Frequently Asked Questions
What CAD file format is required?
For quoting and building the parts, all files should be in Stereolithography (stl) format.
Is the EBM material qualified?
Qualification of the material will depend on the application.
Will small holes (~1.0mm) build?
Small holes will close-up a little. If the small holes are to be machined, machine shops would prefer that the part have no holes to begin with, otherwise they will break off bits frequently. If the file has many small holes redo the file without the holes. Alternatively, if small holes do not need to have a machined surface, increasing the hole size by about 0.040″ will yield a hole closer to the target size.
What will be the surface finish of a Ti64 EBM part?
The EBM process produces a near-net shape part with a surface comparable to a casting. A surface finish of Ra700 micron inch is normally produced. The as-built surface finish can be improved by post-processing if desired.
What post-processing is available?
EBM Parts can be post-processed in many ways. We can achieve any finish in post-processing if the surface is accessible for machining. We can grit blast the parts and that will improve the surface some. We can also grind the surface but not to precise tolerances compared to machining. If a surface is not accessible, it can be cleaned-up using other techniques.
If you would like the parts post-processes such that surface material will be removed, you will have to add about 10 mil stock depending on which post-process technique is used (see CalRAM Design Guide for more information). We recommend that you use your own machine shop supplier.
Is there residual stress in EBM parts?
EBM is a high temperature process. This gives the material time to transform to a stress-free microstructure.
What are the maximum dimensions that can be built?
8” x 8” x 13.5” is the build envelope, or 12″diameter by 8″ high for a radial part. This space can be filled with one large part or many nested small parts.
What is the minimum wall thickness that can be built?
0.040” as built. If this surface must be post-processed, stock will have to be added to the CAD file as appropriate.
What is the maximum angle from vertical that can be built?
Any angle can be built.
Are any modifications to our designs necessary to produce a quality part with EBM?
Yes. Modifications will be needed primarily for machining. For example, the buttress thread would probably be built solid and the machine shop would just machine them in. Typically small holes are easier to drill in. This makes it easier to hit centerline tolerances. Interfaces which have to be machined will need excess stock added (typically 0.05″ added). As far as the passageways, depending on surface finish requirements, the parts may need to be abrasive flow machined. Typically ~0.005″ to 0.01″ may have to be added.
What are the dimensional tolerances?
+/- 0.008″to 0.010″
What are the tolerances for polishing an EBM part?
The as-built EBM surface is rough and to polish it, we will grind off this rough surface. Add .050″ to all surfaces to be polished. The tolerances for grinding are not as precise as CNC machining. Tolerances for polishing, grinding and machining are typical for those processes and are not dependent on the EBM part.
What is the HIP process and what is the effect on an EBM part?
Hot Isostatic Pressing (HIP) heats parts up under high gas pressure. Any internal voids left over from the EBM process are closed up which improves fatigue life.