Affordable Bus systems

Hi guys,

I'm interested to hear your reponse on the following. What is your opinion on different bus systems and affordability compared to the traditional junction box, multi-core systems.

As most of you know as a designcrew where always limited to budgets and so , everytime i suggest to a client to upgrade to a bus sytem they only look at prices of typical remote stations. I find that money saved in the end on installation, commisioning , fault finding and panel wiring usually makes up for the excessive price of the remote units.....

My question : In your opinion. Do you really think its more expensive running bussystems instead of traditional hardwired boxes??

Kind Regards

Rheinhardt

I've just had to price a job using both methods.
The bus system worked about at about the same price for hardware but much cheaper on installation time.
The size of plc rack, and i/o cards where cut from 4 full 7 slot racks to one 5 slot rack.
I used Profibus and P&F's profibus gateways.

We just finished our third batch of machines using interbus and Phoenix's inline I/O.

I have to do a cost analysis, but I don't think we saw a benefit until these last ones. The first two there was a learning curve, both on my part and on shop's. We now know most of the quirks, and the first machine has been in the field for nearly a year.

Just by observing, we saw a singnificant savings, mainly in time, on these last two machines. Some stuff that had to wait until parts of the machine were assembled could now be done on the bench. Our crunch time is always the final assembly stage, and it helped a lot.

My assembler doesn't want to go back.

we use the fieldbus more an more even for smaller stanalone
machines. main reason is in the flexibility when making
modifications (and this is something we live with every day).
it is a lot easier to throw in another node or two in a
junction box somwhere on the machine than to stretch the
plc rack and main panel...
choice of fieldbus and PLC is usually dictated by customer
(we deal with automotive) and money is usually not an issue,
at least not as big as flexibility.

Device Net may appear expensive on the surface but when you take into account wiring to remote places, it really comes into it's own.

If you are only looking at limited I/O on the remotes, Omron Compo Bus S is less than 2 thirds the price of Device Net. It is basically an in house Device Net system with not many of the bells and whistles but works really well for small I/O jobs. Great around machinery. No special cable either, only twin twisted shielded cable. Remote analogues are also available. With the CJ1 PLC you can have up to 16 Compo Bus S masters with 16 x 16 input blocks and 16 x 16 output blocks on each master. You only need one of the cheaper CPUs as well.

Most manufacturers have their own proprietary remote I/O (RIO) systems. For example Telemecanique FIPIO. Goes long distances too but runs at a relatively slow baud rate. Does not matter sometimes. Check out all the major manufacturers for their in house solutions. Most of them do not require configurators or special software.

Another solution may be ASI. Many manufacturers support ASI. Generally it is limited to digital I/O, is inexpensive and works well. Automatically detects new devices as they are added too, provided they have different node numbers. Use the same node number twice and confusion reigns.

ASI is excellent for maintenance staff as well. If you use an ASI compliant limit switch, for example, and it fails, buy a new one, set up the same node number, install the device and the system will automatically detect and begin using the limit switch. Quite nice.

For Device Net go here ODVA
For information on all field busses and very good links go here Fieldbus Page

I'm not a field bus person. I don't like any type of remote I/O. I would rather just use a plc rack with an extension cable.

I think that this is mostly do to the fact that in most plants where I have been a semi-permanent or longer term fixture, there just weren't any electricians or techs that understood using any type of remote or bus system, and they weren't going to learn.

I spent a year at one plant where none of the third shift electricians would load a program into a plc. If the machine was mechanically sound at the end of second shift, third would roll the plc pc caart over, plug it in, get the program ready on the pc, so that all that had to be done was hit enter. Then wait for day shift to come in and push the button. Too good of a union. In a year, I never met my third shift electrician, I did go in early one day and had someone point him out to me.

Price Wise

I have done comparisons, and they are more cost on larger machines, or when spread out across a plant. Maybe someday I'll try some out. One plant ordered a large machine with pc control, devicenet, and SteepleChase software. It came in after I left, and never ran properly. Well, after several years, they programmed the two robots to run independently, and replaced the devicenet with three micro plc's. No one in the plant understood devicenet, and were not going to learn.

I think I'd like to try profibus and devicenet...

regards.....casey

We use mostly Siemens as our main client is BMW(Automotive), i love using profibus nice n easy. I think the engineering world should now get to a point where we imbrace new technological Advancement, i find that some of the older engineers stick to the logig they had used for decades, and are sceptical of learning new systems.

I feel to be a good engineer you should stay on top of technology and advance with it.

What i feel about the bus systems is that i found that the maintenance guys also prefer bus systems once they understand them,
so what i do after a new installation is give a small training course on fault finding on the bussystem, works so far

I'm also doing a document on price differece, installation time,maintenace ect. on both systems and will just submit it at meetings where the topic arises, cause i find it being more cost effective, time effective and who doenst hate it when you get to a panel that you designed after a year and it becomed a spaghetti factory. With bus system less panel wiring to make spaghetti of...lol

Regards

RP

kc9ih said:

e, there just weren't any electricians or techs that understood using any type of remote or bus system, and they weren't going to learn.

Click to expand...

I suppose it depends on the type of machinery, but I forgot we put in a machine in 2000 with and Indramat control and Interbus. They haven't had a single bus related problem, and they love being able to check I/O status right at the station instead of a two-man crew yelling back and forth.

I think that this is mostly do to the fact that in most plants where I have been a semi-permanent or longer term fixture, there just weren't any electricians or techs that understood using any type of remote or bus system, and they weren't going to learn.

Click to expand...

This statement is a truthful as you can find.

The question does need to asked of the end user: "How will you
support this system after startup?"

If the end user doesn't even own a laptop for the electrical
maint. department, you can assume that the 'one point, one wire'
method will work the best, be most acceptable, and allow the
system to be maintained by the enduser.