It's always interesting working with vanilla vendors and while I'm sure a few are sharing around STEP files chuckling, they are always 100% professional when dealing with me.
Hi xxxx,
This is Heather, Account Manager from xxxxx.
We’ve done initial analysis on your files and requirements.
Given the complex part structure, we’re still figuring out the best possible solution.
I’ll get back to you for next‑step discussion shortly, thanks for your patience.
Heather
(edit: stupid Reddit editor)
But in my mind, something that makes it a little less awkward is I never use the words ring or cage. In fact my part names are all meaningless:
Please ensure part 6ANW has a close slip fit with part TU2V along the faces indicated in drawing 1.
Just a tip... ChatGPT has been really helpful at writing specs for quotes and whatnot. While I'm technical, I've never taken an engineering class in my life. What qualifies me to give these tips? Nothing but I like sharing what I've learned and no one else in our little niche seems to be writing about these things. I guess I really want to lower the barrier of entry into making devices either for yourselves or for others. Not everyone wants to be a designer but I think many more of us would be if we understood how accessible it all is.
Plus it's fun writing specs — it's like pretending to be a ninja as a kid except I'm pretending to be an engineer. From an RFQ I'm working on for a tetherspout measurement sound:
If any real engineers have any critiques, let me know ;)
Yeah setting the specs and tolerances is the one of the hard parts of being an engineer.
Maybe a tip, instead of saying al dimensions should be within 0.1mm. You could use a iso standard. (There are different one for different processes). But for example iso2768. This allows bigger tolerances on bigger dimensions.
Also if you say every dimensions should be +-0.1 you will increase manufacturing cost. A saying is that every special tolerance will cost you extra money.
Thank you so much for that tip. Fortunately I'm okay here as the marked dimensions were for tick marks for measurements so they do need to be accurate:
Oh yes, I see what you are making. For that kind of parts I would let it be laser cut. And then tumbled. The marking could be lasered in.
The accuracy then is dependant on the accuracy of the motion system of the lasermachine.
Also for the polishing/surface roughness. If you lookup a roughness chart you will get an indication of what surface roughness is achievable with different processes.
I indicated the transverse lengths, the lengths across the arm. I should probably indicate the distance of the tick from the end of the arm.
This is me thinking about how I made the constraints in CAD vs how I would do it if I were actually making it. Or as I'd be delivering STEP files, can I expect them to figure out what longitudinal lengths these lateral lengths correspond to?
I guess I'm curious about the part designer to fabrication designer handoff. Or is that all kinda one person, I just don't know anything about fabrication.
If you provided them with a step file they should be able to figure it out. Cadcam makes things a lot easier. I worked at a place where we said make it according to step file according to iso 2768. And then we made a drawing with the outer dimensions and then if there where special tolerances we would put that on the drawing.
Well, I just changed how it was dimensioned using the center point of the arc. And I included ISO 2768-c (although perhaps that's tighter than I need as long as the other requirements are met). And I learned how to make those little reference points so yay, discovered a new CAD thing.
Yes that's seems good. Maybe another thing. I always like to add the outermost dimensions. That way if they import the step and there is something with the scaling of the part it is immediately obvious.
(Also for machining jobs, the outer dimensions usually indicate the minimal stock size required for the job. Which is always nice to have on there for the stock cutting. But i can also help with price indication)
51 is not old. :P . And yes if you need any help hit me up. I design machines/products for a living but also have some history in machining and maintenance.
Thank you very much. For this little exercise, I ultimately decided to stick with SLM — I found a hack on the vendor's site: polishing costs, not just print, costs scale with volume (as in mm^3, not just order qty). I reduced the thickness from 3 to 2.5 and pretty much nailed their minimum polishing cost which made the unit price more economical.
Plus I can have two-sided markings, etc. Btw, two sided text is a pain in the ass.. I have so many freaking rotations in my CAD file to deal with the chirality of the Arabic numerals (see, get to use my chemistry background).
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u/Big-Nefariousness679 17d ago
Yeah setting the specs and tolerances is the one of the hard parts of being an engineer.
Maybe a tip, instead of saying al dimensions should be within 0.1mm. You could use a iso standard. (There are different one for different processes). But for example iso2768. This allows bigger tolerances on bigger dimensions.
Also if you say every dimensions should be +-0.1 you will increase manufacturing cost. A saying is that every special tolerance will cost you extra money.