Spindle
Accessories
The housing is a part and parcel of the spindle. The shaft of the spindle and the motor required to run the spindle must be held in a housing , which we refer to as spindle housing. The spindle housing is available in various styles and sizes and and may be an integral part of the machine tool. The spindle housing is connected to the machine tool by using a flange or attaching bracket.
Materials used in making spindle housing
- Cast Iron
- Iron
- Stainless steel
- Cast aluminum
- Brass etc.
Functions of spindle housing
The primary functions of a spindle housing are as follows:
- To locate the bearings: High precision bearings, which run at
dN values, must be located exactly in terms of size, geometry etc.
- To provide the lubrication required by the spindle.
- The housing also provides air seal, cooling water or oil, and other
utilities required by the spindle. If the spindle uses oil lubrication,
then the spindle housing includes drilled passages to transfer the oil
or oil mist to each bearing, and then again transfer the oil out of the
bearing to a return line.
- The spindle housing provides a cooling liquid: This helps in removing heat produced by the spindle motor stator, as this heat would affect the spindle performance as a complete unit.
Types of spindle housing
There are various types of spindle housing and depending on the different housing, different mounting types are there for spindles. They are as follows:
Cartridge spindle housing
This is a popular type of housing used in spindles. This type of housing is the simplest to service, and the tolerances required for high speed are very easy to obtain when the housing of the spindle can be produced as a cylinder. The cylindrical cartridge-style spindle is clamped around the housing with an split-clamp mounting block.
Advantages
Advantages of this type of mount are as follows:
- The split-clamp mounting allows the use of standard off-the-shelf
cartridge spindle designs.
- It permits easy axial and rotational adjustments of the spindle
housing inside the mounting bracket.
- Once the mounting block has been located, cartridge-style spindles
can be removed and re-installed without requiring adjustments of
positions.
- The spindle is easy to remove from the mount.
Disadvantages
- This type of split-clamp mounting block usually occupies more space
than a block-style spindle housing design or flange mount design.
- Increased chances for spindle bearing failure.
- Possible variations in axial location and orientation.
- Additional weight imposed on the machine structure.
Flanged cartridge spindle housing
Most spindle builders offer flanged cartridge spindle housings, which allow the spindle to be flange or face mounted. This is usually the preferred method of spindle mounting in a machining center. The flange is a simple, round flange ring having a bolt hole pattern that is permanently attached to the spindle housing. Special designs are possible also with flats or other cut-outs as required to accommodate the machine or tool changer design.
Advantages
The advantages of this type of mounting are:
- Lower chances for spindle bearing failure
- Guaranteed repeatability in X, Y, Z locations and squareness when a
spindle is re-mounted.
- Very little extra space required.
- Spindle removal is easy.
- The flange design provides additional clearance to the spindle nose if the mounting flange can be located further back on the spindle housing.
Disadvantages
- Spindle housing can be more expensive than an off-the-shelf cartridge-style spindle.
- Spindle can only be removed and installed one way .
Block (box) type spindle housing
This type of housing is designed to be lifted and transported using either eye bolts or swivel type hoist rings. Spindles are arranged with tapped holes in the top of the spindle housing for accepting eyebolts and such spindles are manufactured to be lifted from the top. Block style housing has jack screw holes both sides and keyway in housing. With this design, the spindle housing has one or more flat sides, which allows the spindle to be mounted directly onto one of the sides.
Advantages
The advantages of block type mounting are as follows:
- Lower chances for spindle bearing failure caused by mounting
problems.
- It is possible to design good repeatability in X, Y, Z locations and
squareness in such designs when a spindle is re-mounted.
- Very little extra space required.
Disadvantages
- Some spindle mount design may be special, and the spindle is more
expensive than a standard cartridge-style spindle.
- If the machine design does not include accurate location of the block housing, it becomes very necessary to position the spindle every time it is re-installed.
Parameters to consider for spindle housing design
For any type of spindle, the housing design parameters include the following:
- Precision dimensions from base to spindle centerline
- Spindle-bearing condition
- Spindle operating condition
- Surrounding conditions like
- Assembling tolerance
- Cooling condition
- Geometric dimension
- Thermal deformation
- Air purge housing for virtually contamination-free operation and so on.
