Adding Bluetooth pressure transducers to cnc machines

[plchris]

We have some large horizontal machining centers for drilling castings. They have custom built hydraulic clamps in the stations. We've had issues where operators would not tighten the clamps tight enough or not at all and damaged bits or even damage spindles.

We are wanting to add Bluetooth pressure transducers. I know Bluetooth isn't the best method but it has to be wireless because the fixtures will turn 360° and then switch stations and repeat, so it can't have wires.

We have a single transducer on one of the clamps on there now but we can only use an app to look at the data on a smartphone or tablet. We wanting to use the data to prevent the drilling cycle from starting if any clamp is not tight enough.

I'm thinking about using a Meas M5600 transducer or something similar.

Has anyone done something like this? What PLC or interface did you use? What about an Arduino based PLC that has Bluetooth or add a Bluetooth module. How do I get the data to the PLC?

If I could find a transducer that had an adjustable setpoint and just gave a 1 or 0 would be great. If I have to use the analog data that would just make it more complicated. Whatever method is easier is what I'm wanting to do.

Any suggestions? A different method? Is there a way to use an Allen Bradley PLC and adding a Bluetooth module? How would you do it?

Any help greatly appreciated.

 

[Peter Nachtwey]

We have a single transducer on one of the clamps on there now but we can only use an app to look at the data on a smartphone or tablet. We wanting to use the data to prevent the drilling cycle from starting if any clamp is not tight enough.

This doesn't make sense. Where is the oil coming from and how does it get to a rotating clamp?


Yes, 39 years of hydraulic control. Done many.
Ask this question on a hydraulic forum and you may get an simple hydraulic answers that don't involve electronics at all.
Look up sequence valve. You aren't doing fine control, all you need is some way to determine if there is enough, not the exact, pressure at the clamp.

 

[plchris]

This doesn't make sense. Where is the oil coming from and how does it get to a rotating clamp?


Yes, 39 years of hydraulic control. Done many.
Ask this question on a hydraulic forum and you may get an simple hydraulic answers that don't involve electronics at all.
Look up sequence valve. You aren't doing fine control, all you need is some way to determine if there is enough, not the exact, pressure at the clamp.

There is a small hydraulic unit mounted on the fixture clamps. The operator puts in four parts and uses an impact driver with an impact socket to turn a nut. That clamps the parts in the fixture.

Yes all I need from the sensor is yes or no. Is the pressure at the setpoint. If not don't let the machine cycle. Each station has four sides. So while the operator is loading the 16 parts the other station is getting machined. Each station will have four sensors.

 

[Steve Bailey]

How are you currently getting power to the electrical components on the rotating part? Slip rings? Are there any spare wires?

 

[plchris]

How are you currently getting power to the electrical components on the rotating part? Slip rings? Are there any spare wires?

There are no electrical wires going to the fixture. The current pressure transducer we added is battery powered. The Meas M5600 is battery powered as well.

Using slip rings is something I've thought of. If it was just a rotating fixture it would not be that hard. Since it rotates, moves x, y, z and then flips 180 degrees and repeats it gets more complicated.

 

[Peter Nachtwey]

There is a small hydraulic unit mounted on the fixture clamps.

How does it get power if it rotates with the clamps?

 

[padees]

How does it get power if it rotates with the clamps?

"Living is easy with eyes closed, misunderstanding all you see...."



LOL

 

[drbitboy]

Is there an API to the custom hydraulic clamp monitor on the Android? Because you can talk Modbus to the PLC e.g. see this link.


If stuff like API is greek to you, you will need to hire someone to code it, but yes, the solution should be simple.


Also, a minimal linux box (SBC or laptop with ethernet) should probably be able to do the same thing.


So yes, although this is a bit of a Rube Goldberg/Heath Robinson, it should be straightforward, but you should spend some time googling to see if someone else has already solved the same problem.

 

[Steve Bailey]

You said there is a small (battery powered?) hydraulic unit on the fixture clamps. How does the operator command it to clamp and unclamp?

Can you interlock the command to clamp with the permissive to drill? Maybe include a time delay to allow for the clamping action to take place. Admittedly not a perfect solution since it assumes the clamping action takes place on command.

 

[plchris]

How does it get power if it rotates with the clamps?

It's manual. The operator loads four castings and using an impact driver or drill with an impact socket attached, they screw the nut that clamps the parts. Sorry I should have provided more details and worded things better in my original post. When I get back to work Monday I will see if I can get any nameplate info.

 

[drbitboy]

It's manual. The operator loads four castings and using an impact driver or drill with an impact socket attached, they screw the nut that clamps the parts. Sorry I should have provided more details and worded things better in my original post. When I get back to work Monday I will see if I can get any nameplate info.

Thanks for the added detail; @PeterN usually checks out if the information flow is too slow, but he does like hydraulic problems.

But to me, "hydraulic clamp" is a new concept, so please use simple phrases and short words: does turning the nut actually tighten the clamp directly e.g. like the C clamps in my basement, or does turning the nut generate hydraulic pressure in these custom devices, and that hydraulic pressure exerts force on the clamping elements?

 

[padees]

Boy, this set has an LOL or two.



Sounds to me like you have a dual pallet tombstone. Difficult in that scenario with the indexing and the rotation.


I do have experience with that sensor you want to try. They do work, but very sporadic. Loose connection, have to try again and again, then a day is lost.


I did contact OEM, a couple of emails and phone calls. They told me to contact the place I bought it from, which was Mouser. They have no tech support for these items and neither does the OEM in China.


Yep, we want your money, and too bad if what you bought doesn't work.

 

[padees]

Thanks for the added detail; @PeterN usually checks out if the information flow is too slow, but he does like hydraulic problems.

Hey Bit, wrap your head around mechanical screw pump to create hydraulic pressure. Common...


I wouldn't trust that sensor. Spindles can get expensive!


But, then again, you are an expert... LOL


Boy...

 

[Peter Nachtwey]

"Living is easy with eyes closed, misunderstanding all you see...."
LOL

In this case we see nothing and information is being released a little at a time.

I really hate playing 20 questions.
The OP hasn't explained how the pump that rotates with the clamp gets power. The pump can't be powered by bluetooth. Can't a parallel wire be run from the pressure switch back to the PLC then? The problem doesn't make sense.


In sawmills there are pantographs that run hydraulics and electric power to moving equipment. Obviously the hydraulic lines can't keep rotating the same direction for long.

 

[Peter Nachtwey]

Thanks for the added detail; @PeterN usually checks out if the information flow is too slow, but he does like hydraulic problems.

No I don't.

I can answer most questions quickly if all the information was provided up front.


Instead we must pull teeth.