Why pay for PLC programming? continue

[steve_rb]

I think time is about to over for PLCs. Now a days more faster and userfriendlier programs are about to be developed and will be replaced PLCs. Today CNC machines are equiped with a pc based software and you can do all simulations on PC and download to machine and let it run overnight and tomorrow morning pick your part and all is simple (well not that simple I should say) and cheap. PLCs to todays way of controling systems looks to me just like monocrom 286 PC to pentium 4.

steve_rb

 

[JesperMP]

steve_rb.

Comparing CNCs and PLCs is like comparing apples and oranges.
CNCs and the associated software is a dedicated solution. Of course it is impressive to watch a CAD drawing automatically being converted into a finished piece. But that comes from decades of product development to solve one specific problem.
PLCs are more like general purpose problem solvers. You can throw them at almost any problem. Try to use CNC control to something else than CNC machining - good luck.

The software used to program PLCs is also used to solve almost 'any' problem. You will find several languages aimed at being best for different problems - ladder for just about everything - structured text for mathematic number crunching - grahical state programming etc. The PLC has it already. I doubt that there is any "revolution" on the horizon.

The idea that PCs will take over PLCs is not new, but has so far not materialised. The reson is obvious: RELIABILITY, RELIABILITY and RELIABILTY - PCs can not match the PLC when it comes to reliability. Both software and hardware lets it down.

By the way, what has your header got to do with your post ?

 

[nif]

Hello!
About CNC machines have you ever looked inside one ?
What do you think controls the movements and the other things ?

Normally there is a PLC inside controlling it....
Maybe some small "home"-machines are controlled directly by a computer.

 

[elevmike]

Steve,

PLCs are a very long way from being compleatly subplanted by PCs. Cost and reliability issues are still very far apart and arnt closing in very rapidly. Just as PCs are getting smarter, more reliable, and cost effective, so are PLCs at the same if not faster rate. I doubt that the two lines will cross anytime soon.

Additionally this is an very old debate that is likely to go on for a long time. However I would suggest it's pointless due to the fact that the whole question is application dependent, and theres more posabilities for applications for PLCs and PCs then there are stars in the sky...

 

[Pierre]

Since I am known to mess around with Mitsubishi, I often gtet calls for CNC equipments.

Nobody could beleive how many A serie PLC are runnig complex CNC machine around here.

There is a bunch.

 

[Stephen Luft]

Steve,

The so called death of PLCs has been errouneously reported for years.

What has happened in that time is the evolution of the PLC from a basic relay replacer to a process solution. Now many PLCs offer analog I/O in the forms of temperature, milliamp and voltage. Where, several years ago, you would require separate devices for a process, now can be done with one PLC.

Customers that were using temperature controllers in their applications, in addition to PLCs, can now reduce their components. We are currently developing a next generation version of a solder machine that we will be using next year. The new design will use our PLC and touch screen. We will replace an enourmous amount of wiring, two temperature controllers and an array of lights and push buttons. The new design will be able to store setup parameters for different types of circuit boards.

The amount and type of applications that a PLC can be used in is endless. Believe it or not...there are still companies using relays, timers and counters in their application.

To look at one type of application does not do the industry justice.

Food for thought.

God Bless,

 

[Steve Bailey]

It's true that there are plenty of 'soft CNC' controllers available. But the growth of that segment hasn't sounded the death knell for the dedicated CNC controller.

There has been far less growth of the 'soft PLC' into the dedicated PLC market. The imminent death of the PLC has been predicted for at least a decade. What new data do you have to convince us that your analysis of the market trends is any more accurate than that which has preceded you?

A better question might be, why has PC-based control made greater inroads into the CNC market than the PLC market?

 

[RRobbins]

PLC's will be around until PC's NEVER lock up and have no memory leaks. The PC based market is after equipment that is non-critical and can go off line to be re-booted. CNC is a small market. Many are still using PLC's.

 

[DonsDaMan]

I think the OP put his title as a troll, derived from the title of Stephen Luft's popular (?) thread.

To answer it, though, you pay for PLC programming because you can't do it yourself (for whatever reason: time, convenience, accountability, ability, etc.)

 

[elevmike]

The report of my death was an exaggeration...

 

[akreel]

I'd like to see Doofus Dave, the shop electrician, doing maintenance on a PC based system. Once he's done playing solitaire, he'll get around to REALLY screwing things up.

Seriously, one huge advantage of a PLC system is that ladder logic is very intuitive. Writing code from scratch requires some skill, but you can train MOST people to make program changes.

Many of the users of this message board probably don't want others looking at their code. But, I've worked in machine shops, where the maintenance crew needed to be able to change anything and everything to get the line running (usually at 3am).

AK

 

[Rick Densing]

The header is there because the post was oringinally in that thread.

 

[Rick Densing]

The PLC vs. PC argument is kind of silly.

They are each tools, and will be appropriate for different applications. As designers, it is up to us to evaluate each one and decide which is best and not let our emotions get the best of us.

 

[PhilipW]

All the bigger vendors have had perfectly ok "soft" versions of their PLC's for ages. ControlLogix has a SoftLogix version for example. I am sure that Seimens and others have equivalents.

Both the hard and the soft plc have their place in the market. However the hard plc continues to dominate because it is better suited to the majority (95% plus) of applications at the present time.

This ratio may change in the future, but frankly I don't give a rats patooi whether my ladder logic is running on a microprocessor in a white box or a slot card, just so long as it has the speed, memory, comms bandwidth and stability to do the job I want it to.

 

[nif]

Going back to steve_rb:s original message.
If you have a CNC machine with the designer program, the PC program is made for the end user of the machine. It will simulate how the cnc-machine makes the part.
The program generates a list of parameters for the "PLC" control in the CNC-machine.
It´s never meant that the eg. mill user have to know PLC-proramming only how to use the mill.(give the speed and position and so on.)

The PLC programming has been already made in the machine suppliers plant.

Eg. the new GE fanuc PLC:s have pentium processors inside...

The reason why the PLC:s are always behind PC hardware is beacause all the PLC:s have to approved. These tests take a long time.
It wouldn´t be nice if the PLC gets these normal PC crash faults...