Custom fixturing allows the use of standard Surface Roughness gaging at the point of manufacture without specially skilled users to make critical checks.

More gages are being forced onto the shop floor right to the point of manufacture. Measurements of high-volume turbocharger components, which have a combination of medium to very tight tolerances, once performed by a trained inspection technician, are now being done right next to the machining center, most likely by the machine tool operator. And the gage that the trained inspection technician uses may not perform as well in the hands of a machinist, and it may not be capable of keeping up with the rate that the machine is producing parts.

Because of this, standard off-the-shelf catalog gaging may not be the best choice for specific inspection processes at the machine, or for best throughput by the operator. High production facilities are looking to reduce the amount of interaction the operator has with the part. They are there to make parts, not to handle, measure, and move parts. Instead, standard-off-the-shelf gaging modules may be combined to facilitate measuring performance while keeping up with fast production.

When most people think of automation with custom gages, they envision a large, inline gaging system with parts moving along a conveyor, passed through the automatic gage, measured, and sorted per part requirements. While this is a true example of an automated gaging process, there are a lot of in-between gages that, while not as extensive as fully automatic gages, provide some process automation.

Any time a custom gage replaces or reduces operator involvement, we have provided some form of automation. Every time we reduce or replace human involvement, we speed up the measuring process and reduce manufacturing costs.

Custom gaging is meant to speed the measuring process and reduce the human element, so we can divide custom gages into various levels of automation and look at how these can improve inspection and increase production.

Automating manual gages

If a manual gage makes it easier to stage or gage the part, then we’ve helped automate the process. Or if the manual gage is designed to make multiple checks at once, the same goal is accomplished: the gage reduces human labor.

Special fixturing on a standard gage can reduce operator time to position and measure the part. Something as simple as a stop collar on a mechanical plug gage greatly improves part-measuring performance. The fixed plug gage outperforms an adjustable or tri-bore gage, while the stop collar ensures the measurement is made at the same location on every part measured.

The same fixturing concept can be used to speed the process for making surface finish checks at the point of manufacture. Special surface roughness plug gages, dedicated to the bore to be checked, can be made to hold the surface finish probe in a protected housing. Operators no longer have to align the part to the probe (such as on a bench stand), and a protection device can ensure the probe is not damaged during insertion.

Another way to save time and provide a different level of automation is making multiple checks in sequence. A common shop floor practice is to provide a series of tools for the operator to use in a specialized gaging station. Connected to a gaging computer, the station can provide a guided gaging sequence for the operator: informing him what gage to use in the gaging process; helping him make the measurement with pictures/instructions; and collecting the data to provide feedback for part qualification.

These workstations and the guided sequence provide a sort of automation – giving the user clear steps of the process to follow, while data collection and part qualification are done automatically, reducing measurement time.

Measuring time can also be reduced by building a gage that makes multiple measurements at the same time. Many gage builders have begun using what are known as standard elements to create multi-dimensional measurement systems configured for the part. Standard elements allow a custom gage to be created quickly and potentially allows the gage to be reconfigured for families of similar parts. Multi-dimensional measuring compresses the gaging sequence into a one-shot measuring cycle.

Semi-automatic gages

Even small plastic turbo housing can be automatically placed in a gaging station for complete hands-off measurement of the critical bearing bores.

The next level of automation combines multi-dimensional checks into one measuring station or brings movement into the gaging operation. Parts may have multiple diameters sharing the same axis, allowing fixturing to make multiple diameter checks at once. Others may have to be moved or manipulated to make the checks required – diameter variation, runouts, concentricity, or some other rotational function. Movement can be built into a custom gage, such as rotating a part faster than the operator can or rotating it at a constant velocity without operator influence. There are many ways of doing this, such as effecting the rotation so that both static and rotation checks can be made in one operation. For a custom-configured standard-element system, this is the ultimate in automation – multiple checks, fast rotation, and no operator influence.

When checking dimensions on a turbine shaft and wheel, rotation speed is critical for the part qualification. When the operator loads the part and then lets a motor take over the rotation – along with custom software to control the measurement timing – fast, reliable qualification of the shaft can be accomplished and the results quickly displayed for the user.

Another semi-automatic gage consideration is when the part can be manually placed into the fixture. A loading station provided to allow the user to place the part lets the automatic gage take over measurement. This is common on turbo housings and compressor covers, as they often have multiple diameters and lengths offset at angles, and automated part placement ensures repeatable measurements. Once a part is in place, the automated gage closes access to the operator and moves the part into various stations for dimensional and other checks. The operator is free to ready the next part. Measurements require no operator involvement.

Fully automated gages

Fully automating the measuring process is the ultimate custom gage solution. It takes the operator completely out of the equation and can run lights out.

There are two levels of custom gage automation involving part movement within the gage: the gage can be designed for an automated process as a standalone station; or the gage can be part of the manufacturing process and take over a portion of part handling within the manufacturing cycle.

Gages designed as standalone stations are typically robot-fed and may or may not include part manipulation/movement. Standalone stations have all the gaging components in place with the measuring system sending information back to a main controller. The gage often uses sensors to verify to the process controller when a part is in place, when to take a measurement, and when to provide gaging results for disposal. These custom solutions are specifically tailored to the speed of the process, the part tolerances required, the environmental conditions of the process, and the capabilities of the system bringing the part to the gaging station.

In some cases, part measurement automation is accomplished within the manufacturing process by using a combination of standard automation modules and a standard surface/profiling system. The modules include X/Y slides, rotary tables, probe holders, and custom fixturing. Using gaging software, users can craft completely automated measuring cycles for complex parts.

There are many ways custom gages can help automate the measuring process, whether by simple modification to a standard gage, or building a custom CNC surface measuring system. But they all have the same goals: speed up the process, eliminate the influence of the operator, and generate better measuring results.

Mahr Inc.

www.mahrexactly.com

About the author: George Schuetz is director precision gages at Mahr Inc. He can be reached at george.schuetz@mahr.com.