Posts Tagged ‘fabrication’

A lot of what we offer here on the “DIY” blog is material information; however, as the hobbyist, you actually have to cut, drill, and machine the plastic yourself. It’s beneficial to educate yourself on practical fabrication matters. Most hobbyists grow up working with metal and wood; however, industrial plastic is only usually encountered when one knows to look for them – usually when one is a teenage “DIYer”.

The prevalence of CNC machines in recent years makes machining knowledge even more critical. In the video linked below, Instagrammer Tom Zelickman educates on issues he’s had with machining plastics and how to overcome various challenges including his stressing about one “aggressively” machining plastics and cleaning them.

You can view the whole video on YouTube here:

Redwood Plastics and Rubber, the sponsor of this blog, offers many resources on their website to help their customers work with plastic. Some of these charts and information are ‘overkill’ for what the DIY community really needs, however. In this case, more basic information is best. The good news is their website actually has a page that links to several sub-pages that give general information on fabrication and care for plastics. These guides include some of the most common plastics used by the DIY community: UHMW, acrylic, polycarbonate, and acetal.

You can find the guide and the link to the sub-pages here: https://www.redwoodplastics.com/tools-data/fabrication-machining-guidlines/

 

 

For those not very familiar with plastics, it is sometimes difficult to tell the plastics apart. A plastic rod feels like, well, just plastic and we don’t consider sometimes the nuances of each material. One major consideration for those of us in the DIY community is how a material is fabricated or machined. Acetal is a very hard plastic and machines very well and can be held to tight tolerances (+/- 0.005″) whereas realistically (+/- 0.05″) is the best you can get out of UHMW in a DIY setting. UHMW is much softer and less dimensionally stable; however, it is slicker and more economical.

A short video on YouTube we found shows both plastics being machined and offers a comparison, take a look below:

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
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