Posts Tagged ‘welding’

Admittedly plastic welding is a fabrication technique that is going to be attempted by few “Do-it-yourselfers”. Plastic welding will require the purchase of special tools and filaments which are not always easy to come by.  In addition, since most plastic welding is done by specialists, it is difficult to get fabrication tips from plastics distributors or manufacturers. You’re likely going to have to search the internet for ideas and while we cannot vouch for the tips, YouTube seems to have several good videos to get you started off right.

In particular the company “Techspan” which manufacturers plastic welding equipment has, what looks to us, as a good 4-1/2 minute video on the basics of plastic welding. In particular we like that it talks about preparing the plastic for fabrication/welding (something often overlooked in these types of videos) and it goes into topics such as “tacking” which is welding two pieces on a 45 degree angle to each other. We’d prefer to let the video speak for itself and we’ve linked it below:

 

UHMW polyethylene is probably the most popular engineering plastic for use in DIY projects. But how do you work with it? People often get overly concerned with fabrication, especially in regards to the “tolerances” needed for most home projects, but regardless here are some tips to get the most out of your UHMW application.

Sawing:

UHMW can be cut with either a circular or band saw. A band saw is best as it will vent heat away from the plastic and allow for faster cutting speeds. The band saw blades may be 10-30mm wide and about 1-2mm thick with the circular pitch between 3 and 10mm. To prevent the saw blades from becoming jammed, the teeth must be set at approximately 0.5mm. When using circular saws, saw blades with a minimum setting 0.5mm are also preferred. Normal cutting speed for band saws is 1,000-2,000m/min and for circular saws, 3,000-4,000 m/min.

Drilling:

Lower RPM drilling is recommended unless compressed air, water, or cooling oils are used – UHMW melts easily. Twist drills are most commonly used but pointed drills and circular cutters can be used for higher diameter holes.

Welding

Because of its high melt viscosity, friction and butt welding are the only practical methods for joining Redco UHMW by welding.

Machining

Machining is the principal method used to fabricate finished parts from UHMW. UHMW can be sawed, turned, planed, milled drilled, stamped and welded easily on woodworking or metalworking machines. The following general directions should be observed in these operations: To obtain surfaces of high quality, tools should always be sharp. For the most purposes, normal tool steel is satisfactory through many fabricators use special steels.

The optimum cutting speed is between 250 and 1,000 m/min. At lower cutting speeds cooling is not required, but at higher cutting speed range, water cooling or the use of soluble cutting oil is essential. In all cases, care must be taken to avoid heat build-up in the machining operation, so that the work piece does not smear the cutting edges. In milling and turning, the feed should not be too fast and the depth of the cut should be greater than 0.3mm.

Bonding

Questions about solvent bonding are common but unfortunately this is not recommended with UHMW. It resists most solvents and, at best, will create a below-average to poor bond. Mechanical fixation is recommended wherever possible.

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DIY Plastic Welding Videos

Posted: October 14, 2015 in Uncategorized
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Plastic welding of materials like HDPE or ABS is probably one of the most useful skills for the home hobbyist interested in working with plastics. It seems to be easy and usually free as you can make your own weld rod out of other plastic lying around allowing you to repair damaged items.

A popular technique is to extract some plastic needed for your repair from another part of your item. For example, if you need to repair some molding on your boat, you might be able to cut away some of that plastic hidden under a seat where it won’t be missed. If only a little plastic is needed for a small repair you can make some shavings off of a place where no one will notice. We’re not plastic welding experts, we don’t do it ourselves, but we’ve found a couple videos from Youtubers who seem to know what they’re doing. Of course, this comes with the disclaimer that we do not endorse any of the techniques shown within!

 

 

Plastic welders are used to join thermoplastic materials together. A thermoplastic is a polymer that turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently. Thermoplastic polymers differ from thermoset polymers in that they can be remelted and remoulded.

Plastic-Welding-MachineA plastic welder brings the plastic material up to a specific temperature and then joins the pieces under pressure. There are many types of plastic welders because different plastic varieties require a different joining method. Some welders are self-contained and easily portable; others require an air or gas source and are stationary units. Types of plastic welders include hand-held “stick” welders, airless welders, extrusion welders, and injection welders. Knowing the application and the material to be joined is the first step to selecting the best plastic welder for the job.

Identifying the plastic that is being welded is key to achieving a strong bond. Identifying the type of plastic can be as easy as checking out the identifying number on the material itself or asking your supplier. It also is important to note that different types of plastic will not weld together.

Hand-held hot air welders, or stick welders, are a common portable plastic welder. These use a heat source to soften the plastic while a plastic rod is melted to fill the gap. The key to getting a good bond from a stick welder is to maintain a consistent downward pressure, distance between the heat source and the tool, and working speed. Features to look for in a stick welder include a way to control the air pressure, preferably from a small, portable compressor; some way to fine-tune the heat surce — ones with multiple elements are a bonus; and interchangeable tips that can be selected to best fit the shape of the plastic welding application.

An airless plastic welder is like a stick welder, but uses a heating element to melt a smaller plastic rod without using an outside air supply that is blowing in heat. This type of plastic welder generally eliminates excessive welding rod buildup and can help avoid panel warpage. The final weld usually should penetrate about 75 percent of the base materials, and typically should be allowed to air cool for at least 30 minutes.

Extrusion welders are larger than the previous two units, so if space is an issue, this may not be the welder for you. This plastic welder provides a larger bead and usually is a floor-standing machine. The weight of the machine itself provides the downward pressure during the welding process.

Injection welders are both lightweight and portable — a great option if mobility is desired. Normally they are easy to use and produce a high-quality bond. The key to a decent weld with an injection welder is the ability to change the aluminum tip on the plastic welder to fit the proportions that are required. For a complete list of every type of plastic weld; click here.

Redwood Plastics can also do any welding, fabrication, machining and molding for you. Email us at sales@redwoodplastics.com or call one of our locations across North America. Click here for our list of branches.