Hill Cox 2016-01-25 04:41:30
MEASUREMENT CHOICES ASK QUESTIONS TO IMPROVE YOUR RESULTS Choosing the best measuring device for any application requires you to answer some basic questions to sort out your options before looking at the hardware. The choice you make could be shot down in flames at the end of the process by a ‘basic’ you overlooked at the beginning of the process. HOW MUCH MONEY? Too often this is the major question to be considered, one that overrides and compromises everything else. If you have a budget in mind, you can eliminate a lot of equipment without considering any technical details. For example, if your budget is $100 and you want a digital device, you’re unlikely to get much—if anything—for the money. You might get lucky but when resolution, accuracy, or setting masters—the technical stuff—is considered, these elements may put you in a losing position. The answer? Get more money. One way to avoid this and save time as well is to talk with a knowledgeable technical representative from the supplier you intend on using. Ask for ‘budget’ prices for some of the options you are considering. If the dollars are within your range, it’s time to move on to the next step. WHAT’S YOUR CUSTOMER USING? Technically, a measurement is a measurement so it doesn’t matter what someone else is doing. Except that it does. Many companies take the easy way out of equipment selection problems by duplicating what their customer is doing even when they consider the customers’ methods a bit dodgy. This works well until wheels start falling off things and the customer is looking for someone to blame. You will have received an order to produce the parts to their specifications and/or drawing and that is all that counts when problems arise and the lawyers get on the case. If you reviewed your customers’ procedures at the quoting stage, your quotation should protect you from their lack of technical expertise. A simple phrase such as: “Unless otherwise requested, we will measure this part/feature using the following....” If they accepted your quotation, they will have agreed to your method. If they don’t accept your method of measurement they would question it before they give you an order. This makes for lower confrontational levels compared to defending rejected parts. WHAT ACCURACY? I’ll leave most of the techie stuff for another column but a general look at this is required early in the game if you want to get the measurements right. Too often we are called in after the battle between customer and supplier has begun when it could have been avoided before it got down to hand-to-hand combat. In many cases, both parties are unaware of the realities of dimensional metrology that makes equipment or gage selection a frustrating and expensive exercise. The part drawing shows the expected tolerances but if they appear unrealistic it’s time for a discussion with the customer. Buying another micrometer with finer resolution may not be the answer. If you cannot agree, get someone who is technically savvy to assist you in discussions with your customer. Note that I said ‘technically savvy.’ A catalog sales rep could lead you astray. Another consideration has to be the environment the measurements will be made in and the skill set of the folks doing the work. New and improved hardware can be rendered useless without these considerations taken into account. WHAT HAS TO BE MEASURED? This may seem to be a dumb question, so stay with me. Let’s say it’s a diameter and that’s all that is specified— with a tolerance on it of course. Theoretically, one measurement would do the job but that could change if the parts are tapered too much or are out-of-round. Your customer may measure the diameter at several locations. If you only measure it at one or two locations you can see there’s a chance you’ll miss something. Conversely, your customer may be using fixed limit or go/nogo gages to check the parts so arguments could arise later. If you’ve stayed with me on this so far, you can see that many of the problems I’ve outlined can be avoided by discussions with your customer at the earliest moment. When everyone is singing off the same song sheet, everyone will be in tune. Hill Cox is president of Frank Cox Metrology Ltd. (Brampton, Ontario, Canada). He may be reached at firstname.lastname@example.org.
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