Acorn or Hickory for first time CNC retrofit ?

[Stansonengineering]

Hi everyone
Long time lurker and want to be centroider here

I now have a serious need for an updated machine

I've purchased a used extron CNC bed mill that currently is running a fagor 8050/8055m and DC servos

My plan is to collect required parts and build a new enclosure before pulling the old control and servos off so I can still use the machine for the time being as I've just sold my other CNC mill that I probably should have kept to fall back on but space is tight ATM.

I'm just not sure whether to start with an acorn and AC servos or just go all in and buy a hickory and go ethernet servos most likely deltas
I'm wondering whether the extra cost of the hickory and Ethernet servos will be out weighed by the time spent wiring and setting up servos with acorn, over the Ethernet option as it's my first time doing a retrofit and wiring to this extent

I do have afew centroid knowledgeable people that are reasonably close to where I live but they are all generally very busy and booked out for months in advance so the easier I can make it to figure out most of it on my own will probably get a finished result more quickly
I have quite afew electrician friends that can help out if I can get them a decent electrical cabinet design to work from.

From what I've looked into Soo far
I will likely go a 130 frame servo 1.5-2kw
Replace the original spindle motor with a suitable 3 phase motor and VFD or possibly something like a szgh servo motor and drive if these are compatible
It's a fairly basic machine
Counterweights on Z
Oiler , air drawbar
Currently contactors for fwd/reverse
And spindle speed is not controlled through the fagor

Any advice is welcome
Thanks Daniel

Machine itself

Existing electrical cabinet

Current servos

[centroid467]

Hello and welcome to the forums.

I think either controller would work well for this machine. It does not require a lot of I/O.

It seems you have done some research and some thinking as you are correct that one of the common issues first time retrofitters run into is miswiring the drive control signals. With the Hickory, you still need to run wires for power to each drive as well as the motor power and encoder cables. However, all the control signals are through the fieldbus so you just plug in the ethernet cable to the correct spot.

Then again, the step and direction wiring from Acorn is not very complex so it shouldn't take very long if any of your electrician buddies have motor drive wiring experience. I think the Delta B3A series drives are a good choice for this machine regardless of whether you choose Acorn or Hickory.


Would you mind pulling the servos and posting pictures of the nameplates? We can help with sizing the replacements.

Same with the spindle motor - what are its specifications? What is the reduction between motor and spindle?

[Coolidge62]

Welcome! I'm also retrofitting a bed mill (Chevalier 4020). Are you just retrofitting the CNC stuff or rebuilding the head also?

[cnckeith]

typically these machines have 40 in-lb dc servos which can be run with the Centroid Allin1DC controller. so that is another option for you.
more info here.
https://shopcentroidcnc.com/allin1dc-cnc-controller/

if you are going to put new axis motors on it either Acorn or Hickory would be a good choice for this machine, just depends on your budget.

[WesM]

The other guys here know way more then I do about the centroid controllers, but my understanding is that Hickory and Oak (and Acorn6 I think?) are proper closed loop controller. You can use scales and have realtime position feedback. The regular 4 axis Acorn relies on the servo/drive to do exactly as its told and is not a closed loop controller.

The higher precision machines I have programmed/operated all have linear scale/closed loop feedback. It was explained to me that the controller (in this case Heidenhain) is able to compensate for thermal growth in linear rails/ballscrews via the feedback system. Not sure if that is really a concern on an open bed mill that will probably not see high travel speeds or significant runtime, but its food for thought.

1.5-2kw is a pretty beefy AC servo for a machine like that. Even the largest TRAK bed mills I have run used 1kw delta servos and were rated at 400ipm. I would not want to run a open bed mill any faster then that!

[cnckeith]

on this page, scroll about half way down for a Centroid CNC controller main board comparison chart.

https://shopcentroidcnc.com/

[Stansonengineering]

Welcome! I'm also retrofitting a bed mill (Chevalier 4020). Are you just retrofitting the CNC stuff or rebuilding the head also?

Hello , I had a deep dive through your build thread last night as your machine is very similar to mine.
I'll eventually rebuild the head or replace it with a inbuilt drawbar/motor bt40 spindle if the retrofit goes well.
I have a bt30 all in one spindle I could use but I'd like to keep it bt40 as I already have masses of tooling and bt30 is abit small for the size of this machine

[Stansonengineering]

typically these machines have 40 in-lb dc servos which can be run with the Centroid Allin1DC controller. so that is another option for you.
more info here.
https://shopcentroidcnc.com/allin1dc-cnc-controller/

if you are going to put new axis motors on it either Acorn or Hickory would be a good choice for this machine, just depends on your budget.

Hi Keith
Thankyou for the replys ,
I would prefer to replace the drives and servos with modern AC as these older drives are in excess of $1000aud for a repaired drive locally and it's already had the Z drive replaced 3 times in its life.
I've had a good look at all the control comparisons many times over the years , I have an acorn already so I think I will likely start with that if I can use the b3a ethernet drives with acorn as another user said is possible ?
I was going to ask this question in the initial post but didn't want it getting too long to start with.
If I can start with a ethernet delta drive and wire it up to acorn then down the track upgrade the control to a hickory and swap over to ethernet communications this would be ideal.

[Stansonengineering]

Hello and welcome to the forums.

I think either controller would work well for this machine. It does not require a lot of I/O.

It seems you have done some research and some thinking as you are correct that one of the common issues first time retrofitters run into is miswiring the drive control signals. With the Hickory, you still need to run wires for power to each drive as well as the motor power and encoder cables. However, all the control signals are through the fieldbus so you just plug in the ethernet cable to the correct spot.

Then again, the step and direction wiring from Acorn is not very complex so it shouldn't take very long if any of your electrician buddies have motor drive wiring experience. I think the Delta B3A series drives are a good choice for this machine regardless of whether you choose Acorn or Hickory.


Would you mind pulling the servos and posting pictures of the nameplates? We can help with sizing the replacements.

Same with the spindle motor - what are its specifications? What is the reduction between motor and spindle?

Hello and thanks !

The idea of running ethercats on acorn to start with would be ideal, I was going to Ask this in original post but didn't want to make it too long and too many questions
I can pull a servo and check specs over the weekend will give me a chance to check mounting dimensions and see whether I can fit a 130 frame or will need to drop back to a 86mm

[Stansonengineering]

The other guys here know way more then I do about the centroid controllers, but my understanding is that Hickory and Oak (and Acorn6 I think?) are proper closed loop controller. You can use scales and have realtime position feedback. The regular 4 axis Acorn relies on the servo/drive to do exactly as its told and is not a closed loop controller.

The higher precision machines I have programmed/operated all have linear scale/closed loop feedback. It was explained to me that the controller (in this case Heidenhain) is able to compensate for thermal growth in linear rails/ballscrews via the feedback system. Not sure if that is really a concern on an open bed mill that will probably not see high travel speeds or significant runtime, but its food for thought.

1.5-2kw is a pretty beefy AC servo for a machine like that. Even the largest TRAK bed mills I have run used 1kw delta servos and were rated at 400ipm. I would not want to run a open bed mill any faster then that!

Hi Wes
I've done quite alot of comparing and was originally going to start with oak for full closed loop over acorn
But now hickory is released that would be the better option I believe
The servos are probably on the large side but I already have some hardware to use them.
They may not easily fit under the bed for X and Y though so I may drop back to 1kw in a smaller frame if need be.
I do not need high speed I'll buy an enclosed bt40 vmc after this for repeat work this will be more a 1 off universal machine to replace my old Bridgeport clone with more capacity in Z was the main target of it.