Split Rolls
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Testimonials for Split Rolls
Solid roll tooling, the industry standard for years, is not your only tooling choice for tube and pipe production. One option that is available from ROLL-KRAFT is split roll tooling. Its use can increase the cost effectiveness of your tube and pipe operation by reducing overall tooling cost. Very simply, split rolls are tube rolls made in two sections and bolted together into one unit.
For all practical purposes, they look and work the same as solid rolls. However, the differences between the two are numerous. Rework procedures are different, the “size” of reworked rolls is not the same and down time is reduced when using split rolls due to fewer mill adjustments between regrinds. Let's look at split roll theory and its advantages. After reading this information, you may decide that converting your mill(s) to split roll tooling can be beneficial to your manufacturing operation.
The theory of split roll design is very simple. It states that the throat diameter of the roll is maintained after each rework, holding the mill speed constant with no adverse effect on the roll's ability to drive the tube. In effect, the roll “size” from a shaping and driving standpoint, does not change when a split roll is reworked.
Tool wear and rework are a fact of life in the tube and pipe business. In order to maximize tool life, roll wear must be monitored and rework scheduled on a regular basis. However, using split rolls will change your established schedule for rework to your benefit by allowing you to rework only those rolls that require it. To understand this, it is necessary to look at roll wear and the process of reworking split rolls compared to recontouring solid rolls.
Tube rolls will wear in the areas of the roll that perform the most work (shaping and driving). On a typical roll, this is in the two radii and the throat diameter (see FIGURE 1).
Also, fin pass and sizing rolls wear quicker than breakdown rolls. When a solid roll is reworked, the throat diameter is reduced to restore the contour to its original shape (see FIGURE 2). This reduction in throat diameter can have some adverse effects on mill set up and tube production.
In addition, on driven passes, the bottom line of the tube (metal line) drops in order to make full contact with the reworked bottom roll. If the mill does not allow for shimming of the bottom driven roll shafts to correct for the drop caused by rework, the metal line alignment of the mill will be drastically affected.
For example, if the fin section is reworked and cannot be shimmed up to match the metal line of the breakdown section, the strip will run down hill from last breakdown to the first fin, causing buckling, bending and marking of the tube.
If the fin section can be shimmed, the decreased speed of the reworked solid rolls can be controlled if the mill has multiple drives, and trim RPM control to adjust RPM for each drive. For instance, if the breakdown rolls are driven separately from the fin pass section, the fin passes can be adjusted faster to coordinate with the rest of the line speed. If this shimming and speed adjustment is not possible, the breakdown passes would have to be reworked regardless of the amount of wear.
As you can see, reworked solid rolls require substantial readjustment of your mill before production can resume. On the other hand, split rolls can eliminate most of this readjustment and get your mill back on line in a shorter period of time.
As mentioned, a split roll is made in two sections and joined together as one roll. Wear patterns and wear rates are the same as those seen on solid rolls, but, when rework is required, the recontouring is performed differently. Figure 3 is a cross sectional view of a typical split roll in two sections.
To rework this style of roll, the sides are ground to narrow the overall width, then, the original contour is re-cut into the roll by taking material from the flanges without reducing the throat diameter. The only change required to the mill set up is the installation of longer spacers to compensate for the narrower reworked rolls. The potential problems seen with solid rolls (the shimming up of driven passes and variable roll speed) are eliminated. Figure 4 illustrates the reduction of width on a split roll after numerous regrinds.
Deciding to Use Split Roll Tooling
The real benefits can only be realized if you are set up for large production runs. The savings in set-up time alone can justify the use of split roll tooling because down time on large runs is money. In addition, the extended life of the tooling will offset the extra initial cost.
With experience in designing and manufacturing split rolls, we will help you perform a comprehensive analysis on your mill to determine if split roll tooling can be economically beneficial to your tube or pipe operation. Additional mill requirements are detailed on the back page. Before you decide to convert to split roll tooling, give us a call at 888-953-9400.
Mill Requirements for Using Split Roll Tooling
By design, split rolls are wider than solid rolls for an equivalent tube size. The extra width is found in the flanges. Due to this fact, the mill that is being considered for conversion to split roll tooling must have sufficient roll space. ROLL-KRAFT's engineering department can assist you in analyzing your present mill to determine if split roll tooling can be installed.
Another important consideration is the number of motor drives on your mill. As mentioned, breakdown rolls usually do not wear as quickly as fin and sizing pass rolls; therefore, conventional solid rolls can be used for breakdown passes only if the mill has individual drives for each section (breakdown, fin and sizing). A single drive mill would require a complete set of split rolls in order to keep mill speed constant. One benefit from using split rolls on such a mill is extended tool life. The number of regrinds far exceeds the number possible with conventional rolls. This should offset the higher initial cost of split rolls.
A two motor drive mill should also use a complete set of split rolls. On such a mill, the second drive is for the sizing section. Mixing solid rolls for breakdown (remember, the speed will change after rework) and split rolls for fin passes (roll speed is constant after rework) does not allow for mill speed adjustment. Marking of the tube can result. A partial set of split rolls can be used in this case. Like a single drive mill, cost savings can be realized from longer tool life.
A three motor drive mill is ideal for split roll tooling. Solid rolls are used in the breakdown passes and split rolls are used for the fin and sizing passes. Although roll speed will change when the breakdown rolls are reworked, their speed can be adjusted without changing the speed of the rest of the mill. Keep in mind that if you are using solid rolls, the breakdown passes are reworked to control mill speed when the fin passes are reworked, even though the amount of wear would indicate it is not necessary. Using solid rolls for breakdown with split rolls in the fin and sizing sections reduces the number of times the breakdown passes are reworked. This extends tooling life and saves money.
Another possible combination of split and solid roll tooling in a three drive mill is the use of split rolls on the bottom in the breakdown section. Bottom rolls wear quicker than the top roll in this section of the mill; therefore, it makes sense that the bottom rolls will require rework before the top rolls. If you are using solid tooling, both rolls would have to be reworked at the same time to maintain compatibility with one another.
But, if split rolls are being used on the bottom only, they can be reworked when required, maintaining compatibility with the top rolls and eliminating the need to shim the mill because throat diameter is not reduced.
Additional Resources
Contact a sales rep regarding this product
Contact a sales rep regarding this product
Testimonials for Split Rolls
Solid roll tooling, the industry standard for years, is not your only tooling choice for tube and pipe production. One option that is available from ROLL-KRAFT is split roll tooling. Its use can increase the cost effectiveness of your tube and pipe operation by reducing overall tooling cost. Very simply, split rolls are tube rolls made in two sections and bolted together into one unit.
For all practical purposes, they look and work the same as solid rolls. However, the differences between the two are numerous. Rework procedures are different, the “size” of reworked rolls is not the same and down time is reduced when using split rolls due to fewer mill adjustments between regrinds. Let's look at split roll theory and its advantages. After reading this information, you may decide that converting your mill(s) to split roll tooling can be beneficial to your manufacturing operation.
Split Roll Theory
The theory of split roll design is very simple. It states that the throat diameter of the roll is maintained after each rework, holding the mill speed constant with no adverse effect on the roll's ability to drive the tube. In effect, the roll “size” from a shaping and driving standpoint, does not change when a split roll is reworked.
Tool wear and rework are a fact of life in the tube and pipe business. In order to maximize tool life, roll wear must be monitored and rework scheduled on a regular basis. However, using split rolls will change your established schedule for rework to your benefit by allowing you to rework only those rolls that require it. To understand this, it is necessary to look at roll wear and the process of reworking split rolls compared to recontouring solid rolls.
Tube rolls will wear in the areas of the roll that perform the most work (shaping and driving). On a typical roll, this is in the two radii and the throat diameter (see FIGURE 1).
Also, fin pass and sizing rolls wear quicker than breakdown rolls. When a solid roll is reworked, the throat diameter is reduced to restore the contour to its original shape (see FIGURE 2). This reduction in throat diameter can have some adverse effects on mill set up and tube production.
In addition, on driven passes, the bottom line of the tube (metal line) drops in order to make full contact with the reworked bottom roll. If the mill does not allow for shimming of the bottom driven roll shafts to correct for the drop caused by rework, the metal line alignment of the mill will be drastically affected.
For example, if the fin section is reworked and cannot be shimmed up to match the metal line of the breakdown section, the strip will run down hill from last breakdown to the first fin, causing buckling, bending and marking of the tube.
If the fin section can be shimmed, the decreased speed of the reworked solid rolls can be controlled if the mill has multiple drives, and trim RPM control to adjust RPM for each drive. For instance, if the breakdown rolls are driven separately from the fin pass section, the fin passes can be adjusted faster to coordinate with the rest of the line speed. If this shimming and speed adjustment is not possible, the breakdown passes would have to be reworked regardless of the amount of wear.
As you can see, reworked solid rolls require substantial readjustment of your mill before production can resume. On the other hand, split rolls can eliminate most of this readjustment and get your mill back on line in a shorter period of time.
As mentioned, a split roll is made in two sections and joined together as one roll. Wear patterns and wear rates are the same as those seen on solid rolls, but, when rework is required, the recontouring is performed differently. Figure 3 is a cross sectional view of a typical split roll in two sections.
To rework this style of roll, the sides are ground to narrow the overall width, then, the original contour is re-cut into the roll by taking material from the flanges without reducing the throat diameter. The only change required to the mill set up is the installation of longer spacers to compensate for the narrower reworked rolls. The potential problems seen with solid rolls (the shimming up of driven passes and variable roll speed) are eliminated. Figure 4 illustrates the reduction of width on a split roll after numerous regrinds.
The real benefits can only be realized if you are set up for large production runs. The savings in set-up time alone can justify the use of split roll tooling because down time on large runs is money. In addition, the extended life of the tooling will offset the extra initial cost.
With experience in designing and manufacturing split rolls, we will help you perform a comprehensive analysis on your mill to determine if split roll tooling can be economically beneficial to your tube or pipe operation. Additional mill requirements are detailed on the back page. Before you decide to convert to split roll tooling, give us a call at 888-953-9400.
Mill Requirements for Using Split Roll Tooling
By design, split rolls are wider than solid rolls for an equivalent tube size. The extra width is found in the flanges. Due to this fact, the mill that is being considered for conversion to split roll tooling must have sufficient roll space. ROLL-KRAFT's engineering department can assist you in analyzing your present mill to determine if split roll tooling can be installed.
Another important consideration is the number of motor drives on your mill. As mentioned, breakdown rolls usually do not wear as quickly as fin and sizing pass rolls; therefore, conventional solid rolls can be used for breakdown passes only if the mill has individual drives for each section (breakdown, fin and sizing). A single drive mill would require a complete set of split rolls in order to keep mill speed constant. One benefit from using split rolls on such a mill is extended tool life. The number of regrinds far exceeds the number possible with conventional rolls. This should offset the higher initial cost of split rolls.
A two motor drive mill should also use a complete set of split rolls. On such a mill, the second drive is for the sizing section. Mixing solid rolls for breakdown (remember, the speed will change after rework) and split rolls for fin passes (roll speed is constant after rework) does not allow for mill speed adjustment. Marking of the tube can result. A partial set of split rolls can be used in this case. Like a single drive mill, cost savings can be realized from longer tool life.
A three motor drive mill is ideal for split roll tooling. Solid rolls are used in the breakdown passes and split rolls are used for the fin and sizing passes. Although roll speed will change when the breakdown rolls are reworked, their speed can be adjusted without changing the speed of the rest of the mill. Keep in mind that if you are using solid rolls, the breakdown passes are reworked to control mill speed when the fin passes are reworked, even though the amount of wear would indicate it is not necessary. Using solid rolls for breakdown with split rolls in the fin and sizing sections reduces the number of times the breakdown passes are reworked. This extends tooling life and saves money.
Another possible combination of split and solid roll tooling in a three drive mill is the use of split rolls on the bottom in the breakdown section. Bottom rolls wear quicker than the top roll in this section of the mill; therefore, it makes sense that the bottom rolls will require rework before the top rolls. If you are using solid tooling, both rolls would have to be reworked at the same time to maintain compatibility with one another.
But, if split rolls are being used on the bottom only, they can be reworked when required, maintaining compatibility with the top rolls and eliminating the need to shim the mill because throat diameter is not reduced.
Additional Resources
Contact a sales rep regarding this product
