Replacing an obsolete machine part: the method

The typical case, and what we actually do

The broken part is plastic, it is no longer in the manufacturer's catalogue, or only as a complete sub-assembly at an unrelated price. We do not repair: we remake the part identically, or reinforced where it gave way. That is what most of our on-demand references do: get a machine running again when its part is no longer supplied, to your dimensions and from the very first part.

What we do not do is just as clear: no safety parts, whose failure would injure, and no machining. An FDM-printed part is a stack of layers; for a plastic machine geometry it is the right process, from a single unit and without tooling.

Step 1 — what we need

The original part, even in pieces: the geometry is rebuilt from the fracture faces. Failing that, a dimensioned 2D drawing, or a photo of the part next to a rule with the main dimensions. If a file already exists, STL, OBJ or 3MF for direct printing, STEP if design rework is needed.

Add what the part lives through: the load it takes, the temperature, the environment (oil, moisture, outdoors), and above all where it broke. A part that has failed in the same place twice is a part to reinforce, not just to copy.

Step 2 — modelling

We remodel the part in Fusion 360 and we also deliver the STEP file. For a simple part, modelling is included in the price. The CAD files we create belong to you as soon as the design service is paid: you receive the STEP and the native file, and you can have them made elsewhere. It is written in our terms of sale.

This is when the part gets better: a fillet where the sharp corner started the crack, a thicker wall, a print orientation chosen for the load. A part up to 350 × 350 × 350 mm comes out in one piece; beyond that it is split into assembled sub-parts, with the joint planes placed where they show least.

Step 3 — the material

PETG covers most cases: it bends before it breaks, it copes with moisture, and it goes into most of the functional parts we make. For a part taking repeated impacts, a gear or a transmission part under moderate torque, PA6-GF keeps nylon's toughness. For a jig or a guide that must hold its dimension for months, in contact with oils and greases, PET-CF.

Under permanent load, PA6-CF; outdoors, ASA, which does not yellow and takes 90 °C; near a heat source or under impacts, PC; for a seal, a pad or a damper, TPU, printed in three hardnesses. We recommend the material in the quotation, and we say no to over-specification: an over-specified part has never won anyone's loyalty.

Step 4 — validation

We hold ±0.3 mm as standard, ±0.15 mm on dimensions identified in advance, negotiated one by one: on a machine part, those are the bore, the centre distance, the bearing surface. Above 50 parts, a sample is approved in writing before the run, and systematically offered below: you fit the part on the machine, you check the real fit, and production starts after your go-ahead.

If a part is not to specification, tell us within 14 days with photographs: if the fault is ours, it is remade at no charge, carriage included. If it comes from a wrong dimension in the file supplied, we look for a solution together, and the rework quotation is drawn up first.

Lead times, and the next time

The quotation goes out within 24 working hours. Allow 2 to 3 working days for a prototype, 5 to 8 days for a run of 50 to 250 parts; the lead time written on the quotation is firm. For a machine that is down, say so in the request: the lead time we announce takes the workshop's load into account at the time we write it.

The next time, you have the STEP: the part is reordered in a few minutes, as a single unit or a small repeatable run, in the same material or another. That is the point of having it remodelled rather than buying a sub-assembly: the part stops being obsolete.

On the same subject

• Parts on demand
• Custom parts and prototypes
• PA6-GF datasheet
• Repair rather than replace

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