Not a 3D printing rocket startup, but I think I have enough experience with
DMLS parts to weigh in.
Typically the surfaces that I really care about are going to be interfaces,
not internal geometry. On these interface surfaces the part is
post-machined, and can be made as accurately as required using an old
fashioned drawing or model based definition. DMLS parts are constructed on
a base plate of the same material so one surface gets cut off with a saw
and machined flat anyway.
Manufacturer's will typically specify the tolerances that they are able to
hold in their process and have design guides available. I strongly
recommend understanding their design guides and following best practices
while designing the part. Some people think that 3D printers mean you can
make anything, which is BS. They have their own quirks and rules for making
things.
I have not specified tolerances on an un-machined surface. I might
interpret a 3D printing tolerance to be similar to a profile tolerance.
We know that traditional CNC mills can usually do +/- .005” and lathes canhold it as tight as +/-.001”.
On Wed, 2018-03-28 at 10:31 -0700, Anurag Bonthalapati wrote:
Question for all the 3D printing rocket start ups out there:
I realized that I may not have answered your questions properly.
Hopefully others with more experience will give you better information.
The issue is that different printers have different abilities and
capabilities for holding tolerances. Additionally, it's not only the
printer, but the materials and processes that affect final quality.
Issues to consider are surface finish, stresses, dimensionality etc.
Many of these things can't really be specified in your drawings and/or
3D file of the part and you will need to work with your 3D printer
service provider to ensure that the proper raw materials and processes
are used to get the dimensionality (and other properties) that you
might want. Some of it is an art, knowing how to orient parts for
build, adding supports, stress relieving and post processing. Again,
work with a representative of the service provider to make sure that
your needs are met.
In some cases, your design might need to be modified to avoid problems
that are normally encountered in the printing process.
Here are some articles on some of the issues:
https://www.engineering.com/3DPrinting/3DPrintingArticles/ArticleID/152
02/7-Issues-to-Look-Out-for-in-Metal-3D-Printing.aspx
http://www.machinedesign.com/3d-printing/3d-metal-printing-tips-trends-
and-common-misconceptions
http://www.renishaw.com/en/design-for-metal-am-a-beginners-guide--42652
https://www.xometry.com/manufacturing-standards
https://support.xometry.com/hc/en-us/articles/221360787-Accuracy-for-3D
-Printed-Metals
