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Bosch Rexroth Ball Screw Overview

Published in Galleries on 4/11/2018 by Ballscrew Guys

Ballscrew Guys service and refurbish the STAR, Rexroth, and Bosch-Rexroth manufacture of ball screws and linear way guide components. The most common machine and motion system axis we encounter in the Rexroth line is the X-Axis underneath KOMO CNC Routers with OMAX Flow Systems Waterjets a close second.

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Bosch Rexroth Ball Screw

Ballscrew Guys service and refurbish the STAR, Rexroth, and Bosch-Rexroth manufacture of ball screws and linear way guide components. The most common machine and motion system axis we encounter in the Rexroth line is the X-Axis underneath KOMO CNC Routers with OMAX Flow Systems Waterjets a close second.
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Rexroth Bearing Tracks

The advantage of the Rexroth design are the four separate bearing tracks on the ball screw. In a majority of applications, the ball nut rides only on one of them, making the others available for rebuilds. In the case of any serious internal ball screw failure, the ball nut can be rebuilt and seated on any of the unused tracks, virtually eliminating the necessity of regrinding the screw. Above is a picture taken from the X-Axis of a KOMO Router. Notice the dull stripe on the screw, a sign that the ball nut is filled with debris, probably sawdust, which is blocking the internal lubrication ports. If your ball screw has this stripe, it needs attention.
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Ball Nut Interior

This is a typical ball nut interior after it has been removed from a KOMO Router. This particular ball screw assembly was still functioning when we serviced it. It showed striping on the ball screw shaft. While the balls were still circulating through the bearing raceways and return features, it was with great resistance causing strain on the servo motor moving the X-Axis table. The ball bearings circulate this material through the entire screw, acting like a mild grinding paste on the plastic parts inside.
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Plastic Recirculation Plugs

Above are the stock OEM Bosch-Rexroth bearing re-circulation plugs, or shoes, as taken from one of their ball screws. All ball bearing systems are arranged and situated as a loop. These plugs serve to divert the ball bearings by scooping the ball bearings off the raceway into the ball nut, to be delivered to the beginning of the ball bearing helix on the screw. These plastic parts are critical for ball screw function but may wear and break when the ball nut reaches critical contamination and/or has a lubrication failure. This part is not directly available for sale through Bosch-Rexroth. If you experience failure of this part, you will be directed to remove the screw from your machine and send it to one of their approved refurbishment facilities, or be directed to purchase a new ball screw and ball nut assembly - even if your ball screw has good raceways available.
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Recirculation Plug Prototype

Plug failures are common in KOMO and Flow systems equipment. From the many failures seen over the past decade, and through research and testing in the field, we have developed our own replacement. Above is one of the early prototypes at solving this issue. At first we we experimented with 3D printed plastics to work out the initial part geometry. The problem was, we were working from 3D scans of worn or failed OEM parts. While these do function, they do not factor in the material lost from when the part was new. Caution is warranted if you go this route on your own, or another ball screw outfit other than Ballscrew Guys. Patterning off and making these with a tracer mill may work short term, but will likely have issues over time.
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Plug Design

After a year of trials of parts testing with variations of materials and geometries, we ended up making detailed CAD drawings of ALL the major X and Y Axis screws found in KOMO routers, including the ball nuts for the monster screws used in the dual table systems.
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Replacement Seals and Snap Rings

Ballscrew Guys have also manufactured replacement seals and retainer snap rings, allowing us to fully refurbish your Bosch-Rexroth screw to like new condition at your facility.
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Recirculation Plugs - In Brass

Above is a sample lot of the Bosch Rexroth Ball Bearing Recirculation plugs developed and installed by Ballscrew Guys. Manufactured from brass, our initial torture tests have shown they can run with greater longevity and reliability than the OEM plastic inserts. These are parts we stock for all the KOMO Rexroth ball screws so we are ready on short notice to come and repair the X or Y Axis of your machine with the least downtime possible. Please note, if you request or your ball screw requires this upgrade, it will be an additional charge to our flat rate pricing.

Note: Recirculation plugs can not be sold separately as they are custom fit to match the wear of your ball screw assembly.
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Replacement Rexroth Ball Bearing Recirculation Plug Retaining Snap Ring

We replace excessively worn parts for Bosch-Rexroth Ball Screws. These are snap rings used in the three major Bosch-Rexroth ball screw sizes found in most KOMO X, Y, & V axes including the X-Axis screw found in dual table systems.
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Rexroth Linear Motion Rail

The linear motion rails along with the linear motion sliders / bearing blocks are often sold as a set. Ballscrew Guys can rebuild worn linear motion sliders with over-sized ball bearings giving like new positioning without the cost and downtime of having to purchase and install new rails.
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Rexroth Material Roller Bearing

Material Rollers are found on a wide range of equipment. They are often clogged with dirt and debris. Sometimes damaged. Regardless, they need regular cleaning and lubrication. Seized rollers need replacement.
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Rexroth Ball Screw Tension

It is critical that Bosch-Rexroth ball screws that utilize the INA external rotation bearing be adequately stretched or tensioned between their end mounts.
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INA External Rotation Bearing on Bosch Rexroth Ball Screw

The INA External Rotation Bearing seldom goes bad in our experience. This is mostly due to the lubrication port which direct feeds into this bearing assembly. It is often well lubricated and sealed well. The problems come from the more passive lubrication drip that passes through this rotation bearing into the main ball screw nut. Most commonly, this is through two small holes which often get clogged. Especially when this ball screw type is exposed to sawdust or like media.
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OEM Rexroth Plastic Bearing Recirculation Insert Inspection

While Ballscrew Guys manufactures our own brass bearing recirculation plugs, it doesn't mean your stock OEM plugs are bad. If your ball screw is serviced and cleaned regularly, the stock plugs will last for many years.
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Typical Bosch Rexroth Plastic Recirculation Plug Failure

This image shows how the original OEM Plastic Recirculation Plugs fail. Often the plug cracks in half, causing the bearings to blow out a retainer snap ring and a seal. This typically will make a terrible noise. Sometimes the operator will not shut the machine down. This causes the ball bearings inside to become trapped in the ball nut. Often shearing ball bearings and damaging critical bearing races. While your screw can often still be refurbished if this happens, the number of man-hours to get your screw running again just increased dramatically. Because the Bosch-Rexroth Ball Screw Shafts themselves run only on one of four parallel tracks, it is common that the screw can be refurbished by simply rotating it to a new track. This of course assumes that the damage to the ball nut itself is minimal. Cases where ball bearing shear and damage bearing tracks are often where having the screw and nut reground is required.
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Bosch-Rexroth Ball Nut Refurbishment

When we rebuilt the ball nut, we typically removed the entire assembly from the screw shaft for complete cleaning.
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Reloading Rexroth Ball Nut with Brass Recirculation Insert

Here one of Ballscrew Guys Brass Bearing Recirculation Plugs is being inspected prior to installation onto a Bosch-Rexroth Screw.
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Refurbished Bosch-Rexroth X-Axis Ball Screws for KOMO Routers

Many of our customers, especially with CNC Routers, have acquired many Rexroth Ballscrews over the years. Mostly because they were unaware that their old ones could be rebuilt. Ball Screw Guys offer reduced pricing for refurbishing your Bosch-Rexroth Ball Screws while out of the machine. Rebuilding them on the bench is quicker and easier than doing it in the machine.

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