Machining of pultruded profiles
Machining of pultruded profiles
The machining and assembly of glass fibre reinforced solutions are similar to the work with hardwood. Below you find our recommendations for the machining of GRP profiles. If these directions are inadequate, or if you have further questions in connection with specific projects, please don’t hesitate to contact us for further information.
If the customer enquires a finished, ready-to-install solution, Fiberline can also undertake the machining and assembly of the profiles as an integrated part of the product. In that case we can e.g. undertake the cutting, drilling, CNC-machining, and surface treatment of the profiles, as well as we can make the solution ready for the final assembly.
Tool and machinery requirements
We recommend using equipment that is designed for machining steel due to the abrasive properties of the reinforcement. However, for single-unit production it is possible to use woodworking machinery. For sawing or cutting, diamond tools should be used. Carbide bits can be used for drilling.
GRP pultruded profiles are elastic, and twisting and bending can occur when machining long lengths. Stationary, vibration-free support and retention should therefore always be ensured. If finished profiles are to be used in chemically aggressive environments it is necessary to seal all cuts.
Sawing must be performed using diamond tools. A circular saw or jigsaw is ideal for straight cuts. During sawing, the profile should be securely retained on a stable, vibration-free bed. Diamond blades should be used when sawing large series for smooth cuts without burring. The cutting speed should be 60 m/sec, and to achieve the best results, feed lightly. Too heavy feeding merely increases wear on the blade.
Drilling the profiles is relatively easy. An ordinary metal drillbit can be used to bore individual holes or small series of holes.
Use of a special bit is recommended for drilling large series of holes. This will produce a sharp hole rim without burr – also at the exit. The bit is designed to give as little vibration as possible when drilling perpendicular to the surface, which is an added advantage when using power drills.
For drilling large holes, a spoon bit with a centre bit is recommended. Burr on hole rims can be avoided by drilling part-way through from one side of the profile, and then the rest of the way from the other side.
Grinding and deburring
Pultruded profiles can be deburred with sandpaper. Use of a belt grinder at high speed and slow advancement is recommended.
In this video, we demonstrate three easy ways of mounting square tubes, either with sleeves, inserts or washers. Our square tubes are used for handrail solutions, among others for staircases and bridges.
Carbide plates should be used in turning. Speeds of up to 400 m/min. can be used, and a rake angle on the cutting edge between 10 - 15° will give the best result. Feeding depends primarily on the stability of the set-up, but is typically between 0.05 and 0.5 mm/rev. Depending on the machine and the set-up, the depth of cut can be up to 10 mm. Using rounded tool bits and air or liquid cooling results in the best surface finish. Turning can also be done with a rotating diamond milling cutter in the tool holder.
Milling with a diamond cutter is recommended. In this type of machining, tools with a rake angle on the cutting edge of between 5° and 15° can be used. Feeding can be up to 0.5 mm/rev., and speeds of up to 1000 m/min. will give the best results. Too heavy feeding will cause unwanted heating of the surface and gives less satisfactory results.
Pultruded profiles of up to 4 mm thickness, can be punched with an ordinary carbide punch. For thicker sheets (up to 6 mm), a special-type punch should be used which gradually pierces the profiles. Punched holes are 0.05 - 0.1 mm smaller than the punch. The clearance between punch and die should be approximately 50% less than when punching steel.
Threadcutting cannot be recommended for large loads, although self-threading and self-drilling screws are used to a large extent. If there is a need for threaded attachments in sheets, blind rivet nuts of various types in stainless steel or aluminium can be used.
Water jet cutting
Water jet cutting is used for cutting sheets and solid profiles of up to approximately 20 mm thickness. Using this technique on non-solid profiles can be problematic. The jet becomes diffused on cutting through the initial material and is therefore unable to cut the underlying material with sufficient accuracy. Profiles can also be machined by laser cutting, using a protective gas such as argon.
Demands of working environment
Find more information in our safety data sheets.