The CNC spindle is the most critical part and the most loaded node. For the right choice, always take into account that the motor power and the mechanical strength of the kinematics should exceed 2 times the calculated values. This is required to preserve expensive parts when wedged.
basic information
Programs for CNC machines are written according to structural rigidity and maximum spindle speeds. When milling, the probability of a rotary tool breaking due to heating or metal fatigue should be taken into account. Therefore, safety couplings are often put in place, calculated for the specific dimensions of the motor shaft and the diameter of the cartridge.
All programs for CNC machines are previously worked out step by step without axis movement. When the user is 100% sure that the spindle cams will not be touched, then they start working with movements in step mode or single cycles. When the test ends without blanks, proceed to the direct cutting of the part.
The CNC spindle is an expensive unit and the most powerful; nevertheless, it can be easily disabled due to careless handling of equipment. Some systems have complex corrector calculations, the incorrect determination of which results in lengthy repairs. To work on each new machine requires prior retraining of the operator, even if he already has experience in a similar rack.
Parameters
The CNC spindle should be selected according to the following criteria:
- Type of cooling unit: air, liquid.
- Spindle motor power and gear ratio.
- Engine's type.
- Type of bearings and method of their lubrication.
- Modes of operation, type of braking system.
- Positioning accuracy and type of tracking sensor.
- Spindle mount
In addition to the above parameters, the motor design itself is important: the number of windings, the type of rotor, the method of removing and applying load to the windings. Take into account the torque and the possibility of adjustments for the centers of the node relative to the feed axes. Cartridges must also be changed: self-clamping, hydraulic, manual, pneumatic.
The CNC spindle is selected taking into account the possibility of changing consumable spare parts. You should look at the options of available bearings that are available in stocks, find out about delivery times. It may turn out that due to the small consumable, production will arise for a long period, or you will need to pay a tenfold price for the manufacture of the part. The small spindle for the CNC milling machine should have a lightweight design and small dimensions.
What can you make a node yourself?
The spindle for a CNC milling machine for processing wood, plastic and other soft materials can be a conventional electric drill. It is important to set it according to the level and measure the runout of the cutter. This is a cheap option that allows you to improve your existing design.
As a rotating axis, any engine with a precisely set tool is suitable. Reliable and rigid spindle mount is selected. The axial play should not be more than 0.01 Ξm for most holes. A drill, a revolving drill is suitable, you can even adapt the engine from a washing machine or sewing machine. Which spindle is suitable in a particular case depends on the goal. The type of material, the required dimensional accuracy of the part, the workload in the automatic cycle are taken into account. You can also order ready-made solutions in the online store.
Custom Engines
Numerical control (CNC) is used to improve the accuracy of the parts and reduce the time cost of production. For a single product, the cost of equipment exceeds the amount invested in its production. It will be cheaper to order the part in any company engaged in metalworking.
For a homemade spindle, finished motors are ordered. DC motors, synchronous and asynchronous, are popular. Turnover of 12 thousand for such engines is not the limit. Additionally, a manual or automatic transmission can be used. Powerful spindle motors require steady power. This is their fault. But if you put the simplest drive and motor with feedback, then on such a machine it is already possible to process more complex products. An additional axis is introduced into the CNC, which can hold not only the milling cutter, but also cylindrical parts.
The better engines to order?
At the factory motors, shaft balancing has already been carried out and bearings with a minimum runout have been selected. It remains only to put the finished engine on a standard mount and set the alignment on the indicator stand. Milling accuracy is required in the production of printed circuit boards, kinematics details.
Synchronous motors performed well in the manufacture of jewelry parts by engraving. Permanent motors have a low noise level during operation, which can be useful for managers trying to improve their production. However, they have the property of basking while working at high speeds. Therefore, it will be necessary to separately supply cooling, even air.
Professionals Choice
More expensive spindle motors are necessarily equipped with liquid cooling. They have higher positioning accuracy, quite powerful torque, and reliability is several times higher than indicated. Usually they are mounted on 3-4 bearings, and not on 2, like classic motors. Due to this, a minimum runout of the tool or part in the cartridge is achieved.