BALL SCREW REPAIR
At Express Ball Screw Repair & Engineering our specialty is rebuilding ball screw assemblies, a service for which we have been known and trusted for over 30 years. Typically our customers' two priorities are quality rebuilds and fast turnarounds, so that's what we give them. To achieve both, we utilize our in house engineering, machine shop, assembly, testing and QC departments which assures our customers a rebuilt ball screw assembly that looks and performs as well as new with lead times that are second to none. Most ball screws sent to us for repair will fall into one of three categories to accommodate our customer's needs: 1. Our 5 Day Standard Rebuild Service. 2. Our 2 Day Expedited Rebuild Service. 3. Our Re-Ball Only Service. Both the 5 Day and the 2 Day rebuild services include our one year in service warranty. See below for more details on each of these services.
5 DAY STANDARD BALL SCREW REBUILD SERVICE
Our standard ball screw rebuild service takes our technicians 5 business days to complete. This is our most popular service due to speed of completion paired with also being the more economical option. A detailed description of the rebuild is explained below under "Our Rebuilding Process".
2 DAY EXPEDITED BALL SCREW REBUILD SERVICE
If your machine is down and you are looking to get it operational as quickly as possible, then our 2 day expedited ball screw rebuild service is for you. This service is the same as our 5 day standard service, except that the ball screw is moved through the process much more quickly. There are no corners cut here as we use the exact same repair and testing methods. Often our technicians must work overtime in order to meet these tight deadlines, therefore a 20% up charge is added for our expedited service.
Our Rebuilding Process
Below is a run-down of our rebuilding process for most ball screw assemblies.
Check In, Evaluation & Documentation
The ball screw assembly is photographed to document correct ball nut orientation relative to screw shaft. The overall length, major diameter, pitch, lead, thread profile, thread root diameter, V thread pitches & diameters, key slot sizes, bearing journal diameters and drive journal diameters are all measured and documented. Missing and visibly broken parts are noted.
Disassembly & Cleaning
The ball nut is removed from the ball screw shaft. The ball nut and internal components are disassembled and cleaned along with the ball screw shaft. Ball size and ball return wear is documented.
Inspection & Assignment
Inspect the ball screw shaft. Check for straightness and thread to bearing journal concentricity. Check for thread radius wear and thread damage including brinelling, corrosion, spalling, and fretting. Check for damage to the V threads and key slots. Check for drive journal and bearing journal wear.
Inspect the ball nut and internal parts. Check for thread to ball nut register concentricity and thread to bolt pattern concentricity. Check for ball nut flange perpendicularity. Document if nut is one or two piece, ball return type, ball size, and number of circuits. Check for internal thread radius damage & wear. Check for wear or damage to the ball returns, wipers, spacers, and any other internal parts.
Assign all damaged and worn parts to the correct department to be repaired or reverse engineered. Departments are our thread work department, surface finishing department, engineering department, and machine shop.
Repairs & Machine Work
Most parts for ball screws are not available to order through the OEM or anywhere else, so years ago we set up a machine shop at our facility specifically for the purpose of making parts for ball screws. The most common parts we make are ball returns, wipers, and precision ball nut spacers. Another common procedure is the repair of broken ball screw shaft ends which is done by boring, welding and pinning a new end on the shaft followed by machining and grinding back to OEM specs.
Thread Work & Straightening
Before a ball screw shaft can be reground or abrasive lapped it is crucial that it is straight. A straightening press is used to correct even the slightest bends on the shaft. The thread work performed on the OD of the ball screw shaft and the ID of the ball nut is either by OD/ID thread grinding or by abrasive thread lapping depending on the thread wear. Typically material removed to restore threads is between .0004" (.01mm) to .0020" (.05mm) where case hardening is not affected.
Refinishing
In our surface finishing department we utilize polishing, centerless grinding, and sand blasting techniques to match the original OEM finishes. Mounting surfaces and registers are stoned or lapped to remove high spots which can cause misalignment.
Pre-Assembly Inspection
Before assembly, parts are visually inspected for quality, size, and fit using a digital microscope and/or digital borescope. Often parts are measured with micrometers to ensure correct journal tolerances.
Assembly
Assemble the ball nut and ball screw to the correct preload using custom sized, high quality steel balls. Our extensive ball inventory consists of mostly Grade 10 chrome steel balls in all inch and metric nominal sizes in .0001" increments oversize and undersize. This allows us to easily and quickly adjust preload on single nut ball screws. Spacers are surface ground for a precise fit to preload double nut ball screw assemblies. Install wipers (seals) and lubrication.
Testing & Final Inspection
The ball screw assembly is put through a series of tests and final inspection to ensure quality, precision, and durability. This is a very important part of the ball screw rebuilding process and is done using custom built fixtures in conjunction with industry approved measuring devices.
RE-BALL ONLY
Re-Ball Only Service is only available for new, or like-new ball screw assemblies. If you have a ball nut that has accidentally been run off the end of the screw, you may not need a full ball screw assembly rebuild. Our Re-Ball Only Service includes a complete and detailed cleaning of the ball screw, ball nut, and other internal parts. The screw is reloaded with new precision chrome steel balls, preload is adjusted, lubrication is applied, and quality control tests are performed. Since this is not a rebuild service, no warranty is included.
NEW BALL SCREWS
When there is no viable option for rebuilding your assembly, a new ball screw can often be provided per blue print, or reverse engineering. We can machine a new ball screw that will fit your application. Please contact us to discuss availability.
LINEAR ACTUATOR REPAIR
We can perform a complete rebuild of your ball screw driven linear actuators. This includes reconditioning the actuator's ball screw, repairing and/or replacing worn or damaged internal components, replacing cover bands, and replacing all bearings.
EXTRUSION SCREW REPAIR
If you have a worn or damaged extrusion screw, you will find rebuilding is a much more economical option versus a replacement from the OEM. Savings are often in excess of 50%-75% with a fraction of the downtime and equal in performance & warranty. Contact us for more information on our extrusion screw rebuild process, pricing, turnaround, and warranty.
MACHINING SERVICES
Our in house machine shop is fully equipped to make parts for almost any ball screw or linear actuator. This includes but is not limited to:
- Internal & external ball returns
- Ball nut wipers
- Ball nut flanges
- Ball screw shaft ends (new and repair broken)
- Ball nut precision spacers
- V threads
- Key slots
- Bearing journals (hard chrome)
LARGE CAPACITY BALL SCREWS
Many customers ask us "how big of a ball screw can you rebuild?" We are set up to handle screw shafts in excess of 40 feet long. No diameter limits on shafts up to 20 feet long. Maximum diameter 5.5 inches on shafts over 20 feet long. No size limits on ball nut length or diameter.
INJECTION MOLDING
We recondition ball screw assemblies for injection molding machines. These screws typically are used to open and close the dies (clamp), operate the ejector pins, or injector applications. In addition we can order and assemble new bearings utilizing our large capacity hydraulic H frame presses.
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112 Price Cir.
Ringgold, GA 30736
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