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What to look for when buying used cnc mill center

stephon0913

Plastic
Joined
Aug 12, 2011
Location
Portland, OR
Ive been browsing around off and on looking for a cheap but decent cnc milling center i would prefer a haas or fadal as i know theyre probably going to get me the biggest bang for my buck (budget around $5k no more than $10k). Will be buying local so i can go and check it out in person. Just wanted some advice on what points to check for when i do check the machine out. I know to go thru the gears in the spindle and check the rapid feeding and such, how bout anything else? Thanks open to all suggestions!!:cheers:
 
Wind the spindle up to max rpms and come to a quick complete stop (M5) that will see that the spindle braking unit is working correctly. Have them rigid tap a part and check the threads. Make a heavy milling cut in all directions and check the finish. Profile something and check the finish.
 
The best would be actually making parts on the machine. You'll find the problems then.

Listen to the sounds of the axis' moving. Run the spindle at max RPM in every gear (if geared). Look at gaurds and sensors all over the machine. If you can see that sensors, switches, wires and hoses have been scabbed together with mismatched stuff it hasn't been cared for well.

For $5-10K you're looking at a pretty old machine- Early 80's. You can't go wrong with Fanuc controls for parts support and there are several techs in the PDX area who know the old Fanucs inside and out. A Fanuc 6 is as old as I'd pay money for, but can still do a lot except thread milling and simultaneous 3 axis moves.

For your budget you're going to be buying a pile of shit that ran production for 30 years. Be prepared to fix stuff.
 
the best would be actually making parts on the machine. You'll find the problems then.

Listen to the sounds of the axis' moving. Run the spindle at max rpm in every gear (if geared). Look at gaurds and sensors all over the machine. If you can see that sensors, switches, wires and hoses have been scabbed together with mismatched stuff it hasn't been cared for well.

For $5-10k you're looking at a pretty old machine- early 80's. You can't go wrong with fanuc controls for parts support and there are several techs in the pdx area who know the old fanucs inside and out. A fanuc 6 is as old as i'd pay money for, but can still do a lot except thread milling and simultaneous 3 axis moves.

For your budget you're going to be buying a pile of shit that ran production for 30 years. Be prepared to fix stuff.

well ive heard of and seen deals like that out there, no doubt it will be old and most likely need to be torn down and have some work done, however this will be my first machine, more learning than anything with this one till i go on to bigger and better...hopefully :cheers:
 
A Fanuc 6 is as old as I'd pay money for, but can still do a lot except thread milling and simultaneous 3 axis moves.

For your budget you're going to be buying a pile of shit that ran production for 30 years. Be prepared to fix stuff.

I can say for certain that a 6M is capable of helical interpolation/threadmilling as long as the option is turned on. Gotta agree that the OP's budget is too small for a runner and a new career as a machine tool restorer may be what ultimately happens.
 
What are your size requirements? Your budget may allow for a early 90's Kitamura Mycenter Zero, but you are only looking at a 10" x 12" machining window.
 
Yasnac= No parts anymore. There are guys that are incredibly talented and can troubleshoot and repair anything on a component level. The downside is they're far and few between, booked out for 3 months and cost $90/hr.

Don't buy a machine like an old car project with the intention to "restore it". It's a tool. Clean it, paint it if you want, but don't waste you're time on this planet fixing up an old CNC that should be rebar in a dam in China. Old machines will keep you busy enough keeping them running. A shiny old machine is a pile of scrap metal if it's not able to make good parts.

Also, when you buy an old machine GET THE BOOKS! You don't need a lot of things, but you need the ladder diagrams to have a chance at keeping them running.
 
. Old machines will keep you busy enough keeping them running. .

This is the advise I was given:
Necessary things to inspect, measure, indicate, etc. on the machine with a test indicator and other easily available tools

check spindle run-out with test indicator
blue toolholders to check for spindle taper wear
check repeatability of x,y,z at multiple feeds
check backlash of screws
check ways for visible wear
listen to spindle at different speeds
the "pull on a tool in spindle and see how much the machine gives" test
test cut if possible
Listen to the axes-The indicator test will tell much about their health, but I've seen ballscrew support bearings that measured OK (next to no backlash) that were noisy. Often, there is more than one bearing at each end, so one can be failing while another is taking up the backlash. However, the good one is now taking the load for both, so it's going to have accelerated wear/failure.
Try to determine if the waylube system is oiling all points properly. If not, it might be a general indicator that the machine isn't well-maintained.
Test-cut, as you say. Give it worst-case loading to deflect spindle and check rigidity.

Take an indicator, see if you can push/pull any of the axis'
Check the comp settings
Let the spindle warm up, after warm run it at different speeds to hear noise/vibration
Check the tool changer, see how well it changes tools at different areas of the tool changer

A drawbar test would be nice as well as a ballbar test on the axis'
Check the electrical cabinet for ANYTHING that looks "not factory"
 
When I was in that budget range I was looking at Trak (and open bed-mill style machines). IOW no tool changer and no enclosure. Fadal for $5k sounds like something that immediately needs a spindle or ballscrew(s) etc. Expensive stuff that's going to eat into the next $5k. Also pay attention to the issues I've gotten advice on, needing rigging (possibly twice), supplying power of high enough quality so the servo drives have a long life, tool holders, pull studs, vises, coolant and edge tools to name a few. There are a myriad of issues to be solved, which is an incredible challenge but its a cash eater at first, hopefully you can reverse that trend :)
 
With Yasnac you don't have the availability of parts like with Fanucs. They take standard G-codes but aren't user friendly with cutter comp and setting G54-G59 coordinates. If you shop older Kitamuras you will find the Yasnac controlled one's going for $5,000 less than a similar model with a Fanuc, and there is a reason why they are cheap.
 
Gotta agree that the OP's budget is too small for a runner and a new career as a machine tool restorer may be what ultimately happens.


This notion is something to keep in mind. I've had two CNC machines in my shop (knee mill and small VMC) for a few years now. Neither of them has ever made a chip. The mill is undergoing a VERY slow retrofit process. The VMC needs a little work on the Z-axis, all new lube lines, reloaded parameters, and a LOT of clean-up. Needless to say, I attempted to jump into the CNC game with non-running machines. A few years later, I'm still 0% productive. Do yourself a favor and get a running machine that does not have an antiquated control. The money that I would've made with a running machine in the last three years would been many times what I saved by getting non-op machinery.
 
I have a clean, nice working, 1990 Excel Colt 510 that you might like that fits in your budget. We've been using it mill some little diecast parts and rigid tap 0-80 holes. It works about as good as our 2005 Haas VFO IMO.
 








 
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