When to Refurbish and When to Buy New

Reader Question: Our shop has several older machines that we are looking to replace. We were recently introduced to the idea of refurbishing them, which we hadn’t considered before. They still perform well for our type of work, but at times their age shows. Can you offer your thoughts on how to make this decision?

Miller’s Answer:

There will always be plenty of reasons to buy new equipment. Tax incentives, dealer promos or new tech are all viable reasons for buying new machinery. Even machines with just a few years of service can be updated or retrofitted with automation, or other options like probes or fourth-axis tables can give them new capabilities and keep them competitive and productive. However, in my opinion, one of the most overlooked improvement strategies for shops is refurbishing old equipment.

Refurbishing means repairing or rebuilding the worn components of the machine to squeeze more from the initial investment. The idea is to give the machine new life and reset the clock on years of service by repairing the machine at the component level. Much of the cost of a new machine is in the structure and production of the castings to which the rest of the machine is assembled. It’s also the one component that will essentially never go bad, so why throw away an entire machine when it can be rebuilt on the same chassis. Also, these component-level repairs can be done all at once or over a period of time, further softening the financial burden.

The first step towards the decision of refurbishing or buying new is to get a clear understanding of the health of the machine in question. I suggest breaking it into three points of study, these being the health of the spindle, the health of the axes and the exterior and ancillary components of the machine.

The most intricate single component an older machine will likely need is the spindle. To get the right scope of repairs needed, you’ll want to check a few key aspects. First, you’ll want to assess the taper of the spindle for fretting, chips, dents, rust or otherwise problematic blemishes that impact the connection of the toolholder and spindle. A draw bar strength test is also a simple, but important check to perform. Pulling the tool into the taper with the ideal force can affect many things like cutting performance, tool runout and balance. Often, a spindle in question may seem good, while still underperforming because of a weak draw bar. Next, how true the spindle rotates is an easy check with the use of a test bar and indicator. Check the rotation near and far from the gage line to assess the status of the bearings. Lastly, if all the above checks out, but you still have questions about the spindle’s health, you can check the balance with a dynamic balancer.

Often, the taper can be reground and the draw bar can be replaced on the machine without pulling the spindle out. If it’s determined the runout or balance are bad, then more intricate repairs are needed, and the spindle needs to be pulled and replaced or sent out for rebuild.

For the axis of the machine, three primary tools will be your guide. A qualified square, a ball bar and the laser. Testing the geometry of the machine with the square can give you an idea of the shape of the machine, such as straightness and squareness of the axes. It’s possible the machine may just need to be re-leveled after many years of sitting in the same spot. The ball bar gives us a dynamic assessment of the axes and also produces numbers for back lash, servo error, lateral play and overall circularity. The laser does these as well, but is more precise and focused on a single axis at a time. It is my recommendation to run the ball bar as a preliminary check, and let the laser do a deeper dive if any issues are found. No problem if you don’t own these tools, most shops do not. There are many professional services out there to have this assessment done on your equipment and they may be able to tune the machine using software tools rather than an expensive mechanical repair.

Lastly, you’ll want to assess the overall machine condition and all the systems that support its primary function. This part of the assessment is more of a check list than a series of precise measurements. Go around the machine and all of its ancillary components and simply make a list of the things that could use a repair or refresh. Do the coolant pumps still work well? Do the doors close safely and properly? Are there leaks? Can you still see through the glass into work zone? It’s free to identify them now and the decision to repair/replace can be made later as part of the larger assessment.

After a thorough assessment of the machine using the points of study mentioned above, you can use these to gather quotes for the work needed to get the machine back to its former glory. Here is when the decision point between new machine or refurbishment will become clear. You may find just a few components and some tuning are needed to put a machine near its day-one specifications, or you may find such a long list of needs that a new purchase will save you time and effort. There is also the constraint of parts availability for older machine that are no longer supported.

For commodity machines, it’s likely the cost of repair isn’t worth it compared to simply buying another low-cost machine. For more expensive assets, refurbishment may be a much more attractive alternative, especially if that machine is a proven and critical piece to your operations.

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Do you have a machining question? Ask the expert. John Miller leans on more than a decade of industry experience to answer machining questions from MMS readers. Submit your question online at mmsonline.com/MillersEdge.