The essence of the invention: the grinding tool is placed on the largest diameter of the part in such a way that the plane of its rotation is parallel to its diametral plane. The tool is moved along the generatrix of the motion condition of the plane of its rotation along the diameter perpendicular to it, and the axis of rotation - normal to the specified diameter. After the tool reaches the center of the product, the direction of rotation of the tool and the movement of the rotation axis are changed to the opposite. In this case, the angle p between the direction of feed along the generatrix and the plane of rotation of the tool is chosen according to the given formula. 1 salary, 4 ill.
UNION OF SOVIET
SOCIALIST
REPUBLIC- ((9) ((() (i)z V 24 V 5/16
STATE PATENT
USSR DEPARTMENT (USSR STATE PATENT) /
(21) 4876246/08 (22) 07.25.90 (46) 15;12.92. Bull. M 46 (71) All-Union Scientific Research and Design and Technological Institute of Chemical Engineering (72) E.I0. Feldman and R.N. Friedman (56) Copyright certificate of the USSR " " " No. 1399085, class B 24 B 19/02, 1986.
M 742111, class. V 24 V 5/16, 1975. (54) METHOD FOR GRINDING CONCAVES
CURVED SURFACES (57) The essence of the invention: the grinding tool is placed on the greatest
2 the diameter of the part in this way. that the plane of its rotation is parallel to its diametrical plane.. The tool is moved along the generatrix from the condition of movement of the plane of its rotation along the diameter perpendicular to it, and the axis of rotation is normal to the specified diameter.
After the tool reaches the center of the product, the direction of rotation of the tool and the movement of the rotation axis are changed to the opposite. When the angle (P) between the direction of feed along the generatrix and the plane of rotation of the tool is chosen according to the given formula. 1 z.p.f-ly, 4 il.
The invention relates to abrasive processing of large curved surfaces, for example elliptical bottoms, cones, used in various agricultural sectors.
Currently, large-sized curved bodies of revolution. mentioned above are sanded using a copyless stitching method. When grinding in this way, the abrasive tool cogs the shaped profile of the product without special tracking systems and copying devices, while the wheel is moved in the plane of its rotation along the forming part, with a certain feed per revolution of the product (stitch feed). Copying a curved profile occurs through a combination of vertical and horizontal forced movement of the grinding head and rotation of the latter on the suspension axis; . This method is widely known t1), However, the abrasive tool is moved along the generatrix of the shaped profile of the product along two coordinates - either with a perpendicular direction to the velocity vector of the part and the tool, or with a collinear one (i.e., processing is carried out by part of the end or periphery of the cutting surface of the tool).
Since the abrasive wheel does not have a continuous cutting edge, marks of varying depths, parallel to each other and to the forming parts, will be applied to the surface being processed. During subsequent passes with constant technological conditions, part of the abrasive grains will fall into already cut grooves, therefore, the efficiency of the process is reduced. and to remove a given allowance it is necessary to make additional passes.This leads to an unjustifiably increased consumption of abrasive material.
Re-adjustment of technological modes for each pass increases machine processing time.
As a prototype, a method is adopted, the essence of which boils down to the following; an abrasive tool mounted on a hinged grinding head is pressed against the workpiece, keeping the angle of inclination to the vertical constant, equal to 45°, and the grinding head is moved in the plane of rotation of the tool, along a curved generatrix from line to line from the center to the periphery (or vice versa) bodies of rotation, reversing the tool.
The grinding head moves only in the plane of rotation of the tool, and the ratio of these components is kept equal
Sx/Sy = t9 f °
It is known that BC = 2 /Y, = B2 + 4 dt, VD =
50 where B is the height of the tool;
d – tool diameter:
t is the grinding depth.
Consequently, the line width will increase by
The optimal angle p will be equal to. coinciding with the plane of the generatrix along which the tool moves.
This method provides mechanized grinding of large bottoms, 5 But in roughing operations this process is quite labor-intensive.
The purpose of the invention is to increase the productivity and quality of grinding large curved
10 surfaces.
Figure 1 shows a diagram of the formation of a line when the plane of rotation of the tool is perpendicular to the direction of feed H, Fig. 2 shows a diagram of the formation of a line
15 when the feed direction is at an angle other than direct to the plane of rotation of the tool; Fig.3 shows a diagram of the movement of the tool along the generatrix of the bottom; Fig.4 is a side view, 20 When a line is formed with a feed direction perpendicular to the plane of rotation, the latter removes a layer of metal with a depth t, and the contact surface is a part of the cylindrical surface AB-SD (Fig.1). In this case, the width of the line is equal to the chord BC = AD. This cylindrical surface c. combination with the surface of the part gives a rectangle ABCD, in which AC = WD. If you rotate the abrasive tool at an angle so that the plane of its rotation with the direction of feed makes an angle p. 90О, then the cylindrical contact surface of the tool with the ABCD part will also unfold
35 per angle (Fig. 2) and the width of the line will be determined by the length of the diagonal VD of the rectangle ABCD. In this case, during processing, the feed per line is maintained as the sum of its components
Ags sew quality of the processed surface and p = ags c - -. reduce consumption of abrasive material.
At this angle of rotation, the diagonal is 8D. Figure 4 shows the feed pattern Sx Sy, perpendicular to the feed direction along Sz. the combination of which allows the abrasive line, and the width of the line is maximum. By allowing the tool to move along a given path, the number of lines on the specified (0-0-0 Fig. 3) trajectory decreases. product and machine time for processing. The formula of the invention leads to increased productivity. 1. Method of grinding concave curves process. linear surfaces at which they were grinding. Based on this, the internal grinding tool is rotated and large-sized curved ones are moved along the generatrix of the surfaces, for example elliptical bottoms, of the part that is being rotated, but it is advisable to perform it by alternating in that, in order to increase the tool movement along the O-generator, productivity and improve quality
About, located at an angle to the processing plane 15, the grinding tool rotates the tool, from the periphery, the days are placed on the largest diameter of the part towards the center, and after the tool exits in such a way that the plane of its rotation is parallel to the center of the product, the direction of feed and rotates - to its diametrical plane, the movement of the tool is changed to the opposite direction of the tool along the generatrix. 8 as a result, the risks 20 are carried out from the condition of movement and are flat formed when the tool passes its rotation along perpendicular to the ment along the generatrix 0-0 and the rotation of the product diameter to it, and the axis of rotation is normal to the angle a changes the angle to 90°, but the specified diameter, at the same time, according to Therefore, when the tool will work reaching the center of the product with the tool, along the forming 0-0 microrelief of the processed - 25 change the direction of rotation of the instrumented surface will represent a co-ment and movement of the axis of rotation on the opposite mesh in the form of a cross in the opposite direction . the location of the marks, which leads to an increase in - 2. The method according to claim 1, characterized by increased productivity and improvement in that the angle between the feed direction of the quality of the machined surface, as well as 30 along the generatrix and the plane of rotation, excluding the operation of editing the tool, is selected according to the conditions: ment and idle passes. - g, V. Sx
Even natural stone in some cases can get damaged and scratched, which disrupts the decorative effect of the cladding. If you decide to restore the shiny surface yourself, find out in 10 minutes of reading how to polish and grind marble and granite yourself. All the secrets of our masters are collected in this article.
What you will need for work:
- A power tool is a grinder, without which grinding marble and granite with your own hands is simply impossible (it’s better if it’s a reliable Makita brand).
- A special “adapter” is a holder for grinding and polishing discs, the so-called “caliper”. It looks like a rubber disc with a special fastening. For processing curved surfaces, a convex rubber caliper is purchased; for smooth surfaces, a flat one with sufficient rigidity is purchased.
- Diamond grinding discs and polishing wheels (“turtles”) of different numbers.
Polishing value
Polishing is the final stage of processing natural stone and turning it into a finished product. This process is often underestimated by craftsmen who believe that simply smoothing and adding shine to a stone surface is not worth the serious costs and can be done with cheap improvised means.
In reality, at this stage, natural stone products are given important properties:
Aesthetic
The surface of a perfectly polished stone becomes glassy and partly mirror-like. It has a high reflectivity, but at the same time it allows one to clearly see the structure of the stone and decorative elements (inscriptions, patterns).
Physical
On a smooth surface, atmospheric moisture is less retained - the main factor of destruction. Therefore, its durability directly depends on the quality of polishing of natural stone. This statement is especially true for marble and other “soft” rocks, because their “crystallization” (artificial hardening of the top layer under the influence of special chemical compounds) occurs precisely during polishing.
Naturally, the value (including commercial value) of a product that has these properties increases significantly. But they can only be achieved with the help of modern equipment designed specifically for polishing stone.
Tools used:
(“turtles”) for dry/wet polishing. The set contains on average 7–8 AGShK, with numbers from 50 to 3000 and Buff (“buffalo skin”). The higher the number of the disc, the finer the fraction of diamond powder in it. Disk numbers are called “transitions” and indicate the strict order of their use.
(“grinder”) with speed control function.
(holders) for AGShK with a rigid and flexible base and a Velcro-type surface.
or an emery block, brushes and rags for wiping the stone.
Polishing methods
"Wet"- increases processing time and labor costs, but saves material and extends the service life of diamond blades, and also reduces the likelihood of defects (chips, burns). Requires the use of an angle grinder with a central water supply. Not suitable for polishing at sub-zero temperatures.
"Dry"- a faster method that does not require special operating conditions. Accelerates the wear of diamond discs and requires good skills from the master, because... increases the likelihood of defects.
Polishing stages
1. Grinding- leveling the surface after cutting and peeling, removing ridges and chips. Performed in circles numbered from 50 to 400.
2. Polishing- final smoothing of the treated surface with 500–600 discs, removing all visible scratches.
3. Polishing- imparting shine to the surface. Uses 800–3000 and Buff discs. In the process of adding gloss, polishing pastes and waxes, as well as special compounds for cementation (strengthening) of the treated surface, can be additionally used.
The phased distribution of disks is very arbitrary and differs for different types of stones. For example, the final polishing of some types of marble can end with No. 800.
Recommended disk rotation speed: up to 1200 rpm. (grinding), 1200–1500 (glazing), 1500–2500 (polishing). These figures are also approximate and even very often disputed. Some craftsmen get excellent results with disc rotation speeds no higher than 1500 rpm, while others polish quite successfully at 3600 rpm. But most agree that for soft surfaces it is better to stick to low speeds, and on hard surfaces you can increase them.
Recommended water supply mode: in the first stages - more to wash away large fractions and prevent the appearance of deep scratches; in the future - less, until the surface dries during final polishing.
Important!
You cannot skip transitions, because... this can subsequently lead to a lack of gloss and the need to re-polish the product.
Polishing flat surfaces
It is recommended to place flat workpieces almost horizontally, at a slight angle to the master. In this position it is more convenient to hold the tool, as well as remove dust and dirt from the surface being treated.
The recommended outer diameter of the discs is 100 mm. For fastening, use an adapter only with a solid base that ensures uniform pressure on the flexible disk over its entire area.
It is advisable to move the rotating disk along a flat surface according to the following scheme: linearly along the width of the workpiece, while making smooth circular movements. Make sure that the tool pressure on all parts of the surface is uniform and the processing time is the same. When passing each subsequent “line”, make a small (several mm) overlap with the previous one.
After each pass, remove dust/dirt from the workpiece and wipe it with a rag. If the disk is “greasy” (begins to shine), then you need to “open it”, i.e. - renew the work surface using a roller cutter or rubbing it with sandpaper.
Polishing of ends and corners
For polishing flat ends with sharp corners, it is better to use AGShK with an outer diameter of no more than 100 mm and having large segments with smoothed edges. In this case, it is better to mount the disks on adapters with a rigid base. In this way, chipping on the outer corners of the workpiece and possible rupture of the disk can be avoided. For polishing shaped ends, an adapter with a flexible base is more suitable. Move the disk along the length of the end.
The process of polishing internal corners requires increased attention, because... Accidental careless movement may result in the formation of a notch in the adjacent surface. The most precise fastening of the disk with Velcro and its alignment until there is no runout will help reduce the likelihood of such defects.
Precautionary measures
During the polishing process of natural stone, a lot of dust and dirt and fumes from the chemical compounds used are formed. Therefore, the master’s equipment should include a respirator and goggles. The work area must be well ventilated. When performing “wet” polishing, to avoid injury, it is better to cover the floor with wooden boards. Also, do not forget the general safety rules when moving stone blanks, handling power tools, etc.
Advice from the “experienced”
The widespread use of AGShK in polishing natural stone has given rise to many useful amendments and instructions from experienced practitioners. Here are some of them:
Since polishing can “eat” a considerable part of the stone mass (about 2 mm is considered an approximate norm), competent alternation of “dry” and “wet” methods will help to achieve the exact planned dimensions of the product.
Polishing of internal corners should be done as follows: with the first three numbers (50, 100, 200) do not reach the corner by about 2 mm. With subsequent numbers, you can safely crash into a corner without the risk of making recesses on the adjacent plane.
On very porous types of granite, the polishing process may not darken to the “factory” tone, and the gloss may turn out to be “foggy.” The reason is insufficient polishing. To prevent this from happening, you need to polish especially carefully with a 400 disc, because... It is the discs with this diamond fraction that finally smooth out the smallest pores. Repolishing should also be done starting from No. 400.
There are many other rationalizations. But some of them (such as “wet” polishing in the cold using a mixture of water and ethyl alcohol) are associated with issues of profitability, while others (like adding gloss with a Buff disc with white spirit) are in the field of dubious experimentation. In general, due to the variety of materials used and processing conditions, the technology of polishing natural stone provides a wide field for research.
Despite the fact that the technology of diamond grinding of concrete surfaces has been known for three decades, until now there was no documentation on its use for the restoration of concrete pavements (CPR, Concrete Pavement Restoration).
In what cases is diamond grinding necessary?
Diamond grinding can correct the following damage to coatings:
— gaps in transverse joints and cracks (the most common reason for grinding);
— surface roughness;
— texturing the polished concrete surface to improve friction;
— removal of marks from wheels (for example, forklifts in warehouses or from the use of studded tires for concrete road surfaces);
— reduction of noise level from vehicle movement;
— surface deformation;
— creating a slope for drainage;
etc.
Concrete polishing procedure
The procedure for grinding a concrete surface takes place in several stages.
At the first stage, the top layer (4-6 mm) of the concrete coating, which has been largely destroyed or deformed, is removed. For this, grinding machines and abrasives with a grain size of 30-40 grit (595-420 microns) are used. In some cases, for example, to restore concrete road surfaces, special joint cutters are used, in which circular saws with diamond segments are located quite close to each other - as a result, the treated concrete surface consists of parallel grooves 5 mm deep.
Then the actual leveling and grinding of the surface occurs - the grinding cup cuts off even the smallest irregularities, giving the concrete surface the necessary smoothness. Typically, abrasives with a grain size of up to 200 grit (75 microns) are used to level the surface.
Benefits of Sanding
Diamond grinding of concrete pavements is a quick and effective way to restore the surface. In addition, grinding has a number of advantages compared to other methods of restoring concrete surfaces:
- lower cost of work compared to replacing a concrete coating or applying a new layer;
— increases the coefficient of friction and safety (for example, in warehouses);
— the possibility of local repairs, without closing the entire premises (for example, in shopping centers) or minimal traffic restrictions (for example, when restoring external concrete pavements);
— the ability to repair only problem areas;
— does not raise the floor level, which is especially important in places where equipment operates (for example, warehouses), or the distance from floor to ceiling is important (for example, awnings, canopies, arches, etc.);
— does not affect drainage systems;
etc.
Efficiency
In most cases, concrete pavements that have been diamond polished have a smoother surface than new ones, and to date no negative side effects from diamond grinding have been identified.
Despite the obvious advantages of diamond grinding, there is a significant condition that limits its use: the surface must be in good structural condition, otherwise, before diamond grinding work, it is necessary to first restore the internal structure of the concrete coating.
Recently, a team of analysts Shreenath Rao, H. Thomas Yu and Michael I. Darter published a study on the use of diamond technology for repairing concrete pavements, “The Longevity and Performance of Diamond-Ground Pavements.” Despite the fact that the study talks about the use of diamond technologies in the repair of concrete road surfaces, as well as their durability and performance, a large number of the described techniques are applicable to the repair of any concrete surfaces, primarily for industrial concrete floors. In subsequent articles we will definitely talk about the most interesting aspects of this research.
Sanding wood by hand, although it requires a lot of labor, in return provides a number of important advantages: less aggressive processing, better control over the process and high quality surface finishing in hard-to-reach places - in corners, on smooth bends and other reliefs of any complexity.
Manual technology is indispensable for interlayer sanding of finishing coatings, as it ensures the most delicate work and eliminates the risk of rubbing off the applied finish. When using the same abrasive, hand sanding guarantees a better quality surface than sanding with a sander, grinder or drill.
About grinding pads and making them yourself
Sanding blocks (grinding pads) are an indispensable assistant in a carpenter's arsenal. These simple devices ensure uniform contact of sandpaper with the surface being treated, increasing the speed and quality of the work performed. Using such pads, you will significantly improve the quality of grinding, extend the life of the abrasive, and avoid irreparable defects in the form of depressions and rounded ends.
To acquire such a grinding tool there is no need to spend extra money. It will not be difficult to make it yourself from dense foam or wooden scraps. Check out some easy sanding block projects in our gallery.
With this sanding block, which you can easily make from scraps of wood you have lying around, you won't have to waste time changing sandpaper. Wedge clamps are a simple and functional alternative to traditional clamps. A simple corner block will prevent accidental rounding of edges when sanding the ends. To sand smooth curves, use curved blocks made from scrap wood or foam. When sanding grooves or round woodwork such as balusters, use an additional soft pad. Don’t rush to throw away the profile scraps; they will still serve you as a block. Everything ingenious is simple!
How to choose sandpaper for working with wood?
There are quite a few characteristics by which sandpaper is classified. But the main and most significant parameter that you should focus on when choosing a sandpaper is the size of its abrasive grains - the so-called. graininess index. For specific tasks when working with wood, a certain type of grain size is chosen.
TABLE: SELECTION OF ABRASIVE FOR WORKING WITH WOOD
Practice shows that to perform basic tasks, a master needs a set of five types of abrasives:
- P150; P180; P240(wood processing before applying finishing);
- P280; P400(interlayer and finishing sanding of finishing coatings).
You can read all about the intricacies of choosing sandpaper in.
Dry or wet sanding?
For intermediate sanding of finishing coatings - stain, varnish, polyurethane, etc. Traditionally, two techniques are used - dry or wet.
Dry grinding increases the efficiency of the abrasive and makes it possible to better control the work process, which is especially important at the stages of intermediate grinding of delicate coatings. The disadvantage of this technique is the rapid clogging of the skin. Sandpaper with an anti-clogging stearate coating partially compensates for this problem.
At wet grinding For wooden products, mineral oil, white spirit or ordinary soapy water are used as a moisturizer. With this technology, the abrasive becomes clogged much slower and, accordingly, lasts longer. But the mess formed from foam and shavings significantly complicates the grinding process. There is a need to constantly wipe the surface and carefully monitor the result of grinding.
How to sand wood correctly?
Grinding technique . The wood is sanded with active movements along the grain or at a slight angle, but without excessive pressure on the block. Movements should be as light as possible, on the second or third pass using fine-grained sandpaper with virtually no pressure.
Preparing the surface for finishing . When preparing wood for applying a finishing coating (varnish, oil, stain, polyurethane, etc.), start working with P120 or P150 abrasive (depending on the nature of the irregularities). After that, move on to P180 grit and finish with P240 abrasive.
Intermediate grinding of coatings . When applying the finishing coating layer by layer, intermediate sanding of each layer is carried out with fine-grained sandpaper P280. For final polishing use P400 sandpaper. Use P600 grit abrasive to remove even the slightest imperfections in a glossy finish.
Requirements for finishing coatings to be sanded . Matte types of coatings are not as demanding on the quality of sanding as glossy ones. At the same time, a dark stain will expose all the flaws of unfairly performed sanding.