Part 1: Overview
This article has been written with the aim of creating awareness and the knowledge gained from Robotic Chemical Dosing applications that I have experienced for more than 15 years.
As the writing of the article progressed, I decided to write and publish it in sections, realizing that due to the depth of the subject, dealing with a single title would make the situation too complicated. The first chapter you are currently reading is the Overview. The following chapters will progress towards sectors in particular.
The article contains a large number of definitions. The more precise the need to define the problem before solving a problem, the more vital it is to define the main and sub-components of the process.
First of all, it is necessary to define the concept of dosing.
Dosing is the process of releasing a chemical at the right time, in the right amount and form, to the right place.
Although dosing of solids (powder) and gases can also be mentioned, when it comes to dosing in industrial applications, the dosing of fluid (liquid) chemicals is the operation.
It would be correct to divide this definition into two.
- Right time – Right amount
- The right form – the right place
Right Time – Right Amount
Chemicals in industrial applications;
- Pasting
- Lubrication
- Gasketing
- Protection etc. They can be used for very variable purposes, such as
Each of the above titles contains chemicals with very different properties.
For example, adhesives, according to the raw materials they contain;
- Epoxy based
- Acrylic based
- Polyurethane based
- Silicone based etc. as it may be,
They are also differentiated according to the way they are cured (reaching their final mechanical properties).
- Cured at room temperature
- Hot curing
- Moisture curing
- Cured with a certain gas
- Cures with a specific wavelength of light
As can be seen, the industrial chemicals portfolio presents a very complex, multi-parameter picture, and the solution of dosing processes is not always “so simple”.
Chemical dosing process mainly consists of the following 4 titles.
- Chemical feeding
- Transporting the chemical
- Dosing the chemical
- Curing chemistry
Each of these 4 titles has a lot of equipment and methods under itself.
The following topics should be carefully examined before choosing the Chemical Dosing System components.
- Technical characteristics of the chemical
- Chemical structure of the product on which the chemical will be applied.
- The environment in which the Dosing System will operate
- Requested Certifications
The variations are very high and the solution therefore requires experience and careful examination.
At this point, it is proven by experience that when purchasing the dosing system or its components, the product offered for sale using general jargon (silicone valve, polyethylene hose, mastic pump, etc.) will often bring a series of problems and increase the need for solutions instead of creating solutions. Likewise, the issue of chemical dosing is too deep to proceed with prejudices.
For example, when it is necessary to provide a pressure tank suitable for the adhesive to be used in an adhesive application, looking for a pressure tank alone can have very serious consequences. The material used on the surfaces of the pressure tank that will contact the chemical, the chemical outlet nipples to be used, the valves, the material of the hoses, the diameter, the length, the air permeability, the operating characteristics, sensitivity and hysteria values of the pressure regulators, etc. Many factors such as these can change the results in many different ways in the application to be carried out and make it impossible to obtain satisfactory results.
Although the title of this section is ‘Right Time-Right Amount’, it seems as if what has been mentioned so far is only about ‘right amount’. FALSE!
The parameters mentioned so far will determine the dosage amount of the chemical as well as the dosing moment. The time elapsed between opening the dosing line and starting the application of the chemical is dependent on all these variables.
The viscosity of the chemical alone does not determine its inertia (inertia), its density and the fillers it contains have a great role on the inertia.
The positive effect/negative effect of the chemical valve used, its internal volume, friction coefficient, will determine the process start time of the chemical as well as the moment when the chemical will finish the dosing process.
Right Form – Right Place
If a volumetric (volumetric) dosing valve is not used, it can be said with certainty that the chemical feeding method using a pressure tank is one of the main obstacles to high volumetric precision dosing. Air is a compressible media. Likewise, liquids (chemicals) change volume under pressure, albeit to a small extent. Especially, chemicals such as silicon that can contain a high percentage of air sacs can undergo a serious volumetric change when these air sacs shrink under pressure. This change can be so visible that even the dosing amounts performed before and after the tea break can show very serious differences.
After Dosing
We dosed the chemical needed by the application in the right amount, in the right form, in the right place, at the right time. However, the process does not end here, unfortunately.
There are 2 remaining titles;
- Really the above 4 are true, are they really true? (Quality control)
- The curing process of the chemical
Since these 2 titles contain many parameters and footers, it would be more correct to make a separate article subject.
General Manager @ Pulsar Robotik A.Ş.
If a volumetric (volumetric) dosing valve is not used, it can be said with certainty that the chemical feeding method using a pressure tank is one of the main obstacles to high volumetric precision dosing. Air is a compressible media. Likewise, liquids (chemicals) change volume under pressure, albeit to a small extent. Especially, chemicals such as silicon that can contain a high percentage of air sacs can undergo a serious volumetric change when these air sacs shrink under pressure. This change can be so visible that even the dosing amounts performed before and after the tea break can show very serious differences.
After Dosing
We dosed the chemical needed by the application in the right amount, in the right form, in the right place, at the right time. However, the process does not end here, unfortunately.
There are 2 remaining titles;
- Really the above 4 are true, are they really true? (Quality control)
- The curing process of the chemical
Since these 2 titles contain many parameters and footers, it would be more correct to make a separate article subject.
General Manager @ Pulsar Robotik A.Ş.
1. The size of the area to be dosed is naturally related to the robot working area to be selected. However, it is certainly not limited to this. That is, in dosing applications that require high precision, using a robot with spherical coordinates (5-7 axes) may not always give good results. Dosing quality will also differ, as the vibrations that will occur at the limit points of the elongation and the points close to the center will differ. However, in dosing in a similar large area (where the concept of ‘large’ may differ greatly depending on the application. In some cases, even 10 mm x 10 mm area can be very large), using a cantilever type cartesian robot may also cause problematic results for the same reasons.
In addition, the larger the area to be dosed, the greater the need for the chemical to travel along a longer supply line. In this case, the force (pressure) need to move the chemical will increase, and the total mass that the robot must carry will also increase. In addition, the amount of chemicals waiting permanently on the line will increase. In this case, it should be ensured that the chemical hose with minimum air permeability is selected, especially when it comes to chemicals that cure at room temperature. Otherwise, the amount of waste will increase and the efficiency of the process will decrease drastically.
2. If the area to be dosed is not on a plane – under, over, side surface, inside etc. of the part. if chemical disposal is required – in this case a standard 3-4 axis cartesian robot/ scara robot will not be sufficient.
Therefore, a robot with spherical coordinates will make the application much easier. However, considering the robot extensions and the differences in the axis designs of the robot brands, the catalog data can reveal very misleading results. The most efficient method would be to do a simulation, or better still, a live trial.
Another point to be considered is ‘gravity’ if the application will not be made on the International Space Station. The chemical used will be exposed to the force of gravity before, during and after dosing, and if the application surface is not parallel to the ground or upside down, it will cause you to have very interesting experiences.
3. In continuous/line dosing, if the form precision of the chemical (thickness, height, position, etc.) is important, this is the biggest criterion for system selection. Although the general opinion is that chemicals cannot be formed with high precision, this is not always true.
For example, industries with small part sizes, especially electronic medical, may demand repeatability of up to ±0.1 mm in chemical form sizes. This tolerance requires going outside the standard thinking/design framework. First of all, the technical characteristics of the chemical used become the main variable. Chemical;
- Spreading characteristic
- Form, volume change characteristic over time
- Sensitivity to ambient temperature/humidity
- The stability of the technical properties of the same brand/model chemical purchased at different times should be carefully examined.
Although this last title seems interesting, it is in line with reality. I always liken the manufacturing process of chemicals to cooking. Multiple components are mixed in a controlled environment and passed through certain processes. The slightest difference that may occur in this process may cause more or less changes in the properties of the resulting chemical. This change also leads to a change in the dosing characteristic.
A silicone compound and a grease compound may have similar viscosity (viscosity) on TDS, but their ductility (elongation characteristic) is very different from each other. Ductility information is a feature that is not generally included in TDS documents.
From an experience, I remember how the change in ductility value of medical silicone produced in different batches turned the whole dosing system upside down.
Another requirement for low tolerance (high precision) forming is speed stability. The robot used must have a high speed stability along the defined route length. Since it is not a standard practice to create a feedback loop between the dosing system and the robot, the dosing amount is directly dependent on the speed of the robot along the way. The slightest momentary decrease in robot speed will mean an immediate increase in the amount of chemicals per unit area, and vice versa. This requirement necessitates the use of motors with high speed stability in linear axes. On the other hand, especially in non-Cartesian coordinated robots, following a line requires interpolation between axes and the interpolation skill of every robot is not the same. Although it may seem strange at first glance, different brands/models of robots use different algorithms to move in a straight line. Also, since the math of interpolation depends on many factors such as the processor capacity of the robot, the design of the joints, the motor structure, every robot may not always give perfect results.
The right form and the right place title are not just a responsibility to be imposed on the robot. As the tolerance value decreases, especially the feeding system (the point where the process starts) and the dosing tip (needle) used at the very end (the point where the process ends) becomes important.
If a volumetric (volumetric) dosing valve is not used, it can be said with certainty that the chemical feeding method using a pressure tank is one of the main obstacles to high volumetric precision dosing. Air is a compressible media. Likewise, liquids (chemicals) change volume under pressure, albeit to a small extent. Especially, chemicals such as silicon that can contain a high percentage of air sacs can undergo a serious volumetric change when these air sacs shrink under pressure. This change can be so visible that even the dosing amounts performed before and after the tea break can show very serious differences.
After Dosing
We dosed the chemical needed by the application in the right amount, in the right form, in the right place, at the right time. However, the process does not end here, unfortunately.
There are 2 remaining titles;
- Really the above 4 are true, are they really true? (Quality control)
- The curing process of the chemical
Since these 2 titles contain many parameters and footers, it would be more correct to make a separate article subject.
General Manager @ Pulsar Robotik A.Ş.
At the very beginning of the article, we made a 2-layer analysis while defining dosing.
So far, we’ve focused on “the right time and the right amount” by examining layer 1.
The second layer should be the “right form – right place” review.
Manual (by the operator) dosing is completely out of the question, since the subject we are examining is Robotic Precision Dosing Applications.
The type and characteristics of the robot to be used in chemical dosing application vary according to the parameters of the application.
These parameters are;
- Dosing area size
- Positions of the dosing point or route in space
- Especially, in line dosing, the shape and width-height precision of the form to be dosed
1. The size of the area to be dosed is naturally related to the robot working area to be selected. However, it is certainly not limited to this. That is, in dosing applications that require high precision, using a robot with spherical coordinates (5-7 axes) may not always give good results. Dosing quality will also differ, as the vibrations that will occur at the limit points of the elongation and the points close to the center will differ. However, in dosing in a similar large area (where the concept of ‘large’ may differ greatly depending on the application. In some cases, even 10 mm x 10 mm area can be very large), using a cantilever type cartesian robot may also cause problematic results for the same reasons.
In addition, the larger the area to be dosed, the greater the need for the chemical to travel along a longer supply line. In this case, the force (pressure) need to move the chemical will increase, and the total mass that the robot must carry will also increase. In addition, the amount of chemicals waiting permanently on the line will increase. In this case, it should be ensured that the chemical hose with minimum air permeability is selected, especially when it comes to chemicals that cure at room temperature. Otherwise, the amount of waste will increase and the efficiency of the process will decrease drastically.
2. If the area to be dosed is not on a plane – under, over, side surface, inside etc. of the part. if chemical disposal is required – in this case a standard 3-4 axis cartesian robot/ scara robot will not be sufficient.
Therefore, a robot with spherical coordinates will make the application much easier. However, considering the robot extensions and the differences in the axis designs of the robot brands, the catalog data can reveal very misleading results. The most efficient method would be to do a simulation, or better still, a live trial.
Another point to be considered is ‘gravity’ if the application will not be made on the International Space Station. The chemical used will be exposed to the force of gravity before, during and after dosing, and if the application surface is not parallel to the ground or upside down, it will cause you to have very interesting experiences.
3. In continuous/line dosing, if the form precision of the chemical (thickness, height, position, etc.) is important, this is the biggest criterion for system selection. Although the general opinion is that chemicals cannot be formed with high precision, this is not always true.
For example, industries with small part sizes, especially electronic medical, may demand repeatability of up to ±0.1 mm in chemical form sizes. This tolerance requires going outside the standard thinking/design framework. First of all, the technical characteristics of the chemical used become the main variable. Chemical;
- Spreading characteristic
- Form, volume change characteristic over time
- Sensitivity to ambient temperature/humidity
- The stability of the technical properties of the same brand/model chemical purchased at different times should be carefully examined.
Although this last title seems interesting, it is in line with reality. I always liken the manufacturing process of chemicals to cooking. Multiple components are mixed in a controlled environment and passed through certain processes. The slightest difference that may occur in this process may cause more or less changes in the properties of the resulting chemical. This change also leads to a change in the dosing characteristic.
A silicone compound and a grease compound may have similar viscosity (viscosity) on TDS, but their ductility (elongation characteristic) is very different from each other. Ductility information is a feature that is not generally included in TDS documents.
From an experience, I remember how the change in ductility value of medical silicone produced in different batches turned the whole dosing system upside down.
Another requirement for low tolerance (high precision) forming is speed stability. The robot used must have a high speed stability along the defined route length. Since it is not a standard practice to create a feedback loop between the dosing system and the robot, the dosing amount is directly dependent on the speed of the robot along the way. The slightest momentary decrease in robot speed will mean an immediate increase in the amount of chemicals per unit area, and vice versa. This requirement necessitates the use of motors with high speed stability in linear axes. On the other hand, especially in non-Cartesian coordinated robots, following a line requires interpolation between axes and the interpolation skill of every robot is not the same. Although it may seem strange at first glance, different brands/models of robots use different algorithms to move in a straight line. Also, since the math of interpolation depends on many factors such as the processor capacity of the robot, the design of the joints, the motor structure, every robot may not always give perfect results.
The right form and the right place title are not just a responsibility to be imposed on the robot. As the tolerance value decreases, especially the feeding system (the point where the process starts) and the dosing tip (needle) used at the very end (the point where the process ends) becomes important.
If a volumetric (volumetric) dosing valve is not used, it can be said with certainty that the chemical feeding method using a pressure tank is one of the main obstacles to high volumetric precision dosing. Air is a compressible media. Likewise, liquids (chemicals) change volume under pressure, albeit to a small extent. Especially, chemicals such as silicon that can contain a high percentage of air sacs can undergo a serious volumetric change when these air sacs shrink under pressure. This change can be so visible that even the dosing amounts performed before and after the tea break can show very serious differences.
After Dosing
We dosed the chemical needed by the application in the right amount, in the right form, in the right place, at the right time. However, the process does not end here, unfortunately.
There are 2 remaining titles;
- Really the above 4 are true, are they really true? (Quality control)
- The curing process of the chemical
Since these 2 titles contain many parameters and footers, it would be more correct to make a separate article subject.
General Manager @ Pulsar Robotik A.Ş.