As engineers, we use our skills, knowledge and experience to make good appearance and accurate parts. We are very proud of the products we make. We hope the rest of us can see the conceit of the molded goods. But when we don’t get the result we want, what should we do? In terms of size, the parts meet the blueprint specifications, but the surface brightness and overall appearance are not very dream? When this happens, we need to return to the basics and make sure that we use the good processing methods we know.
We need to look at fixtures and other equipment to make sure that they are solid and that they do not contribute to harmonic problems or vibrations during processing. We need to make sure that we don’t use the long equipment we don’t need. These equipment can be easily turned to or added to the opportunity of waste. In high-speed process, we need to ensure the application of equipment with average quality, which has been rated according to the applied programming rpm. But if all the above are good, what should we do?
Study the following options:
1. Control chip: chip thinning is the main factor of excellent surface brightness. Controlling chips may be the first thing you should study. If the chip is in contact with the workpiece during machining, or if you are cutting the chip from scratch, it is likely to affect your surface brightness in a negative way. Study the possibility of changing the chip breaker style you are using to help break down the chip for better control.
Although the application of air and coolant is a good choice for chip removal, pay attention to the coolant. Prevent the application of coolant when cutting intermittently. Hot cracks in the cutting edge can occur… Due to intermittent heating and rapid cooling of the cutting edge… And can cause premature failure of the blade, which may at least initially affect your surface brightness, because of over stressed cutting edge and failure.
2. Speed up: This is more and more the case when using carbide tools. The increase in speed will ensure a shorter time for the material to come into contact with the tip… Thus reducing the edge accumulation on the tool, which may cause poor surface brightness. Increasing the rake angle of the cutting tool also helps to reduce and control edge accumulation.
3. apply accurate tip radius: larger tip radius will be suitable for faster speed. The inserts can be fed at about half of TNR per revolution and still have excellent results. If the TNR to IPR ratio is exceeded, the device will create more “linear” surface brightness, rather than the color and smooth surface you want. Therefore, the larger the TNR, the faster the feed rate it may contain, and the expected consequences still occur. However, the use of a considerable TNR can cause chatter – reduce cutting pressure – so pay attention to and study the speed required to cut raw materials – use TNR equipment that meets your needs.
It is also worth mentioning that the application of a larger tip radius means that you must leave more material for the finish. In order to ensure the normal operation of the equipment, you must have TNR equal to or greater than TNR, so as to complete the removal of the equipment.
If you run into waste around the corner, you may want to try a smaller TNR. Always apply a TNR smaller than the corner radius you are cutting – so you can “create” the radius you need – all the more on finishing equipment. This will help reduce cutting pressure and eliminate chatter.
When milling, try to use the fillet or spherical end milling cutter instead of the plane end milling cutter. Equipment with a fillet radius will give you higher brightness at sharp corners, and will certainly help to prolong tool life.
4. Try to insert the wiper: as far as possible. The wiper insert has a small flat area adjacent to the tip radius. When the device is fed along the workpiece, the plane essentially “wipes” the brightness and helps to eliminate the linear brightness that may be encountered by faster feed rates – this allows the use of smaller TNR to assist in flutter control.
5. Add the lead angle of the tool. A higher lead angle and a positive skew blade produce better surface brightness than a tool with a shallower cutting angle. For example, a face milling cutter with a 45 ° cutting angle will produce a better surface brightness than a face milling cutter with a 90 ° cutting angle.
6. Eliminate linger and pause: every time the equipment stops moving when contacting with the part surface, all traces will be left. Change the process if necessary, but try to make sure that the tool never stops or hesitates during the cutting process.
