Adhesive and Sealant Applications & Tools
Experts in the tools used for specific applications. The tool may cost you very little, but it accounts for over 50% of the success in the application.
Friday, July 11, 2014
Which is the better tool for powered dispensing, Cordless or Air?
When your sealant or adhesive dispensing project would benefit from a powered tool how do you choose between cordless, battery and air? Each has inherent advantages and disadvantages. Following is a summary to help you make a decision that will help you increase your output & efficiency while reducing hassle & frustration.
Cordless Battery Powered
Feature / Requirement
Wednesday, October 12, 2011
Grouting and Pointing
The standard metal nozzle can be replaced with other metal nozzles as small as 1/8" or as large as 3/4". Alternatively, substitute a cone-shaped nozzle and trim the opening to any size up to 1 3/4". The tapered shape of the cone will result in less back pressure compared to a straight metal nozzle.
To load the gun, remove the front cap, pull the rod completely back and load the barrel by troweling in your mix. Some polymer modified products can be loaded by sucking them up into the barrel, the same way you do with caulk. The finer the aggregate in the mortar or grout, the easier it will be to dispense.
Tap the side of the barrel frequently during loading to remove voids. Wipe the barrel and cap threads clean before replacing the cap. You may need to modify your mix slightly for dispensing by gun; a wetter mix flows better, but too wet and you can get separation of the water and aggregate inside the barrel. The addition of a latex masonry additive (know in the trade as "milk") will also make dispensing easier and help keep the mix together. Some users have reported similar benefits from the addition of liquid dish soap to the mix. Clean the gun after use with water. Periodically disassemble the leather pistons to clean and re-oil the pistons (use standard motor oil or mineral oil) and barrel to maintain a tight seal. If you are doing a large quantity of pointing and the leather pistons require frequent maintenance consider replacing the front one with a nitrile or neoprene rubber piston.
Wednesday, July 13, 2011
Why does my caulking gun drip?
• viscosity of the material—thicker material tends to drip less
• compressibility of the material—less compressible material tends to drip less
• swelling of the cartridge—rigid cartridges tend to drip less
• piston friction inside the cartridge—pistons that retract slightly after the pressure is released tend to drip less
• air bubbles in the material which occur during the filling process—material without any air bubbles tends to drip less
If any of these factors are present, the gun is not to blame. You can prove this by removing a cartridge from a gun immediately after finishing a dispensing cycle. Some cartridges will continue to ooze while standing upright outside the gun!
Dispensing guns can be designed with certain non-drip features to help reduce the potential for run-on. Non-drip guns are useful for when a smooth bead is not required, as in filling small cracks in a number of different locations. Since non-drip guns tend to increase the number of starts and stops during the application, they come in handy when only one or two pumps of the gun at most will fill the crack. Continuous flow guns, on the other hand, should be used when a smooth bead is required over many pumps of the gun, as in filling long or continuous joints. On continuous flow tools, always remember to press the recoil plate with your thumb to release the pressure when you finish your application. Pressure on the rod is instantly removed by releasing this tension.
A caulking gun with a full time non-drip feature is, by design, inefficient. The first 1/4 to 1/3 of each trigger stroke is wasted motion, as it is required to release the non-drip mechanism and reengage the trigger to the rod, thus repressurizing the material before new material flows out the nozzle. When comparing non-drip and continuous flow tools, you will notice that less material is dispensed per pump when using the non-drip tool.
The graph below displays pounds of force as a function of the distance travelled by the drive rod. As you can see, a major disadvantage of a dripless system is that force goes all the way back down to 0 after each pump. In addition, the standard system exerts force over a greater distance interval than the dripless system.
Finally, a quick historical note: Ratchet guns were the first caulking guns to hit the market and in theory they functioned as non-drip tools. In 1933, Albion Engineering Company patented the first smooth rod caulking gun to provide a more continuous flow of material. This is what launched smooth rod drive caulking guns into the marketplace. The first non-drip smooth rod design was introduced by Dripless, Inc. in 1992. Since then there have been many variations using this technology.
To conclude, dripping or run-on occurs primarily due to different issues related to the material or package used to contain the material. Dispensing tools can be designed in such a way to reduce run-on, but guns with a full-time non-drip feature are generally less efficient than continuous flow guns. In most cases, choosing the right tool for a particular application will ultimately come down to whether or not a long, smooth bead is required.
Sunday, January 9, 2011
The Equation F=PA
Force = Pressure x Area
This is a basic engineering formula that you can apply to dispensing tools. Simply put, it takes pressure in the cartridge, sausage, or bulk barrel (a material containment unit or MCU) to get material to flow out of the nozzle. Different amounts of pressure are required depending on:
a. How thick the material is.
b. The nozzle opening. Think of the pressure required to push material through a static mixer. A static mixer is a mixing nozzle which mixes two component materials before the material reaches the substrate.
PRESSURE makes things happen.
To determine the FORCE required of your dispensing tool you must calculate the area of the piston pushing on the material in the MCU. Lets compare the simple 1/10 gallon cartridge and the common quart cartridge. You don't generally see thick material in a quart cartridge. Why?
1/10 Gallon Cartridge Area = (Diameter Squared * Pi/4) = (1.8*1.8*3.1416)/4 = 2.55 square inches
Quart Cartridge Area = 5.19 square inches
The Quart Cartridge Area is double that of a 1/10th Gallon Cartridge Area. This basic engineering formula reveals that it will require double the force to develop the same pressure in a Quart Cartridge versus a 1/10 Gallon Cartridge.
What can we draw from this?
1. Thin material requires less pressure and thus less force... and a lower-end dispensing tool.
2. Thicker material or very small or long nozzles require more pressure and thus more force... and thus a stronger or more forceful dispensing tool.
3. If you increase the diameter of the MCU you will need to develop more force from your dispensing tool. Most materials packaged in a Quart Cartridge are low pressure materials which require large nozzle openings and little accuracy in applying. A good example is subfloor adhesive. Your objective there is to get material down quickly.
In the next blog segment we will talk about how to measure force on a dispensing tool. Also, we will discuss what rod displacement means and how it needs to be factored in when selecting the right tool.
Monday, December 13, 2010
Age before Beauty
This is bragging rights.... a tool came back to Albion just the other day in need of a new trigger. The tool was built in June of 1992 and has been used rather heavily. We did notice that the user replaced the drive rod so it is safe to assume that the tool had at least 100,000 cycles on it.
It is always nice to see an old tool and it is even nicer to see that it still has value.
Monday, March 8, 2010
The Basic Cartridge Gun
The caulking gun gets a bad rap because of the occasional user of the cartridge gun. Someone who has to fix a leak around their bath tub or kitchen sink goes to the hardware store and picks up caulk and a “cheap” caulking gun to get the job done. Generally speaking they are successful, for they do get the caulk out of the cartridge and they use their finger to tool the joint. But they get frustrated when the material ends up all over themselves and everything around them. When they are finished, they put the tool away and rarely use it again.
There are tools designed for such an individual. There are also tools for contractors who use sealants periodically, and for contractors who use the tools all day every day. The user needs to be matched to the right tool for the application in order to ensure success. One way to measure quality in a tool is based upon price. As the saying goes, you get what you pay for.
From a dispensing tool solutions provider - someone who knows tools and can look at a tool and see its value - sometimes you don’t quite get what you pay for. It is very easy to make tools appear better then they truly are. We will get further into the more professional cartridge guns, but for the inexperienced, occasional user, here are a few tips to insure the tool you select is acceptable:
• Is the drive rod parallel to the carriage and on the center line of the carriage? And is the front cap of the carriage perpendicular to the drive rod? Poorly assembled carriages tend to droop downward. This will cause a problem.
• Does the pusher (the disk that pushes against the back of the cartridge) fit nicely on the front cap when the rod is in the forward position?
• Push the pusher up against the front cap and squeeze the trigger.
o If the unit clamps itself together, then the drive functions correctly.
o If the tool creaks, then there could be faulty spot welds. A creak means something is moving.
• Slide a cartridge into the carriage. The cartridge should be held in the back and fit nicely in the front cap of the carriage. Holding the cartridge in the back keeps the cartridge secure in the carriage while dispensing material.
• For smooth, long applications, look for a smooth rod without the dripless feature.
• For short, fill-in-the-crack type applications, consider a simple ratchet driven tool or a smooth rod gun with the dripless feature.
• If your material is thick in any way, then you will be applying more loads on the tool and you will have better luck purchasing a higher end more durable tool.
Always remember to tool the joint after you apply the sealant to insure proper bonding of substrates. To tool the joint, use a tool which mimics your finger pushing the material up against the substrate (ee sell a 958-G01 Streamline Spatula Kit). The units that cut away or trim your joints and make them look nice do not insure proper adhesion.
To close, the caulking gun cost is insignificant if the tool does not perform well during the application. When in doubt, we would always recommend you buy a better tool then you think the application requires, for it is the success of the application which truly matters.
We will address the features of a Professional Cartridge Gun and how that matters in future segments.
Labels: cartridge guns
Monday, February 22, 2010
It is not difficult to load very liquid materials into a standard bulk gun. The biggest issue is that once loaded, removing the tool from the pail quickly enough to minimize material loss results in a mess.
Loading low viscosity sealants and adhesives, often referred to as self-leveling or pour grade, can be almost like loading water into a dispensing tool. Fortunately, many of these products can be loaded directly through the gun nozzle. The front cap and nozzle do not need to be removed from the gun for loading. The benefits of loading through the nozzle are that the gun can be loaded more quickly and with less mess.
The smaller the nozzle diameter, the harder it will be to draw the material in. However, smaller diameters make it easier to keep the material inside the tool. A conscientious mechanic will find the ideal balance between the two. In our experience, smaller is better. The diameter of the nozzle does not need to be closely matched to the joint width as with non-sag sealants because tooling is usually not necessary.
Albion also builds Push-Pull tools. These are bulk guns without a drive system. You simply pull the rod back to load the tool, and push the rod to dispense. Some contractors find this quicker and easier for large jobs using self leveling material.
Mixing Two (or more) Component Sealants Efficiently
At the World of Concrete trade show, Albion provided live demonstrations showing some of the tricks to the trade. A helpful trick which we want to share is how to keep a pail from rotating when mixing color packs or two component urethane kits.
Using an Albion #381 series Catalyst Mixer and a 1/2" drill insures a good mix. See the photograph, by using a RAG KNOTTED AROUND THE PAIL HANDLE AND STANDING ON IT you stabilize the pail. This is a simple and quite reliable method used by many professionals in the field. It ensures a proper mix and cuts down on mess.
Most material manufacturers want to insure the material is thoroughly mixed, especially when mixing two component urethane material. We have heard customers encouraged to look for dents on the outside of the metal pail caused by the edge of the mixing blade to insure the mix is complete. From a tool manufacturer's perspective, we want you to be careful not to puncture the pail. The edges of the Albion mixing head are rounded to minimize denting and reduce the risk of puncturing the pail. It is more effective to follow the sealant manufacturer's recommendation for mix time - typically 3 to 6 minutes - but read the pail or spec sheet to be sure.
Sausages Part III: The mess!!!
Simply put, you have to take care of your tool when dealing with material packaged in a sausage. We have found that it is easier for someone who deals with bulk material (material packaged in a 5 gallon pail) to convert to sausages then it is for someone who deals with cartridges. Why? Because a bulk gun user is used to dealing with exposed material and the issues associated with not keeping your tool clean....while a cartridge user simply cuts the tip of the cartridge and pumps.
Material packaged in sausages expose you to the material; the nozzle, for one, is full of the material. You need to develop a technique to deal with spent sausages so that you don't get the left over material all over.
A couple of things to remember:
1. Sealant hardens when a solvent evaporates. Find out what that solvent is, purchase some, and use that solvent to clean up the tool and/or any mess you have. Keep in mind this solvent is very aggressive; handle it properly and be safe, and understand it could dissolve more then just your sealant. For example, if you are cleaning something that is painted, it could dissolve the sealant and the paint.
2. Always load the tool before opening the end.
3. If sealant or adhesive gets inside the barrel of the tool, clean it immediately. If you reload the tool with a new sausage over the sealant, when you start pumping the tool the sausage will become pressurized and the skin will be forced up against the sealant... bonding it to the barrel. It will force the piston to act like your ice scraper when scrapping ice off your windshield on a cold winters day, or peeling a label off that simply doesn't want to come off. All it does is cause problems.
4. Damaged pistons MUST BE REPLACED IMMEDIATELY. If a piston is damaged due to any kind of issue it will then have a harder time pulling the sausage skin off the barrel of the tool. It is far easier and it will save you more time to simply replace a questionable piston before the problems happen than to wait till a problem does happen.
5. Don't try to save the plastic nozzle, for hardened sealant in a nozzle could deform the beed and hurt the application.
Sausages Part II: The Go/No-Go Gauge
Albion provides material manufacturers a set of go and no/go gauges FREE OF CHARGE to insure that sausages are made consistently and will fit dispensing tools. The gauges are meant to provide a baseline. The two gauges check the diameter and the length of a sausage.
If there are issues with sausages that fit this gauge, then we can work to improve the process.
If there are issues with the gauges, please let us know and we will discuss them. Their purpose is to begin to establish a "STANDARD" to which all sausages for sealants and adhesives are manufactured to.
For more details on these gauges see the instruction sheet associated with the gauges on our web site HERE.
Friday, January 29, 2010
Loading a sausage that is too big and won't drop in.
(I want to appologize... this message needs to be edited.... We were at the World of Concrete Trade Show and tried to keep the pace of the Blog going while at the show... a big mistake. The following is revised 2/22/2010)
Production is never perfect. Periodically there is a malfunction within the process and the sausage is oversize. Generally speaking the manufacturer does his best to catch this, but some do get to the end user.
An oversize sausage is nearly impossible to load into the tool the normal way, simply dropping it into the barrel. What you need to do is draw the sausage into the tool. Albion's DL-45-T14, DL-45-T15, DL-45-T24, and DL-45-T25 all have the ability to pull the sausage into the tool. These are the professional tools.
The Aluminum Barrel, low cost tools.... which includes Albion's B12S20... are not built with that feature. With these tools all you can do is set return the sausage. (If anyone does have a way to load an oversize sausage in a tool like this, please share.)
The video will show you how to draw an oversize sausage into a dispensing tool.
Wednesday, January 27, 2010
Sausages Part I: How they are made.
Machine is built by Poly-clip Systems Corporation.
The Sausage is a package used to contain sealant and is customarily supplied to the market place. We will talk further on this subject.
Sausage Package For Dispensing Sealants
A Sausage (also known as a Chub or Sachet) is sealant or adhesive packaged in a Mylar bag. They are dispensed with full barrel tools. The sausage has its benefits and drawbacks. In this section I am listing some of both...
Benefits over a standard cartridge:
More cost effective
Shelf life is typically longer
Fewer changeovers – Sausages typically hold twice as much material
Reduction in waste, when totally dispensed they are just ½” tall
With sausage guns you get access to a wider variety of nozzles (longer, wider, narrow slots, bendable, multiple beads, etc.)
Requires a different gun
Tends to be messier for the end of the sausage is open at the nozzle end (meaning you must be more careful in loading and unloading sausages from the tool.)
Benefits over Bulk, Material packaged in pails:
Cleaner and easier to load
More portable if the application is in a difficult location. You can simply take a couple sausages and the gun to the location.
When tooling the joint, you must discard the excess material verses putting it back into the pail and reusing the material.
For the next few segments we will be talking more about unique things related to the sausage.
Sunday, January 24, 2010
I have heard numerous excuses to not attend the World of Concrete Trade show and none of them seem justifiable. When you don’t come, you miss connecting with the people and key/new products within your industry.
Yes, I admit it does get old coming year after year but it brings the industry together. People talk, business is conducted, and contacts are made.
Yes, I understand money is tight, but is it so tight that you miss a key gathering of professionals within your industry?
Yes, I feel strongly that the World of Concrete is worth the time and money. What is two days of your time, a cheap ticket, and hotel room in Vegas? That's right, the flights are cheap and the rooms can be too, if you are smart.
I want to encourage you to seriously consider attending. If you are on the fence, do it. Go to the World of Concrete.
Labels: World of Concrete
Tuesday, January 12, 2010
Smooth Rod Caulk Gun & "Dripless"...... What happens
This graph is interesting to talk about. It illustrates the measured results of a standard smooth-rod drive tool versus a similar dripless style tool. The blue line shows the force generated by the standard drive system. Note the small drop in force between each pump. It also shows the displacement (amount of material dispensed) of the drive system with each pump.
The purple line shows the exact same action using an equivalent drive system with a dripless feature. Note that the force drops to zero at the finish of every stroke and the displacement is about 20% less per pump.
What happens? The smooth rod drive tool allows the operator to pump efficient, smooth, long beads of sealant. Conversely, with the dripless drive, at the conclusion of each pump there will be a dramatic bump or lump in the bead.
Conclusion: Choose the right tool for the job! Smooth rod tools are excellent for applications where the bead requires more then one stroke. Dripless is better for small beads or multiple, repetitive dabs such as interior paint prep where you are filling short cracks, nail heads or depressions intermittently.
There is a reason and an application for both types of drive systems.
Friday, January 8, 2010
Trade organizations which may bring value to you….. next is FCIA
What is Firestop? It is sealant that hopefully is never used but when it is needed (during a fire) it does its job and saves lives. It is sort of like an airbag in a car, you never want to use it but when it is needed it had better spring to life and do its job. Firestop is designed to expand and seal off openings in walls to prevent smoke and fire to spread into another part of a building. This enables those in that space to escape. Unlike sprinklers which help to contain the fire, firestop is used to help keep people within the building safe while they work to get out of the building.
From FCIA’s website --- www.fcia.org ---- “The FCIA's mission is for member organizations to be recognized throughout the construction industry as preferred quality contractors of life safety firestop systems. FCIA Member Contractors are committed to providing consistent, high quality firestop systems as a critical part of Effective Compartmentation.
Through active participation in the FCIA and related forums, members contribute to the advancement of the firestop and compartmentation industry and maintain exceptional knowledge of this specialized service.
Through this professional commitment to fire and life safety, member contractors bring considerable value to their customers by enhancing public safety and property protection.”
We surely have learned a great deal from those within this organization. Our part is to help educate them with respect to dispensing tools but to also help deal with difficult applications. The firestop contractor may have to climb up inside a building in a crowded space and apply material. Short guns, bendable long nozzles, supper thin nozzles and on occasion spray tips may be required.
Another excellent resource.
Friday, January 1, 2010
Trade organizations which may bring value to you….. first is SWRI
I have found that it takes well thought out solutions based on solid engineering theories for anything to work and work well. I guess that is what brings me to who I am, an Engineer. You simply can fight gravity, or expect adhesive to truly stick to ice. Basic proven theories allow us to solve problems.
One of the strongest organizations I know in our industry is the Sealant Waterproofing Restoration Institute, SWRI, (www.swrionline.org) an organization of contractors and material manufacturers who focus on sharing technology, finding solutions and raising industries technical level.
Most people feel that anyone can put sealant in a joint, but truly they must understand the characteristics of the joint, match those characteristics to the proper sealant capable and then properly clean, prime and install the sealant. There is some real serious theory behind sealing a joint properly….and I think that is what separates an SWRI contractor from the guys with their pickup trucks and low bids. Think about it for just one moment, sealant is generally there to keep water out of your buildings for a long time….improper installations and/or improper material selection will cause failure and leaks.
Those within SWRI review applications and share their experiences, discuss difficult issues and work to train those within the industry. The connection between the manufacturers brings a higher level of accountability on parties, the contractors and the manufacturers. It also allows issues to be discussed and hopefully resolved possibly through the development of new products. But, again I must emphasis the solutions have to be sound.
I am not an expert for I supply the SWRI contractor with tools, the SWRI contractor is.
My next Blog will be on another organization the Firestop Contractors Institute Association, FCIA.
Wednesday, December 23, 2009
HOT POT --- Cold Weather means thick thick sealant
Winter hit the east coast this week, the upper west and Midwest almost a month ago. Sealants packaged in cartridges, sausages, or in 5 gallon pails stored in a cold warehouse or trailer or even the back of your pickup truck gets really thick. Some people warm the sealant up by putting it next to their car heaters or even on top of their engines. Some build their own heat chests with light bulbs, and some simply bring the material inside.
Energy In = Energy Out
This is a simple Engineering heat transfer equation. The body which is losing the heat (right side of the equal sign) and the body or bodys surrounding it that are gaining the heat (left side of the equal sign). Add to that equation different types of material, depending on their heat transfer coeffecient, absorb or discharge heat at different rates. A great example of how slow or quick heat is transferred take a hotplate after cooking and see how long it takes to cool down.... then put it in the sink and spray water over it. The water absorbs the heat from the hotplate faster then the air surrounding the hotplate.
Now take sealant which is thick and massive. How long do you think it will take to warm up the middle of a cartridge, sausage, and especially a 5 gallon pail of sealant? So, it will take either a long time or a significant amount of heat.
If you have been around the sealant world for maybe 25 years you will remember the "Tremco" heat chests. They were quite popular, and if you still have one you end up guarding it with your life. Over the years Albion has been supplying heat chest kits which allowed contractors to rebuild the insides of these heat chests when the heating elements burned out. And for years we have been looking for a chest like the old Tremco heat chest so we could economically build heat chests.
Before I tell you why this is so important to the sealant contractor, I want to acknowledge the contractor who brought to us the missing link. Philip Porter of the Masonry Preservation Group showed us how he used our heat chest kit to build his own heat chest.....he put it in a drum. Drum's are low cost readily available and perfect for a heat chest.
"Hot Pot" is an Albion heat chest kit in a drum.
Why is this so important? The "Hot Pot" and the old Tremco Heat chest heated the air inside the chest to 150 deg F..... now that is hot....and there is significant heat transferring to the sealant. Both units have lids, you open the lid take out your cartridge and close the lid and what happens? A good portion of the heat is lost. There is a thermostat inside the unit which causes rapid heating of the air inside.
The "Hot Pot" and the old Tremco heat chests are essentially one in the same. Same elements, and nearly the same capacity. They hold at least a case of cartridges, or sausages. The "Hot Pot" can also hold a 5 gallon pail of sealant, but 5 gallons of sealant is really thick and it will take a LONG time to get the heat to the middle of the sealant. You will also have to take the pail out of the "Hot Pot" to apply the sealant.
So, if you use your car heater or light bulbs in a box you and it really isn't as productive as you like then maybe this is a solution worth considering.
The "Hot Pot" is readily available at Albion distributors....
For more information see our website - www.albioneng.com Go directly to the sell sheet --- http://albioneng.com/bulletins/46.pdf
And thank you, Philip Porter of the Masonry Preservation Group, for sharing how you solved a problem.
Saturday, December 19, 2009
Application Example using Bulk Material
This is a quick video showing the insertion of backer rod, loading a bulk gun, and applying the sealant. Note:
1. The backer rod tool places the backer rod at a fixed depth and inserts the backer rod quickly. (This is a bit of an ideal joint, most joints are not a fixed width with nice edges, but this tool does improve the installation of backer rod.)
2. Putting a slight film of oil will help keep the material from sticking to the outside of the barrel.
3. Cordless provides a smooth continuous flow of material. (This applicator is running the tool a bit on the slow side, he could easily have doubled his speed. I guess that is the difference between an Engineer and someone who seals joints for a living.... the Engineer is too careful and slow.)
Wednesday, December 16, 2009
Barrels – So what? Does it really make a difference?
It all depends on what you want to achieve with your tool. Consider:
1. How much do you use the tool? Is it something you make a living with or is it something you use only use on occasion?
2. What type of material are you dispensing; Is it sticky, thick, thin… those types of characteristics play a part.
3. The material packaging you are dealing with; Is it packaged in pails or is it in foil skin (sausage) form?
Some of the benefits of each barrel:
• Durable barrel, ideal for construction environments. Heavy loads can be placed on top of the barrel and it won’t deform or dent. (But, if a barrel does dent see below for how to remove a dent.)
• Will hold true round shape over the entire length of the barrel. This improves the piston’s ability to function and consistent dispensing through the entire length of the barrel.
• Easy to clean. With a steel barrel you can use the 800-G01 or 800-G02 Barrel brush to clean the inside surface of the barrel. A clean barrel improves the piston’s ability to function and increases its life.
Steel Barrel w/Teflon Inside Coating:
• Same strength benefits of a steel barrel
• Surface coating reduces friction between the barrel and piston making it easier to dispense.
• Nonstick surface makes it easy and quick to clean. Flush the tool with solvents and run a rag through the barrel. You cannot use an 800-G01 or -G02 barrel brush. The brush will remove the Teflon surface. If the Teflon surface is removed… the barrel can be used as regular a Steel Barrel.
• Lighter in weight, generally assembled on lower cost tools.
• Better for sausage or low volume bulk use.
• Won’t rust.
• Be careful for the barrel is easy to dent, you can squeeze the barrel with your hand and possibly change the shape making it more difficult for successful dispensing.
• Most aluminum barrels are extruded and therefore there are slight changes in the shape of the barrel over the length of the barrel, causing the piston to work harder.
Clear Plastic Barrel:
• Great visual of material being dispensed.
• Like the Aluminum Barrel the barrel is extruded. The diameter can be inconsistent over the length of the barrel. This makes it difficult for the piston to function correctly through the entire length of the barrel.
• Brittle, will crack when dropped or crushed.
• Difficult to clean if material is sticky.
• Solvents in the material or for cleaning can soften the barrel surface or make it more brittle. (Simple yellowing of the barrel tells us the barrel structure has been changed.)
So, does this help you select and/or understand the background in steel, aluminum, and plastic barrels.
Engineering Tid-Bit: Fixing a Dented Barrel
When a barrel is dented and you can see the dent on the inside of the barrel it causes premature wear on the piston and ultimately material will tend to blow past the piston. To fix a dent like that get a round steel rod long enough to fit inside the gun barrel, maybe 1” in diameter. Secure the steel bar in a vice and slide the barrel on the steel rod to where the dent is in contact with the steel rod. Then take a hammer an tap the outside of the barrel around the dent. The steel rod will flatten the dent on the inside of the barrel and make the barrel as good as new.
You can fix dents in the threaded area also this way. It works on steel and aluminum barrels.