Checking 5-Axis Capability Before You Send a Drawing
The gap between what a shop advertises and what it runs is wider in 5-axis than in almost any other process. This is not usually dishonesty; “5-axis” has become a marketing word, and a machine that can index a part to a fixed angle is technically a five-axis machine.
You need to know which one you are buying, because the two have different costs and suit different parts.
What actually differs
In simultaneous work all five axes move while the tool is cutting, so it can stay normal to a surface that is changing shape. That is what you need for impellers, blended fillets and freeform surfaces.
In 3+2 indexed work the part is rotated to a fixed angle, locked there, and cut with three axes. Then it rotates to the next angle. Most of the benefit of five axes comes from this alone: one setup instead of four, so the relationships between faces come from the machine rather than from re-clamping.
For a housing with ports on three angled faces, 3+2 is usually the right answer and the cheaper one.
Four questions
- Make and model of the machines. Then look them up. This is the only checkable answer.
- Which CAM, and who runs it. Simultaneous work needs full kinematics and collision checking. A shop with the machine and no five-axis programmer will give you indexed work.
- Part envelope with the head tilted. Smaller than the table size suggests, sometimes much smaller. Ask for the envelope, not the table.
- What they measure and what they subcontract. A shop that sends everything out for measurement cannot correct itself between parts.
The one document
Ask for a real inspection report from a comparable part, with the customer details removed. Not a template, not a certificate. A report shows what they actually measure, on what equipment, and to what tolerance they are used to working.
A shop that cannot produce one has either never been asked or does not keep them. Both tell you something.
What to put in your RFQ
State the process you expect, or say plainly that you do not know and want advice. A shop told “5-axis simultaneous” when the part does not need it will quote for it, and you will pay for it.
Send the drawing and we will tell you which process your part actually needs, including when the answer is that it does not need five axes at all.
See also: the 12-question capability check and the map of 5-axis shop classes in Vietnam.
Questions
Is 3+2 indexed machining worse than simultaneous?
No. It is a different process with a different cost. For a part with features on several flat faces, 3+2 usually holds the same tolerance for less money because programming is simpler and proving out is faster. It only falls short on freeform surfaces where the tool has to stay normal to a changing shape.
What single question separates the two?
Ask for the machine make and model, then look it up yourself. A model number is checkable. A sentence like 'we have 5-axis capability' is not, and it is compatible with a 3-axis machine plus a rotary table used only for indexing.
Should I ask to see the CAM system?
Yes, and it is more revealing than the machine list. Running true simultaneous work needs CAM with full machine kinematics and collision checking, and a programmer who uses it daily. A shop with the machine but no one who can post a five-axis toolpath will quote you indexed work regardless of what the spindle can do.
Have a part rather than a question?
Send the drawing and we match it with up to 3 Vietnam shops that run this kind of work. We reply within 24 business hours.