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Lubrication

Please make sure all linear movement components are lubricated prior to use. Using non-lubricated components will have a reduced overall life. The recommended grease for both the Ball nuts and SBR20UUOP bearing blocks is Lithium Soap grease. It's difficult to narrow down the exact grease to use, even SKF recommend 3 different greases, these are LGEP 2, LESA 2 or LGMT 2. I have been using LGMT 2 without issue but don't currently have any long term data so use at your own discression. These greases should be available from lubricant retailers and are around $10 for 450g. It is not recommended you mix different types of greases.

SKF High Load, Extreme Pressure Bearing Grease LGEP 2 Grease developed for SKF Energy Efficient spherical roller bearings LESA 2SKF General Purpose Industrial and Automotive Bearing Grease LGMT 2

 

Ballscrew assembly

 

The BF12 Bearing block

The BF12 Bearing block is a "floating" bearing block. The roller bearing inside is not held in place and is free to move up and down the sleeve in the bearing housing. There are two rubber grommets either side that are designed to keep foreign material out of the bearing. Another part of the BF group is a circlip, this clip will hold the roller bearing on the end of the Ballscrew. The BF12 bearing housing only supports the weight of the bearing and the Ballscrew and is designed to keep the Ballscrew shaft aligned. It's not put under any shear force or other loads form the axis moving so it is only held in place by 2 bolts.

Assembling the BF12
In all likelihood your BF12 Bearing block was delivered assembled, if not, assembling it is very straight forward. Using the image above as a guide, insert the Roller bearing into the sleeve in the BF12 Bearing housing, and, push a rubber grommet into each side of the housing. The grommets are to keep debris away from the bearing and will stop the bearing from falling out when you move it around. The inner hub of the bearing should be visible when unit is assembled. The Circlip will be used on the Ballscrew shat at a letter stage.

 

 

The BK12 Bearing block

The BK12 Bearing block is a fixed bearing block and it's construction is designed to bear all of the loads associate with the movement of the Axis it supports. Because of these loads it has 2 Roller bearings for strength and once assembled they cannot move inside their housing and remain rigidly in place at all times.

The parts above, left to right:

  • Shaft spacer (The spacer goes on the Ballscrew shaft and keeps the Ballscrew thread away from the rubber Grommet)
  • Rubber Grommet (Keeps debris away from the bearing)
  • BK12 Bearing Housing (Main mounting point and housing for bearings)
  • Roller Bearings (2) (Bears any loads and allows the Ballscrew shaft to rotate while being held firmly in place)
  • Bearing Flange (Plate used to hold Roller bearings in place)
  • M4x10mm Allenkey Bolts (Holds the Bearing Flange in place)
  • Rubber Grommet (Keeps debris away from the bearing)
  • Shaft spacer (The spacer goes on the Ballscrew shaft and keeps the Shaft Retaining Nut away from the rubber Grommet), and,
  • Shaft Retaining Nut (Locks the Ballscrew shaft on to the bearings)

 

Assembling the BK12
In all likelihood your BK12 Bearing block was delivered assembled, if not please follow this process. From the Bearing Flange side of the BK12 Bearing housing, insert the 2 Roller bearings in to the sleeve (they cannot be inserted from the other side as the opening is not large enough). Insert the Bearing Flange in on top of Bearings and then insert the 4 M4x10mm Allen key Bolts into the flange. Tighten all 4 bolts.

Insert the Rubber Grommets into either side of the BK12 Housing. The 2 Shaft pacers and Shaft retaining nut are used on the Ballscrew shaft at a latter stage.

 

 

The RM1605 Ballscrew Unit

The RM1605 Ballscrew unit will consist of a 16mm machined rod with thread and mounting surfaces and is fitted with a Bull Nut and Mounting Flange. The most important thing to know about your Ballscrew is you should never wind the Ball Nut past the threaded part of the ballscrew, the ball nut is filled with ball bearings which will spill out and are difficult an time consuming to re-insert. The orientation of the nut is not specific and it could be facing the other way, this will make no difference to operation. The M6 Oiling point will accept an M6 grease nipple.

 

The RM1605 Ballnut Housing

The Ballnut Housing is very straight forward and is designed to connect your Ballscrew with the axis it is going to move

Attaching the Ballnut Housing to the Ballscrew Unit

Align the RM1605 Mounting sleeve on the Ballnut Housing with the Ballnut Body on the Ballscrew Unit and slide on, take care not dent or scrape the Ballscrew thread. Rotate the Ballnut Housing until it aligns with the mounting points on the Ballnut Flange. Insert the 6 M5x12mm Alenkey head bolts and tighten.

Attaching the BF12 Bearing block to the Ballscrew Unit

Insert the floating end of the Ballscrew shaft into the BF12 Bearing block. The shaft should pass through the roller bearing in the BF12 until the Circlip groove is visible on the other side.

 

With a pair Circlip pliers or needle nose pliers open the circlip and slip it over the shaft until it drops into the retaining groove.

 

To test, hold the BF12 in one hand and rotate the Ballscrew shaft, the Ballnut and Housing should move back or forth. You may feel some unwanted resistance, this is most likely from the Rubber Grommet between the roller bearing and the RM1605 thread. To resolve this you can try; oiling the grommet, working the Ballscrew until the action frees up, work the grommet on a larger shaft to try an increase the ID of the grommet, trim the grommet, or (if all else fails), remove the grommet completely. 






Attaching the BK12 Bearing block to the Ballscrew Unit

On the fixed end of the Ballscrew shaft insert a Shaft Spacer, then the BK12 Bearing unit, and then the second Shaft Spacer. The first Shaft spacer should rest up against the end of the RM1605 thread on the Ballscrew. The first roller bearing will sit up against the spacer and the final Shaft Spacer up against the last roller bearing. The thread for the Shaft Retaining nut should be visible.


With an appropriate Allenkey, loosen of the 2 grub screws on the Shaft Retaining Nut.

 

Slide the Shaft Retaining Nut along the fixed end of the Ballscrew until it meets the Retaining Nut thread, tighten the nut on the thread until it is firmly finger tight. The Retaining Nut will need to hold both Shaft Spacer and both roller bearings firmly in position. Tighten both the grub screws, these will hold the nut in position.

 

Attaching the Motor Coupler to the Ballscrew Unit

As there are many types of Motor couplers available and it will be difficult to customize these instructions to the particular type you have received, so instead, I will give some fairly broad instructions and try and cover all bases. First up there are 2 general methods in which a coupler will attach to the shaft. These are Jaw (or clamp) and Grub screw, and, your coupler may have one or the other or a combination of both.

With Jaw (or clamp) style, the coupler will have one or two slits in it which have a bolt running through them. The shaft is inserted into the coupler and the bolt is used to pull the 2 halves of the opening together and clamp the shaft in-between.

With the Grub screw type there will be one or two threaded holes passing from the exterior of the coupler to the interior where a grub screw will protrude. With this type, the grub screw is tightened directly against the shaft to hold it into position.

Your Motor Coupler may have one or both of these types and it may have them in multiple combinations. The important thing to remember is to tighten the Jaw (or Clamp) style ones before you tighten the Grub screws. Tightening the Grub screws first might create a misalignment as it can put the shaft off center if the fit is not tight.


To attach the Motor Coupler, loosen off any bolts or grub screws. Insert the 10mm end of the Motor Coupler on to the fixed end of the shaft, the shaft should be inserted approx 1/3 to 1/2 the length of the coupler. Tighten any Jaw type bolts and then grub screws at the 10mm end of the coupler.

 

To test the Ballscrew Assembly, rotate the Motor Coupler and the Ballnut and Ballnut Housing should move forward or back. Again, if the there is some unwanted resistance to the coupler being turned it is most likely the rubber grommets in the BK12 Bearing unit, please carry out the remedial steps listed with the BF12 instructions.

 

Assembling the other Ballscrew Units

Please repeat the instructions above for all other Ballscrew Assemblies.

 

 

 

 


 

   

This site was last updated 02/15/15