Resources · Design notes
Design notes for parts manufactured in China
Each note says what to put on the drawing. Notes marked “From a past order” come from real orders, anonymized; the others are general engineering advice. None names a customer, a factory or a part.
CNC machining
From a past order
Specify hardness and grade together.
Full-hard 316 is not always available in China. On one order the factory proposed half-hard 316, and the customer approved it in writing before production started.
Engineering note
Mark the faces that must stay bare.
If a coated part has electrical or locating contact faces, show them on the drawing. The factory can mask them, or re-machine them after coating.
From a past order
Give deep pockets a realistic roughness.
A long tool in a deep pocket leaves a rougher surface than the outside faces. If the inside surface is functional, specify it; its feasibility is confirmed before the quotation.
Engineering note
Name the black finish.
Black oxide, black anodizing, black PVD and QPQ are different processes with different appearance, thickness and corrosion behavior. The process named on the drawing is the one used; any change requires your written approval.
Engineering note
Send the PDF as the master.
STEP files are welcome for programming. Where they disagree, the PDF drawing and its revision letter govern unless you specify otherwise.
Sheet metal and laser cutting
From a past order
Check thread engagement in thin sheet.
A #4-40 thread in 2 mm sheet leaves little engagement. The factory raised it at drawing review, before production, and a press-fit nut was agreed in writing.
Engineering note
Hold the temper as drawn.
Aluminum sheet in H32 and H34 bends differently. A change of temper is made only with your written approval.
Engineering note
Dimension from the features that matter.
Dimensions across several bends accumulate tolerance. Dimension to the holes and faces that locate the part in your assembly.
Engineering note
Plan rivets with a fixture.
Flush rivets depend on the riveting setup. State the flushness requirement on the drawing; the factory plans the riveting fixture for the part before production.
Plastic parts and injection molds
Engineering note
Give painted plastic time to cure.
Paint adhesion on cast and molded plastic depends on the primer system and the curing time. Specify the paint system and finish on the drawing; rest and curing times before packing are agreed before production.
Engineering note
Agree gate and ejector positions.
Gate and ejector marks are visible on the part. Show which faces are cosmetic, and the positions are agreed with you before the mold is cut.
Engineering note
Machine before you mold.
A machined or cast prototype costs considerably less than a mold and verifies fit before tooling is committed. The mold is built once the design is released.
From a past order
Name the glass content.
Glass-filled grades differ in stiffness and shrinkage. If a grade is not readily available, this is stated before the quotation, with an alternative for your written approval.
Custom springs
Engineering note
Give load at a stated length.
Wire size and coil count alone do not define a spring. Load at a stated length is the figure the inspection sheet checks.
Engineering note
Show the space, not only the spring.
State the bore it works in or the rod it slides over. Diameters change slightly under load.
Engineering note
Specify whether the ends are ground.
Ground ends add cost and ensure the spring stands square; open ends cost less. The drawing governs.
Jigs and fixtures
Engineering note
Fixtures for assembly steps.
Riveting, pressing and bonding steps are repeatable when the part is held in a fixture built for it. State which assembly steps need one, and it is included in the quotation.
Engineering note
Harden all wear parts.
Locating pins and wear plates touch every part. Specify their hardness and make them replaceable.
Engineering note
Mark the datums.
Show which faces and pins define the part position, so they are inspected and reported.
EVA and custom packaging
Engineering note
Name the master file.
Send the DXF and the PDF together, and state which is the master. Unless you specify otherwise, the PDF is the master.
Engineering note
Approve a sample first.
Foam and print differ slightly between suppliers. A sample with your parts in it is approved before the run.
Assemblies and kits
Engineering note
Agree the scope in writing.
The scope is agreed in writing before the quotation: the steps PAXIS takes on, and the checks that apply to the assembled unit.
Engineering note
One color reference.
Parts painted in different shops can differ. Give one color reference and approve a matched sample set.
Planning
Engineering note
Plan around Chinese New Year.
Factories in China close for several weeks around Chinese New Year, in January or February. Orders placed shortly before the holiday are completed after it. The cut-off dates for your parts are confirmed when you order.
Request a quotation
Send your drawings with quantities, material and finish. Drawing questions are raised before the quotation, and the quotation is issued by PAXIS in US dollars.