cam controller

Hello everyone,

I have a machine with a mechanical cam on a rotating shaft that ativates a prox sensor to turn a spray gun on and off with relationship to the cam. The system is a Siemens S7-300.

I would like to replace the cam and sensor with an encoder. . Can anyone give me advice as to what to look for in a simple encoder, maybe a Dynapar, we have some other encoders of that brand? Also, can I use a simple high speed counter module for this application like a FM350-1 or FM350-2? And use this combinatin to set some simple cams for control.

Any help would be greatly appricitated.

mrt19 said:

Hello everyone,

I have a machine with a mechanical cam on a rotating shaft that ativates a prox sensor to turn a spray gun on and off with relationship to the cam. The system is a Siemens S7-300.

I would like to replace the cam and sensor with an encoder. . Can anyone give me advice as to what to look for in a simple encoder, maybe a Dynapar, we have some other encoders of that brand? Also, can I use a simple high speed counter module for this application like a FM350-1 or FM350-2? And use this combinatin to set some simple cams for control.

Any help would be greatly appricitated.

Click to expand...

Since you mentioned Dynapar, they offer absolute Gray scale, parallel encoders.
You don't even need a high speed card, just a regular DC input card will do.
The inputs used will vary depending on the resolution of the encoder you choose.
And yes, I do this all the time, use encoder current position to turn on and off "cams".

I just did a system like you are suggesting and it works great. We have a number of old cam-driven machines that we have modified over the years, mainly by adding air valves to control other functions. To keep the valve operation timed with the machine, we had been using an "Electrocam" device (www.electrocam.com), which attaches to the drive shaft and has adjustable plastic discs that trigger outputs during certain parts of the cycle. It's a pain in the neck to adjust (you have to use a little plastic wrench to turn the discs) and you can't do it while the machine is running.

So during the last downtime, I yanked out that piece of junk and installed a Turck 360ppr encoder with quadrature A/B/Z output, wired into a small Micrologix 1100. I'm using the high-speed inputs on the PLC to read the encoder, which isn't absolutely necessary since my pulse rate is slow, but it is handy because the HSC function keeps track of the pulse count and even decrements it if the encoder happens to turn backwards (i.e. during maintenance). Most brands of PLCs have these functions. Since my encoder is incremental, it also outputs a zero pulse once per revolution, which serves to reset the count in case the drive shaft would happen to move while the power is off (again, maintenance). The small LCD on the 1100 is nice because I can adjust all the cam parameters without hooking up a PC, even while the machine is running.

My $0.02: Go for it, I'm sure you will be happy with the result.

Hey guys, thanks for the info. I will need to be able to adjust the timing of the cam through Winflex that I am gong to install as well.

I will probably go with a sinple incremental encoder and a high speed counter module S7-300. Any reason why I couldn't use a FM350-1 module with a Dynapar HA62502000111, HR5251000001, or HS351000C344D. If not, what do you suggest I use.

I have sorta messed with encoders in the past and know the basics behing them but have never started a system from scratch.

Thanks again,,,

mrt19 said:

Hey guys, thanks for the info. I will need to be able to adjust the timing of the cam through Winflex that I am gong to install as well.

I will probably go with a sinple incremental encoder and a high speed counter module S7-300. Any reason why I couldn't use a FM350-1 module with a Dynapar HA62502000111, HR5251000001, or HS351000C344D. If not, what do you suggest I use.

I have sorta messed with encoders in the past and know the basics behing them but have never started a system from scratch.

Thanks again,,,

Click to expand...

No reason at all, just cost.
But if you have the FM go for it.
The absolute gray scale works with just a DC Input card, less money, that's all.

Do you need to energize multiple outputs over one encoder revolution?

And how fast?

What the machine is doing is spraying the inside of a tube with a spray gun. The cam tells the gun when to open and close. This needs to be adjustable with different products we make. The cam now has one sensor that when it is high the gun sprays, when low the gun closes.

We run about 60 a minute and I believe only 1 tube per turn of the shaft, very slow. There only needs to be one output to an air valve which ativates the gun. I will need to create a cam in the S7 program to activate the output depending on the location of the shaft. The reason I choose the numbers above is that I found really low prices for them on ebay. I have neither the encoder or the module but need to get them so they play together.

However, maybe in the future I may want to add additional cams with different outputs for other things.

thanks,mrt19