Posts Tagged ‘fabrication’

We found a great little video on YouTube by user “Make:” which in just three minutes (before credits) gives all sorts of great tips for the DIYer using acrylic in their applications. It starts off with a good point that not everyone knows: acrylic comes in both cast and extruded forms. Yes, they have differences that are important in an application. Yes, there is a difference in cost. Other important tips include how to thermoform, glue, and most importantly – drill, the plastic. Drilling is especially important as the plastic can crack easily, so using lubrication and a soft touch is essential to prevent a wasted part. It will help you answer some questions you didn’t even know to ask prior to diving in: do you have all the materials you need? How are you planning to smooth the edges of the acrylic?

We’ll let the video do the rest of the talking:

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.

drill_close_up

 

Perhaps no industrial plastic is more requested by the “do-it-yourselfer” community than acrylic. Prized for its beauty and well-known because it is used in many applications where the public would encounter the material (displays, aquariums, giftware). In short, acrylic has gained an impressive reputation. But when you work with the material, especially if you’re inexperienced, you really need to do your due diligence in learning the strengths and weaknesses of acrylic and learn how to fabricate it properly.

One of the first tips – especially if you’re just starting out – is to temper your expectations. People imagine they can create polished, flawless projects at home similar to what they have seen in existing products or on the internet. But acrylic is “fussy” to fabricate, it can crack easily if fabrication is done near the edges of the material, it can scratch and the nice, polished finish you see is done by a technique called “flame-polishing” which is a skill that needs to be developed and requires special equipment.

We will provide a couple key tips on this blog but also want to direct you to another blog that seems to be an excellent resource for general acrylic fabrication, which can be found here.

Some tips we can offer:

-ALWAYS leave the masking cover on the acrylic (this provides protection from cracking).

-Avoid fabrication such as drilling near the edges of the acrylic (best to leave a couple inches) as the material can be prone to cracking.

-Acrylic has good UV-resistance, use it outdoors in confidence.

-Cure time for glued acrylic is around 48 hours – be sure you have a way of stabilizing your project while the glue bonds.

Lastly, for some quick tips on gluing acrylic check out this Youtube video:

 

Machining PTFE

Posted: April 26, 2013 in machining, PTFE
Tags: , , ,

The flouropolymer PTFE (polytetraflouroethylene) AKA “Teflon” is one of the most popular engineering plastics. Considered a bridge plastic to the “High-Performance” plastics it is one of the best plastics readily available for everyday use. PTFE has a number of advantages, including being one of the slickest solids known to us, but it is also very soft and has poor impact resistance. We highly recommend you do your research before selecting it as a material and learn how to work with the material. Mistakes can be costly, as PTFE is one of the most expensive plastics available.

This short video does not provide specific technical assistance but the person hosting the video does a quick rundown on the beneficial properties of the material and he quickly lathes a bearing showing a little of how the material is worked with. We also have a machinist chart which includes PTFE located here.

 

For more information on plastics contact us today:

E-MAIL: sales@redwoodplastics.com
CDN: 1 800 667 0999
USA: 1 866 733 2684

Sometimes we spend so much time highlighting plastic applications, we don’t cover the basics of working with plastic. So today it’s back to the basics with some literature you might find valuable.

In general plastics are fairly easy to work with. They can be welded (though not MIG welded) and sawed though certain issues come up with a given material. Here are  a few tips:

Are you working with a glass-filled material?

While you can use to a traditional saw to cut these materials, the addition of glass will prematurely wear your saw blade unless you use diamond-tipped blades.

Acetal – Gets hot, hot, hot

When working with Acetal you must choose the highest possible cutting speed, using the sharpest possible instruments. Acetal is sensitive to heat and will deform or, at the very least, finish poorly if machined incorrectly. Don’t clamp the piece you’re working with too hard either – it will store up heat or deform the material due to pressure.

Multi_Wall_Polycarbonate_SheetingPolycarbonate – The Itch That Shouldn’t Be Scratched 

Polycarbonate is an amazing material. It has tremendous impact strength and can be used in everything from mirrors, to greenhouse applications, to safety glass. However, it scratches very easily. It should be cleaned with a very mild detergent and a soft, clean sponge or cloth.

Working with UHMW?rod-uhmw

UHMW is a bit fussy. There are a lot of little facts and tips you need to know. Please check out our UHMW fabrication link here: http://www.redwoodplastics.com/tools-data/fabrication-machining-guidlines/uhmw-fab-guide/

Check out our website’s “hub” page for these fabrication tips and more here: http://www.redwoodplastics.com/tools-data/fabrication-machining-guidlines/

Best of luck with your applications! Contact us anytime.

E-MAIL: sales@redwoodplastics.com
CDN: 1 800 667 0999
USA: 1 866 733 2684

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.

FABRICATION RECOMMENDATIONS

PLANING
Redco UHMW semi-finished material can be planed on conventional, high speed woodworking machines. Using sharp carbide-tipped blades, feed rates of up to 2mm/blade revolutions may be achieved.

 

MILLING
High speed top milling machines are suitable for machining Redco UHMW semi-finished product. Special milling machines with horizontal, vertical, angle, and fly-cutting attachments make economic large-scale production of shaped articles possible. To ensure the most efficient removal of swarf, milling cutters with coarse pitch are recommended.

 

DRILLING
Redco UHMW semi-finished product can be drilled on drilling machines, and on lathes and milling machines. Twist drills are generally used but for larger diameters, pointed drills and circular cutters may also be used. With good swarf removal, local overheating can largely be avoided. If excessive heating should occur in high speed drilling, cooling may be achieved with compressed air, water, or cutting soluble oil.

 

THREAD CUTTING
Threads can be cut in Redco UHMW GUR semi-finished product with normal metal cutting tools, either on a lathe (recommended speed 20-30 rpm) or by hand. In principle, knuckle threads are preferred, but vee threads still possess adequate strength properties because of the high notched impact strength of the material.

WELDING
Because of its high melt viscosity, friction and butt welding are the only practical methods for joining Redco UHMW by welding. In butt welding, the cleaned joint faces are held under slight contact pressure against the heated tool at 200-220°C until a layer of about 4mm deep has become plastic on both sides. The two parts are pressed closely together under an axial pressure of 10-20 bar (depending on the material thickness) until cold. If the material is greater in thickness than 30mm, axial pressures of 50 bar and above are required, and in such cases presses or special welding machines are frequently used.

There is more! Go to: Redco UHMW Fabrication & Machining Guide