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Some things to consider when sourcing a CNC Machine Shop(Page 2 of 3)
The “Print” is the thing
You will do this by communicating your needs to the shop or
shops you are considering.
way to do this is through use of a blueprint.
The blueprint or “print” contains all of the information a machine shop
needs to make your part the way you want.
It should be unambiguous in all detail.
The fewer ways the print can be interpreted, the better.
I have included a sample print on the website. You will find
it on the Sample Print page. It
contains all of the relevant information needed by a machine shop to make a
part exactly to my liking.
On a separate page, "The Perfect Print"”, I have gone over
this print step-by-step explaining the various call-outs, title block, views,
There is one more thing I will say here. In the last 10 years or so, there has been a
large movement in the manufacturing business toward the use of 3D CAD (Computer Aided Design). In fact, we use 3D CAD extensively to help
our customers make the designs they want “come to life” (the print on the
“Sample Print” page was drawn with 3D CAD) and to make machining more cost
effective and accurate.
But it is not necessary for you to run out and buy an
expensive piece of software to get great-machined parts. Even if you draw your print on a napkin, if
all the necessary information is on that print, there is no reason you should expect less
than perfect parts.
Off for Quoting
Now you have your “perfect” print and are ready to send it
out to get pricing. You should pick a
minimum of 3 shops to quote on this part.
5 is better. There is a maxim in
the machining world that says roughly:
“The price of your part is inversely related to the amount of work
flowing through the door of our shop.”
In other words, all other things being equal, the less work a machining
job shop is doing, the lower the price they are going to quote.
The job shop machining business is very cyclical; so don’t
be surprised by a wide variance in quoted prices.
If you get more than 5 quotes, you can probably toss out the
highest and lowest.
Some shops “buy” work and, unless you are willing to relax
your standards, they will disappoint you.
They will not pay close attention to your print.
On the other hand, if the quote is very high, there is a
possibility that this shop is saying in effect “If they go with this price, I
can afford to make another customer unhappy with a late delivery.” This shop is willing to make late deliveries
to cash in on a big score.
This machine shop will not be a good long-term partner. The next time, your company might be the one
put on the back burner.
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