Help a newbie with a new machine

[mikesos1]

My company has been looking for a good condition used CNC mill for quite a while. I think we found the right one. We found a Milltronics MB18 with R8 taper and a centrion VI controller. It is a 1998 model. From the pics it looks very clean.

My question is, What should I look for when inspecting this machine? I am flying to see it under power on monday. Other than the obvious visual inspection and jogging, running a program under power, What are some issues I should look out for? Are there any known issues with machine? Any tell-tale signs that we should walk away?

Thanks for your help on this guys, we are excited about this and want to make sure we do it right.

Mike

[mikesos1]

Nobody can help me out?

[diarmaid]

Hi. I dont have personal experience about this but these might be able to help:

http://www.machinetoolhelp.com/Purch...nspection.html
http://asuwlink.uwyo.edu/~metal/makers.html
http://www.machinetoolhelp.com/Purch...chinetool.html
http://www.machinetoolhelp.com/Purch...oreyoubuy.html


A very thorough discussion of vertical mills and what to look for was in Home Shop Machinist, July/August and September/October 1993, by Thomas Howard. Here is a very brief summary:

Spindle-to-table distance, or "daylight." Remember that by the time you clamp your work in a vise on a rotary table then slap a chuck with a drill into the spindle, you might run out of room. Try to anticipate your needs.
Knee mills: A mill where you can raise/lower the table with a crank, as opposed to only raising/lowering the head and/or quill. Knee mills are generally more useful and accurate.
Spindle brake: Locks the spindle during tool-changing. Very nice to have.
Power downfeed on spindle. A very nice option, relieves tedium when boring, and often yields better surface finish.
Spindle taper: determines what type of tooling you can "plug in" to the spindle. R-8 is most popular, and there's lots of inexpensive tooling. Morse and Brown&Sharpe exist and are less popular.
Bearings: Apparently it's not as important whether they are ball roller bearings, as the grade. And the better the grade, the longer the machine lasts, more than anything else.
Table sizes and travel: Like lathes, you can always use one an inch larger! Don't buy one larger than you have room for. From 6x20 (inch) to 8x30 seems right for most home shops. What will you be doing with it?
Power feed on X/Y axes. Very nice to have, just barely falls into the "luxury" status.
Table and knee locks: Used to maintain rigid setups when one of the axes won't be changed during an operation. Check for easy access and that they lock solidly.
Graduated dials with adjustable zero: an absolute necessity.
Adjustable gibs: a necessity.
Range and number of speeds. An average is 100-2500 rpm, and 12 to 16 speeds. Howard goes into great depth in his article to explain why you need both a wide range of rpm and many speed, and how those speeds should be spread out in a geometric progression.
Motors: be sure you get a motor you can run. Check frequency (60 or 50 Hz), voltage, and 1-phase vs 3-phase. For home-shop use, anywhere from 3/4 to 1-1/2 seems right.
One-shot oilers are nice but in many cases they don't work right and are hard to check.
Look. If at all possible, examine the machine you want, before you buy.
Buying used: you should be experienced enough to know what to test for! Or "borrow" somebody who is.
Will it fit? Be sure it can be moved to where you want it. Don't buy then find the stairwell is smaller than you thought. Get professional movers to do the moving; "real" mills are literally "killers."
Tooling: can sometimes double the cost.

Im sure someone experienced will give you more advice, hopefully before you go to look at it!

[handlewanker]

Hi Mike, why is it for sale? If it needs a rebuild then you had better know what this entails or you'll end up paying full price for a used machine. You'll only know if it will hold size when you toolup and run your own work through it.
There's a good reason why a machine has a life expectancy time. Cars have mileage indicators, they still run but smoke a bit going down hill. The most important factor is the type work you'll be using it for. If you are expecting close tolerance repetivity then a used machine may be just too loose to produce the goods, described in the trade as "nicely run in".
Tooling up is a cost you can't get away from, even for a new machine. Talk to a machine tool rebuilder and if they can't help you, you're on your own, fingers crossed and praying for a sign.
Ian.

[mastermoparman]

i just got into this traid my self but i have been asking some of my coworkers on what it takes to get a full size machine.
one of thy guys i talked to (who him and his 2 brothers have their own cnc machine shop on the side) said there is a taidor magizene that is published every few monts or some ting like that. basicly what happens is it is for selling machines like what you are looking for. it is mainly a compulation of small shops that have gone under trying to make some money back and such so i can try to find out more fo ya if you want(or go to a local machine shop and ask them they usaly get them)

[mikesos1]

Thanks for the responses guys. I know the service history of this machine(it is very clean) and I know it has low hours.

I was looking for some specifics on things like high wear areas, funny noises, common glitches with older controllers, things like that.

Thanks again for the help


Mike