Acorn semi closed loop

[gmacarthur]

I am looking to build a hobby level Avid 4x2 or 4x4 with an Acorn control board and Gecko drives controlling NEMA 23 or 34 motors.

One of the features I would like to accomplish is that the system shuts down if it enters a state with too many missed steps. I know from 3D printing that once a g-code file gets off I would like the peace of mind that it shuts itself down.

My question is: can I accomplish this with gecko drives? I have seen it done with closed-loop drives and an acorn. That is, if the alarm on the drive is triggered from too many missed steps it sends a signal to the Acorn which shuts down. It seems like the Acorn (or the gecko) should know how many steps it is requesting and a closed loop stepper motor encoder should be able to report how many steps were executed. I am at a loss how to get those two pieces of information to be compared. I guess in a closed loop drive, the drive itself makes the comparison and reports an alarm.

Again, it's just a preference for gecko drives and a preference for knowing if there is a missed step situation. If I can't have both I'll figure out which is more important but thought I would ask the expert community. (And again, to be clear I am not looking for true closed loop control where adjustments are made for missed steps, just looking for the alarm feature).

Thanks

[centroidsupport]

Because it's open loop, neither the control, drive or motors have anyway of knowing that there are missing steps. You would have bump up to a semi-closed loop where the loop is closed between the drive and motor or a truly closed loop system such as Allin1dc or Oak for the functionality you want.

[Fastest1]

I am looking to build a hobby level Avid 4x2 or 4x4 with an Acorn control board and Gecko drives controlling NEMA 23 or 34 motors.

One of the features I would like to accomplish is that the system shuts down if it enters a state with too many missed steps. I know from 3D printing that once a g-code file gets off I would like the peace of mind that it shuts itself down.

My question is: can I accomplish this with gecko drives? I have seen it done with closed-loop drives and an acorn. That is, if the alarm on the drive is triggered from too many missed steps it sends a signal to the Acorn which shuts down. It seems like the Acorn (or the gecko) should know how many steps it is requesting and a closed loop stepper motor encoder should be able to report how many steps were executed. I am at a loss how to get those two pieces of information to be compared. I guess in a closed loop drive, the drive itself makes the comparison and reports an alarm.

Again, it's just a preference for gecko drives and a preference for knowing if there is a missed step situation. If I can't have both I'll figure out which is more important but thought I would ask the expert community. (And again, to be clear I am not looking for true closed loop control where adjustments are made for missed steps, just looking for the alarm feature).

Thanks

Is this your first CNC machine besides a printer? Not that I am highly experienced but with the "proper" sizing and pc's steppers can be fantastic. Not that I havent had issues over the years with lost steps. I had them with Gecko and Leadshine but my suspicion in those times were the pc. Steppers and drives are inexpensive by comparison. Just be realistic in your assessment of desired accuracy/resolution. As a hobbyist a few thou still looks beautiful and will fit. Most of us arent going to space Not bashing.

[Upnorth]

The Gecko 320x does detect errors in the way you mentioned. There is an error detection built in. You select the error limits with DIP switches. If the encoder count varies +/- more than the preset error limit it will fault out the drive. I can't recall if it tells you which drive faulted or not.

[gmacarthur]

Thanks all.

Yes, this is my first foray into CNC. Coming from a background of an established woodworking hobby plus and catching the 3D printing bug a few years ago. I'm not looking for NASA accuracy so much as being able to turn my back for a few minutes knowing that a disaster will shut itself down.

I will take a look at the G320x, this might be what I'm after. They call it a servo drive. Does "servo" apply to the style of control and not necessarily that it will only with with a servo motor (as opposed to a stepper)?

Otherwise, I think I'm ready to accept that I am trying to put a square peg in a round hole here.

[Fastest1]

Servo drive is specifically for servos only. Most of the time turning your back will be ok, lights out might be a little different. I get your concern just dont let perfection be a limiting factor. Most issues are user error and there is a learning curve. Buy cheap end mills at first

[Upnorth]

The Gecko 320x only works with servos. If I remember correctly it only works with DC brushed servos so be aware of that when buying motors. Mine uses brushed servos and AMT-102 modular encoders with the gecko's. The combination has worked successfully during bench testing.

[martyscncgarage]

I am looking to build a hobby level Avid 4x2 or 4x4 with an Acorn control board and Gecko drives controlling NEMA 23 or 34 motors.

One of the features I would like to accomplish is that the system shuts down if it enters a state with too many missed steps. I know from 3D printing that once a g-code file gets off I would like the peace of mind that it shuts itself down.

My question is: can I accomplish this with gecko drives? I have seen it done with closed-loop drives and an acorn. That is, if the alarm on the drive is triggered from too many missed steps it sends a signal to the Acorn which shuts down. It seems like the Acorn (or the gecko) should know how many steps it is requesting and a closed loop stepper motor encoder should be able to report how many steps were executed. I am at a loss how to get those two pieces of information to be compared. I guess in a closed loop drive, the drive itself makes the comparison and reports an alarm.

Again, it's just a preference for gecko drives and a preference for knowing if there is a missed step situation. If I can't have both I'll figure out which is more important but thought I would ask the expert community. (And again, to be clear I am not looking for true closed loop control where adjustments are made for missed steps, just looking for the alarm feature).

Thanks

I suggest you go with something like Clearpath SDSK and CNC4PC.com C86ACCP. They are almost plug and play together. I think they are more friendly to a new user with your stated requirements. Yes, they are more money, but I believe you will be up and running quicker and with less trouble.
DC Brush Drives/motors (Like 320X) require a level of tuning which may frustrate a new to CNC user

Another option is hybrid closed loop steppers as was previously mentioned.
https://www.automationtechnologiesinc.c ... -servo-kit
https://www.automationtechnologiesinc.c ... -servo-kit

Do yourself a favor and buy from a respected supplier in the US.
Marty

[martyscncgarage]

Disasters do not always shut themselves down before something ugly happens. Build the control correctly, match the motors to the application, get to know the machine and then you will learn its capabilities

Marty

[gmacarthur]

Guys, thanks for all the input. This is what I was looking for to fill the gaps in my (mis)understanding.