for quick shipping. The packaging was decent and I think the hardware package is well thought out. You get the main board, a relay breakout, a quality 24v/5v power supply, and a quality ethernet cable. The power supply has no cover and I think they should include a cover with a switch for safety but this is in no way a big issue for anyone familiar with the safety risks of live mains exposed terminals. The main board is geared towards industrial grade components using 24v. There is also a DB25 connection to provide connections to "hobby" grade components. The DB25 breakout connections are not isolated. If you wanted isolated 5v connections you'd need to supply and wire your own breakout. I ordered a cable and breakout connector from Amazon and was able to connect my limit switches and stepper motors without much trouble. I would advise you to look at the breakout and ensure it can be screwed to the board. Some breakouts do not include the screw posts. The DB25 configuration path does not provide PWM outputs (i think this is planned) and using a stepper enable signal is not supported which is a bit disappointing. The board includes a multitude of status LEDs which are very nice for giving a visual indication of the status of the signal pins like your end stops or probe. The board also includes a 0-10v analog out for controlling spindle speed. The brains of the board is a seed studio beagle board which can be replaced. it is not really clear what the board is running though I'd expect it is some flavor of linux. All communication with the board is via ethernet. I have not found any indication of how the board is supposed to react to a power off. Generally linux doesn't like to be turned off without running a shutdown sequence to sync the "disks". The documentation seems to just say to "power cycle" the board. It is unclear how safe this is for the device and I would be interested to know how data corruption is avoided. The board is replaceable but they cost around $70 and if you do not get an RMA you need to pay a fee to get the license setup on a new board. The breakout board includes a DB9 connection for an encoder. I made a bad assumption about the encoder specs and assumed a standard quadrature interface would work. A differential quadrature signal is required with a Z pulse (once per rotation) and they recommend 2000CPR minimum.

My experience with the hardware was overall good. I wish I had done a bit more research when ordering so that I could have had all of the components needed at the same time. For hobby grade components you should order a db25 breakout, a db9 breakout (if you plan to use an encoder) and cables for both. The documentation for hobby grade connectivity isn't expansive. For someone who's done a few builds the schematics are clear and it shouldn't be hard to get up and running. For someone doing their first build who does not have much experience reading schematics I think they may have a bit of a struggle.

The software that comes free with the board is fairly feature limited. They supply good charts that show what features are supported under the various software options. For a lathe with spindle sync you must purchase the CNC 12 Lathe pro license. The lathe pro license doesn't change the software much at all other than when running commands. The free version will let you create g-code for threading it just will not run.

Security: The software installation guide goes through great lengths to have users disable security. This includes elevating user privileges to administrator, turning off user account control, disabling the firewall, and disabling antivirus. I suppose this could be fine if they made a very strong recommendation for network isolation. If the machine isn't connected to the internet then your risks with following the installation instructions would be limited however they do not discuss the implications of removing security controls and they do not recommend any mitigation like network isolation. They also do not warn to ensure the machine isn't connected to the internet at some later date which I'm sure will happen to some users. In my case I was planning on using my laptop to control the acorn and I did not want to have to have a 2nd laptop there so I could read the documentation or browse the forums troubleshooting issues so I needed to have internet connectivity. I was able to figure out how to connect to the acorn without turning off all my security but this is likely beyond the ability of the typical user. I'm sure that the multitude of configuration issues created by 3rd party firewalls and antivirus creates a monumental quantity of support issues but I also have not seen much software recently that went the "disable everything" route which honestly seems irresponsible in this day and age. For a non-hobby machine likely to be isolated and dedicated this all makes more sense but I can't say their security posture is friendly to the hobby user.

User Interface: This is where I started to have major problems. The user interface seems to be very focused on a dedicated PC with a touch screen. It feels like DOS or windows 3.1 in 1995. The window management features and best practices of the OS are ignored. There seems to be multiple programs running that must use some IPC to coordinate. The main information screen takes up about 2/3 of the left portion of the screen. The right 1/3 is consumed by a 2nd window for the virtual control panel (VCP) . This panel allows things like spindle control jogging etc. Because there are 3 programs running and none of them seem to use the OS's window management I have had issues with focus/z order and overlays obscuring the main window's display. There is no title bar. There are no minimize/maximize/close buttons. You can't effectively use Alt+Tab to switch programs. If you Alt+Tab the VCP window stays on top and obscures 1/3 of your screen. The icons all look kinda the same so you have to hunt to minimize it. For an expert user this may not be a problem but when you are trying to use a browser to read the documentation or figure something out this quickly becomes a major PITA. if you have a 2nd laptop or computer and don't plan on ever having to read another window this likely isn't a problem.

On the positive side I found the jog controls a breath of fresh air compared to Grbl. Grbl didn't have room for a real jogging implementation which is self admitted by the developers. This makes Grbl pretty easy to crash while jogging. Keyboard jogging with the Acorn worked well and there seems to be good options to use alternative controllers to the touch screen.

The next issue I had was that you have to be connected to use the software. This means that you must stand at your lathe to use the CAM software features or you must trust the device and connect it to your home's network. Based on the security advice they provide for software setup it is hard to trust the device. I would also need to connect it via wifi since I do not have a close Ethernet jack wired which would require another device to purchase. If you want to fully network your acorn this is not an issue. I honestly can't understand why they require the board to be connected to run the software maybe someone else knows.

Documentation: I'm going to try my best to be fair here but this is the biggest issue I've had. There is a lot to be documented and for the most part they do a good job but some of the documentation seems to be made to be paired with training. This makes sense when you think about how they have evolved their business model. Unfortunately this leaves the hobby user to infer quite a lot. My first hurdle was with the procedure to use the auto tool setting features. I dug into the manual and found the bulk of the documentation was focused on the manual process. The automated process documentation was extremely basic and some fundamental elements of the system were not explained. I watched multiple videos on youtube but I was not confident I had a solid grasp of the concepts. I tried to post a thread on their forum to clear up the questions I had. I tried to make it clear that I didn't understand the documentation but the response I got was that "you have a basic misunderstanding of Tool Offset values" I was told to read the documentation and to watch the video. I did both again and tried to contribute to clarifying the documentation and to point out the video covering the manual process didn't translate directly to the automated process. I was told to follow the steps in the video again. I reiterated that I had tried to do that and that it was not clear what the best practices for the automated feature were. I even posted a video documenting my struggles. I eventually got a response specific to auto tool setting but it was more of a hybrid between manual and auto features which left me with more questions that went unanswered. I probed for a follow up and was told to start a new thread or add to someone else's. I believe the responded assumed I had open questions in another thread and didn't bother to read the thread I posted in. I'm guess he was just trying to help in between doing other things but I was feeling exasperated at this point and considering just giving up on getting my documentation questions answered.

I had similar frustration with the CAM documentation but I didn't invest the effort in getting help from the forums. Simularly the CAM documentation seems designed to be paired with training classes. I was able to quickly use the diameter turning and threading features but using the arc and taper functions was much less intuitive so I started looking for alternatives. I've been using Fusion 360 for a while made my first attempt to create some g-code for the Acorn. The problem is that the post processor included with fusion 360 only does milling CAM. Trying to run it for a lathe setup produces an error. I found a lathe CAM post processor by Franco on youtube but it has to be manually installed and downloaded from dropbox. This may be beyond the average hobby user's ability to find and install. If you are forced to use the CNC 12 CAM there is no simulation, no crash detection, and the documentation is fairly limited in my opinion.

Pros: The hardware package is good, the system is highly configurable. It supports spindle sync with little setup effort. Hobby grade stepper drivers, limit switches, and touch probes are fairly easy to configure. Threading was intuitive and easy to get started with.

Cons: Documentation seems to assume pairing with training, some features are not documented, and community support for lathe work seems very limited. The support forums have 2 main folks who seem to reply to most lathe oriented threads and the focus seems to be more on reducing support effort vs great customer experiences. The tone in most of the threads I read was "this is the way it is". I found this tone frustrating. I would prefer to understand why something is done the way it is so that I can have a more fundamental understanding that has a better chance of building on when I run into issues later. I did not get the impression criticism is welcome or that they wanted "hobby" customer feedback on how to improve the product. The software UI is extremely dated and annoying to use when trying to also read documentation or look up a thread table. A 2nd screen may make the software UI issue moot but may not fit in your workspace. There is no part position probing routines though you can use the g-codes like M115/116 directly. You can also write your own macros but it is surprising there isn't a library of community supported macros easily available for Lathe pro. If you buy the $400 digitizing package you can probe part positions via canned routines.

Centroid acorn overall: While the hardware setup was fairly easy the learning curve on the software was steep. I can't say I had a good experience with the support forums. The CNC lathe alternatives which allow for threading are slim pickings. There are 2 or 3 ports of Grbl that attempt spindle sync. LinuxCNC/Machinekit seem to have mature code but the learning curve seems very steep. The Electronic lead screw alternatives seem to offer a much lower learning curve but at a similar overall cost. I think there is an opportunity for Centroid to embrace the community for improvements to the product but the market may not support such and investment. It may make sense to remove the CAM functionality into a separate package and include spindle sync with the hardware. Having auto tool setting but no auto part probing routines doesn't make sense.

Hope this helps someone. This was my experience and I'm sure the experience varies quite a lot between users of various backgrounds and skill levels.


PS: Quick note on my mini lathe build overall: I see these builds as learning experiences. I suppose the main lesson I learned is that lathe CNC is pretty difficult overall and that you can do a hell of a lot with a manual lathe or running it in a semi automatic way. The best thing about the lathe CNC setup is the lack of change gears and automated threading. Threading can also be done with an electronic lead screw. The effort between setting up an ELS and the full CNC is fairly small. The effort to learn how to use the CNC platform (including CAM) is larger than I expected and you should expect a fairly steep learning curve. The full CNC build will put a spotlight on your machine's mechanical flaws. I'm not sure you can cut complex toolpaths with the backlash in the cross slide lead screw or with open loop steppers. A ball screw is ideal but fitting a ball screw to a 7x10 mini lathe isn't exactly easy. The mini lathe was $250. A ball screw for the cross slide might be as much as $100! The controller is $300 and the software is $140. The costs go up quite quickly! Getting very accurate and repeatable tool offsets is critical. General repeatable positioning is difficult without extensive modifications. Open loop motors seem quite a bit riskier for a CNC lathe vs a mill and I think having a missed step fault signal is much more important on a lathe. It is pretty easy to miss steps parting or drilling. I setup a consew motor to drive the spindle but I did not set it up with the acorn. I think it is great that you do not have to integrate the spindle motor controller and still run the acorn however you are not going to have the spindle stop on a fault which is a safety concern. The consew controller is also a bit of a PITA to reverse. I have not found a way to reverse via a controller easily. It also runs hot and a fan on the controller likely extends the live of the unit.