Experience Mechanical Inspection

As a mechanical inspector, my job was to make sure that the parts received at Focal Technologies and the machined parts made at Atlantic HardChrome met the specifications on the engineered drawing and were fit for use. Below you will see some examples of how I achieved this goal. At Both Focal Technologies and Atlantic HardChrome I operated a Co-ordinate Measuring Machine (CMM), as well at Atlantic HardChrome I programmed the CMM.

CMM         mcosmos
Mitutoyo CMM (model used at Atlantic HardChrome)                     MCosmos Software Interface

Most machined parts I encountered had a extremely small tolerances. It was not unusual to have a dimension required to be made as close to .005 to .0002 of an inch. For example a cylinder with a diameter of 6 inches to be made as close to 6 inches as no more than 6.0005 inches and no less than 5.9995 inches. The CMM allows us to measure the .001 inch limit (the average thickness of a human hair).

probe in action                 probe
CMM Probe

Using the CMM software interface (known as MCosmos) I programmed the movements of the probe as seen in the above pictures. To Measure the 6 inch cylinder I would manually measure a plain (flat surface on part), using a probe controlling joystick, usually the top flat surface of the object, allowing for a more accurate measurement of the cylinder. Next I would manually measure four spots (points) on the inside diameter and set this as my origin, meaning my starting point co-ordinate 0,0. Once I have my plain and origin I can have the probe programmed to take as many points as the part or accuracy requires. This process is done automatically, eliminating human error. Once the software has these points I can determine if it fits into the tolerance of plus or minus .0005 of an inch. The results are displayed in a report, along with the exact measurement and whether its in or out of tolerance.

For ease of use and to create a more efficient use of the CMM I created a CMM sub-plate. The sub-plate sits on top of the CMM surface and has a grid pattern of holes, allowing the measured part to be locked into place. As well the grid system allows a part to be placed in the exact same spot each and every time it is to be measured. In the above example the part must be manually probed before the automated measuring begins. With the grid system in place, I was able to program an automated program that takes the plane and origin measurements without any manual touches. By placing a detailed description of where and how to set the part on the CMM along with a picture, any user could set-up the part and run the program easily.

cmm sub-plate
CMM With Aluminum Sub-Plate & Part Locked in Place

With the above CMM plate a machinist was able to place a part on the CMM, set up the part, hit run, and within a couple of minutes have results to ensure fewer parts were scrapped in the manufacturing process. This was particularly helpful for the night shift, who did not have a CMM operator on hand. A secondary benefit was that when I ran a part I was free to concentrate on other work, with the CMM running automatically.

caliper & mic     pins           Vernier Calipers & 0-1 inch Mics                                                 Precision Pins

Depending on the machined part, it may require CMM and hand measurements or just hand measurements. When a part was manually inspected precise measuring instruments were used (examples above), as well measurements were recorded and filed appropriately. Each measurement, like the CMM results have to be within the engineered drawing specification.

sample part
Sample Part

CNC Machine

When a machinist produces a part, it is necessary to inspect the first part produced, to ensure any further parts are within drawing specifications. My duties included producing a report with exact measurements recorded, to document that the first part is or is not within drawing specifications. Before the machinist can move forward with production the part must be within tolerance. If it does not meet specifications, my job was to communicate this with the machinist and work to get the part in tolerance. This may have also included working with the shop foreman, CNC machine programmer or management. Communication in all these cases is very important; if one specification is not clear, time and parts can be scrapped and the process would have to start over again.

Sample Shaft

Another one of my duties included Computer Aided Drafting (CAD). I was either given a part or old drawing and was required to measure the part and create a new drawing, or I was required to produce a drawing for a new part.

height gage        tools
Measuring Tools

In order to create the drawing, I would first use measuring tools to create a hand sketch. Using the hand sketch I would create a 3D model and drawing of the part for manufacturing use.

Sample Drawing (reverse engineered)

sample drawing
Sample Drawing (engineered)

gage            tools
Gage Blocks & Sample Tools

As part of my job I was responsible for the calibration of tools. Simply I had to make sure that tools where displaying the correct measurements. The first step was to clean the tool, then take a set of gage blocks, themselves calibrated to known values, and compare the tool measurement to the known value. This process was done to ISO standards and therefore a step be step guide was used to ensure accurate calibration. The standards would have an allowable deviation, for example a micrometer measuring a 1 inch block may display up to +/- .001 inches and still be in calibration. These measurements are recorded and the tool is labeled with calibration info, like who preformed the calibration, and the tools next calibration due date.