True Grit Costing

A surprisingly simple tool unravels the mystery of what your superabrasive wheels actually cost their users.

Here’s a brain teaser for you.

Let’s assume you are making 1 million parts a year on your grinding machine using a Brand X superabrasive wheel that grinds with a 10-second cycle time and has to be replaced after every 10,000 parts. The wheel costs $100.

You invite a grinding applications specialist from Brand Y to come in and have a look at your grinding operation. He tells you that he can provide you with a better solution using a high performance superabrasive wheel that will reduce your cycle time by 1-second and will make 10% more parts per wheel. The brand Y wheel costs $150.

Do you go for it?

Many users (not you) would laugh at this seemingly ludicrous proposal. They might be thinking “Who in their right mind would pay 50% more for a wheel that will only make a 10% improvement in cycle time and wheel life. No thanks Brand Y Guy, we’ll stick with what we’ve been using.” Was this the right decision?

Brand Y Guy doesn’t think so. He shrugs his shoulders and heads down the road to a manufacturer who has an almost identical problem. So he makes the same proposal. This customer is surprised by the offer, but instead of dismissing it summarily, he pulls out a pencil and paper and spends an hour of his valuable time doing a little bit more thorough analysis.

The Right Answer? Yes!

It turns out this was an hour well spent because, in this case, the wheel substitution actually resulted in a projected savings of $25,000 annually. Not a bad hours work. Next month, after testing the wheels on his equipment, he places an order for the $150 wheels and after a year realizes nearly all of the savings that were projected.

A Simple Cost Calculator: Just Plug In Your Numbers

In this article we will review all the variables you have to take into account to accurately determine if a specific superabrasive wheel can be cost justified. But you won’t have to spend anywhere near an hour doing the math because Meister has incorporated all of these into a simple Cost Calculator – a spreadsheet that will analyze all the cost factors for you.

Know Your Cost Factors

There are numerous cost factors associated with any grinding process. These include:

a) abrasive cost,
b) machine cost (depreciation cost),
c) labor,
d) maintenance,
e) overhead,
f) fixtures/loading/tooling,
g) dressing tools,
h) coolants & filters.
i) scrap and
j) quality/inspection costs.

Abrasive cost is usually what people focus on when considering an upgrade from conventional to superabrasives or when considering an alternative to their existing superabrasive wheel. What must be included in the analysis, however, is the cost to run the machine itself. Cycle time and downtime for wheel changes have a significant impact on the total cost per part.

The Meister cost calculator factors‐in 6 of the variables cited to calculate the true cost of an abrasive wheel:

1. Wheel price (abrasive cost)
2. Hourly machine rate
3. Annual production (parts per year)
4. Wheel life
5. Cycle time
6. Wheel change time

Item #1 is a given. Items 3 through 6 are based on historical data from your current wheel and trials with its proposed replacement. Hourly machine rate is the least straight forward and varies considerably from shop to shop.The range is typically between $100 ‐ $200 per hour, depending on the cost of the grinding machine(s), the size of shop,the volume of parts produced, and the complexity and quality requirements of the parts themselves.

Of course there are other costs (f through j) and potential savings that should be considered in an exhaustive abrasive cost analysis. For example, a wheel that only needs to be dressed half as often is going to save a lot on dressing tool costs.

However the Meister calculation tool can give you an accurate reading on the predominant grinding cost factors. Using the example described at the beginning of this article, the figures below show how enlightening this simple analysis can be:

For your own free copy of Meister Abrasives’ Cost Calculator, visit the Calculation Tools category of this blog.

About joelcassola

Joel Cassola is a commercial journalist who has written feature articles and case histories for clients in more than 100 trade magazines.
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