Used CNC buying advice

What to look for when buying a used point-to-point CNC. April 20, 2001

Q.
I want to buy a used P2P CNC machine. How can I make sure the machine I buy is in good condition?

Forum Responses
Is this a first time buy? Would you buy a computer that is four years old and run four year old versions of software?

When you buy new, you get training and service--the two most important things to look at in CNC!

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I would not discourage you from buying a used CNC. I have a customer that recently purchased his first and second CNC machines, and the newest one was built in 1984. He didn't pay much for them, but he has been able to use them to double his volume and drastically reduce his cost. The CNCs allowed him to do this in the same square feet, and with a minimal increase in payroll.

You need to check everything. A basic checklist will include:

* Backlash on all axes.
* Visual inspection of ways and bearings.
* Visual inspection of screws, racks and pinions.
* Squareness--check X/Y, X/Z, and Y/Z (requires a precision square).
* Runout check on spindles and heads.

* Temp rise and vibration check on spindles and heads.
* Check for proper vacuum system function.
* Check for proper function of all keys and switches.
* Check for proper function of all lube systems.
* Check function of drives and I/O ports.
* Allow at least 30 minutes to cut parts. These don't have to be your parts, but should use all of the heads and spindles and should involve some heavy cuts. Check the parts against the program to make sure no fudging is going on.
* Ask to see the service records. These can give you an idea about how the machine was maintained as well as identify chronic problems that the machine might have.

Don't pay too much. There are a lot of used machines out there and it is a buyer's market.