We’re in the business of making precision parts. These parts are usually designed by our customer.
Sometimes, we’ll provide design advice for manufacture-ability of the part and our customer will often include our suggestions in their final design.
If the part is designed with manufacture-ability in mind, it will be less costly to make, which is why our customers will engage us in their design process.
When the design is finalized, we’ll give our customer the price to build a prototype or a higher quantity.
If our price and lead time is pleasing to our customer, we’ll then begin making parts.
But not their parts.
Well, not right away anyway.
You see, before we can begin making their parts, we have to make parts to secure their parts during each unique manufacturing operation.
Behind the scenes we’re doing this because it’s essential, and our time to make the fixtures are included in our per/each part price to the customer.
Interestingly our customers presume we’re just making their parts. And honestly, that’s all they should care about. They need a precision part and it’s our job to figure out how to make it!
There are many factors that determine our cost to make parts which is represented in the per/each price to our customer. The process to manufacture the designed part is a big factor in the final pricing, which is why I’m discussing it here.
A standard block has 6 sides.
A custom designed part that we’re machining may have 6 unique sides.
Depending on part complexity, we may have to make 6 unique fixtures to secure the part while machining each unique side of their part.
That equals 12 machining operations to yield a 6 sided custom part for our customer!
The fixtures we make are also referred to as work-holding fixtures. Fortunately there are some companies that specialize in manufacturing a broad range of general work-holding fixtures which we can buy off the shelf.
Often, this eliminates the need for us to make custom fixture parts before we make parts for our customer. However, it is inevitable that we’ll need to make parts before we can make customer parts. Fortunately, we’ll re-use the custom made fixtures for future orders of the customer’s part.
If the custom fixtures (either made or bought,) are intricate and costly, sometimes our customer will request the associated costs listed on the price quote as a separate line item. When added as a separate line on the price quote, it’s referred to as a NRE, or, Non Recurring Expense. For future runs of the same part, the manufacturing price will be reduced by the NRE amount.
Obviously parts have to be designed to perform a function and they can be unavoidably and inherently difficult and expensive to make. However, where possible, cost of manufacturing should guide part design.
Let me repeat that; where possible, cost of manufacturing should guide part design!
Note: Most additive type manufacturing processes such as 3-D Printing don’t require custom made fixtures. The manufacturing processes explained here are for subtractive type machining processes. These machining processes require work-holding fixtures for each machining operation.
If machining processes require costly custom fixtures, naturally you’d want to consider additive manufacturing techniques, right? In some instances additive manufacturing processes would be beneficial to make certain parts. However, machining done right is fast and accurate- after the fixtures are made anyway!
As of today, a typical 3-D printer prints a part (layer by layer of material) at about 1 cubic inch per hour. That same size cube, machined with subtractive (material removal methods,) would take about 30 seconds each to make.
If we’re machining your parts, chances are that we’ll have to make custom parts before we can make the part we’ve quoted to make for you! It’s just another part of the parts making process.
And considering the high production output achieved by computerized machining, it makes a lot of financial cents, especially if you need a high volume of parts made.
Source: Jason M LaRock
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