25 frequently asked questions in the field of mold manufacturing

Time:2020-09-18 09:00:17 / Popularity: / Source:

mold manufacturing 

 1) What is the most important and most decisive element when choosing mold steel?

Forming method - can be selected from two basic material types.
A) Hot-worked tool steel that withstands relatively high temperatures during die casting, forging and extrusion.
B) Cold worked tool steel for blanking and shearing, cold forming, cold extrusion, cold forging and powder press forming.
Plastic - Some plastics can produce corrosive by-products such as PVC plastic. Condensation, corrosive gases, acids, cooling/heating, water or storage conditions caused by prolonged shutdown can also cause corrosion. In these cases, it is recommended to use a stainless die steel.
Mold Size - Large size molds often use pre-hardened steel. Integral hardened steel is often used in small size molds.
Mold use times - long-term use (> 1000000 times) of mold should use high hardness steel, its hardness is 48-65HRC. For medium long-term use (100,000 to 1,000,000 times), pre-hardened steel should be used, and its hardness is 30-45HRC. Short-term use: surface roughness - many plastic mold manufacturers are interested in good surface roughness. When adding sulfur to improve metal cutting performance, surface quality will be reduced. Steel with high sulfur content will also become more brittle.

2) What are primary factors that affect machinability of materials?

Steel structure is also very important for metal cutting performance. Different architectures include: forged, cast, extruded, rolled and machined. Forgings and castings have surfaces that are very difficult to machine.
Hardness is an important factor affecting cutting performance of metal. General rule is that the harder steel, the harder it is to process. High-speed steel (HSS) can be used to process materials up to 330-400HB; high-speed steel + titanium nitride (TiN) coatings can process materials up to 45HRC; for materials with hardness 65-70HRC, cemented carbide, ceramic, cermet and cubic boron nitride (CBN) must be used.
Non-metallic inclusions generally have an adverse effect on tool life. For example, Al2O3 (alumina), which is a pure ceramic, has a strong abrasiveness.
The last one is residual stress, which can cause metal cutting performance problems. It is often recommended to perform a stress relief process after roughing.

3) What are production costs of mold manufacturing?

Roughly speaking, distribution of costs is as follows:
Cutting 65%
Workpiece material 20%
Heat treatment 5%
Assembly / adjustment 10%
This also clearly demonstrates importance of good metal cutting performance and excellent overall cutting solutions for economic production of molds.

4) What is cutting characteristics of cast iron?

In general, it is: the higher hardness and strength of cast iron, the lower metal cutting performance, the lower life expectancy from blade and tool. Cast iron used in metal cutting production generally has good metal cutting performance. Metal cutting performance is related to structure, and harder pearlitic cast iron is more difficult to process. Flake graphite cast iron and malleable cast iron have excellent cutting properties, while ductile iron is quite bad.
Main types of wear encountered when machining cast iron are: abrasion, bonding and diffusion wear. Abrasion is mainly produced by carbides, sand inclusions and hard cast skin. Bonding wear with built-up edge occurs at low cutting temperatures and cutting speeds. Ferrite portion of cast iron is the easiest to weld to insert, but this can be overcome by increasing cutting speed and temperature.
On the other hand, diffusion wear is temperature dependent and occurs at high cutting speeds, especially when using high strength cast iron grades. These grades have high resistance to deformation and result in high temperatures. This wear is related to interaction between cast iron and tool, which allows some cast irons to be machined at high speeds with ceramic or cubic boron nitride (CBN) tools for good tool life and surface quality.
Typical tool properties required for machining cast iron are: high heat hardness and chemical stability, but also related to process, workpiece and cutting conditions; cutting edge is required to have toughness, heat fatigue wear and edge strength. Degree of satisfaction with cutting cast iron depends on how wear of cutting edge develops. Fast bluntness means hot cracks and gaps that cause premature cutting of cutting edge, damage to workpiece, poor surface quality, excessive waviness, and so on. Normal flank wear, balance and sharp cutting edges are just what you need to do.

5) What are main and common processing steps in mold manufacturing?

Cutting process should be divided into at least 3 process types:
Roughing, semi-finishing and finishing, sometimes even super finishing (mostly high-speed cutting applications). Residual milling is of course prepared for finishing after semi-finishing process. It is important to work hard in each process to leave a uniform distribution of allowance for next process. If direction of tool path and workload are rarely changed rapidly, tool life may be extended and more predictable. If possible, finishing process should be carried out on a dedicated machine. This will increase geometric accuracy and quality of mold during shorter commissioning and assembly times.

6) Which tool should be used mainly in these different processes?

Roughing process: round insert milling cutter, ball end mill and end mill with arc radius.
Semi-finishing process: round insert milling cutter (circular insert milling cutter with diameter range of 10-25mm), ball end mill.
Finishing process: round insert milling cutter, ball end mill.
Residual milling process: round insert milling cutter, ball end mill, vertical mill.
It is important to optimize cutting process by selecting a specific tool size, geometry and grade combination, as well as cutting parameters and appropriate milling strategies.

7) Is there one of the most important elements in cutting process?

One of the most important goals in cutting process is to create an evenly distributed machining allowance for each tool in each process. This means that tools of different diameters (from large to small) must be used, especially in roughing and semi-finishing operations. Primary criterion at all times should be as close as possible to final shape of mold in each process.
Providing a uniform distribution of machining allowance for each tool guarantees constant, high productivity and a safe cutting process. When axial cutting depth / radial cutting depth is constant, cutting speed and feed rate can be kept constant at a high level. In this way, mechanical action and workload change on cutting edge are small, so that less heat and fatigue are generated, thereby increasing tool life. If latter process is a semi-finishing process, especially for all finishing processes, unmanned or partially unprocessed. Constant material machining allowance is also basic standard for high speed cutting applications.
Another advantageous effect of a constant machining allowance is small adverse effect on machine tool, guide rails, ball screw and spindle bearings.

8) Why we most often use round insert milling cutters as the first choice for mold roughing tools?

If a square shoulder milling cutter is used for rough milling of cavity, a large amount of stepped cutting allowance is removed in semi-finishing process. This will cause cutting force to change and tool to bend. Result is an uneven machining allowance for finishing process, which affects geometric accuracy of mold. If a square shoulder cutter with a weaker tip (with a triangular blade) is used, an unpredictable cutting effect can result. Triangular or diamond-shaped inserts also produce greater radial cutting forces, and because of small number of cutting edges, they are less economical roughing tools.
On the other hand, round inserts can be milled in a variety of materials and in all directions. If used, transition between adjacent cutters is smoother, leaving a smaller and more uniform machining allowance for semi-finishing. One of characteristics of round inserts is that concentration of chips they produce is variable. This allows them to use a higher feed rate than most other blades. Main blade of circular blade changes from almost zero (very shallow cutting) to 90 degrees, and cutting action is very smooth. At maximum depth of cut, lead angle is 45 degrees, and when cutting along a straight wall with an outer circle, lead angle is 90 degrees. This also explains why strength of circular insert tool is large - cutting load is gradually increasing. Roughing and semi-roughing should always be the first choice for round insert milling cutters such as CoroMill 200 (see mould manufacturing sample C-1102:1). In 5-axis cutting, round insert is very suitable, especially without any restrictions.
Through use of good programming, round insert milling cutters can largely replace ball end mills. Combination of a small circular blade with a finely ground, positive rake and light cutting geometry can also be used for semi-finishing and some finishing operations.

9) What is effective cutting speed (ve) and why is it important for high productivity?

mold manufacturing 
Basic calculation of effective cutting speed on actual or effective diameter during cutting is always very important. Since table feed depends on speed at a certain cutting speed, if effective speed is not calculated, table feed will be calculated incorrectly.
If tool's nominal diameter value (Dc) is used in calculating cutting speed, effective or actual cutting speed is much lower than calculated speed when cutting depth is shallow. Such as round insert CoroMill200 tools (especially in the small diameter range), ball end mills, large nose arc radius end mills and CoroMill390 end mills. As a result, calculated feed rate is also much lower, which severely reduces productivity. More importantly, cutting conditions of tool are lower than its capabilities and recommended application range.
When performing 3D cutting, diameter at the time of cutting is varied, which is related to geometry of mold. One solution to this problem is to define steep wall area of mold and shallow area of part. If you have a specific CAM program and cutting parameters for each area, you can achieve good compromises and results.

10) What are important application parameters for successful hardened die steel milling?

When finishing high-speed milling of hardened die steel, one of main elements to be observed is shallow cutting. Depth of cut should not exceed 0.2/0.2mm (axial cutting depth / radial cutting depth). This is to avoid excessive bending of tool holder/cutting tool and to maintain a small tolerance and high precision of machined tool.
It is also important to choose a clamping system and tool with good rigidity. When using solid carbide tools, it is important to use tools with the largest core diameter (maximum bending stiffness). A rule of thumb is that if diameter of tool is increased by 20%, for example from 10mm to 12mm, bending of tool will be reduced by 50%. It can also be said that if tool overhang/extension is shortened by 20%, bending of tool will be reduced by 50%. Large diameter and tapered shanks further increase stiffness. When using ball end mills with indexable inserts, if shank is made of solid carbide, bending rigidity can be increased by 3-4 times.
When finishing hardened die steel with high speed milling, it is also important to choose a special geometry and grade. It is also important to choose a coating with a high heat hardness like TiAlN.

11) When should I use down-cutting and when should I use up-cut milling?

Main recommendation is to use as much milling as possible.
When cutting edge is just cutting, chip concentration can reach its maximum value in down-cut milling. In the case of up-cut milling, it is minimum value. In general, tool life in up-cut milling is shorter than in down-cut milling because heat generated in up-cut milling is significantly higher than in down-cut milling. When chip concentration increases from zero to maximum in up-cut milling, more heat is generated because cutting edge is subjected to a higher friction than in down-milling. Radial force is also significantly higher in up-cut milling, which has an adverse effect on spindle bearings.
In down-cut milling, cutting edge is mainly subjected to compressive stress, which is much more advantageous for cemented carbide inserts or solid carbide tools than for tensile forces generated in up-cut milling. of course there are exceptions. When using a solid carbide end mill for side milling (finishing), especially in hardened materials, up-cut milling is preferred. This makes it easier to obtain wall straightness with a smaller tolerance and a better 90 degree angle. If there is no overlap between different axial passes, tool marks are also very small. This is mainly due to direction of cutting force. If a very sharp cutting edge is used in cutting, cutting force tends to "pull" knife toward material. Another example of use of up-cut milling is use of old-fashioned manual milling machines for milling, where screw of old-fashioned milling machine has a large gap. Up-cut milling produces a cutting force that eliminates gap, making milling movement smoother.

12) Copy milling or contour cutting?

In cavity milling, the best way to ensure a successful path to a milling tool is to use a contour milling path. Milling outer circumference of milling cutter (eg ball end mills) along contour often results in high productivity because more teeth are being cut at larger tool diameters. If spindle speed of machine is limited, contour milling will help maintain cutting speed and feed rate. With this tool path, change in workload and direction is also small. This is especially important in high speed milling applications and hardened material processing. This is because if cutting speed and feed rate are high, cutting edge and cutting process are more susceptible to adverse effects of changes in workload and direction. Changes in working load and direction can cause changes in cutting force and tool bending. Copy milling along steep wall should be avoided as much as possible. When copy milling, chip concentration at low cutting speed is large. In the center of ball-end knife, there is a danger of blade being broken. If control is poor, or machine has no read-ahead function, it cannot be decelerated quickly enough, and risk of chipping at the center is most likely to occur. Upper profile milling along steep wall is better for cutting process because chip concentration is at its maximum at favorable chip speeds.
In order to achieve longest tool life, cutting edge should be kept in continuous cutting for as long as possible during milling process. If tool enters and exits too frequently, tool life will be significantly shortened. This will exacerbate thermal stress and thermal fatigue on cutting edge. It is more advantageous for modern carbide tools to have uniform and high temperatures in cutting area than to have large fluctuations. Profiling milling path is often a mixture of up-cut and down-cut (zigzag), which means that knife is frequently eaten and retracted during cutting. This tool path also has a bad influence on quality of mold. Each time knife means tool is bent, there is a raised mark on the surface. When tool exits, cutting force and bending of tool are reduced, and there is a slight material "overcutting" in exit portion.

13) Why do some milling cutters have different pitches?

Milling cutters are multi-edge cutting tools, number of teeth (z) is changeable, and there are some elements that can help determine pitch or number of teeth for different machining types. Materials, workpiece dimensions, overall stability, overhang dimensions, surface quality requirements, and available power are processing-related elements. Tool-related elements include enough feed per tooth, at least two teeth at the same time, and chip capacity of tool, which are only a small part of it.
Pitch (u) of milling cutter is distance from point on the cutting edge of insert to same point on next cutting edge. Milling cutters are divided into sparse, dense and ultra-tight pitch milling cutters. Most Coromant milling cutters have these three options. Dense pitch means that there are more teeth and proper chip space, which can be cut with high metal removal rate. Generally used for medium load milling of cast iron and steel. Fine pitch is the first choice for general purpose milling cutters and is recommended for mixed production.
Spanning means that there are fewer teeth and a large chip space on the circumference of milling cutter. Spacing is often used for roughing to finishing of steel. Vibration in steel processing has a great influence on processing results. Spalling is a truly effective solution to problems. It is the first choice for long overhang milling, low power machines or other applications where cutting forces must be reduced.
Ultra-precision tool has a very small chip space and can be fed with a higher table. These tools are suitable for cutting of interrupted cast iron surfaces, cast iron roughing and small residual machining of steel, such as side milling. They are also suitable for applications where low cutting speeds must be maintained. Milling cutters can also have uniform or unequal pitches. The latter refers to unequal spacing of teeth on tool, which is also an effective way to solve vibration problem.
When there is a vibration problem, it is recommended to use a toothless unequal pitch milling cutter as much as possible. Since there are fewer blades, possibility of increased vibration is small. Small tool diameters can also improve this situation. A combination of well-adapted troughs and grades should be used—a combination of sharp cutting edges and toughness.

14) How to position milling cutter for optimum performance?

Cutting length is affected by position of milling cutter. Tool life is often related to length of cutting that cutting edge must bear. Milling cutter positioned in the center of workpiece has a short cutting length. If milling cutter is offset from center line in either direction, cutting arc is long. Keep in mind how cutting force works and must achieve a compromise. With tool positioned in the center of workpiece, direction of radial cutting force changes as cutting edge of blade enters or exits cutting. Clearance of machine tool spindle also exacerbates vibration, causing blade to vibrate.
By deviating tool from center, a constant and favorable cutting force direction is obtained. The longer overhang, the more important it is to overcome all possible vibrations.

15) What measures should be taken to eliminate vibration during cutting?

When there is a vibration problem, basic measure is to reduce cutting force. This can be achieved by using correct tool, method and cutting parameters.
Follow proven recommendations below:
- Select a sparse or unequal pitch cutter.
- Use positive rake angle, small cutting force blade geometry.
- Use a small milling cutter whenever possible. This is especially important when milling with a damper post.
- Blades with a small cutting edge passivation radius (ER), from concentrated coatings to thin coatings. Uncoated blades can be used if desired. High toughness insert grades with fine grained particles should be used.
- Use a large feed per tooth. Reduce speed and keep table feed (equal to a larger feed per tooth). Or maintain speed and increase table feed (larger feed per tooth). Never reduce feed per tooth!
- Reduce radial and axial depth of cut.
- Choose a stable holder such as Coromant Capto. Use the largest possible adapter size for optimum stability. Use a taper extension to achieve maximum rigidity.
- For large overhangs, use a damper post that is combined with a pitch-tooth pitch cutter. When installing milling cutter, connect milling cutter directly to shock absorbing handle.
- Deviate milling cutter from center of workpiece.
- If you use a tool with even teeth - you can remove one blade every other tooth.

16) What are the most important measures to be taken to balance tool?

Typical steps involved in achieving tool balance throughout cutting process are as follows:
- Measure imbalance of tool/shank assembly.
- Reduce imbalance by changing tool, cutting it to remove some mass, or moving weight on handle.
- These steps must often be repeated, including checking tool again, fine-tuning again until equilibrium is reached.
Tool balancing also involves instability in several undiscussed processes. One of them is problem of cooperation between shank and spindle. Reason for this is that there is often a measurable gap during clamping, or there may be chips or dirt on taper shank. This will cause taper shank to be positioned differently each time. Even if tool, shank and spindle are in good condition in all respects, if there is contamination, it will cause an imbalance. In order to balance tool, cost of cutting process must be increased. If tool balancing is important to reduce costs, each case should be analyzed.
However, in order to balance tool well, there is still a lot of work to do when choosing right tool. Following points should be considered when selecting a tool:
- Purchase high quality knives and shanks. You should choose a tool holder that has been previously unbalanced.
- It is best to use short and lightest tools.
- Regularly inspect tool and tool holder for signs of fatigue threads and deformation.
Tool imbalance that process can accept is determined by process itself. These conditions include cutting force during cutting process, balance of machine tool, and extent to which two elements interact with each other. Testing is the best way to find the best balance. Operate several times with different imbalance values, for example starting with an imbalance value of 20 gmm or less. After each operation, repeat test with a more balanced tool. Optimum balance should be such a point. After this point, further improvement of tool balance will not improve surface quality of workpiece; or such a point: at this point process can easily guarantee specified workpiece tolerance.
Key is to always focus on process, rather than targeting balance-G value or any other deterministic balance. This goal should be to achieve the highest possible efficiency of process. This involves weighing cost of tool balancing and benefits that result from it, so a reasonable balance should be made between cost and benefit.

17) Which tool holder should I use in order to get the best possible results in conventional and high speed cutting applications?

At high speed machining, centrifugal force is very large, which causes spindle hole to gradually become larger. This has a negative effect on shank of some V-flanges because shank of V-shaped flange only contacts spindle bore on radial face. Spindle hole change assembly causes tool to be pulled into spindle under constant pulling force of pull rod. This can even cause tool to stick or dimensional accuracy in Z-axis direction to decrease.
Tool that is in simultaneous contact with spindle hole and end face, that is, tool that is simultaneously matched in radial direction and axial direction, is more suitable for cutting at a high speed. When spindle hole is enlarged, end face contact prevents tool from moving upward in spindle hole. Tools using hollow shanks are also susceptible to centrifugal forces, but they have been designed to increase with increasing spindle bore at high speeds. Tool and spindle are in radial and axial contact to provide good clamping rigidity, allowing tool to be cut at high speeds. Coromant Capto interface with its unique elliptical triangular short cone design delivers superior performance in torque transfer and high productivity cutting.
Spindle speed ISO 40 HSK 50A Coromant Capto C5
0 100% 100% 100%
20 000 100% 95% 100%
25 000 37% 91% 99%
30 000 31% 83% 95%
35 000 26% 72% 91%
40 000 26% 67% 84%
When arranging high-speed cutting, try to use a tool system that combines symmetrical tools and tool holders. There are several different tooling systems available. Shank is first heated to expand holes, and tool is clamped after they are cooled. This is interference fit system. This is the best and most reliable fixed tool method for high speed cutting. This is first because its runout is very small. Second, connection can deliver high torque. Third, it is easy to build custom tools and tool assemblies. Finally, tool assembly consisting of this method has a very high overall rigidity.
Another outstanding and very versatile tool clamping device is CoroGrip, a Coromant high-precision power chuck. This tool holder system covers everything from roughing to super finishing. A collet can clamp all types of tools from face milling cutter with straight shank, Wyeth or side pressure shank to drill bit. Standard spring jackets, such as hydraulic grips (HydroGrip), BIG, Nikken, NT spring collets, can be used with CoroGrip chucks. Runout at 4XD is only 0.002 0.006 mm. High clamping and torque transmission, balanced design for high speed cutting.

18) How should I cut corners so that there is no risk of vibration?

Method of cutting corner of system is to use linear cutting (G1), and transition at the corner is discontinuous. This means that when tool reaches corner, tool must decelerate due to dynamic characteristics of linear axis. There is a brief pause before motor changes feed direction, which generates a lot of heat and friction. Very long contact lengths can result in unstable cutting forces and often result in insufficient corner cutting. Typical result is vibration—the larger and longer tool, or the larger total overhang of tool, the stronger vibration.
The best solution to this problem: use a tool with a smaller fillet radius than corner radius. Use arc interpolation to create corners. This machining method does not cause a pause at the boundary of block, which means that movement of tool provides a smooth, continuous transition, possibility of vibration greatly reduced.
Another solution is to create a fillet radius that is slightly larger than one specified on drawing by circular interpolation. This is advantageous so that sometimes larger tools can be used in roughing to maintain high productivity.
Remaining machining allowance at the corner can be fixed or circularly interpolated with a smaller tool.

19) What is the best way to start cutting cavity?

There are 4 main methods: pre-drilling of starting hole and pre-drilling of corners. This method is not recommended: this requires addition of a tool, which also occupies tool room. From point of view of cutting alone, tool generates unfavorable vibration due to cutting force when pre-drilling hole. When using pre-drilled holes, it often leads to tool damage. Use of pre-drilled holes also increases re-cutting of chips.
If a ball end mill or a round insert tool is used, boring is usually used to ensure that all axial depths can be cut. Disadvantages of using this method are chip removal problems and use of round inserts can result in very long chips.
One of the best methods is to use linear slope cutting in X/Y and Z directions to achieve full axial depth cutting.
Finally, circular interpolation milling can be performed in a spiral form. This is a very good method because it produces a smooth cutting effect and requires only a small starting space.

20) What is definition of high speed cutting?

Discussion of high speed cutting is still somewhat confusing. There are many ideas and many ways to define high speed cutting (HSM).
Let's take a look at a few of these definitions:
High cutting speed cutting
High spindle speed cutting
High feed cutting
High speed and high feed cutting
High productivity cutting
Our definition of high speed cutting is described below:
HSM is not a high cutting speed in simple sense. It should be considered a process that is processed using specific methods and production equipment.
High-speed cutting does not require high-speed spindle cutting. Many high-speed cutting applications are based on medium-speed spindles and large-size tools.
If hardened steel is finished at high cutting speeds and high feed conditions, cutting parameters can be 4 to 6 times conventional.
In roughing of semi-finished parts to semi-finishing, finishing and superfinishing of any size part, HSM means high productivity cutting.
As part shapes become more complex, high-speed cutting becomes more and more important.
Nowadays, high-speed cutting is mainly applied to machine tools with a taper of 40.

21) What is goal of high speed cutting?

One of main goals of high-speed cutting is to reduce production costs through high productivity. It is mainly used in finishing processes and is often used to process hardened die steels. Another goal is to improve overall competitiveness by reducing production and delivery time.
Main elements to achieve these goals are:
One (less than this) clamping of mold processing.
Improve geometric accuracy of mold through cutting, while reducing manual labor and shortening test time.
Use CAM systems and shop-oriented programming to help develop process plans, improve machine, shop utilization through process planning.

22) What are practical advantages of high speed cutting?

Tools and workpieces can be kept at low temperatures, which in many cases extends life of tool. On the other hand, in high-speed cutting applications, amount of cutting is shallow, and cutting edge has a particularly short cutting time. That is to say, feed is faster than heat.
Low cutting forces result in small, consistent tool bending. This, combined with constant machining allowance required for each tool and process, is one of prerequisites for efficient and safe machining.
Since typical depth of cut in high speed cutting is shallow, radial forces on tool and spindle are low. This reduces wear on spindle bearings, rails and ball screws. High-speed cutting and axial milling are also good combinations. Impact on spindle bearings is small. With this method, there is little risk of using a tool with a long overhang to vibrate.
High-productivity cutting of small-sized parts, such as roughing, semi-finishing, and finishing, is economical when overall material removal rate is relatively low.
High-speed cutting achieves high productivity in general finishing and excellent surface quality. Surface quality is often lower than Ra0.2um.
High-speed cutting makes it possible to cut thin-walled parts. With high-speed cutting, knife time is short, and impact and bending are reduced.
Geometric accuracy of mold is improved, assembly is easier and faster. Surface texture and geometric accuracy of CAM/CNC production can be obtained regardless of person or skill. If time spent on cutting is slightly more, time-consuming manual polishing work can be significantly reduced. Often can be reduced by 60-100%.
Some machining, such as quenching, electrolytic machining and electrical discharge machining (EDM), can be greatly reduced. This reduces investment costs and simplifies logistics. Die cutting instead of electrical discharge machining (EDM) has improved tool life and quality.
With high-speed cutting, design can be changed quickly through CAD/CAM, especially without need to produce new electrodes.

23) Is there a risk or a disadvantage in high speed cutting?

● Guide rails, ball screws and spindle bearings produce relatively fast wear due to high acceleration, deceleration of starting process and stop. This often leads to higher maintenance costs.
● Requires specialized process knowledge, programming equipment, and an interface to quickly transfer data.
● It may be difficult to find and select advanced technical staff.
● There is often a long time to debug and fail.
● There is no need for an emergency stop during processing, resulting in many serious consequences for human error and software or hardware failure.
● There must be a good processing plan - "Providing food to a hungry machine."
● Safety measures must be taken: Use a machine with a safety cover and a debris-proof cover. Avoid large overhangs of tool. Do not use "heavy" tools and posts. Regularly check tools, posts and bolts for fatigue cracks. Use only tools that indicate the highest spindle speed. Do not use integral high speed steel (HSS) tools!

24) What are requirements for high speed cutting on machine tools?

Typical requirements for ISO/BT40 machines are as follows:
● Spindle speed range
● Spindle power > 22kW
● Programmable feed rate 40-60m/min
● Fast lateral feed
● Axial deceleration / acceleration > 1G
● block processing speed 1-20 milliseconds
● Data transfer speed of 250Kbit/s (1 millisecond)
● Incremental (linear) 5-20 microns
● or NURBS interpolation
● Spindle has high thermal stability and rigidity, and spindle bearing has high pre-tension and cooling capacity.
● Air supply/coolant through spindle
● Rigid machine tool frame with high vibration absorption capacity
● Various error compensation - temperature, quadrant, ball screw is the most important.
● Advanced foresight function in the CNC.

25) What are typical characteristics or requirements of high-speed cutting for cutting tools?

Solid carbide..
● High precision grinding with radial runout below 3 microns.
● The smallest possible protrusion and overhang, maximum rigidity, bending deformation of tool as small as possible and large core diameter.
● In order to minimize risk of vibration, cutting forces and bending, cutting edge and contact length should be as short as possible.
● Oversized, taper shank, which is especially important at small diameters.
● Fine grain matrix and TiAlN coating for high wear resistance.
● Internal cooling holes for air cooling or coolant.
● Sturdy micro-groove shape suitable for high-speed cutting of hardened steel.
● Symmetrical tools, preferably designed to ensure balance.
Tool using indexable inserts:
● Designed to ensure a balance.
● High precision on blade holder and blade with a small amount of jitter, maximum radial runout of main blade is 10 microns.
● Grade and groove shape suitable for high-speed cutting of hardened steel.
● Knife has a proper clearance to avoid friction when tool bending (cutting force) disappears.
● Cooling holes for air or coolant (end mill).
● Knife is specifically marked with maximum allowable speed.

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