FABRICATION TIPS AND TRICKS #3

USE CLAMPS AND FIXTURES AS MUCH AS POSSIBLE WHEN WELDING YOUR PROJECTS!

What is distortion? 

Distortion or deformation can occur during welding as a result of the non-uniform expansion and contraction of the weld and base metal during the heating and cooling cycle. Stresses form in the weld as a result of the changes in volume, particularly if the weld is restrained by the fixed components or other materials surrounding it. If the restraints are partly removed, these stresses can cause the base material to distort and may even result in tears or fractures. Of course, distortion can be very costly to correct, so prevention is important. 

What are the main types of distortion? 

There are various types of distortion and dimensional change including longitudinal; transverse; angular; twisting and bowing. Two or more types of distortion may occur at the same time. 

What are the main causes of distortion? 

There are many factors that can cause welding or cutting distortion and it is very difficult to predict the exact amount of distortion that is likely to occur. Some of the factors that should be considered include the degree of restraint; the thermal and other properties of the parent material; inherent stresses induced from previous metal-working processes such as rolling, forming and bending; design of weldment; accuracy of manufacture and the nature of the welding process itself – the type of process, symmetry of the joint, preheat and the number and sequence of welds required. 

What can be done to limit distortion? 

The effects of weld shrinkage can never be entirely eliminated but you can keep them to a minimum by taking a few practical steps as follows: 

•  Reducing the metal weld volume to avoid overfill and consider the use of intermittent welding. 
•  Minimising the number of weld runs. 
•  Positioning and balancing the welds correctly round the axis. 
•  Using backstep or skip welding techniques, which involves laying short welds in the opposite direction. 
•  Making allowance for shrinkage by pre-setting the parts to be welded out of position.
•  Planning the welding sequence to ensure that shrinkages are counteracted progressively. 
•  Shortening the welding time When cutting, it is possible to limit distortion by supporting the plate so it can expand freely without buckling; ensuring the plate is flat; allowing sufficient weld material when cutting in from corners and using a jig-saw pattern to lock the cut pieces together when multiple cutting. 
• Build weld fixtures "Jigs" to hold product in place.

Distortion can be avoided or significantly reduced when welding structural steel work by using fixing devices, such as 
strongbacks or wedges to pre-set seams in plates; flexible clamps to bring parts to the required gap before welding or 
clamps for thin sheet welding. Longitudinal stiffeners can also be used to limit this type of bowing. It is also important to use the correct welding sequence, such as welding the frame before a cover plate. Pre-bending or pre-setting 
techniques may also help to prevent distortion and water can be used to cool the process. Pipes and tubes can suffer distortion after welding and this can be prevented by using strongbacks attached with straps and wedges inside or outside the longitudinal joint; using backing strips to overcome transverse shrinkage or pre-setting or using back to back pairs when welding flanges to pipes. 
In summary, if welding distortion is likely to be a problem, it can be avoided or minimised by advance planning and 
following best practice. 

For All Your Fabrication/ Welding Needs:
Brock Dunlop
602/515/2285
brock@dunlopcustoms.com

FABRICATION TIPS AND TRICKS #2

GENERAL SHOP SAFETY

All tools are dangerous if used improperly or carelessly. Working safely is the first thing the user or operator should learn because the safe way is the correct way. A person learning to operate machine tools must first learn the safety regulations and precautions for each tool or machine. Most accidents are caused by not following prescribed procedures. Develop safe work habits rather than suffer the consequences of an accident.

EYE PROTECTION

Using eye protection in the fabrication shop is the most important safety rule of all. Metal chips and shavings can fly at great speeds and distances and cause serious eye injury. Safety glasses must be worn when working with handcutting tools, since most handcutting tools are made of hardened steel and can break or shatter when used improperly.

There are many different types of safety glasses available in the supply system; however, the ones that offer the best protection are the safety glasses with side shields. Safety goggles should be worn over prescription glasses. For specific information about eye protection, contact the Occupational Health Clinic or refer to TB MED 586.

HAZARDOUS NOISE PROTECTION

Noise hazards are very common in the machine shop. High intensity noise can cause permanent loss of hearing. Although noise hazards cannot always be eliminated, hearing loss is avoidable with ear muffs, ear plugs, or both.

FOOT PROTECTION

The floor in a fabrication shop is often covered with razor-sharp metal chips, and heavy stock may be dropped on the feet. Therefore, safety shoes or a solid leather shoe must be worn at all times. Safety shoes are available in the supply system. These have a steel plate located over the toe and are designed to resist impact. Some safety shoes also have an instep guard.

GRINDING DUST AND HAZARDOUS FUMES

Grinding dust from abrasive wheels is made up of extremely fine particles of the metal and the wheel. Some grinding machines are equipped with a vacuum dust collector. When operating a grinder without a vacuum, wear an approved respirator to avoid inhaling the dust. Whenever possible, use coolant when grinding. This will aid in dust control. Grinding dust can be very dangerous to your health, especially beryllium or parts used in nuclear systems. These materials require careful control of grinding dust.

Metals such as zinc give off toxic fumes when heated above their boiling point. Inhaling these fumes may cause temporary sickness, or death. The fumes produced from lead and mercury are very harmful, as their effect is cumulative in the body and can cause irreversible damage. When unsure of the materials being machined, it is advisable to wear a respirator. For more specific information on respirator safety, refer to TB MED 502.

FABRICATION TIPS AND TRICKS #1

Did you know that if you use a dab of ketchup on a rag you can polish copper? The ketchup will clean off all the tarnishing that naturally acquires over time to copper do to oxidation.

"Copper forms a rich variety of compounds with oxidation states +1 and +2, which are often called cuprous and cupric, respectively.^[8] It does not react with water, but it slowly reacts with atmospheric oxygen forming a layer of brown-black copper oxide. In contrast to the oxidation of iron by wet air, this oxide layer stops the further, bulk corrosion. A green layer of verdigris (copper carbonate) can often be seen on old copper constructions, such as the Statue of Liberty, the largest copper statue in the world built using repoussé and chasing.^[9] Copper tarnishes when exposed tohydrogen sulfides and other sulfides, which react with it to form various copper sulfides on the surface.^[10] Oxygen-containing ammonia solutions give water-soluble complexes with copper, as do oxygen and hydrochloric acid to form copper chlorides and acidified hydrogen peroxide to form copper(II) salts. Copper(II) chloride and coppercomproportionate to form copper(I) chloride.^{[11]" Wikipedia}

If the oxidation is really bad you can add some table salt. The salt helps by adding some grit to the ketchup. Thus making the ketchup more abrasive.  That's right your 57 #Heinz ketchup is not just for french fries and burgers anymore it is also a cleaning agent. 

For All Your Fabrication/ Welding Needs:
Brock Dunlop
brock@dunlopcustoms.com
602-515-2285