Huron Conversion

[tomcradd]

Hello All,

I am considering a retrofit to my Huron CNC and I have a few questions to start with. The control on the machine originally was a Heidenhain 155 and this has developed some fairly serious faults recently, the machine has Siemens DC servos and drives and a contraves DC spindle drive, the machine also features Heidenhain glass scales. Is it possible to re uses the siemens and contraves drives? and also how would I go about using the heidenhain scales?

It also has a 3 speed gearbox and a neutral with a cam on the speed change shaft with another microswitch that allows a cam on the shaft to tell the existing PLC when it is in the correct position on the gear itself. Thats 5 24V DC microswitches. A small motor turns this shaft how would I go about wiring this in as I intend to remove the existing Siemens S5-110U PLC unit too.

I know these might be stupid questions but having never done a retrofit with this system I'm a bit green to say the least!

[tblough]

If using the glass scales is important to you, then you will not be able to use an Acorn as it is open loop and does not have provisions for scale feedback. You may be able to use an AllIn1DC to drive the Siemens DC servos directly, or an Oak board to drive the existing servo drives if they take +-10V analog inputs. Either board can take an additional EncExp board to allow you to add the glass scales for positioning feedback.

Depending on what the motors are currently using for feedback (encoders, tachometers, or resolvers), you may need to add new encoders to each axis motor.

All Centroid controllers include a PLC that can be programmed to handle the gearbox switches, but you'll need more information on how the gearbox motor is controlled.

[tomcradd]

There are tachometers on the motors currently would it be better to change to encoders?, ideally being as tight as I am i'd like to try and keep it cheap as possible so is there no option for +-10V on an acorn board? or with the use of the DB25 connector on the board is there another board that can provide the ins and outs I require?

[Chaz]

There are tachometers on the motors currently would it be better to change to encoders?, ideally being as tight as I am i'd like to try and keep it cheap as possible so is there no option for +-10V on an acorn board? or with the use of the DB25 connector on the board is there another board that can provide the ins and outs I require?

Acorn = no feedback at all and no -10V to +10V for velocity control.

So either need to look at Oak / All in One or get different motors / drivers.

[tomcradd]

Ok Ive got it,

So if I use an allin1DC board and I wanted to use the scales too would these be wired into the encoder ports? The motors currently have tachometers on them, do they need encoders adding too them too or is the scales sufficent?

[tblough]

Motors have to have encoders and those go to the encoder ports on the AllIn1DC or Oak. Centroid does not use tachometers. You can remove those or just leave them unconnected. Glass scale outputs go to the EncExp board and those are used to "adjust" the position.

You will need to verify that the motors will work with an AllIn1DC, and you'll need to verify that the glass scales have a line driver (RS422) quadrature output if you want to use those. If the motors won't work with the AllIn1DC, there is a good possibility that the existing servo drivers will work with the Oak.

[tomcradd]

After doing some reading through the paperwork supplied with the machine, I’ve found the Heidenhain control outputs a +/-10V signal through one wire to each drive controlling direction and feed rate is this the same on the allin1dc? I can see on the board there is a + and a - terminal for each motor but I really want to use my original motor and drive setup as the motors are strong for the machine it’s just the control that’s gone wrong

[tblough]

The AllIn1DC is essentially an Oak board with on-board servo drives. Since you have working servo drives that take a +-10V signal, then you can use the Oak control. It will generate the +-10V signal needed for your drives.

You will still need to add motor encoders to each drive motor.

[tomcradd]

I see on the oak there is a servo drive interface header where you can daisychain up to 4 servos together or there’s 4 individual drive ports. Which would be best for my application and do you have any information on pin outs etc so I can wire my drives in?

[cncsnw]

The DriveBus header is for drives or devices built by Centroid, using their protocols (e.g. their ACDC servo drives, and the OpticDirect interface board).

For third-party analog-mode drives, you would use the four on-board axis headers. The pin-out should be in the Oak documentation, and also on any sample schematics of Oak systems.

In my minimal experience with Siemens DC drives, it appeared that they required a +24V signal (to X31/65) to enable the drives. Since the Oak hardware only supports pull-down-to-enable, you would need to insert a relay in between the Oak board and the Siemens drive (so that the Oak output closes the relay, and the relay applies +24V to the drive enable).