Replacing CNC controls

In the hobby-level arena there is LinuxCNC and Mach(x). There have been lots of flame wars over this.

In the professional level, there are things like Centroid, Ajax and Acorn. (All these are apparently by the same company.) The Acorn uses a Beagle Bone type computer, and is amazingly inexpensive for a commercial control.

I have 2 mills running LinuxCNC here.

Jon

I remember there was discussion here about replacing CNC controls, but could not find it, and what controls were liked.

We have an old Bridgeport in reasonably good condition that has an ancient CNC system that needs to be replaced. What systems should we look at?

Thank in advance.

Stephen

Centroid and Ajax are good controls that are made by the same company. The difference is that the Ajax is much less money as it comes with virtually no support. Years ago I installed an Ajax control on a mill that had the original control fail. I went with 4 axes and it worked well. It still works well. With the Ajax you need to pay extra for every little option. The mill did not have an automatic tool changer so I don't know how well the Ajax control would handle one. The 2 complaints I have with the Ajax are that the documentation at the time I bought it was confusing in some places. It just wasn't written very well and there were contradictions as well as ambiguous portions. And the button placement on the control pendant. The Z- button used for jogging is right above the Cycle Start button. And when jogging it was easy to hit the Start button. At the time there was no way to disable the Cycle Start button when jogging so an accidental button press was easy to do. And I've done it more than once. Eric

Boy Jon, that Acorn really is cheap. If I had to replace the servo amps in a machine I would for sure look at the Acorn option. For Stephen: The Acorn puts out step and direction signals. Stepper motor drivers accept step and direction commands. But there are also several servo amps available for not much money, Gecko Drive being one I am familiar with and use, that also use step and direction commands for controlling the servo amp. This means that the less expensive step and direction control can be used to control servo motors. If your mill has stepper motors then i suggest you look into upgrading to a closed loop servo system. The servo system will allow much faster rapids as well as faster and more accurate machining of contours. I messed around with stepper motors when I first built CNC positioners but quickly swtiched to servo motors when step and direction input servo amps became available for such little money. I think you can get one now for about $120.00 that will drive servo motors at 80 volts and

20 amps. It may even be to your advantage to get an Acorn and replace the existing servo amps if your machine has servo motors. Eric

The Acorn does NOT contain the motor drives! It is only a step/direction control. But, yes, even considering that, it is a very good looking option. A guy here has one that he is just setting up on a mini-lathe, so i can report how it works out for him.

But, you also have Mach(x) for Windows, and LinuxCNC, for Linux. LinuxCNC supports a wide range of machine types (mills, routers and lathes, but also robots and hexapods) and can operate step/direction drives, digital servos and analog servos. LinuxCNC also has a built-in ladder logic system to handle tool changers and such.

The Gecko 320 works, but it makes the CNC control blind, like a stepper. Mesa and Pico Systems (my company) have cost-competitive controllers and drives for various types of motors that allow LinuxCNC to be aware of the status of the motors in real time.

Jon

That is a problem with the Gecko, the only feedback to the control being a fault signal when the amp shuts down for whatever reason. The next time I need to build another CNC machine I'll take a look at your Pico Systems stuff. Having the control aware of the actual position at all times is really much better than a control that just stops when it gets an error signal. Eric

I own a Bridgeport Interact. I replaced the broken Heidenhain control with Linux EMC2 using hardware that I bought from our member Jon Elson. Everything works great.

i

Depending what it's got when you've ripped out the old, GRBL can be a remarkably affordable new control system for steppers or stepper-like drives. Or you can rip all the way to replacing motors, and still come out pretty affordable - but if the old drive is steppers, they are often just fine.

No parallel port / old style serial port required.