Steel Times International on Byblock
Rod-mill pass designers already benefit from BYBLOCK, a dedicated software
program that speeds roll pass design by three orders of magnitude. The program
has been further developed for use by shift foremen by offering a manual mode
to modify the pass design rapidly should a roll fail and an exact replacement
not be immediately available.
SOFTWARE SOLUTIONS TO SHOP FLOOR PROBLEMS IN WIRE ROD BLOCKS (*)
By Annibale Izzo, Linebow (**)
Seen from the operator's pulpit, wire rod blocks look like black boxes. They
accept 100 m of 12mm round bar at a rate of 25 m/s and then, shoot 400 m of
6mm wire rod at 100 m/s into a coiler - in 4 seconds. These machines are
extremely sophisticated pieces of mechanical technology. Once the rolls are
properly machined, mounted and set up, all the operator has to do is "fire and
forget".
With this kind of efficiency already available, it is not surprising that if
problems arise in the process they are operational rather than mechanical.
The problem this paper addresses appears when a pair of rolls needs to be changed
and an identical pair is not available. The mill crew must immediately determine
the proper gap setting. An error of a few hundredths of a millimetre could cause
a cobble.
The software solution
The solution to this problem is BYBLOCK, a software program designed to run on
any PC powered by any 286 to Pentium microprocessor. BYBLOCK is a unique tool
for two user groups - block manufacturers and pass designers - to carry out
wire rod block design operationsą.
During BYBLOCK's development, practical shop floor requirements were taken into
account, to help when rolls break and the available new rolls have different
diameter and/or groove dimensions.
This is why the final version of BYBLOCK has been developed to meet the needs
of three user groups: block manufacturers, roll pass designers and shift foremen.
Using BYBLOCK in automatic mode (A-MODE), block manufacturers can assign round
diameters at each pair of stands: BYBLOCK calculates all the necessary
transmission ratios, groove dimensions and rolling loads.
Roll pass designers can also use BYBLOCK in A-MODE, specifying entry round
conditions and transmission ratios at each stand: BYBLOCK then calculates groove
dimensions and rolling loads.
Shift foremen can use BYBLOCK in manual mode (M-MODE), which puts them in control
for specific situations.
The following illustrates the BYBLOCK modes, with special attention to M-MODE.
Only two modes have been mentioned so far, but there is also a third option,
semi-automatic mode (S-MODE), allowing the designer to assign roll gaps.
A-MODE and S-MODE
A-MODE allows the program to determine roll gaps; S-MODE requires the designer
to assign roll gaps, otherwise the modes are the same. Both modes can operate
with or without Tau ratios (Tau is the rotational speed of stand M divided by
the rotational speed of stand M-1) assigned.
Tau assigned is the most complex case: the block exists and roll pass design
must be performed; the exit section areas must both respect the law of constant
flow and be compatible with the fixed rotational speeds.
Roll pass design starts from an entry round (with its speed and temperature),
a finished round and an N-stand block (with N-1 values of Tau). The exit bar
speed is immediately calculated and, through approximate values of forward slip
and working diameter, BYBLOCK determines the related rotational speed. This
means determining N rotational speeds, hence N linear speeds and N areas A'.
Then BYBLOCK calculates the dimensions of N grooves (half of which are ovals,
OV, and half of which are rounds, RD). Each groove is capable of delivering a
section with cross-sectional area A'.
All these operations are automatically performed by BYBLOCK both in A-MODE and
in S-MODE. The algorithm ensures that each groove be correctly filled AND that
each exit section area Q' (from calculated groove dimensions) be almost
identical to A' (from the Law of Constant Flow).
After starting the program, users are prompted with the following options:
* if you know entry round area and finished round diameter, press "A"
* if you know number of stands and finished round diameter, press "B"
* if you want to force round diameters at even stands, press "C"
Options "A" and "B" are equivalent for the pass designer's convenience.
Option "A" returns the number of stands to use (note that in any block,
users can deactivate pairs of stands). Option "B" returns a suitable
entry-section area value (which the user can confirm or modify).
This example illustrates option "B", which after a preliminary input section
prompts the user with these choices:
* for automatic operation (passes to be designed) press "A"
* for semi-automatic operation (gaps assigned) press "S"
* for manual operation (grooves already machined) press "M"
For purposes of the example, a user chooses option "S", to be free to assign
lower gaps to the final part of the block in order to avoid possible pass
overfilling.
After the user presses "B", the first question the program asks is: "Source
stand?". If the entire rolling mill consists of 16 stands followed by an
8-stand block, the answer to the question is 16: block stands will
automatically be labelled 17 to 24. Answering zero allows labelling block
stands 1 to 8.
S-MODE: an Example
Input data are entered through a question-and-answer procedure. The mill is
the one mentioned above: a 16-stand rolling mill plus an 8-stand block. The
program suggests that the entry round area be 92.8 mm˛, but we force it to
90 mm˛. The remaining input data are shown in Fig 1.
--------------------------------------------------------------------------
Final round diameter 5.6 mm
Entry round speed 25 m/s
Entry round temperature 1050 °C
Rolled stock: C=.56%, Mn=.28%, Cr=.12%
Tungsten carbide rolls (4x210mm + 4x170mm)
Roll gaps: 4x1mm + 4x0.5mm
Values of Tau:
17->18 1.1163
18->19 1.1987 19->20 1.1643
20->21 1.1996 21->22 1.1679
22->23 1.2015 23->24 1.1667
Relief angle (same for all rounds: A=25°
--------------------------------------------------------------------------
Fig 1 - Input data for semi-automatic operation
------------------------------------------------------------------------------------------------
The shift foreman doesn't know yet, but tonight at, say, 11.35pm the rolls
of stand 21 will collapse after a microstructural defect. This is why you
should keep an eye on stand 21 in the output of this example - condensed for
space reasons into one line instead of the standard 8 lines per stand
(Figs 2 and 3).
--------------------------------------------------------------------------
OV b1t h1t b1r h1r r maxw gap dnom dwor
RD drn h1r b1r maxw gap dnom dwor
17 OV 13.37 8.19 12.42 8.19 7.50 12.81 1.00 210 203.92
18 RD 9.43 A 25 9.43 9.43 9.94 1.00 210 202.40
19 OV 12.50 6.61 11.42 6.61 7.57 11.76 1.00 210 205.25
20 RD 7.96 A 25 7.96 7.95 8.31 1.00 210 203.72
21 OV 10.15 5.81 9.28 5.81 5.89 9.84 0.50 170 165.48
22 RD 6.73 A 25 6.73 6.73 7.20 0.50 170 164.40
23 OV 8.25 5.01 7.74 5.01 4.65 7.97 0.50 170 166.23
24 RD 5.67 A 25 5.67 5.67 6.03 0.50 170 165.40
--------------------------------------------------------------------------
Fig 2 - Summarised output data after semi-automatic operation
--------------------------------------------------------------------------------------------------------------
__________________________________________________________
KEY:
- A is relief angle for rounds [degrees]
- b1t is theoretical width of the oval pass [mm]
- h1t is theoretical height of the oval pass [mm]
- b1r is bar width out of current pass [mm]
- h1r is bar height out of current pass [mm]
- maxw is width of groove on the roll barrel [mm]
- r is oval radius [mm]
- drn is round groove diameter [mm]
- dnom is roll barrel diameter [mm]
- dwor is working diameter [mm]
__________________________________________________________
At 11.45 that night, something went wrong in the block. After the cobble,
the EOHT crane finished clearing the twisted stock from the mill.
The rollerman announced that there are broken rolls at stand 21, but the
roll shop has no 170mm rolls available, only a pair of 164mm rolls, machined
with a nominal gap of 0.5 mm. If the smaller diameter rolls are mounted (with
the rotational speed unchanged, then the peripheral speed will be slower and
there will be a need for a larger section), the nominal gap will have to be
increased, but how much?
The shift foreman finds the original roll pass design report, turns on the PC
and launches BYBLOCK in M-Mode. The program's answer is:
increase the roll gap at stand 21 from 0.50 to 0.67 mm.
Let us see what happened.
M-MODE in Action
BYBLOCK's M-MODE starts exactly like S-MODE, except that the users read the
input data from a previously obtained Roll Pass Design Report (RPDR), ie the
fully expanded version of Fig. 2.
After getting answers to the questions pointed out in Fig 1, in M-MODE, the
program asks for some additional information about each stand. Theoretically,
if users enter exactly what they see on the RPDR from S-MODE, they get
identical reports from M-MODE. In practice, minimal differences may come
from numerical rounding.
The additional information required determines if anything has changed in
groove dimensions and in roll diameters within the block. At each block
stand, users are requested to provide the following information:
- radius (ovals) or diameter (rounds)
- max. width (ovals) or relief angle (rounds)
- nominal roll gap (*)
- section area (*)
- roll diameter (if changed)
The asterisk (*) indicates the sole data that cannot be modified when switching
from semi-automatic to manual operation.
The shift foreman copies exactly what he reads on the RPDR at stands 17-24.
When he comes to stand 21, he is questioned:
"roll diameter changed?"
He answers "yes" and enters 164. Using BYBLOCK is that simple.
From the new output report, the changed states of stands 21 and 22, as shown in
Fig 3, are easily seen.
--------------------------------------------------------------------------
OV b1t h1t b1r h1r r maxw gap dnom dwor
RD drn h1r b1r maxw gap dnom dwor
17 OV 13.37 8.20 12.41 8.19 7.50 12.81 1.00 210 203.91
18 RD 9.43 A 25 9.43 9.44 9.94 1.00 210 202.41
19 OV 12.50 6.60 11.41 6.60 7.57 11.76 1.00 210 205.25
20 RD 7.96 A 25 7.96 7.95 8.32 1.00 210 203.71
21 OV 10.15 5.80 9.15 5.97 5.89 9.84 0.67 164 159.46
22 RD 6.73 A 25 6.73 6.92 7.19 0.50 170 164.50
23 OV 8.25 5.01 7.76 5.01 4.65 7.97 0.50 170 166.23
24 RD 5.67 A 25 5.67 5.66 6.02 0.50 170 165.40
--------------------------------------------------------------------------
Fig 3 - Summarised output data after manual operation
------------------------------------------------------------------------------------------------
After replacing 170mm rolls with 164mm rolls at stand 21, BYBLOCK advises
the operator to increase the roll gap from its original 0.50 mm to an actual
0.67 mm. Consequently, the actual oval height becomes 17 hundredths of a
millimetre greater than the theoretical oval height, which here was affected
by one of those minimal differences mentioned above - 5.81 in Fig 2 and 5.80
in Fig 3. The actual oval width shrank from 9.28 mm to 9.15 mm.
Similar adjusting calculations could have been performed in M-MODE if the roll
shop supplied rolls with same diameter but slightly different groove dimensions.
__________________________________________________________
BOX
BYBLOCK is one of the programs developed for automatic
roll pass design by the LINEBOW software house. For full
details about the LINEBOW production, see the LINEBOW
Home Page - World Wide Web site http://www.passdesign.com
__________________________________________________________
Reference
1 A Izzo, Roll Pass Design Software for Wire Rod Blocks, Steel Times,
Jan 1997 (p14)
(*) Published by Steel Times International, March 1998 (p31)
(**) Via Garda 2, I-10015 Ivrea, Italy. Phone +39 0125 616 768,
fax +39 02 700 500 073, e-mail info@passdesign.com