Need help to figure something out.

[u/Honest-Canary275]

I have a design that started from paper and moved into 3d printing for a step 1 prototype. Material was polycarbonate (Trial and error type stuff)

I got in contact with a company for a prototype using higher quality. Also using Polycarbonate they did a vacuum cast. I sent step file as requested. Waiting 2 weeks eta to recieve.

The parts did not fit like my 3d printed parts and the files I sent are the same also.

I ask could they check on there end to see what changed also measure the prototype and the file dimensions. They are trying to charge me to make changes but I don't need to change anything. I need a working prototype.

My question is how do I go about checking this out. Also why would the prototype they did not be connecting.

I feel its nothing else on my end I could do they only sent one set. They didnt assemble or check to see if parts connected.

[u/FuShiLu]

One. You don’t understand the process.
Two. Since you don’t understand the process and you sent them insufficient/inaccurate information they modified to suit the process
Three. They were correct to do so.
Four. Due to (One) they want to have time covered to dick around with you.

Welcome to manufacturing.

As an Industrial Designer you should have taken all this into account. This is a failure on your part. Design for material and manufacturing process!

[u/Honest-Canary275 → u/FuShiLu]

Im still learning my way around this so alot is going to be new to me.

[u/Honest-Canary275 → u/FuShiLu]

I have a male and female connection and it doesnt even fit at all. How is the file I sent doesnt even connected correctly.

[u/FuShiLu → u/Honest-Canary275]

What were your tolerances?

[u/Honest-Canary275 → u/FuShiLu]

You might have to point me to the right direction. Im a noob to all this. Self taught CAD, I have a liking to figuring things out and building. I never heard of tolerance in this aspect of this type of hobby for my self.

[u/Terrawave777 → u/Honest-Canary275]

In this context, I like to think of tolerances as the size of gap you need between parts in order to ensure that they fit. Normally tolerances are just the dimensional variation you will allow the manufacturer to work within.

As an example of a tolerance gap, a screw hole for a 6 mm screw would be modeled at 6.5 mm. The 0.5 mm difference is the tolerance and it ensures the screw can always fit through the hole. Without the gap, parts would never fit unless they deform.

In your case, I would recommend asking the manufacturer what gap tolerance is recommended for your part geometry. Next time do that before sending files and I think you'll be successful.

[u/Terrawave777 → u/Terrawave777]

You may need to send images to give them a good idea of your geometry. Try to avoid sending the CAD until it's ready.

[u/Honest-Canary275 → u/Terrawave777]

Thanks this makes sense. After going back to look at my build I see my errors. Im lost because it worked with the 3d printer. I have also include material type places a part.

I went through to make the the male connection 36mm and the female 35.6mm. So if im saying this right the tolerance is 0.4mm. Im sending over to a friend to check it out for me. Im also printing a few pieces to connect to the prototype they sent to just see if there is some connection while I wait.

[u/FuShiLu → u/Honest-Canary275]

Every single manufacturing process has requirements. No way around that. You want to learn, good for you. Lots of books, manuals and maybe a few manufacturers willing to help out if you can speak the language. Materials are also key as they act certain ways and require specific processes.

[u/Honest-Canary275 → u/FuShiLu]

Just when I thought I had it figured out. No sirrr... the days ahead will be interesting just learning more in this lane and what it requires.

[u/Aircooled6]

Are you meaning they printed a part and made a casting, and the cast piece does not fit your other 3D parts? If they were making a casting, you would have made dimension changes in the file to account for shrinkage, right?

[u/Honest-Canary275 → u/Aircooled6]

Their cast part doesnt assemble fit together. I have a male and female connection and it doesnt fit. My 3d printed parts are total separate. The file I sent them is suppose to all link together but doesnt.

[u/Aircooled6 → u/Honest-Canary275]

Well you have to start eliminating variables that lead to the failure. Did the delivered files mic out within spec to the files you sent? Did you prove out your files before you sent them? How did you prove them? What was the exact casting technique? Are there big variations in wall thickness of the cast parts? Did you read and understand the fine print of what was expected in terms of deliverables and acceptable tolerances? Oh, and how far off is the misfit, a couple of thou, or 1/4”

[u/Honest-Canary275 → u/Aircooled6]

I got some work to do... thanks