Machined Components for Robotics: Small Series Guide

Robotics and automation builders buy mostly lightweight machined parts in small series: joint and actuator housings, tool flanges, gripper fingers, brackets and base plates, milled and turned from aluminium or steel to their own drawing. A supplier for these parts is judged on four checks: material and temper, the fits and geometric tolerances on bearing seats and interfaces, the route from prototype to repeat batch, and the documents that come with each lot.

What machined components does a robot or automation cell contain?

A robot arm or handling system combines bought-in parts (motors, gearboxes, bearings, sensors, cables) with a smaller set of parts made to the builder's drawing. Those are the parts a contract machinist supplies:

• Joint and actuator housings, which carry the bearings and gearbox stages.
• Link arms and base plates, which carry the load between joints.
• Tool flanges and adapter plates, which connect the end effector to the robot.
• Gripper fingers and jaws, which touch the workpiece.
• Brackets, sensor mounts, covers and cable guides.

Quantity starts low and grows after the first units are tested, and the drawing changes in between. The supplier therefore has to know which drawing revision each piece was made to. Our robotics and automation page lists the industry side of this work.

Which part type needs which material and process?

Table 1 maps each part type to the usual material and process and to the entries the drawing needs. It describes common practice; the drawing and the load case decide. Grinding, heat treatment and coating are separate operations that appear on the drawing, and their availability is confirmed per part.

Table 1. Robot and automation part types: material, process and drawing entries

Source: editorial summary of common practice; material values in Table 2; standards named in the text.

How do aluminium and steel compare for robot parts?

Table 2 sets three materials from Table 1 side by side. The two ratios are calculated from the data-sheet values in the same table.

Table 2. Aluminium 6082, 7075 and stainless steel 1.4301 compared

Source: Bikar Metals data sheets for EN AW-6082 and 7075 (EN 485-2 minimums), Deutsche Edelstahlwerke data sheet 1.4301 (EN 10088-3 minimums). Ratios calculated.

Stiffness per mass is the same within about 3 % for all three. A straight swap from steel to aluminium in the same geometry makes a link lighter and proportionally less stiff. Aluminium pays off when the section is redesigned, with deeper walls and ribs that milling can produce, which is a decision for the design review before the drawing is released. Strength per mass is where 7075 stands out, and 7075 is not weldable by fusion welding in practice: Bikar rates it 5 (unsuitable) for gas, TIG and MIG, against 3, 2 and 1 for 6082. Temper, product form and anodising are covered in Aluminium for CNC machining. Anodising standards are ISO 7599:2018 (decorative and protective) and ISO 10074:2021 (hard).

Expansion matters where an aluminium housing carries a steel part. With the 20–100 °C coefficients above, the aluminium-to-stainless difference on a 25 mm seat changes by 7.4 × 10⁻⁶ × 25 mm × 50 K, about 0.009 mm, for a 50 K temperature rise. The H7 band on 25 mm is 0.021 mm wide, so the effect takes up about 44 % of it. Bearing steels differ from 1.4301, so use the bearing maker's data for the final check.

Which tolerances belong on a joint housing and a tool flange?

A general tolerance covers dimensions that carry none of their own. ISO 2768-1:1989 gives class m ±0.2 mm for sizes over 6 to 30 mm and ±0.3 mm over 30 to 120 mm. Our network works to ISO 2768-m as standard and tighter where the drawing specifies it. The standard is still published, and ISO lists a revision in preparation. Three features of a robot part need more than that:

• Bearing seats: a 25 mm seat at ±0.2 mm is a band 0.4 mm wide. An ISO 286 fit of H7 allows 0 to +0.021 mm, because the standard tolerance grade IT7 is 21 µm for sizes of 18 to 30 mm. ISO 286-1:2010 was confirmed in 2026. See ISO 286 fits and IT grades.
• Coaxiality and squareness: two bearing seats that sit 80 mm apart must share an axis, and the flange face must sit square to it. ISO 2768-1 covers only linear and angular dimensions. These features take geometric tolerances under ISO 1101:2017, which ISO confirmed in 2022.
• The tool flange: ISO 9409-1:2004 defines the main dimensions, designation and marking of the circular interface plate. It does not rate loads, so the size follows the robot maker's data. ISO confirmed it in April 2023, and two revision drafts were abandoned.

How does a part move from prototype to small series?

Run these five steps in order.

1. Prototype in the series material: machine the first pieces in the alloy and temper the series will use. A prototype from different stock measures a different part.
2. Review for series: fold in the changes from prototype tests, add the tolerances and the datum scheme that match how the part will be measured, and release a new drawing revision.
3. First article: measure the first piece from the series setup against every drawing characteristic and keep the report. AS9102 comes from aerospace and is used outside it; see first article inspection.
4. Freeze the setup: fixture, program and tooling stay tied to the approved revision. A change goes through a new revision and, where the change touches a measured feature, a new first article.
5. Repeat batches: each lot carries the documents the order names, such as an EN 10204 type 3.1 material certificate. Road transport from Bursa to central Europe takes 5 to 10 days typically.

This article makes no claim about quantity bands, because they depend on the part and are agreed per drawing.

What stays with the robot builder?

Conformity of the robot or cell stays with the builder or integrator. ISO 10218-1:2025 sets safety requirements for the industrial robot as an incomplete machine, and ISO 10218-2:2025 covers its integration into applications and cells. Both were published on 5 February 2025 and replaced the 2011 editions. Regulation (EU) 2023/1230 applies to machinery from 20 January 2027, and machinery placed on the market before that date must still meet Directive 2006/42/EC (status as of 2026-10-30, per the European Commission).

A machined part is a component, and the supplier delivers it to the drawing. Edge breaks, burr limits and surface condition therefore go on the drawing, where the supplier does not have to assume them.

Frequently asked questions

Which machined parts does a robot arm need?

Joint and actuator housings, link arms, base plates, tool flanges, gripper fingers, brackets, sensor mounts and covers. Motors, gearboxes and bearings are bought in. The parts made to the builder's drawing are the ones a contract machinist supplies.

Which aluminium alloy suits robot housings, 6082 or 7075?

On the Bikar data sheets, EN AW-6082 T651 plate of 12.5 to 60 mm guarantees a yield strength Rp0.2 of at least 240 MPa and EN AW-7075 T651 plate of 12.5 to 25 mm at least 470 MPa, at densities of 2.70 and 2.80 g/cm³. 7075 is rated 5 (unsuitable) for gas, TIG and MIG welding, so welded frames use 6082.

What does ISO 9409-1 define?

The main dimensions, designation and marking of a circular plate used as the mechanical interface between a robot and a hand-mounted end effector, so that end effectors can be exchanged and keep their orientation. It gives no load ratings. ISO 9409-1:2004 was confirmed in April 2023.

Does ISO 2768-m cover bearing seats?

It applies to them only if the drawing gives no other tolerance, and then allows ±0.2 mm on a 25 mm size. A bearing seat needs an individual fit such as H7, which allows 0 to +0.021 mm on 25 mm, and a geometric tolerance for coaxiality or run-out.

How do you move a robot part from prototype to small series?

Make the prototype in the series alloy and temper, review the drawing for series, inspect a first article against every drawing characteristic, then freeze fixture and program to the approved drawing revision. Later changes go through a new revision.

Sources

1. ISO 9409-1:2004, mechanical interfaces, plates: edition 3, confirmed 2023-04-17 (ISO catalogue)
2. ISO 9409-1:2004, stage 90.93, revision drafts abandoned (ISS, national ISO member)
3. ISO 9409-1:2004, scope and status (AFNOR)
4. ISO 10218-1:2025, Robotics, safety requirements, industrial robots, published 2025-02-05 (ISS, national ISO member)
5. ISO 10218-2:2025, Robotics, safety requirements, robot applications and robot cells, published 2025-02-05 (ISS, national ISO member)
6. Machinery: Regulation (EU) 2023/1230 applies from 20 January 2027 (European Commission)
7. ISO 286-1:2010, ISO code system for tolerances on linear sizes, confirmed 2026-06-19 (ISO catalogue)
8. ISO 286-1:2010 standard tolerance grades, IT7 for 18–30 mm (table reproduced on Wikipedia)
9. ISO 2768-1:1989, stage 90.92, revision listed (ISS, national ISO member)
10. ISO 2768-1 linear tolerances, classes f, m, c, over 6 to 120 mm (AmesWeb table)
11. ISO 1101:2017, tolerances of form, orientation, location and run-out, confirmed 2022 (ISO catalogue)
12. EN AW-6082 data sheet: density, modulus, expansion, EN 485-2 minimums, ratings (Bikar Metals)
13. EN AW-7075 data sheet: density, modulus, expansion, EN 485-2 minimums, ratings (Bikar Metals)
14. Acidur 4301, 1.4301 data sheet, 27.11.2015: density, modulus, expansion, EN 10088-3 minimums (Deutsche Edelstahlwerke)
15. ISO 7599:2018, decorative and protective anodic oxidation coatings, confirmed 2023 (ISO catalogue)
16. ISO 10074:2021, hard anodic oxidation coatings, in systematic review 2026 (ISO catalogue)

Questions on a drawing? sales@ertas.engineering

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