Machining pultruded profiles

Sawing

An ordinary hacksaw can be used for a limited number of cuts, and a profile can be shortened the same way as wood with an ordinary handsaw. A circular saw is ideal for straight cuts. During sawing, the profile should be securely retained on a vibration-free bed. A diamond saw blade should be used when sawing large series for smooth cuts without burring. The cutting speed should be 60 m/second, and to achieve the best results, feed lightly. Too heavy feeding merely increases wear on the blade.

Boring

Boring in the profiles is relatively easy. An ordinary metal drill can be used to bore individual holes or small series of holes.

Use of a specially designed drill is recommended for boring large series of holes. At speeds of between 3600 and 3900 rpm and used in a pillar drill, this type of drill delivers a machine time of approximately 30,000 holes (Ø 10 mm). The drill produces a sharp hole rim without burr – also at the drill exit. The drill is designed to give as little vibration as possible when boring perpendicular to the surface, which is an added advantage when using hand drills.

For boring large holes, a spoon bit with a centre bit is recommended. Burr on hole rims can be avoided by boring part-way through from one side of the profile, and then the rest of the way from the other side.

Grinding and deflashing

Pultruded profiles can be deflashed with sandpaper. Use of a belt grinder at high speed and slow advancement is recommended.

Turning

Hard-metal 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 lathe tools and air or liquid cooling results in the best surface finish. Turning can also be done with a rotating diamond milling machine mounted in the tool holder.

Milling

Milling with a hard-metal edge or diamond mill is recommended. In this type of machining, tools with a rake angle on the cutting edge of between 5° and 15° are recommended. 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.

Punching

Pultruded profiles of up to 4 mm in plate thickness, can be punched with an ordinary hard-metal punch. For thicker sheets (up to 6 mm), a specially designed punch should be used which gradually punches through the profiles. Punched holes are 0.05 - 0.1 mm smaller than the punch. The clearance between the punch and the matrix ought to be approximately 50% less than when punching steel.

Threading

Threading 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 or plates, blind rivet nuts of various types in stainless steel or aluminium can be used.

Water jet cutting

Water jet cutting is used for cutting in plates and massive profiles of up to approximately 20 mm in thickness. In non-massive profiles, using water jets can be problematic. The jet becomes diffused on cutting through the first plate, and is therefore unable to cut the plates to the rear with sufficient accuracy. Profiles can also be machined by laser cutting, using a protective gas such as argon.