Encoders and proximity switches are how a machine control knows where the spindle is and what it is doing. When they fail, or when something makes them report the wrong thing, the resulting faults are the most confusing on the floor: orientation errors, tool change problems, and alarms that come and go with nothing audible and nothing obviously wrong.
Tested on every spindle that carries them
Encoder testing and proximity switch testing are standing steps in the MZI inspection room, alongside motor winding testing and the mechanical measurements. Sensor checks go deeper than pass or fail: in one documented MZI investigation, that meant testing the sensor itself, its location settings, its gap, and its pickup diameter before ruling the sensor out. Feedback devices earn that attention because the faults they explain, and the faults they get wrongly blamed for, both start with the same symptoms.
The case where every sensor tested fine
An aerospace manufacturer running about fifty CNC machines had spindles losing orientation and jamming the automatic tool changer, with nothing audible and nothing on the controller. Faults like that are normally a proximity switch issue, so that is where the investigation started, and everything checked good. The real cause was mechanical: on that spindle model, the compression rings could not hold the drive coupling fully in place, so it turned slightly and the controls read a lost position. The fix was four engineered pins locating and locking the coupling, built from OEM components. The failure analysis guide tells the full story.
That case is the reason this page exists. Feedback faults sit on the boundary between electrical and mechanical, and a shop can spend a long time replacing sensors that keep testing fine. Testing the devices properly, and knowing when to stop believing the obvious answer, is the difference between a fix and a parts subscription.
If your machine is throwing feedback faults
Describe the fault, when it happens, and what has already been replaced. With a little information we can diagnose the problem and determine your best action, and some feedback problems can be narrowed down without the spindle leaving the machine. If it should come in, encoder, proximity switch, and motor winding testing are part of the same no-charge inspection and quotation as the mechanical checks, covered in the motors and gearbox pillar.
Start with a phone call
Edward Zitney
President
(714) 475-4016
He has spent more than 44 years in spindle rebuilding and remanufacturing. He learned the trade over more than two decades at Precision Balancing & Analyzing, the shop long regarded in the industry as the standard for spindle work, later oversaw SKF Machine Tool Services, held service leadership roles at Setco, and wrote a published column on spindle remanufacturing for Fabricating & Metalworking.
Marco Guerrero
Partner
(949) 374-0060
He came up on the shop side of this industry. He started with his hands, welding and fabricating for the racing industry, then spent fifteen years as general manager growing a machining job shop, the same kind of shop that sends MZI spindles today. He has sold CNC machines too, so he knows what new equipment costs and when a rebuild is the smarter call. Today he and Ed are partners in MZI Precision, and his standard is simple: every customer feels informed and supported from the first call to the day the spindle ships back.
Call (714) 379-6505 and describe what changed. With a little information about your spindle we can diagnose the problem and determine your best action.
What to expect on the call:
- You talk directly with a spindle expert.
- Some problems can be diagnosed over the phone, and a few do not require removing the spindle at all.
- If your spindle should come in: disassembly, inspection, failure analysis, and a line-item quote, at no charge until your purchase order approves the rebuild.