Do-it-yourself bumper repair cracks

In detail: do-it-yourself bumper crack repair from a real master for the site my.housecope.com.

Often in the road stream you can meet a car with a cracked or deformed buffer. What can you do, no one is immune from an unsuccessful parking or a light accident. However, this is not a reason to continue to drive a car that has lost its "brilliant" appearance - there is practical experience in restoring the original state of this element.

External plastic structural elements are mainly made of thermoplastic plastics. The technology for the restoration of such products is based on welding, which allows you to get rid of through cracks and even recreate broken fasteners. Actually, the procedure is not much more complicated than preparing and spray paint damaged section of the car body.

Some motorists assure us that we repair the bumper with our own hands using metal brackets. But an experienced car owner knows that similar things are treated with similar ones, that is, repair plastic rods are used for soldering. Their composition, color and profile are different, the desired rod is selected according to the marking on the buffer.

Making the right choice means guaranteeing a quality repair, because the mismatch of materials will significantly shorten the life of the automotive element. To find out what a cracked bumper is made of, just carefully examine the inside of the part. Depending on the marking, the following conclusions are drawn:

PP - polypropylene base.
ABS (GF, PAG 6) are hard plastics.
PUR - polyurethane.

Plastic welding requires high temperatures, for example, 400-450°C is suitable for propylene, and 500°C is indispensable for the restoration of an ABS structure. Many car owners will learn how to repair a bumper with their own hands in a video where craftsmen use an ordinary 100 W soldering iron.

Video (click to play).

You can also restore a damaged part using pieces from a bumper with a similar marking. They are cut into strips 8 mm wide for PUR, and 4-5 mm for polypropylene.

Almost any breakdowns are treated by welding, even broken parts are reanimated. However, no one has canceled the economic feasibility of such work, because the restoration of numerous defects can hardly be called justified. The cost of a complete restoration and staining will cost more than a new buffer.

To perform repairs, you will need certain tools. It can be both ordinary household appliances and professional tools. The perfect kit includes the following:

Orbital sander or sanding block.
Grinding wheels of various grain sizes.
Dremel type mini drill or drill.
Clamps and rubber spatula.
Soldering iron and building hair dryer.
Metal tape.

Of the materials to restore a cracked buffer, you may need:

Putty and primer.
Brass mesh for crack reinforcement.
A can of paint or a can of paint.
Plastic repair rods of the desired configuration and composition.

The damaged part must be dismantled in order to eliminate, firstly, excessive stress in the area of cracks. Those who have already done such work will say that now we clean the bumper and only then repair it with our own hands.

Cracked parts fit together. For reliability, they are fixed with metal tape on the outside of the part. If the gaps are quite significant, then you will need clamps that clamp the edges of the cracks. Their number depends on the complexity of the repair.

When restoring parts on a PP base, reinforcing mesh is not used. The process begins with the fact that a nozzle with a nozzle with a diameter of 5-7 mm is installed on the hair dryer. Further work is carried out according to the points:

On the inside of the buffer, along the junction of cracks, make a groove for the plastic rod with a Dremel mini-drill.
Using a hair dryer, melt and place the repair rod into the prepared groove.
Clean the front part of the bumper with an orbital sander with a P240 attachment and repeat the welding procedure in the same way as for the inside.
Grind the cooled seam from the outside with a nozzle with the same grit P240, then remove dust from the surface.

Smooth out irregularities with a special putty for plastic, try to make sure that the layer is minimal.
Dilute the primer with a solvent 3:1 and apply two coats to the degreased surface. The drying time of the first layer is 15 minutes.
Apply a developing layer in a contrasting color, followed by sanding with a wheel or sandpaper with a grit of P800 and P1000.
Eliminate the detected defects with the help of nitro putty, followed by polishing with P1000 sandpaper.
Remove dust with a damp cloth and degrease the part, after which paint plastic decorative paint with a border overlap of 50-100 mm. Apply paint in 3-4 layers with intermediate drying cycles.

Anyone who is interested in how to properly repair a bumper on a video with their own hands should take into account an important detail. 30-40 minutes after applying the last coat of paint, the part should be varnished. Thus, we get an impeccable appearance of the repaired part. Don't forget to follow a few simple rules:

It is necessary to try to apply a minimum layer of putty.
Maintain a temporary pause for the complete hardening of the putty layer.
Treat the puttied place with a grinding wheel or sandpaper with a grit of P800, and after - P1000.
It is desirable to apply a developing layer of primer.

In the case of a polyurethane buffer, the preparatory stage in the form of grooving is excluded. A reinforcing mesh of brass is superimposed on the crack; steel is not recommended for use, because it is susceptible to corrosion. As an alternative, staplers can be used every 10-20 mm. They are recessed into the body of the part across the seam, it is imperative to ensure that the bracket does not pass through the part.

Further, the repair technology does not differ from the restoration of a polypropylene part. Metal mesh or staplers must be recessed into the plastic layer. Only after that the seam is filled with repair plastic and soldered from the opposite side. Some important points of technology should be taken into account:

You need to solder the mesh or staples carefully so as not to overheat the plastic, otherwise it may deform on the opposite side.
For a complete do-it-yourself repair of a polyurethane bumper, the width of the reinforcing mesh should be 15-20 mm.
It is better to press the mesh or staples with a flat object.
If the legs of the staples pierce through the plastic, then they should be shortened with side cutters.
For the convenience of working with metal elements, you can use tweezers.
To prevent the new enamel from peeling off, it is necessary to sand the paint on the entire plane of the part.

The puttying stage and painting are carried out in the same way as described above - according to the traditional scheme. Repair work on the restoration of the buffer can be combined with car painting , so the consumption of materials will be more rational. It is important to determine in advance the feasibility of carrying out restoration work. If significant costs are visible in the future, then it is better to buy a new part.

If the bumper on your car is cracked, there is no money to buy a new one, and the appearance of the repaired plastic part may differ from the new one in the presence of visible traces of repair, then the following life hack will definitely come in handy for you.

This repair option is really not accurate in the understanding of most car owners, but at the same time, it has its own special charm and attractiveness for young people, especially for those who adhere to the automotive sports subculture: drifting and motorsport in general. It is unlikely that it will be a discovery for anyone that car racing often turns out to be a tough contact sport, dents and cracks in bumpers are common here, so in near professional racing circles, young athletes prefer to deal with breakdowns on their own.

Of course, there are some of the most popular ways to join several pieces of a broken bumper together (using resin, using an epoxy mesh, and even using a soldering iron), but we will look at mechanical fastening using plastic ties. To make the process clearer, first watch the video in English (you can turn on subtitles and translation):

Looked? Is the structure of work clear? Then, you can start laying out the most important stages of work.

For repairs you will need:

Repair actually does not take much time and does not require special preparation. As they say: "If the arms were straight".

I. First, connect the two parts of the bumper crack together. The gap in this case should be minimal, all parts and sides of the bumper should lie in a single plane. Then you will need to tape these parts together so that you can proceed to the next step of the repair. At 2.50 minutes, the video shows how to tighten a cracked bumper.

As you can see, it is better to repair with two people. An assistant can insure when you run out of hands.

II. Now it's time for drilling. But before that, one more life hack - apply duct tape along the crack. This will prevent the paint on the ends from cracking when drilling. 4.20 minute video. You need to drill at a distance as thick as a finger. In this way, you will not damage the bumper even more if the drill jumps off to the side, and the plastic screed will not wipe a too narrow wall over time and the structure will not fall apart.

The pitch between the holes is as thick as a finger. A crack line is visible under the adhesive tape. Follow her line. The more accurately you can drill holes, the stronger the structure will be.

III. 6.00 minute video. Quilted bumper. There are two contraction patterns: parallel and criss-cross. The first is easier to do, the second option holds the bumper pieces together better.

First stitch type: Parallel

In order to get to the inside of the bumper, "crazy hands" remove the fender liner. The workflow is shown at 6.55 minutes of the educational video. A couple of minutes and the bumper is ready!

Attention! The flat surface of the plastic fastener should be on top.

You need to tighten the ties strongly until the characteristic clicks stop.

Ready! It looks stylish, and most importantly, it really works. The bumper again received rigidity and lost functionality.

None of the motorists is immune from the fact that his bumper will last all the time without damage. Therefore, when chips and scratches appear on it, many people think that nothing can be done, and begin to look at the new one. But there is a way out, since you can make repairs with your own hands. How to repair a crack in the bumper will be discussed below.

How to repair a cracked plastic bumper - in our new article

Before you talk about how to remove a crack on the bumper, you need to figure out what materials these structures are made of. You need to make a reservation right away that if the part is metal, then it will have to be repaired in a specialized workshop if the motorist does not have the skills of a professional welder.

But on modern cars, these parts are made of two types of plastic:

thermoactive material, its cracks are sealed with a hair dryer or soldering iron, as well as the formation of a special metal frame, its characteristic feature is that it melts under the influence of a certain temperature;
thermosetting material, it is better to close cracks on it using special fiberglass or reinforcing plastic mesh, which must be impregnated with epoxy resin, since when exposed to high temperature this plastic will not melt.

The labeling of thermosetting plastic is usually as follows: PP, PPTV and other analogues. Typically, such designations are placed on the inside of the bumper.

The marking will tell you what material the part is made of.

The marking of thermosetting plastic is PUR, which refers it to the class of polyurethane materials, as well as PAG 6, GF, ABS, which refers it to the class of solid plastic masses.

Based on these parameters, it will be necessary to select materials for repair.

It is important to understand that if there is no reliable information about the material from which the bumper is made, it is better to find out, since repairs can turn into buying a new one. This can be done at the service station or refer to the technical documentation for the car.

Before repairing a crack in a bumper made of thermosetting materials, you need to prepare the necessary tools.

a powerful soldering iron or a special machine hair dryer, which will be needed to soften and solder the plastic;
primer, which is needed for the treatment of soldered surfaces;
paint in a special spray can, for painting a repaired area or the entire bumper;
putty;
small diameter drill for drilling holes along the edges of the crack;
gasoline for degreasing treated surfaces;
metal fine mesh or staples of a furniture stapler;
sandpaper, preferably zero, as well as one and two, for thorough rubbing and grinding of surfaces.

With everything you need at hand, you can repair cracks yourself.

Here is a list of tools you will need to make the repaired bumper look like new.

Before sealing a crack on a bumper, which is made of thermosetting material, you must also prepare the necessary materials and tools:

a small diameter drill so that holes can be drilled along the edges of the crack;
glue needed for gluing joints, or simple adhesive tape;
epoxy resin;
sandpaper zero, one and two;
putty.

This list of materials and tools will help you repair a cracked thermoset bumper.

How to repair a crack on a bumper made of such material will be described below, since you first need to find out how to carry out the preparatory work. They will consist of the following steps.

This part must be removed, as it will work better and better with it when it is separate from the car. To do this, you need to unscrew it and put it on a separate stand or other elevated surface.
The next step is to clean the bumper from dirt and other deposits. First, it must be washed with water, and stubborn dirt and other layers should be removed with a spatula or coarse sandpaper. Everything must be cleaned carefully.
Next, you should carefully examine the crack. This is an important step, because before you close the crack, you need to mark its edges.
After all this, it is better to carefully re-examine the product for the presence of imperceptible cracks, chips and dents in order to carry out a complete and high-quality repair at a time. If nothing else is found, you can proceed with the repair.

Immediately you need to make a reservation that the restoration of the bumper from a thermosetting material will occur without surface heating. How to seal a crack will be described in the following algorithm:

first you need to clean the surfaces of the crack well with sandpaper until the paint surface is removed, and degrease everything with a rag soaked in gasoline;
then the edges of the crack must be connected with glue or tightly tightened with adhesive tape, it is better to give preference to the first option, and for this you need to choose a special glue that acts instantly, the adhesive is applied evenly with a brush;
stick fiberglass or its substitute on the inside of the bumper in the place of damage;

Stick fiberglass on the inside of the damaged part

then the fiberglass is impregnated with epoxy resin and glued to the outer surface of the bumper at the site of damage, after such actions the surface in the damaged area should be leveled;

then you need to wait about an hour for the surface to dry well, and start cleaning it, for this you need sandpaper, this happens with strong pressure and circular movements;

then putty is prepared, as written in the instructions, and applied with a spatula to the damaged surface, after which it is smoothed out;

after the putty dries, a primer is taken and applied to the crack in vertical stripes, in two or three layers;

then the primer is rubbed with sandpaper, all this is wiped with a rag soaked in water, and after everything dries, a paint and varnish coating from a spray can is applied to the surface.

The repair has been made, and the sealed bumper can be put back in place.

If a bumper made of such plastic is cracked, then its repair will be carried out according to the following algorithm, while the preparatory work will be the same as for thermosetting plastic.

Use a special hair dryer to solder the edges of the damage

The algorithm is the following.

Here's how to clean the damage on such a bumper.When the bumper cracked, how to repair is of interest to many drivers. The repair process is not very difficult, and you can do it at home, while following the instructions given above.It is rather difficult to imagine a vehicle in the design of which there would be such a necessary element as a bumper. The main purpose of the part is to protect the body from damage and deformation. When a difficult situation arises, he takes on all the impact and damaging factors. It is for this reason that the question of how to repair a plastic bumper with your own hands is one of the most relevant.It is easy to guess that the bumper with a high degree of probability can be damaged with a sufficiently intensive and even with very careful operation of the car. The bumper can be damaged not only due to lack of driving experience, but for reasons such as:

actions of other careless and inexperienced drivers;

departure of small stones from the movement of other vehicles.

Regardless of the cause and nature of the damage, the appearance of the vehicle after a bumper breakage deteriorates significantly. The owner of the car automatically has a desire to solve a similar problem by repairing the bumper with his own hands.Ways to fix the problem and mechanical damage directly depend on what plan the defect was applied to the car part. The most common types of damage include:

scratches, which can be superficial and deep, that is, reaching the ground or the main layer of the part. This damage must be repaired immediately, as cracks may subsequently appear at the site of the scratch.

cracks - this is a more serious damage to a car part, which is classified as dangerous. Without removing it, it is not recommended to operate the machine.

dents - are formed by strong mechanical impact on the bumper. These injuries are often accompanied by other adverse manifestations.Near dents, scratches and cracks almost always appear.

Chips and breakdowns. These are special through damages that have a fairly large area. They appear most often at the edges of the bumper after a car collides with a certain obstacle.

Of course, you can contact any service center, but in this case, the cost of restoring the bumper, even with minor damage, becomes much higher than the cost. Of all the options listed above, it is self-repair that will become the optimal and affordable method of restoring the bumper.In direct proportion to the degree of damage, repair work aimed at restoring the bumper can be divided into local and complex. Various scratches and small chips on the surface of the paintwork can be eliminated without first dismantling the part.It is necessary to work with this element in such a way that access to the external and internal surfaces of the element is provided. Installation of the part to its original place is carried out after the required repair and restoration work has been carried out.When carrying out such a process as self-repair of a plastic bumper, you will need to prepare special tools and materials. Among the most important of them are:Properly thought-out protection will allow you to comprehensively protect the respiratory organs, eyes and hands from exposure. This is automatically a guarantee that the body will not be harmed by the dispersion of harmful substances in the air and from high temperatures.Along with the acquisition of the necessary materials and tools, in the process of preparation, it is necessary to carry out certain work with the bumper itself. Among the most important points are:

Removing the bumper from the body of the car.

Thorough cleaning of the part from dirt and dust. The surface must be dry and clean.

Determination of the material from which the bumper is made.

In areas where restoration work will be carried out on the bumper, it is imperative to remove the applied paint. It is necessary to thoroughly clean and degrease not only the damaged area itself, but also the adjacent space.

The crack before repair must be drilled with small through holes at the ends. This will avoid the subsequent spreading of damage, its increase in size.

Any crack has special connecting edges. Therefore, before the crack is repaired, the joints will need to be filled with a special composite.

After completing all the above processes and manipulations, you can start repairing the bumper with your own hands.In direct proportion to the degree and level of damage depends on the scheme by which the repair of plastic bumpers will be carried out. The following recovery techniques may be applicable:

Gluing - used for parts produced by cold forming. It uses a special adhesive based on polyurethane.

thermowelding - suitable for bumpers that were made by hot forming. The bumper fragments are connected using special welding equipment.

lamination - the method is suitable for restoring lost fragments with similar ones. It uses a special reinforcing mesh and putty.

Use of flat electrodes. The technique is based on the use of a special building hair dryer, which melts the electrodes and effectively closes the cracks.

Soldering - the best option for repairing the bumper in normal home conditions. You will need to use a soldering iron, sandpaper and paint.

Brazing with reinforcement - suitable for repairing large cracks. The process is based on the use of double-sided soldering and simultaneous reinforcement with special staples or metal mesh.

sealing - the crack is repaired with fiberglass and epoxy glue. The restoration material is applied to the adhesive and strictly on both sides of the bumper.

Below is a description of the most common and labor-intensive methods for restoring a car bumper, depending on the damage caused.The previously prepared putty must be prepared according to all the rules of the instructions, add a special hardener there. After that, the resulting mass is applied to the area of the bumper on which the damage is located. It is required to wait about 10 minutes, take sandpaper No. 80 and grout the composition with special circular movements. The result becomes visible after several manipulations.Priming work is carried out no less simply. It is required to take a prepared rag and rinse the bumper very well. Once the surface is dry, you need to inspect the entire bumper for correct shapes. If there are no dents, you can proceed to the primer. This process is carried out according to the following rules:

The primer must be applied in a circular motion towards the left or right side of the element.

The composition must be allowed to dry completely.

After that, sandpaper No. 800 is taken and everything is carefully rubbed.

Using a regular water bottle, you need to wash the bumper. In this case, it does not matter where a crack or other damage has formed, the bumper must be completely washed out. As soon as one layer is completely dry, the plastic automatically takes on a matte finish. The top soil is then completely washed off.

Only then can a second layer of primer be applied.

Once all applied layers have dried, a thorough inspection of the part using a lamp will need to be made. The layers must be completely even and form one whole together.If, after inspecting the part, it becomes clear that all coatings are applied with the highest quality and evenness, you can proceed to such a process as painting. Be sure to prepare the room, close all surfaces that need to be protected from the paint used. The pigment is applied strictly in two or three layers. Allow 5 to 10 minutes to dry between each coat.After applying the necessary paint coverage, two layers of varnish are applied to the surface of the bumper. Intermediate drying is also important here. At the end of the painting work, it is necessary to once again check the quality of the applied compositions; if smudges are found, it is necessary to carry out light grinding and carefully polish the surface.

In the process of restoring the integrity and appearance of the bumper, the work ahead will depend on the type of damage found. This is an important point, since one option is used for scratches and chips, a completely different method is required to repair a dent.

If you need to do the repair yourself, or the insurance does not work, or you don’t have the funds and the desire to contact the service center, you will need to carefully study the nature of the damage. If the driver understands that the bumper is very badly damaged, you should not try to restore the part on your own, but it is better to purchase a new one. If relatively small chips or dents are found, the problem can be completely eliminated on your own, knowing how to act in this or that case. So, how can you quickly and effectively eliminate scratches, dents and cracks.

This problem can be eliminated by using sandpaper. Material No. 50 is taken and grouting is carried out. In this case, it is necessary to carefully eliminate all irregularities, acting until the surface becomes a completely regular shape. In the process of carrying out this process, the damage may become slightly larger in size, but their depth will become much smaller. Do not be afraid of this, after a thorough cleaning, all the irregularities will be filled with putty.

If there is a desire and certain skills, then instead of putty, you can use a special liquid plastic that is fully consistent with the type of material from which the plastic is made. After applying this composition, after it has completely dried, it will also be necessary to clean the surface and carefully sand it, grinding it to the most even surface.

To repair a minor dent that did not cause damage to the paintwork, you just need to heat the deformed part of the bumper. The concave part of the plastic must be heated with a pre-prepared thermal or technical hair dryer until the material becomes soft enough. After that, the dent is manually straightened out, while at the same time giving the damaged area of the bumper the correct geometric shape.

If cracks appear on the surface of the bumper, it will be necessary to use a pre-prepared metal mesh and a soldering iron. The sequence of actions in this case will be as follows:

The edges of the damage must be brought together and soldered to one side of the grid. It is advisable to drown it as deep as possible in the plastic, but do not overdo it, as a hole may form.
The end of the mesh is smeared with molten plastic.
Similarly, you need to walk along the entire crack.

If the damage to the bumper is small, special building brackets can be used instead of the mesh. In the process of soldering them, it is recommended to use tweezers, which will prevent brush burns. Bonding actions should be placed 2 cm apart and along the entire length of the crack.

To prevent metal mesh and staples from rusting after a while, objects must be covered with special liquid plastic. Upon completion of all work that is carried out on the inner surface of the bumper, its front side immediately acquires its original appearance.

The question of how to restore and repair a car bumper with your own hands is relevant for all modern motorists without exception. If you follow the instructions and tips presented in the article, you can repair bumper damage with minimal money and time.

The bumper of a car usually suffers from parking curbs, stones on the road. And no one is safe from troubles on the roads in the form of a small accident. In car services for the restoration of this part, they ask for considerable sums. The ideal way out of this situation would be to repair a plastic bumper with your own hands. We will tell you how to repair a bumper with your own hands without huge material and time costs.

Plastic bumpers on modern cars are made from two main types of plastic - thermoset and thermoset. It is necessary to know the differences in these types of materials in order to choose the right method for auto bumper repair. To find out what plastic the autobumper is made of, you need to look at its reverse side.

Thermosetting plastics can be recycled, as when exposed to high temperatures, they soften and become plastic. Easily weldable. These include:

various polyethylenes (pet, PET, PVD, HDPE) — are used in the production of pipes, tanks of cars, bottles, children's toys, food containers and packages, bags, rugs;
polystyrene (PS) used in the manufacture of containers for dairy products, audio and video cassettes, various dishes;
polyvinyl chloride (PVC, PVC) used in the manufacture of windows, flooring, bottles, packaging film, cable insulation, credit cards and medical products;
polypropylene (PP, PP) used in the production of food containers, batteries, bottle crates, automotive parts.

This type of plastic is used much less often in production, because they are not recycled.

When exposed to high temperatures thermosetting plastics do not melt and break. Very difficult to weld. However, they are very durable and resistant to damage.

These are the following types of plastics:

polyurethane (PU, PU) used in coatings, finishes, gears, membranes, cushions, mattresses and car seats;
epoxy resin used in adhesives, sports equipment, electrical equipment, automotive equipment;
phenolic resins used in ovens, cutlery handles, automotive parts, circuit boards;
fiberglass (ABS/MAT) — used in car bumpers and other reinforced parts.

The bodies of modern sports cars are made from such plastics - fiberglass and carbon fiber .

Both the front bumper and the rear bumper are subject to various damages. Depending on the degree of damage, one or another method of restoring the car bumper should be chosen. Damage are of the following types:

We repair the bumper with our own hands - we remove scratches from the body. To repair bumper scratches, do the polishing. Take a sandpaper and carefully smooth out all the bumps to an even, smooth surface. Then apply putty on the surface and, after drying, a primer. Now you can start painting.

You can also get special liquid polymer, according to the composition corresponding to the marking on the bumper. Apply a layer of resin according to package directions, then sand to a perfectly smooth finish.

To rid the car bumper from dents, use a building hair dryer or a gas burner. Heat the deformed area, softening it, and give it the correct geometric shape. This method is suitable for thermosetting plastics - polyvinyl chloride or polypropylene.

With significant deformations of the geometry, it is not recommended to straighten the bumper yourself - it is better to contact a car service specialist.

Carefully: do not overheat the treated area, this can cause even more deformation.

Bumper repair do-it-yourself is impossible without knowledge about repairing cracks. Cracks in car bumper can be eliminated in many ways. Be sure to look at the markings on the back of your part to select the appropriate option. Depending on the type of material, do-it-yourself plastic bumper repair can be done:

welding with a hot air gun or electrodes;
using fiberglass and liquid polymer.

For various methods of repairing plastic bumpers, it may come in handy the following materials:

A soldering or building hair dryer, or a soldering station with a hair dryer, you can use a gas burner.
Soldering iron industrial or household.
Solder for plastic (like bumper plastic).
Fiberglass fabric.
Metal mesh.
Set of liquid polymers.
Epoxy or polymer two-component adhesive.
Sandpaper of various grain sizes.
Primer.
Putty.
Rag or rag.
Roller for painting works.
Glue brush.

Using various techniques at home, you can restore the auto bumper from various types of plastic. Consider the most common methods of how to repair a bumper with your own hands.

The best way for repairing fiberglass or polyurethane bumpers - Restoration with a fiberglass patch. You will need a piece of fiberglass cloth, liquid polymer composition or epoxy glue (two-component). Procedure is:

Preparatory work: remove paint and carefully sand and degrease the surface.
After stripping, cut a piece of fiberglass to the size of the damaged area.
Mix the two components of the glue and mix.
Apply glue to the surface and stick the fiberglass.
Apply the adhesive in several layers with blotting movements until the fiberglass turns white.
Walk on the resulting fiberglass layer with a roller, moving in different directions. This is necessary to compact the layer.
After drying, carefully sand the surface with sandpaper, moving in a circle.
Then apply an even layer of putty to even out the bumper.
When everything dries, apply a primer in 2-3 layers and dry. Treat with sandpaper.
Now you can start coloring.

Only thermosetting types of plastic can be welded, and if your part is made of thermosetting plastic, choose a different repair method.

Before you repair the bumper with your own hands by welding or soldering, clean it thoroughly and dry well. Now you need to choose a plastic solder that is suitable for the material of your car bumper. On the reverse side there is a plastic type marking - select plastic rods with the same designations.

Work order will be like this:

Clear the place damage with sandpaper or a grinder.
Powerful soldering iron (power from 100 watts) solder an even groove along the entire length of the crack. This should be done very evenly, try not to overheat the plastic, so as not to smudge or damage it.
Get a welding rod made of plastic and attach to the resulting recess on the front side of the part. Warming up with a high-temperature hair dryer for a better connection. It is recommended to heat both the solder and the groove itself at the same time along the entire length of the crack. You should get a reliable, strong seam.
When the outer seam hardens, do the same with the inside of the bumper.
To make the weld stronger, make a several cross bridges. To do this, weld small pieces of solder 3-4 centimeters in size alternately across the seam. Do not forget to put such bridges on the ends of the crack so that it does not spread further.
The resulting seam sandpaper or sandpaper to level the surface.
Now the autobumper can be puttied, primed and proceed to restore the paintwork.