You Cannot Remove Ejector Marks. You Can Choose Where They Land.
Why they are unavoidable
Every die casting is pushed out of the cavity by ejector pins, and each pin leaves a witness where it contacts the casting. The pin must bear on the casting with enough force to release it without distortion, and the local pressure inevitably leaves a mark — a slight depression, sometimes a raised ring where metal flowed around the pin face.
The practical question is therefore not whether there will be marks but whether they are on a cosmetic face, a sealing face, or a surface that will be machined away. Those three categories lead to completely different tooling and cost outcomes.
Specifying the requirement
State the ejection requirement as a surface classification on the drawing: which faces are cosmetic, which are sealing, which are as-cast and non-critical. The tool designer then places ejector pins on the non-critical faces and adds ejector sleeves or alternative release features where a critical face cannot take a pin.
Two further points save arguments later. First, if a face will be machined, say how much stock is being removed — a mark shallower than the machining allowance disappears entirely, and that is the cheapest solution available. Second, agree the acceptance criterion for a visible mark: depth, whether a raised witness is allowed, and whether it must be flush. "No ejector marks" is not an achievable specification and will be argued about at first article.
FAQ
Can ejector pin marks be eliminated?
No. Every casting is ejected by pins and each pin leaves a witness. They can be relocated, minimised, or removed by machining.
Where should ejector pins be placed?
On as-cast non-critical faces. Cosmetic and sealing faces are kept clear, with ejector sleeves or alternative release features used instead.
How do I remove an ejector mark from a visible face?
Machine it. If the mark is shallower than the machining allowance on that face it disappears completely, which is usually the cheapest route.
What is an achievable drawing requirement?
A surface classification per face plus an acceptance criterion for mark depth. "No ejector marks" cannot be met and will be disputed at first article.
All figures above refer to standard product data sheets; final confirmation is subject to written quotation.