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fburgos

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Today reading a reply by vibe-rate, got me thinking about advantages of having rpm to mpm, in my previous job my analyzer didn’t have this but I had clients in industries like steel rolling and galvanized metal sheets, they have similar process to paper machine where I think rpm to mpm could be very use full.

In my experience with this industries they have variable speed machines, depending on the product been made they change speed, but have a constant speed on any particular product, my solution was doing surveys on same product, the common or the one that had the fastest speed, this was to have same speed/condition while analyzing at that time was the best I come up with.

But always struggle with one thing, one client had an un-coiler (beginning of line) and re-coiler (end of the line), this machines varies their speed depending on the diameter of the coil which varies on every turn, then smearing on the spectrum happens every time what’s the best solution for this.

vogel

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Reply with quote  #2 
Synchronous sampling, if you can install a tacho.
Other machines that need synchronous sampling are wind turbines.

See this article: https://community.plm.automation.siemens.com/t5/Testing-Knowledge-Base/Order-Tracking-Fixed-Sampling-versus-Synchronous-Sampling/ta-p/541928
and this one (starting at page 10):
https://oaktrust.library.tamu.edu/bitstream/handle/1969.1/162702/TurboTutorial4.pdf?sequence=1&isAllowed=y

The first article makes an unnecessary distinction, in my opinion, between Frequency spectrum and Order spectrum that may lead to confusion and the other one is wrong (I think) when it talks about MHz sampling, but overall they provide very good explanations.
Vibe-Rater

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Reply with quote  #3 
Hi  fburgos,

Paper machines are essentially fixed speed machines although they are variable speed. meaning that they are able to run at many different speeds. As you mention above they will run at different speeds for different products so the thicker the paper the slower the speed.  So for me I am familiar with about 10 GSM and up to 415 GSM.  (think #2 Sinsk) The lower / lighter end of that range is toilet paper / tissue the upper end the paper cardboard boxes are made of. Newspaper is about 50 gsm??) To put things in perspective 80 GSM is the paper you will be loading in your printer.

So what links everything together on a paper machine is the MPM.  So CSI came up with a MPM --> RPM ratio.  That was there when I started in this field in 1992. So the way that works - for those that might not know (sorry to bore you Rusty, Danny & Ralph) is that the roll surface speed can be related to it's rotational speed by virtue of it's diameter. So as we walk up to do some data collection on a paper machine we would typically see a control panel and see the machine speed in MPM. or feet per minute for the imperial people among us.  You just enter that speed into your instrument. For CSI there is a beautiful function called "global speed set" which enables you  to set the speed in 1 fell swoop for all the machines in your route. Fantastic! for the 3 or so other brands I used that function did not exist.  Why.... I have no idea.

So when setting up a database we start with an Excel sheet of all roll diameters. Then auto calculate the ratios. 

It is also why we should all be thinking in orders as everything relates to shaft speed, either synch or non synch.  Anyway. rgds
trapper

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Reply with quote  #4 

We have plenty of stuff like that and about every line has a letoff and windup consisting of the motor, gearbox and roll controlled by a plc and vfd.

The stuff that changes speed very quickly use low-cost motors and gearboxes. These don't fail very often because: 1.) the motor rarely gets above 600 rpm and the loads are not that great and 2.) The gearbox and rolls most often run in the range of 4 to 40 rpm output. I don't even worry about the smeared spectrums as long as I don't see impacting in the waveform and PeakVue waveforms. You could try using just one average when you take your readings and adjust Fmax or resolution to where the data block doesn't encompass too much of the change in speed.

The larger (and more important) stuff tends to change speed a little more slowly although some rubber "recipes" call for quite a variation in speed. Most of the time, the capture time is short enough that I can get a steady speed during the data collection. The gearboxes that have output speeds of 10-25 rpm I have to live with sometimes.

Order tracking would be nice on some of the larger stuff but it's not going to happen around here, especially for route data collection.

Noknroll

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Reply with quote  #5 
MDF (Medium Density Fiberboard) continuous Presses, (where I cut my teeth) are same as Vibe-rater describes and also benefit from the MPM - RPM feature. although MDF press speeds are in mm/sec and thickness' range is 2.5 mm to 32mm and speed of press is faster or slower accordingly, but still same principle of drum diameters/circumference being critical in calculation. Only difference is we don't wind on and off, but cut and stack on the fly
Vibe-Rater

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Reply with quote  #6 
Years ago in Mastertrend days "global speed set" wasn't there yet.  That was when you had to set up all dryers and felt rolls in each dryer section under the same machine. Which meant you only had to enter machine speed once per dryer section. then along came global speed set. and then you were able to have each dryer cylinder and felt roll as its own "machine" .  Last time I sat down with a commtest expert it still could no do that - meaning global speed set. OLi? 
Vibe-Rater

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Reply with quote  #7 
And Nok,''MDF does sound a lot slower than what I'm used to. And the MPM -> RPM is brilliant., 
OLi

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Reply with quote  #8 
Commtest Ascent software don't have that AFAIK now and it is shifting to GE software, who knows what comes and goes. My favourite the stacked FFT aka waterfall at run up/down with a cursor so you can extract a run up/down trend for any frequency is likely not there any more as it is a speciality sort of. It used to have a clickable report so you click on a alarm and it pulls all the data plots, very convinient for the lazy. SKF/Palomar used to have that feature in the DOS version :-), so maybe Mr. Moore also was lazy, all gone now anyway.
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Sinski

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Reply with quote  #9 
Also for those who monitor paper machines will know about winders. These are for winding the large jumbo rolls of paper into smaller customer rolls and this is something that ramps up and down speed all the time. Easier to have a tach point on one shaft and refer all rolls to that point. Then like my machine which has a unwind motor that is constantly changing speed as the jumbo roll gets smaller and so will be a different speed at each point collected.
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