What is CFRP?
CFRP (Carbon Fiber Reinforced Plastic) is an advanced light weight composite material made up of carbon fiber and thermosetting resins.
Machining Carbon Fiber for Post Processing
Machining carbon fiber – post processing is the final phase and once complete, the CFRP part is ready to be put into assembly. In post processing, carbon fiber trimming removes excess material if needed and cutting carbon fiber is used to machine part features into CFRP. Using a robotic waterjet or robotic router- unrivaled accuracy and speed using robotics for CFRP post process trimming, and laser software and router software technology can make all the difference.
Robotic carbon fiber trimming systems are easy to use, easy to maintain and easy to recover. Learning Path Control (LPC), and Learning Vibration Control (LVC) combined with Adaptive Process Control (APC) technologies supercharge the speed of the robotic trimming up to 60% beyond what is possible out of the box. Accufind and iRCalibration are technologies that use IR and CCD vision technology to keep pinpoint path accuracy while maintaining high speed cutting of the CFRP.
Waterjet, dry router and wet router technologies can all be suitable for carbon fiber trimming or cutting carbon fiber depending on the properties of the part and the production requirements. A variety of studies and tests are available to find the most optimal carbon fiber cutting solution for the specific CFRP part.
The Fiber in CFRP
CFRP starts as an acrylonitrile plastic powder which gets mixed with another plastic, like methyl acrylate or methyl methacrylate. Then, it is combined with a catalyst in a conventional suspension or solution polymerization reaction to form a polyacrylonitrile plastic.
The plastic is then spun into fibers using one of several different methods. In some methods, the plastic is mixed with certain chemicals and pumped through tiny jets into a chemical bath or quench chamber where the plastic coagulates and solidifies into fibers. This is similar to the process used to form polyacrylic textile fibers. In other methods, the plastic mixture is heated and pumped through tiny jets into a chamber where the solvents evaporate leaving a solid fiber. The spinning step is important because the internal atomic structure of the fiber is formed during this process.
Then the fibers are washed and stretched to the desired fiber diameter. The stretching helps align the molecules within the fiber and provide the basis for the formation of the tightly bonded carbon crystals after carbonization. Before the fibers can be carbonized they must be chemically altered to change their linear atomic bonding to more stable ladder bonding. To do this, the fibers need to be heated in air to around 380-600 F for an hour or so. This makes the fibers pick up oxygen molecules and rearrange the atomic bonding structure. Once this process is complete the fibers will be stabilized.
Once the fibers are stable, the carbonization process begins. The fibers are heated to 1800F to 5300F for a few minutes in a furnace filled with a gas mixture and no oxygen. A lack of oxygen prevents the fibers from catching fire at the high temperatures required for this step. The oxygen is kept out by an air seal where the fibers enter and exit the furnace and keeping the gas pressure inside the furnace higher than the outside air pressure. While the fibers are heated they start to lose their non-carbon atoms in the forms of gasses like water vapor, ammonia, hydrogen, carbon dioxide, nitrogen and carbon monoxide.
As the non-carbon atoms are removed, the remaining carbon atoms start to form tightly bonded carbon crystals that align parallel to the long side of the fiber. After this carbonization process is finished, the fibers will possess a surface that does not bond well. In order to give the fibers better bonding properties their surface needs to be oxidized, giving the fibers a rough texture and increasing their mechanical bonding ability.
Next is the sizing process. For this the fibers are coated with a material such as epoxy or urethane. This protects the fibers from damage in the winding and weaving phase. Once the fibers are coated they’re spun into cylinders called bobbins. The bobbins are then put in a machine that twists the fibers into yarns. Those yarns can then be used to weave a carbon fiber filament fabric.
In the next step a lightweight, strong durable skin is created using a process called overlay. In this process carbon fiber fabric is laid over a mold and combined with resin to create its final shape. There are two methods that can be used to for the overlay process. The first is called “wet carbon fiber layup”. For this process a dry carbon fiber sheet is laid over the mold and wet resin is applied to it. The resin gives the carbon fiber stiffness and acts as a bonding agent. The second process is called “pre-preg carbon fiber lay up”. This process uses fiber that is impregnated with resign. Pre-preg lay up provides much more uniform resin thickness than the wet lay up method due to superior resin penetration in the carbon fiber. There’s also Resin Transfer Molding (RTM)- which takes place in the next step but combines the molding step and preform carbon fiber resin transfer step into one process; more on RTM below.
Now that the CFRP prepared for forming, it’s time to mold it into a permanent shape. There are variety of techniques that can be used for the molding process. The most popular is compression molding. Compression molding involves two metal dies mounted in a hydraulic molding press. The CFRP material is taken out of the lay up and placed into the molding press. The dies are then heated and closed on the CFRP and up to 2000psi of pressure is applied. Cycle time can vary depending on part size and thickness.
Recent breakthroughs such as BMW’s “wet compression molding” process have dramatically decreased compression mold cycle time. Resin transfer molding or “RTM” is another commonly used molding technique. Like compression molding, it features dies mounted in a press that close on the preform CFRP. Unlike compression molding, resin and catalyst are pumped into the closed mold during the molding process through injection ports in the die. Both the mold and resin may be heated during RTM depending on the specific application. RTM can be preferable to other molding methods because it reduces the steps to create CFRP by combining some of the tradition preform phase steps into the molding phase.
Work order software (CMMS software) is a key part of a successful equipment maintenance program. Work orders are typically one or more tasks assigned to one or more maintenance personnel for the purpose of equipment item. These tasks are for preventive maintenance, projects, repair maintenance or other types of work. The maintenance staff enters, updates, assigns and closes work orders. This requires a certain level of commitment to the work order software and the expectation of benefits for the expended effort. As such, promoting the benefits of maintenance software is every bit as important and making the work order software easy to use.
- What are the benefits of work order software to your organization?
- How are the benefits of work order software promoted to maintenance employees?
Benefits of Work Order Software to Your Organization
The immediate and short-term benefits of using this software are as follows.
- Easier delivery and communication of work assignments.
- Balanced workload.
- Improved spares management.
- Better management and accountability of work assignments.
- Improved equipment reliability.
- Cost savings through analysis and resulting process improvement.
One of the main benefits this software is the ability to deliver the work assignments to personnel using a paperless system. Work orders are emailed in user-friendly formats such as Adobe Acrobat. This saves paper and consistently delivers the work assignments to the same place every time. Alternatively if a paper system is preferred, then automatic printing of assigned tasks is possible. Some more advanced software solutions provide scheduled automatic task assignments. This capability also frees up the maintenance manager as manual assignments ate reduced substantially with this automated system. Lastly, work orders are accessible directly from the software itself. This avoids email and paper use; however, access to a computer that either has the software loaded or has a web link to the CMMS system is required in this case.Balancing the workload over time and resources is possible with a scheduling tool such as work order software. Organizing tasks based upon available resources optimizes these resources and results in more work completed in the same amount of time. Spares linked to work templates results in automatic spares usage and allocation to the task. This feature of many CMMS solutions results is consistent use of the correct spare part for the job and better accounting of spares use. Some CMMS systems provide live links to equipment runtime components (such as hour meters) further automating the work assignment procedure.
In addition to immediate and short-term CMMS benefits long-term benefits may accrue in as little as six months depending upon level of use. The more the software is used the greater the benefits in general. Below is a listing of some of the long-term benefits of using work management software.
- Querying the work history database simplifies compliance reporting.
- Analysis of work history guides the maintenance manager in allocation of work.
- Reporting spares usage provides a guide for restocking.
- Reliability and overall equipment effectiveness KPIs optimize task assignments adding tasks in some cases and removing tasks in other cases.
Promoting the Benefits of Work Order Software to Employees
Choosing equipment maintenance software that is intuitive and accessible is a key factor in promoting the use of the software. Additionally, user screen customization is beneficial in that it gives the user a sense of personalization and control over the system. This user-level customization generally relates to screen colors, default screen, screen labels and other preferred settings. Configuring the software so that maintenance users are able to manage their own work has benefits as well. Studies have shown that a sense of accomplishment with work is a primary job satisfaction indicator. Use of work order software provides this satisfaction as maintenance employees see exactly what work is required and close out their own work orders. In many cases, this leads to improved morale and greater productivity. This is only possible if user level roles and permissions are available within the software.By adopting this management style, users feel empowered and feel a greater sense of ownership of the equipment they are working on. Once again, this leads to improved morale and productivity.
Another group of software user are the personnel that request work. Making it simple for an inexperienced worker to submit a repair ticket to the software encourages the use of the system. In many cases a web interface is best for this function as it is accessible from many locations and various devices.
Promoting the benefits of work order software benefits your organization with the ultimate result of improving equipment reliability and the reducing maintenance costs.