Warco GH 18, bench top gear head mill fetteling

[GazzParticipant @gazz]

Here is the new main electrical box mounted on the wall, next to the mill:

The 4 oblong items are indicator lights, from top to bottom they are:
24 volt power indicator.. for the axis motors when i fit them.
VFD power.. just confirms power it on to the VFD.
VFD fault reset, That's a button as well as an indicator light.
12 volt control power indicator.

The round white light is the main power button, this turns on or off power to everything in the box and the outlet to the DRO.. that's what the keypad is in the bottom left of the shot.

And the keypad with the red led display is for the VFD, it's showing the motor speed is set to 43.3 Hz, i.e. slightly slower than normal 'max' speed of 50 Hz, and the 2 red led's above the digits show that it's in forwards and stop modes.
Pressing the 'func-data' key on that panel can change the display to show things like current consumption, voltage in, motor speed (but not spindle speed due to the mills gears) etc,
The other buttons allow settings to be changed, and the knob can be used to set motor speed if it's not been set up to use an external speed control input.
The black round thing with a triangle is just the door lock, like used on a gas/electric meter cupboard

Below is what's hiding behind enclosures door… watch for rats jumping out the nest of wires in there….

On the door back you can see the panel indicators and main switch (i have since made a 3D printed cover that protects me from the 240 volt terminals on that… this whole enclosure is powered from a standard 13 amp plug, so i 'should' pull that before opening the door)

Top left, that long silver thing is the 24 volt 15 amp psu that will eventually run the Z and X axis motors.

Top right is the VFD that runs the mills motor, that depression with that grey ribbon cable coming out of it is where the VFD programming / display keypad clips into, i've moved that to the front panel of the main enclosure as shown in the 1st pic.

There is a cover missing in this pic that screws over the terminals with wires at the base of the VFD, those terminals on the green strip at the front are all low voltage (5 volts)
The 'spicy ones' are a layer below them, and need a screwdriver poking in to access… but even with the terminal cover in place there's large holes in the bottom of the VFD that objects could be poked up to touch live terminals by a kid, so this type of VFD should always be housed in a proper electrical enclosure,

The standard VFD case is not dust proof at all, any metal grinding dust in the air could easily get in and short things out…. there is a small fan mounted on the rear of the VFD's heatsink.. which could help suck in any of that grinding dust… the good news is that fan only runs when the VFD is running the motor, so you wont usually hear it over the mills main motor.

Back to the electrical enclosure description…..
The silver square box in the middle between the psu and VFD is a 20 amp EMI filter, power to the VFD runs through that.

Bottom left, the square dull grey with holes in it is the 12 volt 3 amp psu, this runs the control circuits so that only 12 or 5 volts DC is on any of the wires to the button box,

To accomplish this the VFD and 24 volt PSU are switched with contactors, i used normal 240 volt coil contactors as 12 volt DC ones were rather expensive, and to switch them from the button box with low voltage, the 2 din mount relays to the right of the 12 volt PSU switch the contactors themselves.

There's 3 MCB's in there too, a 2 amp type B MCB is for the 12 volt "control" PSU and main switch,
A 6 amp type B MCB is connected to the 16 amp contactor for the 24 volt PSU.
And a 10 amp type C MCB is connected to the 25 amp VFD contactor… that contactor is rated for a 9 amp motor load BTW…
The 'type B and C' bits relate to how much short term 'overload' the MCB can sustain and how fast it trips, type B is normal as found in most houses, type C is used for big inductive loads like motors, transformers, and in this case the big capacitors in the VFD, as they appear as a short circuit for a few milliseconds when first turned on.

There is also a 10 amp fast blow fuse in the black holder to the left of the VFD MCB, some people say that's not needed as the MCB is there, but some VFD manufacturers say you must still use a fast blow fuse to get the fast disconnect time to try and protect the VFD in a fault condition.. thos it's probably more for the users protection than the VFD's… as we know, mosfets usually blow faster than a fuse can.

The black items on the top and bottom of the main box are vents, the top one has a filter in it only… more to stop any dust getting in from above, and the bottom one has the 120mm fan as well as an inlet filter, the fan is a thermostatically controlled one, it's thermistor is taped above the EMI filter with that yellow kapton tape.

Finally, you may just be able to see a 'barrier strip' block on the left side wall, there's nother on the right, and i just use them where i may need to disconnect wires in the future, i.e. the 6 wires from the tapping function switches and ring light go through the right hand one.

Continued in next post… character limit blah blah blah

[GazzParticipant @gazz]

So the wall mounted electrical cabinet houses all the control gear, 2 cables come out the top of it, loop upwards and come back down and attach to the mill, they are the motor power wires in the black conduit, and the 6 core cable for the tapping limit microswitches and the ring light,
Both cables are screened and that screen is earthed at one end only, to help reduce the chance of the cables acting like antennas with the switching noise of the VFD (the 3 motor power wires also have ferrite rings on them as they exit the VFD terminals)

I made up some 3D printed clamps to hold the grey cable to the conduit, and rotated the motor's terminal box cover 90 degrees so the cable inlet is at the top instead of the rear side,
This allows the mill head to traverse the ~400mm up and down the column, and the cables move with it nicely and are always out of the way.

On the bottom side of the electrical enclosure are a few cable glands and a C-13 female connector, that is for the DRO's power supply,
Through the cable glands passes the 13 amp 240v supply into the enclosure from a wall socket, a 'spare' gland that will have the 24 volt wires through it to another wall mount enclosure that will house the Z and X motor drivers later on, and the 16 way screened cable between the wall box and the control box.

The new control box is mounted at an angle below the mill's chip tray on the left hand side, it's fixed to the workbench front instead of the tray so that the mill can be moved if needed and the control box stays put.. as it's cable goes to the wall mounted box and not the mill.

The controls are as follows: Top Row, from the left:

An illuminated latching green push button for turning the VFD on and off, so it's a main power switch for the mill.

Next is the 3 way rotary switch that selects milling or tapping functions on the mill, this is from the original control panel, so centre is off, and triggers the E-stop command of the VFD.

A red mushroom latching emergency stop button, this signals the VFD's E-stop function as well as interrupting power to the 24 volt PSU's relay / contactor, this is so that operating this button will stop the spindle and the Z or X axis feed motor if it is running, so as not to drive the workpiece into a now stationary cutter… it will be linked to another similar button on the feed motor control panel when i make it.

Final button on the top row, an illuminated white latching push button, turns the ring light on and off.

Lower Row, from the left:

A speed knob, this turns a 10K potentiometer, which adjusts the speed of the spindle by varying the frequency and voltage the VFD puts out to the motor, the best part of a VFD run motor that was not taken advantage of on the mill when it was stock!

Next is a flush green momentary push button that sets the spindle rotation backwards / anti clockwise.

Then a raised red momentary push button which stops the spindle, by raised… i mean this button sticks out and makes it easier to hit than the go buttons.

And finally another flush green momentary push button that sets the spindle running forwards / clockwise.

When the mill is put in 'Mill' mode, the forward and reverse buttons work and you can press either at any time, if the spindle is running and you press the opposite button, it will quickly stop and go the other way, due to the motor being 3 phase this happens almost instantly.
The stop button works as you'd expect, so does the speed knob and E-stop button.

If the Mill / Tap button is moved whilst the spindle is running it will stop due to an E-stop signal being sent in the off / centre position.

When the mill is put in 'Tap' mode, the reverse button does nothing, pressing the forwards button starts the spindle running clockwise, and you would have (hopefully) set the depth stop up before starting the tapping mode.
You'd then pull the quill down and engage the tap in the hole, it will drive in and pull the quill down it's self, when the depth stop is reached a microswitch is activated and this sends the reverse signal to the motor, and the tap winds its self out of the hole.
When the quill is returned to the upper position another microswitch is activated, and the spindle stops.
Pressing forwards starts this sequence again.

This is all done via the control buttons and microswitches of the quills depth stop, the VFD is just responding to pulses telling it which direction to run the spindle in and when to stop, theres no computerised logic board or special VFD settings here, there's nothing stopping you from tapping in H-3 gear.. which is about 1400 rpm! tho most would use L-1 gear and maybe even wind the speed down to about 30 rpm.

With 2 microswitches that can be activated by a quill depth stop rod, you could add this function to almost any mill or drill if you wanted, if not VFD controlled then you'd use latching contactors…. Please note, a single phase A/C motor needs to be totally stopped before reversing it, otherwise it will just carry on the same direction, so the single phase version of this mill had a timer that was activated when the depth stop microswitch was hit, the motor would not get the reverse signal until this timer ran down.
So instead of the instant reverse of the 3 phase model, you'd get a pause between direction changes.

To Be Continued….

[GazzParticipant @gazz]

Here is a photo of the mill set up ready to use:

Hopefully it shows that the button box's new location, and that it is mounted at an angle making it easy to operate, especially as i use the mill sitting down 99% of the time, you'll also notice the DRO is fully installed here, i will describe that in the next 'chapter'

But now for a sort of mini rant using thousands of words where a single paragraph could likely have said it better, it's something that probably wouldn't bother most people, but it did me so i changed things to 'fix it'

To use the automatic tapping function on this mill, first you set the depth stop up by turning the knurled adjuster under the front of the mill head,
The knurled adjuster rotates the depth stop screw which winds up or down a chunk of metal, this has a red arrow 'tab' screwed to it, and this sort of lines up with a '1mm per division' printed ruler scale on the front panel of the mill head,
Theres ~75mm of quill travel in total, so setting the depth stop reduces this travel to allow you to drill/mill to the same depth every time.

What makes this automatic tapping function work is that when that depth stop is reached, a microswitch is operated, and when in tapping mode this signals the VFD to reverse the spindle direction, so the tap winds it's self out of the hole at that point, and when the quill is returned to the top of it's stroke another microswitch is operated which signals the VFD to stop the spindle… you can then position for the next hole and press forwards and repeat the process. simple and clever.
This is why this mill doesn't have the little digital caliper style quill depth display that other bench top mills have.

So… the first time i tried the tapping function out…. this was before i'd made any mods at all, the mill was 100% as it came from the factory.

I've set the depth stop up, im in gear L-1, which is 95 rpm / ~ 1 and a half rotations per second i think,
i've turned the 'mill / tap' switch to 'tapping' then press the forwards button and the spindle starts rotating… all's good,
But i then noticed i'd made a mistake, maybe the tap wasn't lined up with the hole properly or i was going to try and tap M12 down a 6mm hole or something stupid ike that, so i wanted to cancel the tapping operation.

I press the stop button, nothing happens, i press it again and again, it wont stop the spindle, i'm worrying now… ok nothing bad was happening but damn it i expect the spindle to stop when i press the stop button, i eventually remembered there's an emergency stop button and used that to stop the spindle.

I thought there was a wiring fault, or a bad connection / contact in the stop switch or something, but when i tested the buttons with a multimeter all seemed correct, only when i traced the wiring that i figured out what was happening.

The VFD is set up to respond to pulsed signals from the momentary buttons, all the mill / tap switch does is change how the signals to the VFD are routed through the buttons and microswitches themselves, i.e. in milling mode the depth stop microswitches are switched out of circuit so do nothing.

But when the quill is at the top of it's stroke in tapping mode, i.e. before you have moved the tap down into the hole and started cutting threads, the depth stop rod is holding the upper limit microswitch in, this means that the VFD can't 'see' any pulses from the stop button, the spindle is already stopped when you switch to tapping mode, and it can 'see' the forwards start button pulse as that's a different pulsed signal on a different input terminal.

So to stop the spindle once it's been started in tapping mode you need to move the quill down enough so it releases the upper limit microswitch, only then does the stop button on the button box work, so there's no problems using the stop button if you were halfway through tapping and noticed something going wrong, and of course as long as the distance from the tap to the hole is more than the distance to release the upper microswitch, you can simply pull down and release the quill and it will operate the upper limit switch again and send the stop pulse.

Also note… when you are testing the depth stop distance whilst setting it up without pressing the forwards button in tapping mode, when you trigger the lower limit microswitch the reverse signal will be sent to the VFD, so the spindle will start up in reverse, it'll stop if you press the stop button or return the quill to the top of the stroke,
But if you don't want this to happen, put the mill/tap switch in the 'OFF' or 'MILL' position, or press the E-stop in.

To Be Continued ….

[GazzParticipant @gazz]

So as you can probably tell, i really didn't like this stop button operation in tapping mode, it probably doesn't bother most people, and i imagine it works properly on the single phase versions of this mill?

But i wanted a button marked stop to .. .well stop things, i didn't have enough room on the button labels to put 'STOP..except when you are in tapping mode and the quill is at the top of it's stroke'

I wanted to 'fix' this, and did so when i wired up my new button box, but it can be done to the stock button box if you wanted of course, so just incase someone else wants to do the same, i'll go over what i did…. i bet there are users of this mill with the VFD that didn't even know this 'problem' existed and hate me for pointing it out, i know some people never want to use the tapping function, and i heard of one person who removed all that stuff and fitted a digital caliper style quill depth readout in it's place in the mill head.

I tried a few ways to fix it, handily the industrial style buttons used are modular, so you can add extra contact blocks just by clipping them on the back of the button's clamping block, and you can even stack them up.

.

First thing i tried was rearranging the inputs to the VFD to free one of them up and setting it to a second stop command…..
To do this i changed the 2nd 'Forwards' signal (on X4 input) that is used when in tapping mode, to a 2nd stop signal via the programming of the VFD (simply 1 parameter change, P053 from 11 to 4, changes it from forwards to stop pulsed input)
Then i put 2 diodes in the wires from the mill / tap switch to the forwards button, doing away with the 2nd contact block (the diodes stop back feeding on the wires and ensures the quill depth stop microswitches are only in circuit when in tapping mode, that is usually done using 2 contact blocks on the forwards button)

But that didn't work, seems the VFD can't 'see' a button pulse if the same command is continuously on from another switch, even tho the pulse is sent to a different input terminal… bugger.

So i changed the wiring and VFD settings back to try something else, but i now know that if i needed a spare input / output terminal on the VFD, i can use the 2 diode method again to allow a single 'forwards' input to work with both milling and tapping modes.

Below are wiring diagrams for the stock button box, showing just the control wires (things like the VFD reset button and led's wires are not shown etc… they are all shown on my wiring diagram of this mill )

The first image below is the stock method of separating the 2 forwards commands needed for milling and tapping modes:

And next is the diode version i came up with, this allows you to free up an input on the VFD if you ever need it for something else (maybe to require the reset button to be pressed to re-start the mill when the E-stop has been pressed or something)
It uses a single contact block on the forwards button, and the 2 diodes now prevent the signals back feeding the tap limit microswitches when you are in mill mode, so the spindle doesn't suddenly reverse when you are milling and reach the depth stop.

To Be Continued…

 

Edited By Gazz on 20/05/2021 22:22:38

[GazzParticipant @gazz]

Kerikey, i've gone way off topic again, back to trying to make the stop button work no matter what mode the mill is in etc….

.

Next i tried a stack of contact blocks on the stop button, first a N/C type then below it a N/O type,
Wired so that pressing the stop button in first operates the N/C contact block, which breaks the feed to the limit microswitches .. thus turning off the continuous stop signal it was sending,

Then as the button goes further down it presses on the N/O contact block, which sends a stop signal as normal, this worked but only if you didn't press the button too fast, once the quill was down a little and off the upper limit microswitch, she speed the stop button was pressed at didn't matter, as the VFD always 'saw' the stop pulse,

But if i had to remember to press the stop button slowly when the quill is up in tapping mode against the upper stop, i may as well just press the E-stop button instead.

And that's where i got the next idea from….

Use the stop button to trigger the E-stop signal when in tapping mode.

To do this i added another contact block to the stop switch, and wired it so that only when in tapping mode it sends the signal via this contact block to the E-stop command as well as the normal stop command.

So it's basically like pressing the E-stop mushroom on the button box when in tapping mode, but using the normal stop button still, when the quill is returned to the top of stroke and the upper limit microswitch operates, it sends the normal stop signal and stops the spindle motor.

I found i had to use a diode on the 'tapping buttons common' wire to get it all to work, but i am now happy that i can use the standard stop button and at all times it will do as it's supposed to.

So if anyones interested, the diagram is below:

You need to add another contact block to the stop button, this will need to clip onto the bottom of one of the existing contact blocks (which they are designed to do) as the stop button on the stock wired mill also has a VFD fault reset contact block on it (connected to X3 on the VFD) and an led to light up when the VFD is in fault lockout mode.

A diode is needed to be inserted between the tapping microswitch common wires and the connection to the tap/mill switch as shown.

 

At last, that's over, i'm sorry it took me so long to explain this, if you haven't guessed yet… yes i am on the bi-polar spectrum, so my mind wanders all over the place as i try to recall things, and also why i have so many hobbies that i flit between.

To totally finish this bit off, my new button box wiring diagram, i did away with the led and contact block in the stop button that is for resetting the VFD fault condition, instead this is handled by a separate button and led on the front of the electrical enclosure.

As can be seen i now have 8 controls in this button box, all operate on low voltage DC which is just a personal preference. and the main new control is the bottom right which is the remote variable speed potentiometer, that allows me to use the mill taking advantage of the VFD fitted to it.

That's it for now,

Next will be the DRO instal, which is a 4 axis lcd type with RPM readout built in.

Edited By Gazz on 20/05/2021 22:24:43

[Sam BernardParticipant @sambernard62918]

Hi Ive really enjoyed reading about all the work you have done to your GH18. Ive just brought one so im very interested in the topic.

Do you have any updates regarding how you fitted your dro scales? Epecially the one on the quill.

Ive got my eye on the sino SDS200 monitor.

All the electronic work you have done is amazing unfortunately im not very skilled in that area. However I would like to fit a potentiometer if I can work out how.

Thanks

[petro1headParticipant @petro1head]

I have just posted asking if anyone had moved the control box and then found this

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