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Why are tolerances on a custom plastic extrusion worthy of discussion? Let’s explore this topic further in this week’s blog.

Custom extruded profile being inspected on optical comparator

     Optical Comparator in use at Formtech

Certainly, tolerances on plastic extrusions impact fit and function, and contribute to overall performance of the plastic part. But, at what cost? Technology has progressed in plastic extrusion equipment, extrusion tooling, thermoplastic materials and even methods of measurement. There are, however, limitations to tolerances on the product before the cost of the custom extrusion is impacted. Even with advancements in extrusion technology, tolerances that are extremely tight are one of the leading contributing factors in increased costs. In the design of a system that includes custom plastic extrusion, it is a best practice to consider which areas of the profile need to be maintained as critical, and how tightly they need to be held from a tolerance perspective based on the attended use. When a custom plastic profile extrusion company is dealing with extremely tight tolerances, we are forced to look at available options to control the cooling and sizing of the profile. Some options are listed below:

  • Reducing output rate for increased control over the extrusion cooling process
  • Additional vacuum calibration to keep the extruded plastic profile, at an increased overall tool cost
  • More expensive compounds to allow better control over the plastic extrusion

All the above options can improve tolerance control, but they do increase the cost of the end product. There is definitely a balance between tolerances and economics when it comes to custom profile extrusion. The extrusion must perform for the intended use, but design for manufacture and making sure tolerance limitations are reviewed during the design of the plastic profile as part of the overall system can save you money on the finished extruded plastic part(s). The table below outlines typical tolerances on profile extrusions in a variety of raw materials including Rigid PVC (uPVC), Polystyrene, ABS, Polycarbonate, Polyethylene Polypropylene and Flexible, or plasticized PVC. This table is based on industry experience, and can be used as a guide during the design process.

 Rigid PVCPolystyreneABS/
PolypropyleneFlexible PVCPolyethylene
Wall Thickness (+-)8%8%8%8%10%10%
Angles (+-)2 Degrees2 Degrees3 Degrees3 Degrees5 Degrees5 Degrees
Profile Dimensions (+-)
To .125"0.007"0.007"0.010"0.010"0.010"0.012"
0.126" to 0.500"0.010"0.012"0.020"0.015"0.015"0.025"
0.501" to 1.000"0.015"0.017"0.025"0.020"0.020"0.030"
1.001" to 1.500"0.020"0.025"0.027"0.027"0.030"0.035"
1.501" to 2.000"0.025"0.030"0.035"0.035"0.035"0.040"
2.001" to 3.000"0.030"0.035"0.037"0.037"0.040"0.045"
3.001"to 4.000"0.045"0.050"0.050"0.050"0.065"0.065"
4.001 to 5.000"0.060"0.065"0.065"0.065"0.093"0.093"
5.001 to 7.000"0.075"0.093"0.093"0.093"0.125"0.125"
7.001" to 10.000"0.093"0.125"0.125"0.125"0.150"0.150"

In addition to tolerances required for function, there are other important factors in making your custom plastic extrusion work well for you in the end application. Experienced Formtech technical sales and engineering staff are ready to help make your plastic extrusion project a success. They will ask several questions to make sure the extrusion meets your needs. The questions center around these functional areas:

  • What are the dimensions of the part, and which dimensions are critical? What type of tolerance is required to insure function of the product? We will need a drawing of your profile to quote from, and CAD formats (DXF, DWG, etc.) are preferred to allow more rapid response to your needs.
    Red custom extruded profile by Formtech

    Custom color for Plastic Extrusions by Formtech

  • What are your material requirements for function?  Have you already identified specific material that you would like Formtech to use for the extrusion?  What physical properties are most important for function in the application?
  • What color(s) are needed for your profile(s)?  Does your plastic extruded profile need to match another part?
  • Is your product going to be used in an indoor or outdoor environment?  What temperature range will the plastic extrusion be subjected to during use?
  • To the extent it can be shared, how is the product used, and in what application? Are there mating parts the plastic extrusion will be used with? If this is the case, can mating parts be supplied to be used during our extrusion process as part of our quality checks, to insure fit and function before the finished plastic extrusion is packaged for shipment?
  • Will the plastic extrusion require additional fabrication? Does it require adhesive or magnetic tape application? If the extrusion is exposed, does it require embossing, or texturing? Formtech offers a wide variety of value added services which can help enhance appearance and improve functionality of extruded plastic profile manufactured at both our Athens, GA and Fairview, PA production facilities.
  • What finished lengths and tolerances are required?
  • Do you have special packaging needs?
  • Information about volume expectations is important for both tooling development costs and pricing. What is the estimated annual footage or pieces, and how much would be released for each shipment?

After answering these questions, Formtech will be able to make recommendations from a design for manufacture standpoint to insure you are pleased with the parts received.

Formtech Enterprises has been making custom profile extrusions since 1970, and we service the building & construction industry extensively. We also service the electrical and electronics markets, merchandising (point of purchase), packaging, commercial refrigeration, office furniture and carpet/mat industries with a wide variety of custom and proprietary extruded profiles. Give us a call at 614-531-9954 or email at for more information or a quotation.



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