Tormach CNC Milling Machine PCNC1100

Warning: This procedure requires trained personnel with PPE!

Cleanliness of the cover and surrounding area

Presence of proper oil film on way surfaces and ball screws

Condition of the X, Y, and Z slideways

Condition of the protective bellows

Enter the number of operation hours since last lubrication

Has the mill stood unused for 48 hours or longer?

Each axis utilizes a double-nut, pre-loaded ball screw. The pre-load in the ball nut is set at the factory by placing a precision ground spacer between the two ball nuts. Lost motion attributable to the ball screw assembly is less than 0.0004”. Ball nut preload is not operator-adjustable.

The ball screw mount bearings are located near the driven (motor) end of each ball screw. These are a pre-loaded angular contact bearing pair and are operator-adjustable. Under typical use, these bearings should be adjusted so that observable lost motion is between 0.0005” to 0.0013”.

Figure 9.4 and Figure 9.5 show a cross section of a typical ball screw shaft mount. The ball screw shaft is in the center and the crosshatched section in Figure 9.5 is the axis motor mount that houses the bearings. There are two angular contact ball bearings, forming a pre-loaded pair. The ball screw Cover Plate holds the two outer races together, along with the Spacer that is between them.

The inner races are held between the Sleeve (left side) and the shoulder cut into the ball screw shaft (right side). The Sleeve is held against the left inner bearing race by the Adjustment Nut and a Lock Nut. When the Adjustment Nut is screwed tighter toward the bearing pair, the preload increases.

Over time, it may become necessary to adjust the ball screw bearing preload to account for bearing wear. The bearing preload will also need to be adjusted if a bearing replacement becomes necessary.

Improper ball screw bearing preload will result in either excessive backlash in the mill if it is too loose, or rapid wear and excessive friction if it is too tight. It should be noted that if your ball screw, ball nut, or angular contact bearings are worn, or if your gibs are adjusted too tight, you will not achieve appropriate lost motion values.

Figure 9.6 shows how the force of preload is transmitted through the bearings, from the inner race to the outer race. In a preload pair, this force is then transmitted back to the inner race by an opposed bearing. It should be apparent that the correct orientation of the angular contact bearing is critical to the operation.

To adjust the angular contact bearing pair preload, the following kit is required (see Figure 9.7):

Check oiler level and top off as needed

Retract and release manual oiler plunger each time mill is powered on and after every four hours of operation

Clean chips from ways, carriage, and bellows’ covers

Spray exposed, non-painted metal surfaces with WD-40® or similar to prevent rust

Sign off on the daily mill maintenance

When correctly adjusted for preload, sustained high spindle speed will bring the spindle bearings to about 155°F (68°C). This is a normal condition. Higher preload in the spindle bearings will result in even higher temperatures and excessive wear.

NOTE: For information on rebuilding PCNC 1100 spindle cartridges, refer to Tormach service bulletin PCNC 1100 Spindle Rebuild.

During operation, sustained high spindle speed will bring the spindle bearings to about 155°F (68°C).

This is a normal condition. Spindle bearing preload is set at the factory and is not operator-adjustable IMPORTANT! Do not attempt to adjust spindle bearing preload on PCNC 770 spindles. Failure to do so will adversely impact spindle balance.;

Regular maintenance of the flood coolant system will prolong the service life of the coolant pump.

• Collect tramp oil with an absorbent pillow or a mechanical oil skimmer. Replace pillows as needed.

• Coolant can scum if allowed to sit for a prolonged period. Replace coolant as needed.

• Check the impeller for obstructions.

• Clean coolant reservoir regularly.

NOTE: Check with local authorities on proper handling and disposal of new and used coolant.;