How to choose the VMC machine for our workshop?
What factors we have to consider in purchasing a vertical machining center or VMC:
Everybody has got the general basic information about machining center, spindle within the purchasing time. Information like, max speed of spindle, torque and spindle power….
Power is the point that based on the range of parts you have would be chosen. However, torque, speed and power are the key factors but it’s essential to consider other issues.
Initially it seems that spindle has not the special role in machine tools, tools cut the work piece, table moves, control systems monitors the movement and accuracy and its feasible actions, software runs the rest of job and coordination and spindle is not except the holding device of tools as the intermediary to transmit the power from motor to tool. The stated explanation is generally right, but spindle dampen many failures and amend many functions. The parts used in spindle has very crucial effect on longevity of machine and its proper accuracy. Spindle is truly the heart of your machining center.
The quality of parts used I your machines’ spindle not only causes the longer life of spindle but it exactly defines spindle at what speed and at what amount of torque could tolerate the vibrations. At the time you start to search and study about spindle and its technology, bearings are at the center of this issue which is difficult and needed to investigate more about because you are faced with many standards and figures like ABEC, DB and …
Bearing system in spindle:
In this system, bearings are placed in the inner and outer steel race. The material used in bearings are effective on temper, level of vibrations and longevity of spindle. The ceramic bearings which called also as the hybrid have the special advantages compared to the steel. Bearings have different types.in the design of high speed spindles utilizing the angular bearing is common these bearings are placed in the very accurate cycling path and could tolerate the axial and radial pressures.
Ceramic bearings have the 60% ls mass compared to the steel bearings this is very important because in high speed bearings due to the centrifugal forces push to the re and will cause the deformation in race out the shape of bearings.th ceramic are different. Due to the lighter mass they can reach 30% more speed.
Better action of ceramic type in lower tempreture:
Because of lower friction they produce lower heat and will provide more longevity.
Lower vibration level:
The test and surveys have proven, spindles using the ceramic bearings have more rigidity and more natural frequencies this item directly effect on longer life and functionally better result in spindle feedback.
The other types of bearings are roller type and cylindrical can be used for increasing the level of tolerances and better rigidity in spindle.
Different types of spindles:
Based on your necessities, speed, torque, time of shift, accuracy level and other cases you can find your applicable spindles as following:
1- Belt type
2- DDS direct drive spindle
3- Gearbox
4- Built-in type
We have studied the vary spindles in other article which you can refer to know figure out more.
enemies of spindle:
after selecting your spindle its better know how you can save it and longer life.
There are two major enemies:
1- Heat
2- Contaminations (chips, dust, cooling liquids and micro contaminations)
Generally, the most report on destructing spindles are contaminations entrance.in many cases due to the assembly problems in seals, contaminations have found way of penetration inside.
Be assured the manufacturing company of spindle is enough know-how and has the strategy implementing of pneumatic air blast cleaning of Labyrinth seals. This system can be use at the end and beginning of seal as the dual purge.
Heat is also very destructive factor against the spindle because doe to increasing the temperature, expansion would occur. The manufactures have to specify which elements and indexes for maintaining the spindle considered which consequently axes Y & Z will not meet any problem.
The cooling devices as oil chillers and heat exchangers are some devices are available for reducing the tensions about the temperature. They would be very effective on the life of spindle and their function specially when the machine uses the higher speeds.
Other factor which needed to be considered is using the appropriate tool equipment. Using the unbalanced tools will reduce the life of spindle.
Other considerations:
Study your machining process and time of productions based on your study you can use the other components for your vertical machining center.
Like spindle heat could effect on tools. You have to figure out, do you need deep hole drilling functions, the nozzles could satisfy you in reducing the tools and work piece temperature or not ?, otherwise you will need the CTS system implemented on your spindle at the time of machine tools production and assembly which most of the time it is as the option not standard. Coolant through spindle is the ability which can transmit the cooling liquid within the spindle and through the tool.
Article above is just very small but important guidance of purchasing the machining center prepared in sales department of Ksp-group.
