A mechanic who makes dies must be able to identify defects in dies, which depend both on the poor quality of their manufacture and on improper installation and adjustment, and know the causes of defects and how to eliminate them.
During the stamp testing period, one cannot limit oneself to a small number of stamped parts, since a small number of stampings will not give a complete picture of the operation of the stamp. It is necessary to make at least 50-70 stampings and, if all of them are of satisfactory quality, remove the stamp from the press.
A lot of defects finished parts Caused by incorrect installation of the stamp on the press.
The first sign of improper installation of the die on the press will be one-sided friction on the guide columns, the appearance of a shiny cut surface on any side of the part (this shows that there is no clearance on this side) and rapid dulling in this area cutting edges punches and dies. This defect is, as a rule, a consequence of the skew of the press table, the non-parallelism or unevenness of the spacers under the die and the displacement of the upper part of the die relative to the lower.
The distortion of the press table and the inaccuracy of the dimensions of the gaskets can be determined by freeing the bottom plate from the fastening and measuring the gap between the bottom plate of the die and the press table with a feeler gauge. You can also, by turning the stamp 180° and securing it, make several test cuts again, in this case one-sided friction on the columns will appear on the opposite side and burr (excess metal) on the part will also be on the other side.
The displacement of the matrix relative to the punches is obtained by changing the order of attaching the die, when the bottom plate is attached first, and then the top of the die. In this case, a gap may remain between the shank and the plane of its attachment. After clamping the shank with the cheek of the slider, the upper part of the stamp will move away by the amount of the gap. In block dies, this will cause bending of the columns and their one-sided friction in the bushings, as well as displacement of the punches relative to the dies, which will lead to the appearance of a one-sided burr on the parts being cut out.
In columnless stamps, this will cause the cutting edges of the matrix to be scored, burrs to appear, increased wear of the guide plates and loosening of the punches and knives. All these defects can be eliminated by repeated, more careful installation of the stamp on the press. Contamination of the strip of material with earth, sand, etc. leads to rapid abrasion of the cutting edges of the die and cutting of incomplete parts (due to the tape not being brought to the stops), which can lead to breakage or loosening of the punches, jamming of the strip of material (due to its uneven width) in the passage between the guide rulers. Possibly incorrect geometric shape parts due to skew of a narrow strip.
Poor performance of the stamp as a result of poor manufacturing quality can lead to the following defects and malfunctions.
Violation of the dimensions or shape of a part. These deviations are the result of an error in the die manufacturing drawing or failure to follow the drawing instructions. They can be eliminated by correcting the working parts of the die, fine-tuning or reworking.
Bending the workpiece. This defect occurs when there is no taper in the die window, when the exit window is narrowed, when there is a large gap between the die and the ejector, or when the ejector is poorly designed. To eliminate bending, the shortcomings of the die must be corrected.
Burrs on the cut surface. Burrs are produced when the gap between the punch and the matrix is too large or uneven, or when the cutting edges are dull.
These defects are eliminated by remaking the punch (if there is a large gap or its taper), correct installation punch (if the gap is uneven), work hardening of the matrix (if it is not hardened) with subsequent grinding of its surface, repeated heat treatment poorly hardened punch or matrix and sharpening.
Irregularities on the cut surface. The reason for their appearance is insufficient clearances. Irregularities are eliminated by changing the gaps to the required ones by grinding the punch or increasing the contour window of the matrix.
Blocking the matrix window. Clogging occurs as a result of misalignment between the die windows and the bottom plate and leads to die rupture. This defect is eliminated by widening the window in the bottom slab.
Jamming of the stamped strip. Jamming occurs when there is insufficient clearance in the passage after the knives. This drawback can be eliminated by increasing the gap by grinding the guide surfaces of the rulers.
Violation of walking distance. As a result of violation of the step distance, sharp and rectangular whiskers remain on the tape, preventing it from moving all the way. The cause of the defect is the rounding at the junction of two cutting planes of the knife window and the gap between the stop and the cutting plane of the knife. A defect may also appear as a result of the stop being displaced or crushed. work surface due to sudden impacts.
The defect is eliminated by rearranging the stops or altering the die.
Shearing (notching) the cutting edges of the stamp. Shearing occurs when the gaps between the punch and the guide plate or the bushings and the guide columns are too large, as well as when the punch is not installed correctly in relation to the die and the die plates are not parallel. The defect is eliminated by replacing the relevant parts or reinstalling the punch.
Lack of smooth closure of stamp parts. The defect appears due to too tight fit of the guide columns in the bushings, non-perpendicularity of the axes of the columns and shank relative to the supporting surfaces of the die, bending of the punches at the moment of entering the guide plate windows due to incorrect installation of the punches in the holder or mismatch of the windows, non-parallelism of the die plates. This can be eliminated by appropriate alteration of the stamp parts.
Pulling out punches or knives. The defect is the result of poor mounting of the punches and knives in the holder, excessive force in ejecting the stamped part or cutting from the punches with a positive slope on the punch, or tight fit of the punches and knives in the windows of the guide plate. The defect is eliminated by correcting the punches, hammering them more firmly in the holder, and widening the windows of the guide plate.
Shift of the workpiece during bending or rupture during drawing. The defect appears due to insufficient regulation of the workpiece clamping force. To eliminate the defect, the force of the springs should be adjusted: increase it when shearing or decrease it when breaking.
Curvature of the bent section during bending. To eliminate the defect, deepen the matrix.
Sharp impressions on the molded surface. The defect appears as a result of insufficiently careful fitting of the punch to the matrix (or vice versa) and unevenness of the gap. The defect is corrected by adjusting the forming surfaces (maintaining a uniform gap).
Wrinkles and folds on an elongated workpiece. To eliminate the defect, you need to increase the clamping force of the workpiece.
Waviness or scoring on the bent part of the part. To eliminate waviness, the gap between the punch and the matrix should be reduced, and to eliminate scoring, it should be increased.
Deflection of the hood bottom. To eliminate defects, it is necessary to ensure the release of air from the die by drilling a hole in the punch and the top plate of the die. Shiny marks on an elongated part. If the defect is observed along the entire circumference, it is necessary to increase the gap, and if only along the generatrix, eliminate the misalignment of the matrix and the punch.
The workpiece does not fit correctly onto the clamp. To eliminate the defect, you need to check the workpiece and adjust it.
Uneven workpiece flange width. This defect is caused by the fact that the clamping rods different lengths create uneven pressure on the workpiece. To eliminate the defect, the length of the rods should be made the same.
Displacement of the flange relative to the axis of the part. The defect appears as a result of improper fixation. To eliminate the defect, you need to check the accuracy of the assembly and correct the fixing parts of the stamp. Wrinkles on the cylindrical part of the drawn part during the second operation. The defect appears as a result of incorrect calculation of the metal set at the first operation. To correct it, it is necessary to change the technology (reduce the height of the drawn workpiece during the first operation). Wrinkles on the flange and waves or wrinkles on the walls of a rectangular or asymmetrical part. The defect appears when the workpiece is not clamped sufficiently. To eliminate the defect, it is necessary to change the design of the stamp by installing tension ribs on the clamp and matrix. Bottom cylindrical part doesn't come out flat. The defect occurs when there is no pressure from the punch on the ejector at the end of the press stroke. The height of the ejector needs to be increased.
Wear and tear usually takes its toll. Of particular concern to table owners are the joints at the top of the legs.
When placed under significant pressure, they can weaken and even fall off. Problems that often arise include existing drop boards that may sag and extensions that break or jam. Many problems can be easily fixed if you know how to repair a table.
Most tables designed for home use, consist of a table top, which is attached to a frame and represents rectangular base made of horizontal narrow straps, tightly connected to the upper sides of the existing legs. Sometimes the frame is connected to the top and the legs are bolted to the frame. In tables of simple design, the legs are attached directly to bottom side existing top. Similar connections held together different ways: glue that can lose its strength; dowels and tenons that can break; screws, plates or bolts that may be loosened. Adhesive bonds that have lost their adhesion can easily be restored by applying a new layer of glue there. But to repair serious breaks between individual parts, it may be necessary to disconnect the connections, as well as subsequently replace the broken parts. To complete the repair and make it as high quality as possible, the connection can be strengthened using metal corner plates or wooden blocking.
Repair of a table with a sliding mechanism
How to repair a table that has sliding mechanisms? To repair tables with moving parts, other measures are needed. Damaged mechanisms sliding tables can be corrected by cleaning and lubricating its sliding parts; If they are broken, bent or lost, they need to be replaced. The simplest method to repair a sagging board is to wedge it and then glue the wedge to its underside.
It's good to have a glue injector. It will help to introduce glue into all hidden places. The most important tool clamps also protrude. You'll need G-clamps to seal existing cracks, and girdle clamps to ensure equal pressure is maintained across all glued frame-to-leg joints. When using clamps, you need to place the thinnest pieces of soft wood or cork under their grips to avoid damage to the surface of the clamped elements. In order to close the glued sections, you need to apply the minimum required force, since excessive pressure can lead to all the applied glue being squeezed out, leaving the joint dry and weak.
If you need to secure a part with a keyed joint, you will need a keyed jig (to guide the drill) and keyed metal centers. These tools help ensure accurate placement as well as alignment of all key holes. Dowels that have special grooves, which are made stronger by adhesive bonds, are also useful.
How to get to damaged areas
To get to the damaged connection, you should turn the table over and place it on a fabric folded in several layers at once or on a rug. Remove the tabletop. If it is attached by compressive metal plates, which are inserted into a groove on the frame straps, you should remove the screws and these plates and disconnect the tabletop. If it is supported by screws or bolts to the frame or corner blocks, you need to remove these fastenings.
How to repair a crack
If a crack appears around the socket in the upper area of the leg, glue should be injected into the crack and into the hair hole between the tenon and the socket. It is necessary to compress the connection using two clamps. First, you should install a G-shaped clamp on the upper area of the leg in order to close the resulting crack; then place a girdle or tubular clamp, stretching it from the outer side of one leg to the outer side of the other, in order to hold the tenon in its socket. Let the glue dry overnight; then you should remove the clamps.
To level an overhanging folding board, The farthest point should be noted where the table leg or supporting slide touches the bottom side of the board; scrape off the old glue and trim and attach a small tapered wedge to the board. Cut a wedge out of a piece of hardwood, apply glue to the top side of it, and push it between the board and the sled, adjusting it until the board is level. You need to place a weight on the top of this board while the glue dries. After reading this article, you will know how to repair a table.
Stooping is a condition characterized by a strong deflection of the thoracic spine. Normally, in a healthy person, the spine has curves (cervical, thoracic, lumbar and sacral). Their increase leads to poor posture.
With normal posture, a person’s stomach does not protrude beyond the chest. When slouching, the head is tilted forward and the chest becomes sunken. This pathology is otherwise called pathological thoracic kyphosis. There are 2 known forms of stoop: functional and associated with various diseases. Children and elderly people most often face this problem. This pathology is often combined with increased lumbar lordosis. Distinctive feature stoop is that it disappears when the back is straightened. This is a functional disorder.
Causes
A slouched back occurs for several reasons. The main etiological factors are:
- physical inactivity;
- improper organization of the workplace;
- psychological problems;
- scoliosis;
- underdevelopment of back muscles;
- low physical activity;
- congenital anomalies of the spine;
- rickets;
- back injuries;
- polio.
In children and adolescents, stooped posture is most often caused by a sedentary lifestyle. IN Lately motor activity decreased sharply. This is due to the use of computers, phones and tablets. Children spend a lot of time at school at their desks. They began to play less sports. Physical inactivity leads to weakening of the back muscles and stooping.
An interesting question is the issue of diseases. She was trained by Louise Hay. She revealed the mechanism of development of various diseases with psychological point vision. At a young age, poor posture is often caused by social and personal problems. Risk factors are:
- complexes;
- fear of communication;
- constraint of great height.
Such children begin to slouch. All this happens unconsciously. In some children, poor posture is observed due to increased flexibility of the joints in the spine. This condition is congenital. Slouching may be one of the first manifestations of scoliosis, but no changes are detected when X-rays are performed.
In an adult, this condition can occur due to improper exercise in the gym. This happens when there is a heavy load on the pectoral muscles. The latter begin to pull their shoulders towards themselves, which causes poor posture. The appearance of stoop in adults is also possible against the background of osteochondrosis and osteoarthrosis.
Symptoms and possible complications
You need to know not only psychological reasons stoop, but also how it manifests itself. People with this pathology have specific appearance. They walk with their head and belly pushed forward. The legs are often slightly bent at the knees. There is a rounding of the back. In some cases, pterygoid blades are identified. These people's shoulders are raised. Every experienced doctor has seen a photo of a person with poor posture. Along with stooping, the following symptoms are possible:
- pain;
- feeling of heaviness in the back;
- rapid fatigue.
If a person is left untreated, a hump will form over time. Postural scoliosis often develops. This is a persistent sideways curvature of the spinal column.
Survey plan
Before straightening your back, you need to clarify the diagnosis. You need to see a doctor. To clarify the diagnosis you will need:
- radiography;
- visual inspection;
- palpation;
- survey;
- physical examination.
During the first X-ray examination, the picture is taken only in a standing position. Subsequently, radiography is performed in 2 projections at once. With functional kyphosis (stooping), no changes are observed, since the person’s back is straight during the photo. No laboratory tests are required. Treatment is carried out after examination and questioning of the patient.
The doctor must determine:
- duration of poor posture;
- chief complaints;
- possible risk factors.
It is necessary to exclude various diseases of the spine (ankylosing spondylitis).
Treatment tactics
You can restore your posture at home, but to do this you need to see a doctor. There is no medical or surgical treatment for this condition. The main aspects of therapy are:
- physiotherapy;
- massage;
- manual therapy.
The presence of stoop is not an absolute indication for wearing corsets. In this condition, it is possible to use chest belts, correctors and reclinators, but they will only be effective when combined with exercise therapy. These products help strengthen muscles. The most effective are thoracolumbar correctors. These devices have a temporary effect.
They encourage people to take correct position body, but after removing the belt or corrector, signs of stoop may reappear. The most effective way to correct posture is through an active method. It involves training the muscles of the back and shoulder girdle. Children, teenagers, people 30 years old and older are engaged.
The main objectives of exercise therapy are:
- stretching the pectoral muscles;
- strengthening the gluteal, rhomboid and trapezius muscles;
- increase in motor mode.
You need to do gymnastics for stoop for at least six months. It all depends on the age of the person. At 30 years old, it may take 2-3 years to correct your posture. After 40 years, correction is almost impossible.
A set of exercises is selected by the doctor individually, taking into account the person’s age and fitness level, as well as contraindications.
Performing therapeutic exercises
A variety of exercises can help combat slouching. When conducting exercise therapy, you must adhere to the following rules:
- exercise for at least 30 minutes;
- repeat exercises 6–10 times;
- gradually increase the load;
- pay great attention to the muscles of the middle back;
- relax the muscles of the neck and lower back;
- do not use heavy dumbbells and barbells;
- refuse exercises to train the chest muscles.
To straighten your back, you may need the following exercises:
- placing straightened arms behind the back with a slight delay in a standing position;
- abduction and adduction of the arms parallel to the floor;
- raising the shoulders and shoulder blades up as you inhale, followed by lowering as you exhale;
- raising the upper back followed by a delay in the position lying on the stomach;
- tilting the body with straightened arms to the left and right with legs apart;
- lifting the hands and feet up with the chest lowered while lying on the stomach;
- bending the body upward with hands resting on the floor while lying on the back;
- bending forward with straightened legs in a standing position;
- arching the back while standing on all fours;
- lifting the pelvis and hips up from the floor while lying on your back.
After class it is very important to relax. The most effective exercises for stooping should be known to every physical therapy doctor. It helps many patients. Its essence is not only in physical training, but also in psychological relief. When practicing yoga, it is very important to breathe correctly. If you do not do the exercises and self-medicate, then it is possible Negative consequences in the form of scoliosis.
Lifestyle change
To correct your posture, you will need not only yoga and gymnastics, but also lifestyle changes. Necessary:
- choose the optimal furniture for work;
- teach your child to sit up straight;
- move more;
- exercise;
- swim more;
- Spend less time sitting on the sofa or chair in front of the computer or TV.
When purchasing furniture and equipment for homework you need to pay attention to the equipment of the chair, the height of the slot and chairs, the size of the computer monitor. A person will not slouch if properly organized workplace. The chair must be equipped with a backrest, armrests, headrest and footrest.
It would be better if it is height adjustable. The armrests should be in line with the table. The monitor is installed in the central part of the table at eye level. Slouching people need to sleep on a flat and firm mattress. When walking, you need to keep your posture straight. In the morning you need to exercise. It is recommended to swim in a pool, as moving underwater strengthens your back muscles.
Some people may need help from a psychologist. It is necessary if the appearance of stoop is due to a person’s isolation or fears.
If your posture is poor, you should stop doing weightlifting. If you are stooped, push-ups and bench presses are not recommended.
Prevention of slouching
Slouching posture can be prevented. To do this, you must adhere to the following recommendations:
- train your back muscles;
- lead a healthy lifestyle;
- periodically swim in the pool;
- do not have complexes about your height;
- walk and sit with a straight back;
- sleep on a hard surface on your back;
- use special orthopedic mattresses;
- exclude any spinal injuries;
- distribute the load evenly when exercising in the gym;
- eat well;
- move more;
- do not sit in one place for a long time.
Parents and teachers should monitor the posture of children and adolescents, otherwise deformation (curvature) of the spine is possible.
Thus, the occurrence of stooping does not pose a great danger. Posture can be improved by performing muscle training exercises prescribed by your doctor.