WHAT YOUR SHOP NEEDS TO KNOW ABOUT PORTABLE CMMs

So, what are some of the other aspects that make rapid shop floor inspection so quick, easy and convenient? Following are a few of the most notable.

Minimal Setup
Like all hand tools, there is no pre-programming needed to start the measurement process. Simply pick the features to be measured to get the required inspection data. Another time saver is that there is no fixturing needed, which is not the case for CMM inspections and many manual measurement methods. Since the physical object is aligned to the CAD model, it can be in a random orientation. Just place the part on a table and measure a few datum points to automatically align the arm to the CAD model and begin real-time inspection.

Another advantage is that most inspections can be completed with only one or two part orientations. With a basic CMM, there are only three axes of motion, so features on sidewalls and the bottom of the part cannot be measured without another set-up. With six deg of freedom (DOF), the arm can measure everything but the bottom surface. So, in most cases two orientations expose all features of the part that are to be measured.

Portability
Although it has already been stated, portability is an advantage that is worth mentioning a second time. Lightweight and ruggedized for shop floor operations, the arm travels to the part or tool that needs to be inspected. Since the arm comes to the object, there is no wasted time or effort in transporting the work piece to a CMM and back to its original location. The arm intercepts the part or tool in its work flow to minimize process disruptions. In some cases, parts will remain on a CNC mill or in a welding fixture while measurements are made. This avoids breaking down the setup, which saves time and eliminates any possibility for repositioning error when the part is returned to its original setup.

Portability is especially crucial for oversized objects that are too big or too heavy to be transported to a CMM. With an arm, the item stays in place yet gets the thorough inspection of a 3D measurement device. Without the PCMM, the only option is to make do with gages and single dimension measurement devices. On occasion, a machine shop may want to inspect its suppliers’ parts at their facilities to avoid any surprises at the time of incoming inspection. The portability of the arm makes this possible. There is no difference in transporting the rapid shop floor inspection system 100 feet or 100 miles.

No Size Limits
The stroke of a dial indicator, Z-axis travel of a CMM or throat of a micrometer limits the size of the part that may be measured. Gages, hand tools and CMMs have fixed working envelopes or maximum linear dimensions. Although an articulated arm does have a maximum reach, its working envelope far exceeds that of the measurement tools common to a machine shop. Even a small arm with a two-foot span has a working envelope of nearly four ft. And if that is not enough, it can be repositioned to capture the balance of the dimensions that were previously out of reach.

Automated Collection, Calculation & Reporting
With any manual inspection, using either hand tools or CMMs, someone has to note the measurements, do the math and log the data to be able to report if a part is acceptable. This manual process is not only tedious and time consuming, it is also prone to error. With rapid shop floor inspection, there are no hand calculations and no manually entered data. As each measurement is taken, the software logs the data, performs background calculations and compares the result to the quality spec. When the inspection is complete, it then outputs the inspection report. This saves time, reduces labor and eliminates the possibility of clerical errors.

Rapid shop floor inspection is a versatile tool that is multi-function and multi-purpose. It offers a great deal of flexibility in how, when and where it is used. It can be used for one-time measurements like a hand tool, or it can be an alternative to a CMM for thorough evaluations to a carefully planned inspection. It can be used by the skilled tradesman, or it can be leveraged by a QA professional. It measures IDs, ODs, depths and distances like basic gages, and it calculates parallelism, true position and concentricity like an advanced CMM. While machine shops retain the traditional measurement tools, many find that they use them much less frequently after acquiring a rapid shop floor inspection system. The height gages, gage blocks, calipers and CMMs still have their uses but just not as frequently.

When to Use
The flexibility of the tool and the quickness of the process make rapid shop floor inspection a viable tool for everything from incoming inspection to final part inspection approval. Virtually anywhere that hand tools are used or nearly any inspection that relied on a CMM is a candidate for this alternative method of inspection. When a machine shop’s staff becomes comfortable with its new tool, it will also find new applications that were not considered in the past because the traditional tools were not up to the task.

Incoming Inspection
When the truck backs up to the dock, roll the arm over to meet the incoming parts. Instead of sending them to wait in the queue at the CMM, they can be thoroughly inspected as they arrive. With immediate, on-screen feedback, each is passed? or failed? before being carted into the plant. Also, the system will record all results for traceability and trend analysis.

In-Process Inspection
With the focus being shop floor inspection, the majority of the time the PCMM will be on the floor while the manufacturing operations are in process. Following are some typical examples.

(1) Checking parts in/out of the process. Before starting a new manufacturing operation or sending parts on to the next process, use the arm to confirm the quality of the part. As noted earlier, in/out inspection can even be performed while the work piece is fixtured in the CNC mill, router or lathe.

(2) Verify tooling. The quality of jigs, fixtures and dies is important to the quality of the parts that they make or align. So, use the arm to inspect them when put into service. For long-running tools, use it for routine measurements to check for wear, damage or distortion.

(3) Align parts and tools during the build. Rapid shop floor inspection is ideal for fine-tuning part alignments before assembling components. For example, use the arm to check the positioning of pieces held by a welding fixture. Adjust the parts as recommended by the inspection software before hitting them with the first tack weld.

(4) Monitor process controls. In the day-to-day operations of most machine shops, lot sizes are too small for statistical process control (SPC), PPAPs and CpKs. But this does not mean that machine shops do not have to worry about process control. Over time, process parameters shift and tools wear, so the machine shop needs to routinely check output quality to catch variance before it becomes a problem. In this area, rapid shop floor inspection helps in two ways. First, it is an ideal tool to assist in identifying the process variables that must be controlled to produce good parts. Second, it is the perfect measurement tool for spot checking to confirm that those parameters are stable.

Problem Detection and Diagnosis
When problems occur, turn the arm into an investigation tool. Rather than inspecting parts or processes to a pre-defined plan, use it to query the part to determine where the problem lies and what its root cause is. The arm offers the flexibility to conduct “what-if” diagnosis to understand the cause and effect.

Customer Approval
Before investing in an exhaustive first article inspection, confirm the critical-to-function dimensions with the arm. Since the process is easy, quick and visual, many elect to inspect the parts in front of the client. These shops claim that they have better communication with the client that leads to faster approvals. Since the inspection shows results on the CAD model, anyone on the client’s review team will be able to see the true quality of the part. This gives them immediate qualification of the features that are important to function. It also lets the shop perform impromptu measurements to clarify an important point or investigate an area of concern.

Supplier Site Inspections
When the machine shop becomes the client, the portability of the inspection tool allows it to perform all of the inspections that have been discussed at its supplier’s facility. They use the portable CMM to confirm first articles before they are loaded onto the truck. In these instances, the shop gets early detection of quality problems and a thorough set of data information that helps to diagnose a process that is no longer in control.

CONCLUSION
Rapid shop floor inspection is a versatile process that is used throughout manufacturing operations. Although sophisticated enough to satisfy the demands of the aerospace industry, it is perfect for the small or medium machine shop. Simple to learn, easy to operate and quick to report; this is an inspection system that companies of any size can easily incorporate into the manufacturing work flow. While aerospace suppliers had little choice concerning adoption of model based definitions and PCMMs, these companies have become advocates of the tools. They see how efficiently they can gather data that confirms the quality of their parts, tools and processes or identifies the source of process variance. And from their experience, they predict that this aerospace-promoted inspection process will rapidly extend into all commercial industries.

Ron Branch is a manufacturing engineer with V&M Precision Machining and Grinding, 1130 Columbia Street, Brea, CA 92821, 714-257-4850, Fax: 714-257-4820, [email protected], www.vm-machining.com.

Verisurf Software, Inc., 1553 N. Harmony Circle, Anaheim, CA 92807, 714-970-1683, Fax: 714-701-0280, www.verisurf.com.