London Irish became the latest victims of the financial crisis gripping the Premiership after they were suspended by the Rugby Football Union on Tuesday.

The Exiles join Worcester and Wasps on the sidelines as the bleak outlook of the sport in England continues, with the top league now having 10 teams.

But the trio aren’t alone with struggles as here the PA news agency looks at their fate and those clubs that have also been affected by the grim outlook.

Gone

Worcester Warriors

The first club placed into administration back in September, Worcester‘s future is still uncertain despite being taken over by Jim O’Toole’s Atlas Group. Entrance into the second tier Championship has been blocked by the Rugby Football Union for their failure to meet certain conditions and their plan of joining with Stourbridge and relaunching in the fifth tier appears dead in the water.

Wasps

The month after Worcester folded, Wasps followed them into administration as the league suffered the crushing blow of losing one of English rugby’s most famous brands. Further misery was to come as having targeted rebirth in the Championship, the failure to meet certain conditions forced the RFU to revoke their license and demote them to the foot of the rugby pyramid.

London Irish

Burdened by debts of around £30million and with owner Mick Crossan desperate to sell, London Irish have followed Wasps and Worcester out of the Premiership. The RFU granted an extended deadline of June 6 for either the proposed takeover by an American consortium to be completed or for Crossan to prove he can finance Irish for the entire 2023/24 season. Neither came through, resulting in the club being suspended from the entire league structure.

London Irish GONE

Wasps GONE

Worcester GONE

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Another dreadful day for club rugby union

— Alex Spink (@alexspinkmirror) June 6, 2023

Shaky foundations

Leicester Tigers

Leicester needed an emergency cash injection of £13million from directors Peter Tom and Tom Scott in February to address what chief executive Andrea Pinchen described as “very challenging conditions”. A letter from the club to shareholders sent in March stated that if the funding was not approved, there would be no option but to appoint administrators.

Exeter Chiefs

Even Exeter, one of the few clubs in the pre-pandemic era to operate at a profit, were forced to take special measures in December. Chiefs owner Tony Rowe bought a stake in a hotel owned by the club in order for it to service its debts, including Covid loans issued by the Government. Rowe’s intervention has shored up the finances for the time being.

Blues skipper Dalton Papali’i waxed lyrical about his star winger Mark Telea ahead of the Aucklanders’ final game of the season against the Highlanders at home.

The 2023 regular season may not have been as glittering as last year but the Blues sit in a comfortable third place on the table heading into the final round.

Red-hot Telea

One highlight of the year so far has been the continued rise of Telea, who has shown his venom with ball in hand throughout and is establishing himself as one of the most effective runners in Super Rugby Pacific.

He makes people look SILLY 😵

Mark Telea is the full package right now 📦

Catch The Breakdown at 7.30pm Sundays on #SKYSportNZ and Youtube 🏉 pic.twitter.com/tUFwb1Qovf

— Sky Sport NZ (@skysportnz) June 2, 2023

Papali’i labelled Telea as a problem but not within the squad, rather one for any defenders trying to stop him.

“He’s unbelievable, man, seriously crazy,” said Papali’i. “He’s got really good balance, and for his size he’s bloody powerful. I’ve played him at NPC and gone to tackle him, and he’s just given me a bullet fend. Its like, ‘hey, I’ve got to think how to tackle this guy’.

“He’s been a problem, and he’s always going to be a problem.”

Will only improve

The captain joked about having Telea slow down once he almost inevitably breaks the line to let him catch up. Papali’i only expects him to get better.

”If he makes a break I tell him to pipe it down a little bit, let me catch up,” said Papali’i. “He is in exceptional form and if he carries on I’d say he’s either the best or one of the best wingers in the world. He’s just got to keep doing what he’s doing.

“He’s a hard worker, and has the gifts to take it all the way. I’ve seen him grow on and off the field. He’s already one of the best or if not the best winger in the game, and he’s still getting better.”

Papali’i is searching for a complete performance from the Blues to gather some momentum going into the play-offs.

“We’ve got to put an 80-minute-plus game together. We tend to fall off during games,” said Papali’i. “We know that’s the problem and we’ve talked as leaders that we need to bring the boys in … we call it a grip moment, where we need to take it by the hands and execute.”

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Table of Contents

In the modern manufacturing industry, CNC machining centers, as a kind of high-efficiency and precise machining equipment, are widely used in the machining of metals, plastics, and many other materials. However, in the actual operation process, many operators may encounter the problem of abnormal spindle speed. This will not only affect the machining quality but also may lead to equipment damage and increase production costs.

Therefore, understanding the causes and solutions of abnormal spindle speed is essential to ensure the normal operation of the equipment. In this paper, we will discuss the problems related to the abnormal spindle speed of CNC machining centers in depth, and discuss in detail the preparatory work, fault investigation, cause analysis, solutions, preventive measures, and other aspects.

 

CNC machining center spindle maintenance before the preparatory work

 

1. Tools and equipment preparation

 

Before performing any maintenance or inspection, make sure you have the necessary tools and equipment. This includes:

(1) Multimeter: for measuring voltage, current, and resistance to help diagnose electrical problems.

(2) Lubricant: for checking the condition of the lubrication system and replenishing the lubricant.

(3) Wrenches and screwdrivers: for removing and installing parts.

(4) Paint brushes and cleaners: for cleaning equipment and removing oil and debris.

2. Recording phenomena

 

Before starting the inspection, record the specific manifestations of abnormal spindle speed. This includes:

(1) Frequency and range of speed instability.

(2) Changes in spindle speed under different operating conditions (e.g., idling, cutting).

(3) Any accompanying unusual sounds or vibrations.

3. Familiarize yourself with the equipment manual

 

Familiarize yourself with the operation manual of the CNC machining center, especially the maintenance requirements and troubleshooting guidelines for the spindle section. This will help you to diagnose and repair problems more effectively.

4. Personnel Training

 

Ensure that the operator is properly trained in the basic operation, maintenance requirements, and common troubleshooting methods of the equipment. Good operating habits and proper maintenance knowledge can significantly reduce the frequency of failures.

Pre-maintenance survey of CNC machining centers

 

It is vital to conduct a thorough investigation before getting your hands dirty with repairs. Here are a few survey points:

1. idle state observation

 

Observe the performance of the machining center in the idle state. Note if there is any instability in the spindle speed, especially at different idle speeds. This will help you make an initial judgment as to whether there is a problem with the equipment itself.

2. Performance under cutting conditions

 

When performing actual machining, especially under high loads and large depths of cut, carefully observe the change in spindle speed. If there is a noticeable loss of speed under these conditions, it may be related to the cutting force or load.

3. External environmental factors

 

Check the surroundings for factors that may affect the operation of the equipment. For example, unstable supply voltage, excessive temperature, or humidity may cause abnormalities in the equipment. Recording these environmental conditions can help you determine the source of the problem.

4. Equipment History

 

Review the equipment’s maintenance records and history of failures to see if the equipment has had similar problems. This can provide important clues to the diagnosis of the current problem.

Analyzing the Cause

 

After the investigation is complete, the cause of the abnormal RPM needs to be analyzed in depth. The following are some common causes:

1. Signal interference

 

The signal received by the spindle servo amplifier (inverter) of the CNC machining center may be interfered with during transmission. This interference can come from the external electromagnetic environment, wiring problems inside the machine, or poor connections. This can cause the spindle to receive incorrect speed commands.

2. Unstable voltage

 

Unstable power supply voltage can affect the normal operation of the equipment, especially if the load varies greatly. Voltage fluctuations may cause the servo system to fail to control the spindle speed correctly. Ensuring a stable power supply is an important measure to prevent abnormal speed.

3. Timing belt wear

 

A long or worn synchronous belt that transmits the spindle can lead to slippage. This is especially obvious at high speeds, and slippage will directly affect the spindle speed. Regular inspection and replacement of the synchronous belt is the key to ensuring the stable operation of the spindle.

4. Encoder Failure

 

Damage to the spindle encoder or poor feedback signal may cause the control system to be unable to accurately determine the actual spindle speed. Regularly check the status of the encoder to ensure its normal operation.

5. Bearing problems

 

Damaged or poorly lubricated bearings supporting the spindle will increase the spindle’s resistance to rotation, resulting in abnormal speed. Maintenance and replacement of the bearings are important to ensure the smooth operation of the spindle.

6. Lubrication system failure

 

Poor lubrication of the spindle may also lead to unstable speed. Insufficient or contaminated lubricant will affect the normal operation of the spindle, resulting in increased friction and thus affecting the speed.

7. Software setting problems

 

Improper parameter setting in the CNC system may also lead to abnormal rotation speed. Check the relevant parameter settings in the CNC system to ensure that they meet the processing requirements.

Determine the CNC machining center spindle troubleshooting steps

 

After analyzing the cause, you can start to gradually troubleshoot and solve the problem. The following are specific steps for troubleshooting:

1. Measure the voltage

 

Use a multimeter to measure the voltage of the CNC machining center. First, make sure that the power supply is turned on properly and check whether the input voltage is within the range specified by the equipment. If the voltage is found to be normal and other machines next to the machine using electricity from the same grid are working properly, the cause of unstable voltage can be ruled out.

2. Check the lubrication system

 

Check the amount of lubricating oil in the CNC machining center to ensure that it is within the normal working range. Confirm that the lubrication system is working properly and that there are no oil leaks or open-circuit faults in the oil circuit to rule out lubrication faults. If an oil line blockage or oil pump failure is found, it should be dealt with in time.

3. Bearing sound check

 

When the spindle is running, use a long rod (such as a screwdriver) to lean near the spindle box, with one end leaning on the ear, and listen to the sound of the bearing when it is running. If no abnormal sound is heard, the possibility of bearing failure can be ruled out. If there is noise, the bearing may be damaged or lacking lubrication.

4. Check the synchronous belt

 

Open the spindle box and check the synchronous belt connection between the spindle motor and the spindle. Press the belt between the two pulleys by hand to confirm its tightness. If the timing belt is found to be worn, it needs to be replaced promptly.

5. Encoder Inspection

 

Check the synchronous belt between the spindle and the encoder to make sure it is not worn or slipping. If problems are found, replace the timing belt promptly. At the same time, check the connection line of the encoder to make sure the signal transmission is normal.

6. Signal line check

 

Check the signal line from the encoder to the servo amplifier to make sure there is no external interference. If there is a problem with the signal line, it may need to be rewired or shielded.

Table 1 Troubleshooting Steps for CNC Machining Center Spindle Failures

 

Solution

 

After completing the troubleshooting, take appropriate solutions according to the problems found:

1. Replace the timing belt

 

If the timing belt is found to be worn, it needs to be replaced with a new one. Select a high-quality timing belt that matches the equipment to ensure its stability during operation.

2. Repair or replace the bearings

 

If the bearings are faulty, repair or replace them in time to ensure smooth rotation of the spindle. Use reliable bearings to avoid the recurrence of failure.

3. Optimize the lubrication system

 

If there is a problem with the lubrication system, clean the system and replace the lubricant to ensure good lubrication to reduce friction. It is recommended to use a high-quality lubricant suitable for the requirements of the equipment.

4. Adjust the power system

 

If the power supply voltage is unstable, consider installing a voltage regulator or UPS system to ensure the normal operation of the equipment. Make sure the power supply line is good to avoid failure caused by power supply problems.

5. Software parameter adjustment

 

Check the parameter settings in the CNC system to ensure that they meet the processing requirements. If necessary, carry out software upgrades or resets to solve software problems.

Table 2 CNC machining center spindle speed abnormal solution

 

Preventive measures

 

To avoid the recurrence of the problem of abnormal spindle speed in the CNC machining center, the following preventive measures are recommended:

1. Regular Maintenance

 

Develop and follow a regular maintenance schedule to regularly check the condition of key components such as lubricants, synchronous belts, and bearings. It is recommended to conduct a comprehensive inspection once a month to ensure that the equipment is in good condition.

2. Power supply management

 

Ensure that the power supply is stable and use a voltage regulator if necessary to ensure the normal operation of the equipment. Check the power lines to make sure there is no looseness or aging.

3. Operation training

 

Provide relevant training to the operators to improve their ability to recognize and handle equipment faults, find problems, and handle them in time. Organize regular technical training to ensure that the operators have the latest maintenance knowledge.

4. Use of monitoring system

 

Consider installing a monitoring system to monitor the operating status of the spindle in real-time, so that potential problems can be identified and solved promptly. Through data recording and analysis, early warning can be given to prevent problems from expanding.

5. Strengthen site management

 

Ensure that the site environment is neat, and regularly clean up debris around the equipment to avoid interference with the equipment. Develop a site management system to ensure that the equipment operates in a good environment.

Table 3 CNC machining center spindle speed abnormal preventive measures

 

Summarize

 

Abnormal spindle speed of CNC machining centers is a common problem, but through systematic troubleshooting and analysis, a suitable solution can be found. Maintenance and management are the keys to preventing the problem from occurring, through regular inspection and timely processing, it can effectively extend the service life of the equipment and improve processing efficiency.

I hope that the sharing of this article can help the majority of operators in the use of CNC machining centers to ensure smooth production. In the future, with the continuous progress and development of technology, we have reason to believe that the CNC machining centers will be more intelligent, and the failure rate will be reduced, thus bringing greater development opportunities for the manufacturing industry.

New Zealand’s two-time Rugby World Cup-winning captain Richie McCaw has backed arch-rivals Australia to spring a surprise in France.

After reaching the World Cup final in 2015, the Wallabies have struggled to remain at the top table of the global game.

They exited the 2019 showpiece at the quarter-final stage before Dave Rennie took over from Michael Cheika.

Rennie would only last until the start of 2023 when he was sacked, ending his tenure with a 38 per cent win record.

Former head coach Eddie Jones, who led Australia to a runners up spot in 2003, has since returned and McCaw knows the immediate impact he could have.

In the mix

“Eddie Jones, whatever team he takes over, he usually causes some change pretty quick and they get a real bounce and he will probably do the same with the Aussies,” he told World Rugby.

“You might think they might not be where you would usually consider them to be, but they have a unique way of using what they have got to be right in the mix.”

McCaw doesn’t have a clear favourite for the Webb Ellis Cup and believes that the upcoming tournament is “pretty wide open”.

“You are not too sure what might happen. So there is that side of it and, I guess from a New Zealand point of view, in the past you have sort of always knew that if they can put it together they can go and get the job done, whereas after the last year you sort of go, ‘jeepers, there is going to have to be some improvements to put the team in the right spot’,” he said.

Ireland and France

“I guess from a northern hemisphere point of view, Ireland have set the pace in the Six Nations and the French aren’t that far behind, so it makes it pretty intriguing.

“There is no doubt that people consider the French and the Irish have got a pretty good chance of winning.”

The top two ranked teams are currently Ireland and France, with the latter also benefiting from having home advantage.

McCaw sees both teams as title challengers but has been particularly impressed by how Andy Farrell’s men have progressed.

“As we have found out in years gone by, where you are ranked going into a World Cup, actually doesn’t necessarily count for a whole lot,” he added.

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“But just to put aside the rankings, I got to see the Irish in New Zealand last year for three Tests and there is a quite a strong resolve about them, of knowing they are on a mission.

“The way they put together that series win was pretty impressive and they have backed it up again just recently so it is going to make it interesting.”

Wallabies head coach Eddie Jones has claimed that he will be leaving the side after the 2023 Rugby World Cup in France. 

The news comes as a surprise with Jones’ deal signed until the 2027 World Cup which will be hosted in Australia. The prescribed tenure over his contract period would also include the 2025 British & Irish Lions tour down under.

However, Jones seems insistent that he will be leaving his role after the World Cup regardless of their performance.

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“It will be time to go”

“I’m only coaching to this World Cup. I’ve signed, but as I’ve made the mistake before, I’ve stayed too long. So we win the World Cup it will be time to go. If we lose the World Cup it will be time to go,” Jones told The Evening Standard podcast.

Rugby Australia (RA) responded swiftly by claiming that Jones is still locked in and they have no concerns that he will leave the job.

“Eddie’s contract runs until 2027,” the RA spokesperson told the Sydney Morning Herald.

Meanwhile, Jones is hoping for changes in Giteau’s Law that restricts the coach to selecting only three overseas-based players with a minimum of 30 Test caps. It is designed to incentivise players to remain in Australia and offer reward to locally-based talent.

Jones suggested that even though he has not approached the RA regarding a policy change he believes there will be a good response.

“Can’t snub that sort of talent”

The veteran coach outlined four stars who could not be looked past including gargantuan lock Will Skelton who has recently added another Champions Cup medal to his collection.

“They [Rugby Australia] had a law called the Giteau Law which was you could only get three players outside Australia with 30 caps,” Jones said.

“But we haven’t tabled that [a policy change] with the board yet, but I’m sure we’re going to get a positive response about more players. Because we’ve got [Will] Skelton, who’s probably the best right-hand-side lock in the world. Richie Arnold at Toulouse, who’s a fantastic player in the Top 14. Quade Cooper, [Samu] Kerevi, [Marika] Koroibete, we can’t snub that sort of talent.”

Big packs are important at Test level

Jones, who coached the Barbarians against a World XV last weekend, outlined the importance of a big pack of forwards in the modern game especially considering the physicality of teams like France and the Springboks.

“You look at the game statistically, 70% of the game is played within one pass, so they’re big man carries,” he said.

“Just yesterday with the Barbarians we had a tighthead prop from the Sharks, [Carlu] Sadie, comes on the second half; he’s got no leg speed but when he carries he takes men with him so it gives you a good base to work off.

“So a big right-hand side lock, big number eight, big number three [is what we need] mate.”

Plenty of time to make a difference

Jones’ second stint with the Wallabies well and truly kicks off against the Springboks at Loftus Versfeld in the Rugby Championship on July 8. Even with the limited time to prepare for a World Cup charge, the veteran is upbeat about his chances to improve the side.

“We’ve got five Tests matches, which is plenty. [World Cup-winning coach] Bob Dwyer used to say if you can’t change a team in a week, you can’t coach. So we’ll give it a go,” he added.

Ligue 1 side PSG are interested in signing Bayern Munich winger Douglas Costa, according to Gianluca di Marzio.

Juventus are also pushing for the Brazilian in a major way and hope to convince him to join Serie A this summer.

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Manchester City have presented AS Monaco with a €130m offer for striker Kylian Mbappé, according to Téléfoot.

The media outlet claims that Real Madrid have also raised their original proposition to this amount.

The report does not provide any other specific details in a story which will certainly develop in the coming days.

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The processing section of the twin-screw extruder is mainly composed of the extruder barrel, screw elements and mandrel. It is the functional area of the twin-screw extruder to complete plasticization and mixing. Screw gap, volume ratio, rotation speed, mandrel strength and screw element life are the key indicators for evaluating the performance of twin screw extruders. The development trend of international advanced twin-screw extruders is: small extruder screw gap, large volume rate, high speed, high strength mandrel, high wear-resistant threaded elements. At the same time of high efficiency and large output, the service life of the whole machine can be further improved, and the product quality is stable.

1. Small gap technology of extruder components

The small gap technology refers to the gap between the front and back of the meshing screw, the gap between screw and barrel, and it is controlled at a very small level (0.15-0.2mm). The stable output of the transmission system, small and stable output shaft runout are the foundation and guarantee of the small gap technology. The small gap technology ensures the uniform residence time distribution of the material in the extruder barrel, thereby ensuring the stability and consistency of the product quality, and making precise and stable extrusion possible. Small gap technology is also the basis of the high screw speed. High speed and small gap can ensure that the processed materials are cleaned up in time and quickly sent out of the extruder barrel; and if the screw is running at high speed at the regular clearance level, the materials cannot be cleaned in time with long residence time and unevenness can easily cause material degradation.

2. Extruder screw, extruder barrel and mandrel

After the breakthrough of torque distribution technology, the factors restricting the development of twin-screws have undergone fundamental changes: the previous restrictive factors were the output torque and service life of the gearbox, that is, the strength coefficient of the mandrel was higher than that of the gearbox, but now the stronger is the gearbox. The strength of the mandrel has become a limiting factor, so now the manufacturers of twin-screws have focused their research and development on the mandrel, barrel bushing and screw elements, and developed higher-strength mandrels and more wear-resistant barrels bushings and extruder screw elements. One of the solutions is the use of high abrasion resistant materials manufactured by hot isostatic pressing powder metallurgy molding process (PM-HIP).

Small gap technology, efficient twin screw extruder parts, and reasonable screw combination can further improve the performance of the twin-screw extruder, increase output, reduce energy consumption, and improve product quality. This is the software core technology of the twin-screw extruder. Only by combining these hardware core technologies with software core technologies can we create the most cost-effective and competitive modern co-rotating twin-screw extrusion equipment.

2021 was undoubtedly a year full of surprises, where China’s crude steel output declined on-year for the first time in five years and where Chinese steel prices hit historical highs under the twin thrusts of improved domestic and overseas market conditions.

In the past year, China’s central government acted more proactively to help maintain domestic commodity supply and price stability, and steel mills rolled out ambitious plans for carbon reduction amid the global drive towards peak carbon and carbon neutral. Below we summarize some the Chinese steel industry in 2021.

China issues 5-year plans for economic, industrial development

2021 was the first year of China’s 14th Five-Year Plan period (2021-2025) and during the year, the central government announced key economic and industrial development targets it aims to meet by 2025 and the major tasks it will undertake in order to meet these.

The officially titled 14th Five-Year Plan for National Economic and Social Development and the Long-Range Objectives Through the Year 2035 released on March 13 2021, is quite ambitious. In the plan, Beijing set the major economic targets covering GDP, energy consumption, carbon emission, unemployment rate, urbanization, and energy production.

Following the release of the general guideline, various sectors issued their respective five-year plans. Critical to the steel industry, last December 29 the country’s Ministry of Industry and Information Technology (MIIT), along with related ministries, released the five-year development plan for the country’s industrial commodities including oil and petrochemicals, steel, nonferrous metals and construction materials.

The development plan aimed to achieve optimized industrial structure, clean and ‘smart’ production/manufacturing and emphasized the supply chain security. Significantly, it stated that China’s crude steel capacity cannot increase over 2021-2025 but must be cut, and that capacity utilization should be maintained at a reasonable level given that the country’s steel demand has plateaued.

Over the five years, the country will still implement the “old-for-new” capacity swap policy regarding steel making facilities – new capacity being installed should be equal or lower than the old capacity being removed – to make sure there is no increase in steel capacity.

The country will continue to promote M&As to enhance industrial concentration and will nurture some leading companies and establish industrial clusters as a means to optimize industrial structure.

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Post time: Jan-18-2022

Table of Contents

Machine tool fixtures are commonly used in machining. Traditional fixture design, there is detailed information and mature experience for reference. CNC milling machines and machining centers have been widely used in recent years, with their high processing efficiency, high precision, and high adaptability to the workpiece so traditional machining has undergone great changes. But in the file, about CNC milling machine and machining center fixture design content is very little. In this paper, according to the processing characteristics of CNC milling machines and machining centers, to explore its fixture design methods, so that CNC milling machines and machining centers can give full play to the processing potential.

Fixture design utilizes multiple workpieces in a single clamping.

  

CNC milling machine to compressed air as the driving force, loosening, and clamping tool, It is easy to manually change the tool, while the machining center can realize automatic tool change. Processing tool change can realize the sequential processing of a variety of surfaces, but each time the tool change is more time-consuming, especially the automatic tool change sometimes fails (machining centers, most of the failures in the automatic tool change system). Therefore, under the premise of meeting the processing requirements, reducing the number of tool changes can save auxiliary time, can improve the reliability of CNC machine tools. In this paper, a reasonable fixture design (such as the use of clamping multiple workpieces) to properly adjust the process can minimize the number of tool changes.

Such as the workpiece shown in Figure 1, to complete the vertical machining centers to expand, reaming hole a and hole b original fixture design each time the clamping of 1 workpiece, the machining process for change hole a reaming cutter, reaming a → change hole b reaming cutter reaming b → change hole a reamer a → change hole b reamer b. From the above machining process to see that the machining of each 1 workpiece needs to be changed 4 times.

Fig1  Workpiece

Now according to the dimensions of the workpiece and machine travel, the fixture design for each clamping 8 workpieces, as shown in Figure 2, the process is as follows: change the hole a reaming cutter, to expand the workpiece 1 ~ workpiece 8 of the hole a → change hole b reaming cutter, to expand the workpiece 1 ~ workpiece 8 of the hole b → change hole a reamer, to ream the workpiece 1 ~ workpiece 8 of the hole a → change hole b reamer, to ream the workpiece 1 ~ workpiece 8 of the hole b.

Fig.2 Clamping 8 workpieces at a time.

From the above machining process, it can be seen that for machining 8 workpieces, only 4 tool changes are required, which saves a lot of auxiliary time (relative to the machine table movement time).

Multi-piece clamping fixture design points

 

1. Reasonable arrangement of workpieces

 

According to the dimensions of the workpiece, the size of the machine table, machine travel, and production batch determines the number of workpieces clamped each time and layout. The distance between the workpiece should be appropriate, such as Figure 2 to take the appropriate distance between the workpiece m and n to load and unload the workpiece and remove chips. In addition, the openness of the workpiece after installation should be good, to realize the process of centralized machining.

2. The distance between each group of positioning elements should be accurate

 

The distance between the positioning elements is shown in Figure 3. In Figure 3, the fixture adopts two pins on one side for positioning, and the distances between the cylindrical pins and diamond-shaped pins in each group of positioning elements are determined according to the dimensions of the workpiece. Distance between each group of positioning elements, such as the distance between the two cylindrical pins should be accurate to ensure that the moving parts of the machine tool (such as tools) according to the program to move, relative to the workpiece have an accurate position.

3. Reasonable clamping

 

Clamping elements as simple as possible, so that the tool movement has more safety space. Try to consider linkage clamping, and realize simultaneous clamping of multiple workpieces, to reduce the number of clamping elements [2]. As shown in Fig. 3, each platen clamps 2 workpieces at the same time. Due to the CNC milling machine’s more centralized processing, roughing and finishing are sometimes difficult to separate, so the clamping force is large clearly. This is easy to leave the pressure plate indentation on the surface of the workpiece. A simple and effective solution is to solder a layer of copper on the part of the pressure plate in contact with the workpiece, as shown in Figure 4.

Fig. 3 Distance between positioning elements

Fig.4 Platen Soldering Copper

4. Vertical CNC milling machine fixture design

 

In vertical CNC milling machine processing, metal chips are easy to fall on the workpiece and fixture. When designing fixtures, special consideration should be given to chip removal, which is particularly important for the process of centralized continuous processing of machining centers. Reasonable chip removal should make the chip does not affect the tool cutting automatically; so that the chip does not easily fall on the positioning elements of the fixture to ensure positioning accuracy; so that the cutting fluid is easy to flush, take away the chip; so that the compressed air to facilitate the blowing off the chip.

5. Fixture design for horizontal CNC milling machine

 

A horizontal CNC milling machine or machining center is generally equipped with an indexing table (or rotary table). In the process of machining, the fixture should also rotate with the table. The design of a multi-piece clamping fixture should ensure that the workpiece on the position of the same machining elements before and after the rotary can be accurately coincidentally (see examples). A fixture as close as possible to the edge of the table, so that the distance between the workpiece and the spindle taper hole end face is small, which is conducive to reducing the length of the tool holder, but also conducive to chip removal.

Example of Multi-Part Clamping Fixture Design

 

This fixture is used on a horizontal machining center for machining 2 end faces and 2 coaxial holes of the workpiece shown in Figure 5.

Fig. 5 Workpiece 2

1. Workpiece processing requirements

 

Face C, face D, and hole 2-ϕ15H7 ( ₀^+0.018 ) of the workpieces have already been machined. This process involves milling face A, and face B, reaming, and boring coaxial hole 1 and coaxial hole 2. Because of the small diameters of the holes in the middle of coaxial hole 1 and coaxial hole 2, machining needs to be done from both ends.

2. Clamp Functions

 

The workpiece face C (D) and hole 2-ϕ15H7 ( ₀^+0.018 ) are selected as the locating datum, and the fixture uses two pins on one side (a cylindrical pin and a rhombic pin) to locate the workpiece. Through the clever design of the fixture, a set of fixtures can be used in the same process to complete the processing of the workpiece and can realize the installation of six workpieces at a time. The horizontal machining center fixture is shown in Figure 6.

3. Machining process with fixtures

 

When the workpiece is mounted, face C is in contact with the fixture-locating surface. Now the face A on the workpiece is located at the edge of the fixture.

The machining process is: milling is located in the fixture Ⅰ – Ⅰ edge of the workpiece face A → proceed in sequence expanding, boring the workpiece with the coaxial of the hole 1 and hole 2, in which the length of the central hole should be processed more than half the size of the hole(the length of the small hole in the middle should be processed more than half.).

The table turns 180°. At this time, the fixture Ⅰ – Ⅰ and Ⅱ – Ⅱ side of the interchange, Ⅱ – Ⅱ side to reach the processing area. After rotation, the end faces of the workpiece and the position of the coaxial holes 1 and 2 are the same as before rotation.

Next, the face A of each workpiece on the II-II side of the fixture, as well as the coaxial holes 1 and 2, are machined, with half of the length of the small hole in the center being machined. This completes the machining of face A and the hole from the end of face A.

Release the workpiece and turn it over by 180°. Face D of the workpiece is now in contact with the fixture locating surface, face B, at the edge of the fixture. Next, face B and the hole from face B are machined. The table is turned 180° in the same way as before. The small hole in the center should be connected to the previously machined part.

4. Key points of fixture design

 

1) Set up the rotary center and side alignment datum. The rotary center of this fixture is ϕ30H5 hole, when installing, ϕ30H5 hole coincides with the rotary center of the indexing table. Select the long side of the fixture with high precision as the calibration reference when the fixture is installed.

2) Determine the position of the cylindrical pin and rhombic pin. The cylindrical pin and rhombic pin position determine the position of the workpiece in the fixture. Workpiece installation, to meet the following requirements:(1) the center of the hole to the center of the rotation distance should be symmetrical and consistent.

Such Figure 6, the distance was X₁ 、X₂、X₃. (2) the processing end face (hole end face) to the center of rotation distance should be symmetrical and consistent. As in Figure 6, the distance at the same time for. This makes the corresponding point on the workpiece to the center of the rotary distance equal, such as in Figure 6, two dimensions l. This ensures that the table rotates 180 °, the workpiece on the position of holes 1, holes 2, and end face and rotary before the complete coincidence (one of the benefits is to facilitate the preparation of CNC programming and call subroutines). Design, through the appropriate cylindrical pin, diamond pin position to meet the above requirements. As can be seen in Figure 6, to meet these requirements, the distance from the locating pin to the center of rotation in the X and Y directions is marked with tolerances.

 

Fig. 6 Horizontal machining center fixture

3) The edge of the workpiece extends beyond the edge of the fixture. As shown in Fig. 6, the edge of the workpiece extends 4mm in the Y-direction to facilitate the machining of the end face and the removal of chips.

5. Clamp positioning accuracy analysis

 

This process is part of the processing requirements as shown in Figure 5 (due to the subsequent rigid boring and reaming process and floating grinding process, the requirements of this process are not high). The diameter of the two positioning holes is ϕ15H7 ( ₀^+0.018 ), the center distance is 140±0.03, the center distance of the two pins is 140±0.01, the diameter of the cylindrical pin is ϕ15 _-0.014^-0.006, and the diameter of the rhombic pin is ϕ15_-0.023^-0.015, as shown in Fig.6.

As shown in Fig.5, among the process dimensions, the hole diameter dimension (not shown) is guaranteed by the fixed-size tool, which is not affected by the fixture positioning accuracy. Hole depth size (not shown) and end face dimensions are low-precision, no tolerance, and fixture positioning accuracy has little effect on it. Now analyze the fixture positioning error on the process size of 35 ± 0.1 and 85 ± 0.15.

1)Positioning error on the size of 35 ± 0.1. Positioning error Δ_D, including datum non-coincidence error Δ_B and datum displacement error Δ_Y. Dimension 35 ± 0.1 of the process reference and positioning reference coincide, so Δ_B ＝0. Reference displacement error on the size of 35 ± 0.1 of the impact of the following three factors is analyzed as follows.

Fig. 7 Datum displacement for the positioning of a cylindrical pin and a rhombic pin

(1) Due to the positioning pin and positioning holes between the existence of clearance, so that the benchmark displacement, results in the benchmark displacement error. The cylindrical pin and rhombic pin positioning of the benchmark displacement shown in Figure 7, consider the extreme case, in the cylindrical pin at the existence of the maximum gap X_1max, and the rhombic pin at the existence of the maximum gap X_2max  respectively.

Where: D_1max with the cylindrical pin with the maximum diameter of the workpiece hole, D_1max ＝15＋0.018; D_2max with the rhombic pin with the maximum diameter of the workpiece hole, D_2max ＝15＋0.018; d_1min for the minimum diameter of the cylindrical pin, d_1min ＝15-0.014; d_2min for the minimum diameter of the rhombus pin,d_2min＝15—0.023; X_1max is the maximum clearance at the cylindrical pin, X_1max ＝（15＋0.018）—（15—0.014）＝0.032; X_2max is the maximum clearance at the rhombic pin, X_2max ＝（15＋0.018）—（15—0.023）＝0.041.

In the dimension 35±0.1 direction, the maximum clearance that exists results in a reference displacement error Δ_Y. The datum displacement error Δ_Y includes linear displacement error Δ_Y1 and angular displacement error Δ_Y2. The linear displacement error Δ_Y1  is the maximum clearance between X_1max and X_2max The angular displacement error Δ_Y2 is caused by the corner error ± Δ_α： tan Δ_α ＝ （X_1max＋ X_2max ）／（2L）Where: Δ_α for the corner error, can be deflected in both directions, so ± Δ_α; L for the center distance, L = 140.

Since the clearance at the rhombic pin is large, the resulting error is large, so calculate the datum displacement error at the rhombic pin. The datum displacement errors Δ_Y^‘ are largest at face B on the workpiece near the end of the diamond pin:

Where: Δ_Y^‘ is the reference displacement error generated at face B, Δ_Y1 is the linear displacement error, at the rhombic pin, Δ_Y1 ＝X_2max ＝0.041; Δ_Y2 is the angular displacement error, considering the deflection in both directions, at face B, Δ_Y2 ＝ 2 L₁ tan Δ_α; L₁ is the distance from face B to the rhombic pin, L₁＝ 15.

(2)Due to errors in the distance from the positioning pin to the center of the table rotary table 180 ° rotary table, positioning reference displacement (the program determines tool position, is unchanged), resulting in the benchmark displacement error o f Δ_Y^“ 。Δ_Y^“ size for the positioning pin to the table rotary center of the size of the tolerance, as shown in Figure 6, X-direction size of the deviation of ± 0.01, so Δ_Y^“ ＝0.02.

Fig. 8 Table rotation angle error generates datum displacement.

(3)due to the table rotary angle error, resulting in the rotation, positioning reference displacement, resulting in the benchmark displacement error Δ_Y^“‘。 Study and rotary center of the largest distance from the positioning pin. Figure 6, from the center of the rotary X direction of the largest size of 215, Y direction of 165. now the table rotary error for ±2^“. Table rotary angle error generated benchmark displacement shown in Figure 8, after the ideal position in the rotary pointＯ, the maximum deviation from the position in the pointＯ′and pointＯ″. Benchmark displacement error  Δ_Y^“ forＯ′Ｏ″ in the 35±0∙1. The square direction of the projection, that is, theＯ′Ｎof the Length.

The reference displacement error Δ_Y that affects dimension 35 ± 0.1 is the sum of the reference displacement errors from the three factors:

The positioning error Δ_D, which affects dimension 35 ± 0.1, is the sum of the datum non-recombination error Δ_B and the datum displacement error Δ_Y :

The positioning error Δ_D is calculated to be approximately 1/3 of the 35 ± 0.1 tolerance of the process dimension, which meets the requirements. The calculation of the positioning error here is obtained by analyzing the geometrical relationships. It is also possible to get an accurate drawing using CAD software.

2) The effect of positioning error on dimension 85 ± 0.1 is similar to that on 35 ± 0.1.

Conclusion

 

The fixture design of the CNC milling machine is different from that of the traditional fixture design. According to the processing characteristics of the CNC milling machine and machining center, reasonable design fixture, try to use a clamping multiple workpieces, to make full use of the processing potential of the machine tool.