@Jesse is looking to get the Shopbot PC off the floor to make it easier to clean the area. I’m glad to help but have a few questions:
Does LinuxCNC have any special hardware requirements?
It looks like the current set-up is using a parallel cable. Instead of finding a computer with a parallel port can we just use a USB-to-Parallel cable? Would that require special drivers?
There are a lot of directions one can go with a computer. I’m in the process of evaluating my plasma table and considering a pi4. At one time EMC2 would only run on certain machines, but now, as long as the hardware will support a RTOS and latency can be managed, it can be made to work. That said, upgrading the PC to something more modern might have a snowball effect. A newer PC might require a new BOB, for example. Etc.
I don’t recall the current hardware configuration, so I don’t know what that upgrade path looks like, or rather, where it starts. I like the idea of going to a pi for my application because it’s easier to stuff it into the control box with my BOB and stepper drivers. That means it’s easier to keep the fine metal dust out of it, and hopefully eliminate the need to replace the PC every few years. That’s my application though.
That link is a good starting point. LinuxCNC has come a long ways since then and there is good community support. Maybe some of the computer folks here can provide a little more insight.
The challenges for something like this are things like, how difficult is it to maintain and set up? We are fortunate that there are many who are computer literate enough to help with that. It’s also helpful that a router is pretty simple, having only 3 axes, though it would be cool to set up a 4th axis. Then we could “turn” totem poles!
Are you saying a USB-to-Parallel cable is a lost cause and not worth pursuing? Is it worth converting the whole thing to USB on both ends? I’m guessing the answer isn’t short and sweet.
I’m not a hardware guy. What are the best options for getting away from a parallel interface?
There are multiple issues with USB-to-Parallel converters with respect to LinuxCNC. They don’t implement all of the functionality of a Parallel port since they are generally designed mostly for sending data to things like printers. And even if one was able to support everything a parallel port does, the USB interface adds a layer of uncertainty to the system. LinuxCNC requires a realtime operating system to control the pin timings within acceptable parameters. USB however is not realtime and can add unpredictable delays that would cause inaccurate step signals. CNC machines that use USB ports mitigate this issue by moving the control of step timings to the hardware on the machine and having a buffer of G-code or other commands from the computer so it can move continuously if there are small delays in communication.
It can be done, but more hardware changes would be needed. LinuxCNC doesn’t support any USB interfaces, so new software would be required if converted to a USB interface. It does support some cards that use a PCI or Ethernet interface, so that would be a better option: LinuxCNC Documentation Wiki: LinuxCNC Supported Hardware
There are Ethernet boards available that would allow more modern day flexibility. I don’t know how extensive you want this upgrade to be, but it has the potential to become a full on replacement with modern boards.
If the goal is to get the computer off the floor, I have a couple suggestions. The simplest would be too build an arm off of the frame of the machine that will support all of the hardware currently on wheels. This has been brought up before and decided to be undesirable because it limits the user access to the controls. This could be overcome to a large degree with a pendant.
The other possibility that doesn’t really address the first concern is to move the computer to the back of the machine near the controller and just put the monitor and keyboard on wheels. Again this doesn’t eliminate something to clean around.
The idea I think would be best would be to move the computer to the back and mount the monitor, etc. on an arm. The weight could be kept down so the arm could be made longer and articulated so it could be swung around to allow easier access.
You make a great point by taking us back to the original request. I imagine putting the monitor, keyboard and mouse (and USB port?) on an arm would be the quickest and cheapest solution. Thanks.
The Thursday night CAD group has been rebuilding the control system for the plasma table. On that project we are using an ethernet controller and we are nearing completion of that project. We have talked about doing a similar system for the shopbot. So, if there is interest amongst the wood shop folks, we could help, or at least share what we have learned, or whatever you want to do.
I’ll let @Jesse respond for the wood shop but I’d like to get the CNC equipment in the FabLab functional. I think I’ve been told those have hardware issues more than software issues.
In a related question, do all these machines use similar control systems or is there a way to reduce variation in the systems so they’re easier to support? Maybe this isn’t an issue.
We did a lot of electrical drops from the ceiling for much of the wiring. Could a computer platform be hung from the ceiling or one of the beams? A piece of the boiler return piping, left in the room could be removed and re-purposed.
Thanks everyone for their thoughts and input. I appreciate everyones knowledge, there are lots of great minds here. This is not my area of expertise so I would tend to err on the side of caution and leave well enough alone if there isnt an easy fix. Maybe a “pendant” from a ceiling beam is a good solution. That being said if the plasma CNC fix is easily applicable to the ShopBot i would be interested.
