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Howdy! We have access to a single point lathe at a local college. We have a great ultra-precision machinist turned mechanical engineer. We are interested in iterating on some freeform optics, and looking for the shortest path to getting there. Outsourcing the DT gives longer leadtimes than...

Howdy folk! WE have a new project that requires us to diamond turn some optics for prototyping. I'm relatively new to the optical game, so i don't even have a manufacturer of material to start with. Please let me know if you know who to approach to buy high pmma blanks intended for optics in...

Hey all, I have created some custom threads in my model using the helix command. Whenever my mouse overflies the feature in the tree, all of the edges of the threads are sequentially highlighted in orange. this takes several seconds for each feature, and as such, is slowing down the operations...

I work in the polymer industry, while I used to work in the marine industry. The ocean is massively polluted by polymer waste. The waste is harmful to almost all forms of ocean life. Without healthy oceans, we all die. This post is entirely self serving. Claiming that there is no ocean gyre...

Hello folks, I am reviewing a design that uses unfilled ultem as a structural component with a sustained load. Cheap FEA (Nastran, linear) predicts low strains in the bulk at around .2%. This part, however, requires very high physical precision, so if it creeps at all, could knock out...

I have a structural PLA part that has been submerged in fresh water for 3 years in the California sun. It is still perfectly functional. That said, PLa is crap, and unless it works with your spcific use case, it will not work!! what is your use case?

Hello all, I am looking for information about stress relaxation in unfilled PEI. Specifically, I have a design where the sustained load induces a ~3000psi stress in the unfilled ultem. Looking for creep data for room temperature PEI to determine whether this is acceptable for long term service...

3D Dave, thanks for the info- good stuff. I need to read up on cycloidal profiles. our molds are made with wire edm, so the shape is totally independent of the tooling needed to create it (except wire diam, of course). we are not bound by hobbers. my assumption regarding backlash, based on my...

Hello folks, I am involved an instrumentation application where molded gears are needed. Originally, the gears were customized by a consultant using Kissoft. When we went to tooling, the molding team redesigned the geartrain using AGMA profiles (to ease the inspection). This molding house makes...

Nice, thx Brian. I hadn;t thought about the zero velocity issue. of course.

It is strange, because on several different production examples that i have, the ball was made in two steps. when I say production, only ~100k per year. I examined ball surfaces with a micrograph. It appears that the ball was machined with a stub on the very apex, which was subsequently...

I was trying to avoid the flat, but the flat on flat seemed fine in an informal examination.

Hello all, I am designing a shaft detail that requires a spherical on the end of a shaft. the ball fits into a socket, which allows minimal torsional coupling, while allowing a strong axial connection, and is self centering between elements. It's a spring biased push shaft that does not couple...

Hello experts! I am in need to an adhesive that ca bond with a glassfilled polypro. Bond must retain up to 121C (250F) loads are low- this will be used for a product badge, but it must remain bonded indefinitely. anyone have any experience, please drop a link! Or, ideally, anyone know of a...

3DDave, nice. i was thinking that he misunderstood the mechanism of the spiral cut shaft. your explanation makes more sense. thanks!

Hi all, I have a sliding interface with low very PV and I am looking at options for materials. It is a handheld application, so friction must me minimized. We started with ultem for concerns other than friction, but it turns out that ultem is a *terrible* sliding component. It has very high...

Have you tried some FEA for a truth-check? It seems like a relatively straightforward setup. I had always assumed it woudl be a dual cantilever analysis for this case, but you are right in that there is cross talk between the flexures. I have not done the analysis to confirm this statement!

Hi all I have a weird (to me) application for a "compression" spring. If axial torsion is applied, does the length of the spring decrease or increase, depending of the direction of torque? Or does only the coil diameter change? (for my application, imagine a die-spring) Are you familiar with...

Thx dgallup. this was my assumption. I've only worked with 17-7 a couple times, and it was a few years ago. Was doubting my memory.

Hi all, I just received some springs from vendor that appear to have a rusty finish... the bag is covered in orange dust. Springs are supposed to be 17-7, and vendor provided a copy of the cert when requested. My print says "17-7 treated to H900 after coiling". I realize now that it should be...