CNC production is one of the most sophisticated fabrication processes in the industry because of its ability to produce complex, intricate, precise, accurate, and structurally reliable parts. There are intensive series of phases to go through before arriving at a finished product with the desired quality, starting from customer parts design, planning, production proper, quality assurance, and finally, packaging and shipping. Below is a brief description of each of these phases in CNC manufacturing:
1. Customer parts design
The starting point of CNC manufacturing begins with the part design provided by customers. Their design may come in the form of 2D technical drawings or 3D CAD models. This will then be interpreted/ converted into a CAM (computer-aided manufacturing) program for the CNC machine to run on. CNC parts must be carefully designed to avoid mishaps and undesired losses when pushed through in the CNC production. A poorly designed part will waste plenty of resources, including time, effort, and material. Explore more Low volume production services here.
One thing to note about CNC fabrication is that the complexity and tolerance requirement for the finished part will greatly impact the production cost as a whole. The reason for this is that special features require different processes. With this, it is important to consider the constraints and complexity in designing for machining parts.
2.Technical and Production Planning
After the design of the part has been dealt with, it is now time to start cranking up the production plan. Depending on a fabrication shop, this plan may be split into two divisions: the technical and the production aspect.
Technical planning is the skeletal framework of CNC manufacturing to enable a successful production process. The people involved in this phase will be manufacturing engineers. They are responsible for plotting out CNC programs, planning for toolings, and arranging efficient and economical machining processes. See our CNC machining capabilites here.
Technical plans must be created and designed to be “foolproof” so that fabrication can be smooth and error-free. In this phase, manufacturing engineers define what processes are necessary for fabricating a product (e.g., profile milling, turning, boring, drilling, facing, slotting, etc.). Moreover, they identify what the needed parameters to be maintained are. Such parameters involve cutting speed, feed rate, tooling configuration, cutting depth, and gauge length. In technical planning, the key point is dealing with the technical aspects of how a part will be processed and machined.
On the other hand, production planning is different from technical planning because it involves the arrangement of necessary factors regarding how a part will arrive as a finished part. This means planning for raw material acquisition and setting up production schedules. The production planners are responsible for drafting out prioritization plans and workforce scheduling to balance the workload and finish the products as scheduled. In short, this is the allocation of the available resources to cater to the customers’ demands.
3. Production Phase
After all the planning has been carried out and properly arranged, the production phase can now push through. It is in this proper where all the machining and production procedures are done (e.g., milling, turning, deburring, finishing, special processes, etc.). Looking at a different perspective, CNC production is not just all about the “cutting action”; it is also about maximizing all the resources for fabricating a part effectively.
In a typical CNC fabrication shop, all the movements of things are critically controlled and monitored to optimize the production capability. The CNC machines and workstations are arranged so that it will be very efficient in lessening wastes (transportation, motion, and waiting) for the whole value stream of machining a part.
Depending on the volume of parts involved, this may require a series of operations done to arrive at a finished part. Low volume parts with three or fewer quantities may be machined directly in one operation, meaning that all the necessary features will be done in one single loading until the finished product is produced. On the other hand, parts with more quantities (5 or more) involve subdividing the process into various operations for improved production efficiency. An example is, doing the roughing process for all the piece parts before going onto the finishing process. This method of production enables the efficient use of resources like tool stations. In addition to these, it makes the process convenient and easy to control.
During CNC production, it is important to stick to the process planned by manufacturing engineers as much as possible. This is where the process quality engineers enter. They ensure that the whole shop executes their processes properly. In addition to this, they evaluate the existing process in which they may plan for necessary process improvement.
4. Quality Assurance
Before sending out parts to customers, these should be checked to ensure the part’s conformance to the requirements set by the customer. The factors inspected to ensure machined parts’ quality are dimensional accuracy, surface requirements, and structural integrity. The dimensional accuracy of the part may be measured by calipers, micrometers, height gauges, and coordinate measuring machines (CMM). While, the surface requirements can be measured by surface finish gauges, surface testers, and profilometers. Finally, the structural integrity may be measured by non-destructive testing methods (e.g., magnetic particle inspection, penetrant inspection, etc.)
Depending on what standards are followed by a manufacturing shop, low volume parts production may require a 100% inspection of the parts produced. In contrast, for high volume production, inspection by sampling per lot may be done. This required quantity to be in-depth inspected will depend on the number of parts per lot.
In cases where a part is non conforming, it will undergo a product review board. Wherein a panel will deliberate what will be the necessary action to be done for the product, whether to rework a part or to scrap a part completely.
5. Packaging and Shipping
Finally, after all the procedures and the necessary quality checks are done, the machined part may now be packed and delivered to the customers. It will be in this phase where the required labels and markings are placed on the part for traceability.