Hardware Pairing Homing and Squaring Methods

[cnckeith]

Previously Centroid did not advocate or promote any type of Auto Squaring with Acorn in conjunction with Hardware Pairing of two axis motor such as a CNC Router with a moving gantry. We did support Auto Squaring with Software pairing from an early date with Acorn but, this method of software pairing two axis motors has one draw back, it uses up the 4th axis drive signal for the software paired motor on the gantry effectively turning the 4 axis CNC controller into a 3 axis CNC. So, how can we have our cake and eat it too? How can we have 5 axis motors on a 4 axis Acorn with the 4th axis being available for Rotary (or another type of 4th axis)? We hardware pair the axis motors on the gantry and come up with a way to auto square the gantry. An old 'trick' used for many years by cnc controllers in the same situation was to Hardware Pair the gantry motors but have the step signals for those motors run through a relay that was then controlled by the homing macro. This homing macro would simply disconnect either of the gantry motor step signals that would result in independent gantry motor motion allowing the macro to seek homing switches on each side of the gantry one at a time to 'find square'. Once squaring was done the relays would return the two axis motors to be joined at the hip again. We call this "Relay Auto Squaring". Centroid provides all the necessary G and M g-codes for the user to create their own "Relay Auto Squaring" macro and over the years a few power users have done just that so they can have a 4 axis CNC machine tool that has 5 axis motors when using an Acorn CNC controller.

An alternative to Relay Autosquaring that works even better in most regards is Hard Stop Homing with AutoSquaring , this feature is currently only available with the Teknic Clearpath servo motors. Information on how to setup Clearpath Hard Stop Homing with Acorn or AcornSix is detailed in Centroid Tech Bulletin # 319 Here is the link. https://www.centroidcnc.com/dealersuppo ... ds/319.pdf



Below is Overview of the various Acorn Hardware Pairing Homing and Gantry Squaring Methods

With Hardware Pairing there are several ways to both home and square the paired axis machine tool.

a.) Manual homing with Manual Squaring: Operator manually squares the gantry axis and then Jogs machine to the home position, press cycle start and then the control sets home at this position.

b.) Auto Homing with Manual Squaring: Operator manually squares the gantry axis then “Auto Home to Switch” is used to home automatically. The auto homing cycle seeks the home switches and sets the home position automatically.

c.) Auto Homing and Auto Squaring: Auto Home to switch is used in conjunction with “Relay Auto Squaring”. This is a fully automatic method to both home and square up the machine tool.

d.) Auto Homing and Auto Squaring to hard stop with Clearpath axis motors.


We will be adding Wizard support for "Relay Auto Squaring" soon. and i am working on updating the Acorn Axis pairing guide as well.

-Keith

[ShawnM]

Thanks for the update Keith. My ShopSabre 5x10 plasma table is set up with hardware paring. I started to use the software pairing and auto squaring but the machine is just so rigid I cant see it ever getting out of square. It does have Clearpath motors so the stall homing would be an option but I think that's just an archaic way of homing given todays technology. I wondered about disabling one Clearpath by running its enable line through one of the NC outputs on the Acorn relay board. I wasn't sure it would be a good idea but maybe it would have worked.

I will admit with the fiber laser in the shop we only use the plasma for a few odd jobs now.

Thanks for the update and keep up the great work you guys are doing.

[Gary Campbell]

I wondered about disabling one Clearpath by running its enable line through one of the NC outputs on the Acorn relay board. I wasn't sure it would be a good idea but maybe it would have worked.

You won't want to dessert the enable while homing as that motor will not "hold", effectively losing position AND HLFB could also trigger a drive alarm. Neither IMHO are desirable

[ShawnM]

I wondered about disabling one Clearpath by running its enable line through one of the NC outputs on the Acorn relay board. I wasn't sure it would be a good idea but maybe it would have worked.

You won't want to dessert the enable while homing as that motor will not "hold", effectively losing position AND HLFB could also trigger a drive alarm. Neither IMHO are desirable

Makes sense Gary, I abandoned the whole idea anyway and just hardware paired the motors. I can't push on one side of the gantry without the other side moving with it. This ShopSabre table and gantry are both very robust, solid steel, it's not going to move out of square.

[Gary Campbell]

Roger that. There is no need for autosquare homing on a rigid machine that has been built square. That said, many DIY and lesser expensive consumer machines can put it to good use

[Tealfixie]

New to the forum here, I have recently purchased an Acorn board and I have studied the wiring schematic that for this setup extensively. I am now awaiting all the other parts to arrive before I begin wiring up my control cabinet. This method of wiring is the direction I want to take with retrofitting my CNC. I will be posting a build thread soon. Any ideas when the wizard support will be ready?