Manual Mode

Recently a coworker and I was discussing the "Manual Mode" of our machinery. He feels that in manual mode the machine should move (with the necessary guarding closed) unconditionally. If he wants to extend a slide before raising it, it hits a fixture, and tears up the tooling, then it should happen. (I wonder about him sometimes.)

I told him that the machine should be able to move, but must stay in sequence. I would tend to think that this would be cheaper for the company, easier on the equipment, and give less downtime. Production people tend to be button pushers and not thinkers. On some of our equipment they have actually numbered, with a marker, some of the panel buttons. Doesn't matter why the station went down. They feel that if they push the buttons in the numbered sequence everything will be come back to life.

Things like this tend to tear up machinery and if the person at the helm has no brain at least give the machine one.

Once I installed a pushbutton on a panel and didn't hook it up. Told the operators if they had any problems just push it 2 times. They loved it. Never had a complaint again.

Any thoughts on the subject?

Steve

We have had similar discussions on the "definition" of manual. In almost all instances where the machine was allowed to function unconditionally, crashes have occured.
Most of the time I find myself adding to the original code, taking almost all of the potential of unsequenced movement out.



I like the "magic potion" pushbutton idea!! lolis

Some machinery require clamp pressures to hold parts.
With Manual operation and no part in place it is common for the machine to crash or damage itself.
Be carefull of what you want as 'manual'
some machines require a two step manual system.
I.E. tool in position or no tool.
I have had a Proximity smashed in manual mode for the same reason.
The clamp extended past the normal jig maximum position.
The normal manual control is locked off for maintenance use only.

On button pushers...

My boss, Steve, is a sheer genius. This guy is great, and since he has no idea this forum exists, you can tell I'm not sucking up

Some time ago, he set up a button on one of his machines and put a sign above it : "Do Not Push!"

Within a week, operators were "informing" him that, they didn't know what that button did, but when they pressed it, the machine ran better!

What did the button do?

It incremented an Omron counter. That's all it was hooked up to. 962 pushes in one week.

TM

We make special machine tools. We place jog buttons at each machining station to jog it through sequence in manual mode. In CNC speak it is really Semi-Auto. I write the program to prevent as many crashes as possible. Sometimes, you can't do anything to prevent them, like trying to tap a non-existant hole, but we do our best to prevent that. Our customers seem happy with this arrangement.
Lately, expecially with servo-driven stations, we have been adding a second form of manual usually called setup mode. This is activated by a key switch. This allows full, free movement of the station. Yes crashes can occur, but the key switch at least keeps the operators away. This also seems to work well for our customers.

To me, manual mode implies single-stepping through the sequence of operations. The same conditions apply as for full automatic operation, but each step of the sequence is triggered by the operator rather than automatically. You frequently have to make judgement calls, such as when an actuator triggers an event before it reaches end-of-travel.

Whenever you set up a manual mode, personnel safety has to be the primary concern, followed by preventing damage to the machinery.

I've often toyed with the idea of installing dummy controls, but I've found that it's better to actually let the controls do something, even if that something has minimal influence on the operation of the machine. That way, the operator feels more involved in the process. When he's involved, he tends to feel less threatened by the automation and more likely to look for ways to improve the process.

You can put all the interlocks you want onto the sequence control, but a creative operator will figure out a way to get around them. I'd rather have that creativity working to improve the system, rather than fighting it.

Sometimes you have to give your Operators control in Manual Mode.
This is in order to Set up the job.
Of course you still have controls like not letting a top ram come down if a feed shoe is in the way.
These controls are in your ladder logic, so they work whether in manual mode. or Auto.
Sometimes Manual Mode just steps through the sequences slowly. It really depends on the application.

Output Processing

My boss's preference is for "limited unconditional movement", i.e. he wants to be able to move everything separately, but with all limit switches still in effect.

Just my two bits

To me, manual mode means that the operator, not the sequence has control. Manual is not stepping through the sequence, but doing things in any old order you please.

But I acknowledge that users can make mistakes. Therefore I impose a whole bunch of interlocks. These aren't (necessarily) the safety ones (that should be hard-wired anyway), but conditions that prevent bad or just plain dumb things from happening.

If the machine will tear its arm off if it raises it with the arm extended, then I make that an inerlock (perhaps a better term would be "permissive") so that the arm CAN'T be raised extended.

The sequence will have that interlock implied in it ("first retract, then raise, then extend", but I code all those things anyway, so that yes, an operator can do what they please, as long as it dosn't cause harm to another human being or the machine.. (Hey - that sounds like the First Law of Robotics. Hmmmm.....)

The interlocks are easy enough to set up just go through each output and ask, "Is there any condition which should prevent this from firning". AND all the conditions together into one coil, and add it to the device logic.

The hard part comes in giving good feedback to the operator" "I tried to start it in Manual mode, and it wouldn't go". (ReplyA, ater a code search) "That's because you're trying to start it when this is going on."

It's easy enough to put an 'I' next to the 'MAN' indication on the HMI to indicate that there is an interlock proplem. The hard part is making it clear just which interlock is affecting it, without duplicating the interlock logic in the HMI. (As in - click on the 'I', and a popup opens showing all the interlocks for that device, and highlighting which one(s) is/are active.)

This works, and works well, but it's a lot of work, and it means that if changes are made to the interlocks, they have to be make in both the PLC and HMI. It's not that big of a deal to deliver such a system, but I worry about the plant maintaining it after I'm gone. Chances are that when someone finds that they can't do something they want becasue of an interlock, they take out the interlock

I do process controls, not manufacturing machinery, so my viewpoint is a little different. To me "manual" should allow running each individual motor or actuator to allow for troubleshooting or emergency operation. Manual may bypass the PLC for operation and allow operating various devices out of sequence, but manual should NOT bypass safety or equipment protection functions.

If you are going to bypass safety or protection functions then a separate, difficult to get to, operation should be required, clearly labeled as "Protection Override" or similar. Key switches, internal panel switches, or jumpers should be required. This keeps production staff from toying with them. And, obviously, lockout / tagout procedures should be in effect before doing this.

To me, once personnel safety is taken thoroughly into account, how "free" manual controls are is a question of accountability. Who is going to be held accountable for the results of a poorly utilized "free" movement and consequent crash and then, who is accountable for the decision to allow it in the first place? This is normally an organization-by-organization call.

It has been my experience that regular machine operators rarely have the recognized authority to decide the level of freedom a machine will or will not have. Maintenance folks usually do not either. Obviously, these Maintenance folks will often have the tools to implement such decisions and will often take it upon themselves to make them, but this can be a risky career decision and many organizations frown on the practice. Usually plant management wants to be involved in such decisions and will make these generalized calls.

But since you ask, my personal preference falls right in with TimothyMoulder's boss's: "Limited Unconditional Movement". Let the operator make any movement he/she wants provided any foreseeable "crash" is prevented…incorporate all limit switches and require sequential moves when they are really required (for instance, you don't want to allow the drive to push if the mechanical stop is still engaged.)

Steve

light curtain muting or not

i,ve had the debate over a machine that had ,two-hand operation manual
operation. whether-or-not light curain should be muted or not. maybe
so a helper can adjust a prox-switch for instance while part is clamped

What the hell IS Manual Control???

Manual Control is...

From one extreme, Manual Control is to be able to actually execute your system sequence ( or exercise ANY other functions ) in Manual; As if the PLC is nothing more than a switch-handler and that you don't in fact have an automated system!

This allows any (and hopefully, only an... )"allowed" function to occur at any time. The operator MUST know what he is doing! Although the system will not (at least, it should not...) allow obvious logical conflicts.

The code should always display a reason why an operator can not do what he is trying to do!

At the other extreme, Manual Control is to be able to STEP through your process. This is nothing more than a "stepper". This is like Semi-Automatic. The system moves from one pre-defined step to another. Not exactly what I call a trouble-shooting tool or trouble extricator! What if you need to move backwards through the process? This might serve better to bring a machine into sync. I consider this to be the LEAST Manual-like.

From my perspective, Manual Contol should allow any legitimate move to occur; as long as it does not conflict with the "Can not have two or more bodies in the same space at the same time (or a fluid driven up against a dead-head)" Rule. The operator MUST know what he is doing!

This allows for un-f*cking-up a f*cked situation.

The operator should then bring the situation to a KNOWN-GOOD situation before going back to AUTO.

As far as who should make the determination as to what is a legitimate move to make... Someone has to step-up to the plate and say that someone is ME! That "someone" had damned well better know what he is doing and willing to keep his a$$ on the line daily!

If you ain't willing to do so, then you either don't know the situation as well as you should or you are too afraid to take the heat for doing what you believe to be right!

In either case, you need to find a new job!

As Lefty suggested, I do indeed have several PB's that are abnormal and labeled as such. When using those, the operator had DAMNED WELL better know what he is doing! The PLC tracks the number of occurences and times of those abnormal events.

Bravo Terry ... Well put.

I offer these home-grown mode definitions which are based on some previous machine/sequential control adventures:

Automatic: Turn on the machine and turn off the lights. Who needs an operator as the control system handles it all ... I mean ALL.

Semi-Automatic: Requires some outside trigger (perhaps from a human) to initiate the next sequence. Steps within a sequence occur automatically once triggered.

Semi-Manual: Each step requires a "trigger". The control system maintains coordination of triggered sequences and prevents those nasty operator-induced crashes from occuring. All safety measures remain in full effect. (Isn't this what were all talking about here?)

Manual: No "supervisory" control system. Might as well be directly "hot-wiring" the output devices. No safeties. No checks. No way!

Finally ...

Auto-magic: "Hey, did I make THAT happen? Not exactly what I meant, but pretty cool"

Hello mmw.

I use the same classification as you, with the difference that I call Manual Mode your Semi-Manual and Emergency Mode your Manual

Ciao da Gianluca