Industrial flow

Optimizing job flow through improvements in cutting, sorting and bending operations

by Kurt Debbaut, Cadman product manager, LVD Co. nv

 

 

 

The explosion of Industry 4.0 and the associated trends such as Internet of Things, Smart Factory and Big Data has complicated the understanding of the next industrial revolution and its significance. But moving to Industry 4.0 is fundamentally about optimizing production flow.

 

How can small and mid-sized fabricators stay competitive in this age of small batches, complex parts and tight margins? When fab shops are forced to turn around jobs in days or hours as opposed to weeks, how can build cycles be shortened? These are just some of the questions addressed by the introduction of Industry 4.0 on a shop floor.

 

To create a more productive and profitable shop, fabricators should start by evaluating the big picture – a view that comes into focus by using software and machines that provide historical and real-time data to inform decisions, which will inherently optimize job flow.

 

An industrial-strength Windows-based tablet provides real-time data of the entire fabrication operation.

 

 

 

The essence of flow

There are three primary processes in sheet metal fabrication: cutting, sorting and bending. Improving production flow starts with gathering the data to help analyze the performance of these processes. Machines that work with and communicate to a centralized database are able to generate this data.

 

Traditional sheet metal production methods have mostly grown out of a cost-based system. In this system, the operator touch-time is calculated, creating work in process (WIP) and stock, but less focus is placed on overall lead times.

 

According QRM methodology, the only important key performance indicator is delivery performance. 

 

 

With industry evolving toward ultra-short lead times, it’s necessary that the production focus shift from cost-based to flow principles where Quick Response Manufacturing (QRM) is key. QRM is an improvement method designed for high-product-mix operations.

 

An Industry 4.0-enabled sheet metal shop uses a combination of a cost-based and time-based system and operates using real-time information to drive the flow. In the Industry 4.0-integrated shop, the QRM approach means that no or only minimal buffers are allowed. A longer buffer threshold improves overall equipment effectiveness (OEE), but also increases lead times and WIP. The only important key performance indicator is delivery performance. 

 

A 3-D file importer makes generating estimates from imported CAD files faster and easier. Files are imported and stored as OSM (open sheet metal) in a centralized database.

 

 

The QRM doctrine states: Working on an order destined for a downstream workcell that is not available will only increase inventory and lead time. In other words, launch the job in production the moment there is capacity at every step of the production process.

 

A job that is sitting in a queue as WIP impacts flow and, therefore, throughput. Production bottlenecks, such as sorting parts out of a combined nesting order and organizing the parts belonging to the same production order after laser cutting operations, also disrupt flow.

 

Considering this, creating a nesting for a part needs to happen at the last possible moment, just before the cutting process starts for the orders that are due first. This guarantees that the nested part program is the most efficient nesting and that the subsequent cutting process will produce the parts that are due. Getting the flow right is all about finding the right balance between flow efficiency, which leads to less WIP, and resource efficiency, which leads to better OEE.

 

An integrated software system connects the front office and shop floor to generate and manage jobs for increased throughput, minimized setups and streamlined work flow.

 

 

An integrated system

How can any fabrication shop realize better flow? First, it’s important to keep the digital communication lines open with master/upstream business systems, such as ERP, production planning, MES, CRM and quotation management software.

 

Second, use offline CAM software for fabrication machinery (for bending, laser cutting and punching) in conjunction with production management software. These independent software modules should be able to connect to one centralized database where they can share data.

 

Sheet metal fabrication machines equipped with Industry 4.0-enabled controllers can also connect to the centralized database and, upon finalizing a job, can provide real production data, which can be used to create the reverse calculations.

 

Let’s consider how an example of how an integrated system would flow. It starts with a request or quotation of a 3-D drawing of the product, which is sent to the drawing importer software. This software module imports the drawing, checks if the CAD drawing is correct, stores the OSM (open sheet metal) in the software database and calculates the cost drivers based on part level.

 

 

 

 

 

Today’s offline bending software automatically calculates the correct unfolding of a part considering the necessary bend allowance and internal radius based on the selected machine and available tooling.

 

 

 

In the master business level, the quotation management software can then generate the quotation with the calculated values coming from the drawing importer software. A quotation is sent out.

 

The next step is generation of the actual order. The order needs to be entered in the ERP system, which is where all the operations are scheduled. For sheet metal parts, all the relevant information is recorded: part, quantity, due date for 2-D, due date for 3-D, operations and possibly documentation such as instructions, additional information and so on) and then sent to the production control software.

 

Based on the part level, the production control software launches the offline bending software, which is running in watch mode on the server. This will in turn calculate the correct unfolding of the part, taking into account the correct bend allowance and internal radius based on the selected machine and available tooling.

 

From this, the software calculates the bend solution (tool position, tools stations, bend sequence) and generates the 2-D DXF file with cutting contours. Because this is handled almost entirely automatically, most of the CAM work is reduced to virtually zero. This means operators and engineers can focus their expertise on finding solutions for complex parts for which the software is not currently able to calculate automatic solutions. 

 

Just before the due date for 2-D, the production orders are sent to the nesting software (laser cutting, punching, waterjet, plasma cutting, etc.) within a certain time buffer. This results in a program for the cutting machine.

 

In the shop, the operator receives the job list on his controller with the relevant information needed to load the machine (material, sheet size and thickness, quantity of sheets in the job and calculated cutting time). The operator loads the sheets on the machine. Within the batch, the different jobs are optimized in sequence to minimize tool changes (nozzle and/or lens). Then the parts are cut.

 

Once the parts are cut, the operator needs to know how to “sort and validate” the parts. Using a tablet computer, the operator receives the relevant information about the production orders in the nesting and gets information about the next operation (“sort”). The operator then confirms the quantity of parts available on the pallet (“validate”).

 

This information is visible in real time via the offline programming software. Back in the office, the production manager can decide to send these production orders in a job list to the press brake controller where the operator receives the relevant information to execute the job.

 

All the bundled jobs sent to the controller are optimized in function of fewest possible tool changes. The operator finishes the bend job by entering the quantity of produced good/not good 3-D parts (“validation of the 3-D process”). The production data from all machine controllers is logged into the software database, and detailed information, also for reverse calculation, is fed back to the ERP system, closing the loop.

 

Optimizing production flow inevitably helps fabricators address the shortage of skilled labor. A better job flow reduces the burden on the operator. Because the software develops every step needed to make the part, it simplifies the operator’s tasks, reduces the likelihood of mistakes and removes the need for highly trained workers, allowing fabricators to do more with less.

 

LVD Strippit

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