If you are a rollerman with a drive to optimize mill practice, improve wire rod tolerance and save a lot of money, we have two good pieces of news for you.
The first is that today, after modifying roll diameters, you can determine quickly and with considerable accuracy the gap settings to ensure push-free and pull-free operations in your wire rod block. Which will let you save an incredible 10,000 US dollars a month!
The second is that you don't need to read all the stuff below. Just click here and download GAPS0600 (for free!). With it you will be able to experiment on how modifying roll diameters affects roll gap variations. And it's extremely easy to use!
Back to the Sixties
I don't know about you, but my first memory of wire rod blocks in technical literature goes back to 1969. Mr. Norman A. Wilson, from Worcester, USA, presented a paper at the 38th Working Meeting of the Arbeitsgemeinschaft Europäischer Kalibreure with the title "A high speed rod finishing mill". The paper was published by
"Der Kalibreur", no. 11, September 1969.
So, how long have these machines been rolling around? Thirty years? Well, they were 30 years of malpractice.
Mill floor (mal)practice
A wire rod block is a strong, powerful technological jewel. Its bevel gears and helical pinions operate at such velocities that, in Wilson's words, "it became necessary to manufacture the gearing to a standard of accuracy commonly specified for aircraft applications".
Both on the designer's desk and in the assembly shop everything works. The problems arise on the mill floor, where sometimes, at the first stoppage for roll changing, the rollerman has to "take arms against a sea of troubles". Modifying the diameter of even a single pair of rolls alters the delicate balance of bar speeds at each stand: if a stand "pushes" too much a loop will occur, with immediate danger of a cobble; if a stand "pulls" too much, the roll grooves will tend to be
underfilled, and the bar will be overstretched.
And you know what the common practice on the mill floor is? Grind down all the roll diameters to the amount necessary to repair the most damaged pair and set the mill with the nominal roll gaps. If you think this is the way to restore the basic situation (that with rolls having nominal diameters), think again.
The problem
What are the difficulties? To put in a nutshell what is extensively explained in a paper of mine about roll pass design for wire rod blocks, there is a fundamental operational difference between a continuous bar mill
(CBM) and a wire rod block (WRB): that the CBM has one motor per stand, while the WRB has one motor for all stands. Period.
What does this mean? That if we raise the exit speed of the finishing stand in a
CBM, the other stands can be adjusted by variating the rotational speed of their motors, without necessarily altering roll gap settings.
If we raise the motor speed in a WRB because roll diameter at the finishing stand is diminished and peripheral roll speed (or, better, exit bar speed) must remain unchanged, we raise the rotational speed of all the block stands. If roll diameters at these stands were unchanged, the peripheral speeds will be raised, and the hot iron current will be severely altered.
A first attempt to restore the constant flow throughout the WRB can be made by modifying roll gaps. But careful: if you modify inconsistently oval
thicknesses, your rounds at the even stands may become potatoes. And what about quality? The fix still remains even if all rolls are ground down to the same diameter, because the gear ratios among the WRB stands are everything but regularly distributed. All this results in uncontrolled pulls and pushes within the block.
We have the solution
The truth is that no one in three decades was able to predict with any accuracy the gap variations necessary to cope with the introduction of new roll diameters.
This is probably the cause of an average 2 cobbles a month occurring in each
WRB, with an estimated loss of 20 to 30 thousand US dollars a year. And, more: because traditional practice produces out-of-tolerance front ends and tail ends, these are currently scrapped. What if a new gap setting practice eliminated those defects? Well, in terms of mill yield, correct gap setting could result in saving some metres of wire rod per coil or, at a conservative estimate, some 100,000 US dollars a year.
No one solved this problem – until now, we mean. Because it seems that we did. (Click also here.) We were able to temper the need to keep constant iron flow and the need to respect fixed rotational speed ratios. There was no hocus-pocus in this. We just "unleash the iron dog" and let the gaps fluctuate adjusting themselves to the real situation.
In fact, if you examine an output report obtained with our programs (see below), you will find that, while gaps change, the product of exit area times exit speed remains constant AND that the factory-set ratios among rotational speeds are respected.
What we do: create planets
We take our BYBLOCK program (roll pass design for wire rod blocks) and modify it.
Using an outer space metaphor, we take the Sun and derive from it a number of planets.
A planet is a new program dedicated to a particular WRB and to a particular finished round diameter. A planet only requires roll diameters as input data.
Of course, creating a planet requires modifying source code, and for this reason it can only be created in-house (in our house, we mean). The process involves setting the original input variables (all but the roll diameters) as constants. We extract these constants from an input form we must receive filled out by the customer. (Click here for an input form in Imperial units.)
As you will see after printing the input form, there may be two cases. In the first case,
you give the WRB data but not the basic pass dimensions (basic meaning those used when rolling with nominal roll diameters). We will complete the input form by using
BYBLOCK. In the second case, by filling the input form with "data that MAY be supplied", you also give the basic pass dimensions. In both cases, we eventually obtain a basic pass schedule to start with.
After creating the proper planet, we deliver it to you as an executable file attached to an e-mail. The planet's name is
GAPSYYYY, where YYYY indicates the finished round diameter. For example GAPS0750 is your planet for round 7.5 mm (and, when using Imperial units, GAPS9355 is your planet for round 0.355 in.).
What you do: derive satellites
When you receive a planet, you can create as many satellites as you want. A satellite is an ASCII file containing a pass schedule similar to the basic pass schedule, only with different roll diameters and with new gap settings. Each satellite regards a certain distribution of roll diameters in the
WRB. The satellite filename is up to you: maybe you can set an alphanumeric code to identify a number of possible patterns and create a database of satellites.
In any case, you don't necessarily need to have "canned" satellites. You can create a suitable satellite in a few seconds, even on the shop floor (if you have a laptop and a couple of laps handy), and shout to the crew the correct gap settings in real time.
CLICK
HERE FOR DETAILED EXAMPLE
Planetary marketing
We can provide 10-stand, 8-stand, 6-stand, 4-stand and 2-stand planets, in seven national versions, including the American version in inches. For each planet we have set two prices: a standard price, for partially filled input forms (2nd part left blank); and a lower price for fully filled input forms. Here they are:
standard price: US$ 1200
lower
price: US$ 1000
Not bad, considering that
if you buy a planetary system for, say, 10 finished rod diameters,
your investment may pay off in less than a month.
If you want to experiment immediately
with how easy working with our planets is, just click here and download your free planet NOW!
We'll be glad to answer your questions about delivery times and payment terms. Just send us an e-mail
(no obligations implied) specifying your requests, with "Planet info" in the Subject field.
