Scrap Tracking

 One of the benefits of computer integrated manufacturing (CIM) on a roll forming machine is the fact that the machine controller knows a lot about the material that is run through the machine.  When properly configured, the controller knows every bit of good or scrap metal that is processed on the roll former.  This information can be recorded and tracked for subsequent analysis.  With CIM, you can see how much scrap is generated, the reasons behind the scrap, and possible correlations (with machines, operators, products, vendors, etc).  This information can be used to:

• Determine actual profitability
• Support continuous improvement projects aimed at scrap reduction
• Review material vendors' performance
• Justify capital improvement spending
• Improve operator performance
• Direct maintenance efforts

The XL200 machine controller and Eclipse production management software from AMS are perfectly placed to help manufacturers see exactly how much scrap is being produced and the causes for this.  At the machine, the XL200 monitors every millimeter of material that goes through the machine.  Every machine operation that creates good parts or scrap is carefully tracked and recorded.  In cases where significant scrap is created, the XL200 will require that the operator indicate the reason for the scrap.
 
Reasons for Scrap

The causes of scrap can vary based on the industry and type of equipment.  For this reason, Eclipse is designed so that you can decide how you would like to categorize scrap in your operations.  Additionally, you can organize or group your scrap reasons into areas of responsibility.  Here are some common examples of such groupings:

• Engineered - This includes shear kerf (amount of material lost due to the cutting process)
• Changeover - Scrap caused by switching products or coils
• Vendor - Material defects (finish, camber, out of specification, etc)
• Operator Induced - Scrap due to improper machine adjustments or procedures
• Unplanned Maintenance - Scrap related to machine reliability (i.e. dull shear blade causing a crash)

When scrap-generating events occur on the machine, the XL200 will prompt the operator for the reason for the scrap.  So that the operator isn't overwhelmed with a huge selection of scrap reasons, it is usually best to keep the number of reasons to a minimum.  For some customers, this may be 5-10 and for others the minimum might be as high as 25 (the XL200 is capable of 99 maximum).  It is possible to setup different lists of scrap reasons per machine or per machine group.  For reporting purposes, it is very helpful to keep as much consistency as possible.  This is especially true at the scrap grouping level.  For example, machines that run pre-painted material might have a much different list of scrap reasons than a machine that only runs galvanized steel.  Even so, if the groupings are defined correctly, it should still be possible to compare how much scrap was generated because of material defects regardless of the machine.

How Scrap is Generated

In the raw data that is captured by the XL200, scrap is defined as the difference between the material used and the length of good products produced.  For example:

 
After running these 5 parts, the XL200 would create a production record showing that 7525mm of material was consumed from the current coil for the 5 parts produced.  Each part consumes 1505mm because of the kerf.  Therefore, the scrap is calculated as: material consumed - (quantity produced * part length).  In the example given, the scrap = 7525 - (5 * 1500) = 25mm.

The following is a list of the typical events on a roll former that generate scrap:

Kerf - Typically this is because of a shear operation although there are some cases where forming presses can "consume" material.

Manual Shear - This occurs when there is some length of material past the shear and the operator manually fires the shear.  The XL200 has a parameter to specify the maximum length that can be manually sheared without requiring a reason.  For example, if the operator is only cutting off 2 inches, it is probably not worth the time to ask for the reason why.  In this case the scrap is reported back with a code of 0 (normal production scrap).

Coil "Tail-Out" - When a coil is completely used and the end of the coil goes past the tail-out sensor on the roll former, the XL200 will automatically stop the machine.  Since the tail-out sensor is normally located at the same distance as the encoder, the material is no longer being tracked by the encoder.  The XL200 remembers the length of material past the shear when the end of the coil hit the tail-out sensor.  This length is added to the "shear to encoder distance" setup parameter and that total is reported back to Eclipse as scrap.  There is a parameter in Eclipse which can be used to assign this scrap to a particular scrap code.

Coil Loading - As soon as the leading edge of a new coil hits the tail-out sensor, the XL200 sets the current length past the shear to a negative number (shear to encoder distance).  The material can be jogged (inched) through the machine until it is through the shear.  The operator would then manually shear to get a clean edge.  The length of the manually sheared part should be fairly accurate.  In cases where there are punches, there are punches on the part, there is a method to load the machine in a semi-automatic mode that minimizes the scrap (described in an article about using 2 encoders for scrap savings).  Very often, the outer wrap (or more) is damaged and cannot be used.  The operator will jog out enough material past the shear until the quality is acceptable.

Remaking Bad Parts - There are two ways to make up for defective parts on the XL200: the increment quantity key or the remake function.  Increment quantity is used to make up for defective parts while the machine is still running the item.  Each time the key is pressed, the XL200 reduces the quantity completed for that item by one.  The remake function can be used for any item regardless of whether or not it has been completed.  With this function, you can tell the controller how many parts to remake and what scrap reason to use.  In both cases, the new parts produced will show up in the production data as material consumed but no parts produced (scrap). 

Running Out Bad Material - In cases where the operator can see there is a section of bad material on the coil, he can add a temporary item to the controller and run scrap parts from that item until the defective material clears up.  These parts are commonly sold as "seconds" or might be used as cover sheets in the case of roofing or wall panels.  For these parts, the bundle number field can be used to indicate what scrap code to use.  Any bundle number 900 or above is considered scrap.  For example, if scrap code 5 is for bad paint, the operator would program an item with bundle number 905 and run parts from this until the paint was okay again.  Once the material is back to normal, the operator can switch back to the production order.

Weld Quality Sensors - Many tube & pipe machines have sensors that monitor the quality of the weld.  If there is a problem with the weld, these sensors turn on the weld detect input on the XL200CLT controller (tube version) and the controller will automatically start cutting up these bad parts as scrap and dump the parts to the scrap side (if the machine has this option).  These parts are recorded in the production data as scrap.  Once the weld is okay again, the controller automatically returns to normal production.

In some cases it may be possible to rework previously scrapped parts and use them on another production order.  In this case, the operator can use the "decrement quantity" function to reduce the number of parts left to produce for the item.  This is recorded in the production data as negative scrap (since there are parts produced but no material consumed).  In some of the reports in Eclipse, this will show up as "reclaimed scrap".

Reporting

Each production record that is generated by the XL200 has a wealth of information including the date, time, operator, order, product, material, coil ID, part length, scrap produced, etc.  This information is used as the basis for all reports in Eclipse and also can be uploaded to your ERP system on a real-time basis.  The following reports include details about scrap generation:

Production Summary - Shows a summary of information for each machine and shift over a specified date range.  The data displayed includes total good production (length & weight), total scrap produced (length & weight), scrap %, reclaimed scrap, total parts produced, number of coil changes, material changes, tooling changes, run time & percentage and average running speed.

Scrap Summary - With this report, you can see a summary of scrap generation from various angles.  One of the most common is a Pareto analysis showing scrap reasons in descending percentages (the first scrap reason listed is the largest percentage).  For each scrap reason, the following is shown:  total scrap length, percentage by length, scrap weight, percentage by weight, the average length per occurrence and the total number of occurrences.  The scrap reasons can also be listed with groupings and sub-totals.  This report can be shown by machine, machine group, shift, operator, date, material type, material thickness, product code, etc.  These variations are helpful to show correlations.

Coil Summary - This series of reports can show the amount and percentage of scrap per coil as well as a detailed breakdown of the reasons for scrap for each coil.

Operating Efficiency (OEE) - This report shows the OEE values (Overall Equipment Effectiveness) for each machine and date.  OEE includes three sub-factors: availability % (run time/available production time), speed % (actual speed/target speed), and yield % (good production/total production).  The yield factor is simply 100% minus the scrap %. 
 
Summary

The scrap tracking and reporting features of the XL200 machine control and Eclipse production management software can provide your organization with key information that can help you improve profitability and stay competitive.