BORING MILLS S&M Machinery Sales, Inc.
11430 Kaltz Ave, Warren, Michigan 48089 USA Phone (586) 755-1234 • Fax (586) 755-9876 sales@usedmachinerysales.com
INSPECTING CNC BORING MILLS Inspecting CNC boring mills is both gut feel and science. What looks good in a shop may or may not be what you think. Each machine needs to be carefully examined. The fact that one machine is ten years newer than another does not mean it is necessarily a better piece of equipment. Start with a clear head and no assumptions until you see the environment the machine is in. My first inspection is strictly visual without even seeing the machine operating. I start my inspection with a list of questions that need to be answered. What is the product they are producing? What material do they run? How many shifts is the machine running? Do they have a maintenance department? If not, who does the maintenance and how often is that done? Next, I find out why they are selling the machine. Do they need more capacity? Did the seller buy the machine new or used? So what I am doing is framing the picture by finding out as much as I can about the history of the machine. Now I am ready to get into the meat of the machine and see it running. You should be able to run the machine at full capacity. Any excuses for why it can’t be run while you are there should raise a red flag. If the seller tells you that they can’t run it because of “small issues” such as only needing a switch then that should alert you to be looking for possibly bigger issues. Small issues take little money and time to repair versus big issues. If a “small problem” isn’t addressed by the current owner, that tells you that there are one of two scenarios. Either they do not have an adequate maintenance plan in place or that there are larger issues that they may not be disclosing to you. On boring mills, the first thing you inspect is the heart of the machine - the spindle. Check the chrome for any wear marks, including scoring and rust. Next have the operator run the spindle through a range of speeds. Don’t let the operator dictate what speeds he will run the spindle through. Have him run through the entire range - taking note of changes in overall noise as the speeds change. Then have the operator engage the draw bar to ensure proper operation. Next you should run through all the travels on the head, saddle, and table. Listen to the sound and then obtain indicator readings on the table. If the readings come back within your required tolerances, that’s great. If any of the axes show large variances when indicated, that could potentially be more serious issues including worn screws, nuts or worn way surfaces. Visually confirm lubrication on all way surfaces as well. If the machine has a tool changer, that is next. Make sure all pockets are present and complete. Have the operator cycle through the magazine to make sure it moves smoothly. Also have the operator do a number of tool changes to ensure it is handling tools properly. Ideally you will want them to use tool holders when cycling the tool changer to show that both the tool arm and spindle handle the tool holder smoothly while installing the new holder into the spindle and putting the used holder back in the carousel. If applicable to the machine you are inspecting, coolant thru spindle, chip conveyor, 4th or 5th axis rotary tables should be inspected. If the machine has coolant thru spindle, ensure that all pumps are present and you can verify if the machine has a standard or high-pressure unit included. You will also want to perform a visual inspection of the electrical cabinet. Check the fans, wire harnesses, drives, and boards. A clean and tidy electrical cabinet shows that the machine has been well maintained, whereas a dirty and unorganized one may indicate lack of maintenance and possible previous issues with boards, drives, and wiring. As far as the CNC control, there are easy ways to access a wealth of information including hours, backlash compensation, and alarm history. Although hours can show you a lot in terms of how much the machine has been used, do not let this be an overriding factor in machine condition. The steps above are a much better indication of what you are getting for your money. Make note of backlash settings to get a feel for how much wear the machine has and also make note of the alarm history to see if there have been any major issues previous to your inspection. A final check would be to have the operator run through a program they are currently using on the machine. This will give you an overall perspective on how the machine functions in a working environment. It should show you most functions of the machine working in unison on a job. Lastly, overall shop cleanliness will send a clear message on the condition. A dirty shop - versus a clean and well-maintained one – can be a telltale sign of what to expect before you even begin an inspection.
Visit us online to see our full inventory at www.usedmachinerysales.com About the Author: Spencer Minns is Owner and President of S&M Machinery Sales, Inc. – specializing in late-model CNC Equipment including Vertical and Horizontal Machining Centers, Boring Mills, EDM and Turning Equipment. With an extensive on-site inventory, S&M Machinery has been an industrial equipment leader for over 35 years. 12
April 2016
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