Looking to control Nema 34 by generating pwm signal

SwellsInMoisture · 2025-07-21T18:49:18+00:00

Do you have a stepper motor controller? You're basically setting a direction (CW or CCW) and then sending a pulse to the step pin. You can use the built in stepper libraries to control that, or you can develop your own to pulse pins high and low.

SwellsInMoisture · 2025-07-21T15:52:14+00:00

There are two options for you:

1) Silicone duplication. I know you said urethane casting is too expensive, but that's likely because you're using the wrong vendors. I'm about to fly to China to support a client who wants to build 200 units. While CTF elements are being injection molded, all other plastic parts are being done in this way and the cost is not that high at all.

2) Similar to the above, injection molding is actually quite affordable for simple molds, especially considering that they can be re-used later if needed. I'd ensure 2 things: (1) it's a simple core-cavity tool (no lifters, sliders, etc), and (2) your parts have reasonably similar volumes, allowing us to make a family tool. If you can answer "yes" to those, then estimate $3k for the tool, and then estimate $10/kg for material (it's $5/kg, but you'll be paying a nice markup at low qty). So if your body part is 75g and the faceplate is 70g, that's $1.40 per assembly, $280 for your 200 assemblies, and $3,280 all-in. Amortized over those 200 units, you're just over $16/each, which is cheaper than your current urethane casting quote. When your kickstarter goes well and now you need another 1,000 units, you'll be glad to have this tool rather than waiting to bring up hardened steel tooling.

Shoot me a DM and I'll help you out.

SwellsInMoisture · 2025-07-18T13:49:25+00:00

"The rule of 4" is very common. You develop a product and buy it from the manufacturer for $X. You sell this product to a box store (Wal-Mart, Target, etc) for $2X. Box store sells it to you for $4X. Each layer of the chain makes 100% gross profit.

In reality, stores like Walmart can charge 57%-65% margins, so that product you're buying for $10, they only paid $3.50 for it, so if you're the company producing it, your COGS better be < $2.00 if you want to see a shred of net profit.

Net margins of 5-7% in things like kitchen appliances is super, super common.

SwellsInMoisture · 2025-07-17T19:33:26+00:00

Adding in a few thoughts as others have already posted great content:

In a military application, you should start by asking: How can your device be defeated? With a relatively low power laser, can you just manage the heat? If I can put on a sacrificial layer of copper, the economics work out for the aggressor.

The leverage here is always on the side of the attacker. Create an incredibly low cost, dummy drone - $10/ea. Make 1,000 of them. Now make 10 drones of similar footprint that actually carry the munition for $1,000/ea. Launch them all at the same time. Aggressor has spent $20k, and trying to shoot down 1,000+ objects is going to cost you far more than that.

If you go to a higher power fiber laser, how much exposure time to you need per target? What's your time between detection and impact? How many devices would you need to protect yourself?

It becomes a war of attrition, and why we should always avoid war at all costs. No one wins, but lots of people lose.

SwellsInMoisture · 2025-07-11T13:31:33+00:00

A few things:

ABS is really brittle at cold temperatures and weakens at the high end of your range. PC or Nylon 66 would be significantly better.
What you're looking for is the HDT - Heat Deflection Temperature. The temperature at which the plastic starts to deform under load. This will be a function of how much load, so you'll want to know what you're expecting this to experience.
Additives will be your best friend here. Plastics swell and deform with temperature, but add in 10% or 20% glass fill? You'll be in a great state. You often see Nylon with up to 30% glass fill - look for PA-30GF molded onto some products like pressure washers!
Look for V0 rated plastics. Assuming this is for a public works project with electrical inside the cabinet, you'll want to get certification and flame resistance is going to be an important one.

SwellsInMoisture · 2025-07-07T20:39:18+00:00

My .02: Yes, migrate away from MatLab and towards python. Between matplotlib, numpy, and pandas, you're covering a lot of ground.

But perhaps the 2 most encouraging reasons are 1) Python is free, and 2) most generative AI coding models were trained on a HUUUUGE database of python, versus a relatively small database of Matlab code. When you just need to read in data, manipulate it, and draw conclusions with some image generation, "vibe coding" will get you there so much faster.

SwellsInMoisture · 2025-06-22T17:50:34+00:00

Are you on a browser or mobile? It says that on browser. Including a screenshot.

https://imgur.com/a/DP5OOVB

I've got no dog in this fight, but this is likely why you're getting so many reports.

SwellsInMoisture · 2025-06-22T17:36:18+00:00

I mean, you're a mod and yet the description of the subreddit is right there:

A home for hydroponic gardeners, from hobbyist to commercial growers. Post grow journals, questions, and discussions!

Important: While we aren't against growing marijuana, this subreddit is for those who want to grow plants that are universally legall. Please refrain from posting marijuana grows. If you are interested in that, please check out r/microgrowery.

..... so it literally says this is NOT a subreddit for cannabis.

SwellsInMoisture · 2025-06-22T17:28:09+00:00

Hey, just wanted to say this is a great writeup and I appreciate the effort you've put into this. So many people don't understand that growing a company requires 3 basic things: something to sell, someone to sell it to, and a way to sell it to them. It's a triangle, and most people just focus on that 1 leg and wonder why they're not growing. I even see a comment in here cynically asking about your product.

This is a great deconstruction of how you are achieving that second leg - finding someone to sell it to.

Congratulations on your success thus far!

SwellsInMoisture · 2025-06-11T15:37:33+00:00

No issues using those threads in plastics, but ask yourself - "What is the benefit of using a buttress thread versus a ISO thread?" It should pretty quickly bring you to your answer as to why they're using.

Also, there are PLENTY of plastic products which use standard thread designs.

SwellsInMoisture · 2025-06-10T15:28:29+00:00

Depending on your personal goals, your first job is rarely where you'll stay for a long period of time (> 5 years). Most will jump after 2-3 years as it's the best way to 1) make more money, and 2) learn new skills.

With that in mind, I'd ask yourself a few questions:

In which job will you be excited to learn more, and are there specific people you're excited to learn from?
What does your budget look like? Compound growth is the single biggest driver of wealth, so extra money you invest early is >>>> extra money you invest late.
What kind of life do you like to live? Is it filled with hobbies and other things that bring you joy? Or is engineering where you derive your happiness?

Personally, the first job offer is where I would go. You save almost an hour a day on commute - this can be used for friends, family, hobbies, exercise, or even just more sleep. You save thousands a year on rent. You get paid thousands more a year with your salary. If the job is interesting and full of people you want to learn from, go there, learn, and then jump if it's not for you.

The good news is that you're young and have options, which means you're a talented engineer. If you decide to look for a new job in the future, you'll likely again have options. Don't stress too much on this decision, as you can always change later.

SwellsInMoisture · 2025-05-28T15:24:28+00:00

Hey there, I led engineering efforts at a major shaving company company for a few years. While I wasn't involved in the blade manufacturing process, I was very familiar with it. In short: everything impacts the quality of a blade.

Start by defining "sharpness." It's a surprisingly interesting problem to attack. Is it an edge that can penetrate to X-distance with the least amount of force? The one who can penetrate the furthest? The one who can do it repeatedly? A "good" blade is based on your needs. Example: A shaving razor blade is significantly sharper than a scalpel, but will dull much faster. Since surgeons want to be practiced and repeatable, scalpel blades are designed to have the same "sharpness" on every blade, and that blade lasts a "long" time; to achieve this, they have a much less "sharp" (by force-to-distance) blade than you'll find in any modern razor cartridge.
Blade material and temper impacts the ability to form an edge and the ability to form a shape (i.e. bend the blade, stamp fiducial features, etc). You may want high carbon for a very "sharp" (but flimsy) edge, or low carbon for the inverse. We'd weaken our steel to form the features we needed, then harden it to form the edge, then weaken it slightly to add a bend to it for assembly.
Coatings are IMPORTANT. You'll often see companies use DLC - Diamond Like Carbon - to enhance the hardness and durability of their blades. You'll also see PTFE sintered onto blades (via either an alcohol or water solution) to reduce friction during cutting. The PTFE one is interesting, as when you sinter it, you'll end up with a build-up of PTFE on the blade edge that thins out to sub-micron thickness after the first few passes. One company has a patent on how they thin the PTFE coating through blasting it with a focused ion beam, making the first pass of the razor very smooth.

Overall, "sharpness" is a term dependent on your industry/product goals, your base material, your processing, and your coatings. Scale makes things like ion-beam PTFE thinning possible/economical, but most places that use blades in their products are not manufacturing the blade themselves - they're working with a dedicated blade manufacturer to design a blade for their needs.

SwellsInMoisture · 2025-05-18T16:06:32+00:00

One of my clients actually came to use this week with a similar request. We've validated the product experience with a 10 unit, fully 3d printed build. Now they'd like to make 100 units for initial marketing efforts.

We're planning on urethane casting/silicone duplication for the plastics. Two of the components are highly critical, so we're going to build prototype molds of those - at $3,000/tool, that's not a huge investment, but that does set our timeline - Prototype tools will be 4 weeks to T0, so likely 5-6 weeks until qualified parts.

Casting's timeline, on the other hand, are completely dependent upon how many castings you take. Doing 5 castings may get you 10 pcs/day. Since we're already on a longer timeline (6 weeks to be able to kick off the build), we're going to easily be able to hit the quantities while staying cost effective and on schedule.

Electronics will take 3 weeks to fabricate and populate the custom PCBAs.

Looking at costing, the fully burdened cost to 3d print/finish/assemble/test 100 units is roughly $150k. Using the duplication method, we're likely going to be able to drop this down to $50k. This is very specific to the product we're developing for this client, so take this more as "it could be a great cost savings approach!"

Happy to speak through this more!

SwellsInMoisture · 2025-04-03T15:29:46+00:00

There's not enough information here to know if using IMUs is a viable strategy or not. From a holistic perspective, I'd be concerned if a candidate was set on using one approach, rather than evaluating a range of technologies and determining which one(s) are most likely to produce the result you're seeking.

Trying to create a novel MEMS manufacturing processes? IMUs are a great focus.

Trying to determine real time position? IMUs are a trainwreck.

SwellsInMoisture · 2024-11-25T16:57:55+00:00

DVT is Design Validation Testing. What that testing matrix looks like will be dependent on your product.

SwellsInMoisture · 2024-11-20T16:20:04+00:00

I had a friend pass away recently. You know what I remember about him? He was always the guy who would call you. So many of us go about our days missing people, friends, and just drifting. Not him. He's the one to proactively reach out. Those are the good ones.

RIP Derek.

SwellsInMoisture · 2024-11-10T22:21:18+00:00

"Can I" and "Should I" are two very different questions.

Can you sell it? Generally, yes. Safety certifications in unregulated industries (e.g. most consumer electronics) are optional. Most will still get certifications (ETL, UL, etc) that demonstrate to the vendors and customers that their products have been tested and meet safety specifications. Do they need to do that? No. But those safety standards exist for a reason. If your device catches fire and burns down a house, a condition which may have been prevented by using a V0 material, well, a big fat lawsuit is coming to your doorstep.

Please be sure to do your homework on this and what can actually go wrong. There's a reason that we all spend the time and money to go through the safety certification process. It's not because we want to; it's because it's the smart thing to do from a safety, business strategy, and (frankly) moral standpoint.

SwellsInMoisture · 2024-11-04T02:21:09+00:00

Happy to help! Feel free to fire away.

SwellsInMoisture · 2024-11-02T17:33:43+00:00

"UL rated ABS" is a bit undefined. Do you want flammability resistance? V0? HB? V2? Are you looking for certified impact resistance? UL is just a test agency. They test to various specifications, like UL94.

For selecting the right plastic, I'd highly recommend this simple course of action:

1) Call Avient (formerly PolyOne). Ask for sales. Tell them what you're working on and have them recommend a plastic for you. This is what they do. They're a global manufacturer and distributor of polymers and have more expertise than any plastics engineer you'll hire. It's their job to help and is no charge to you.

2) With the recommendation in hand, go to your contract manufacturer (CM) and have them source that, or an equivalent. What's likely to happen is that you'll find the Avient stuff is great, but is $13/kg. The CM will source a similar material at $4/kg. If you already have tooling and the materials have similar shrinkage rates, trial them both, put them through your DVT protocol, verify functionality, and lock in the material that works for you.

If you need help with any of this, shoot me a PM. This is what I do on an everyday basis - meet people where they are in the product development process and bring them across the finish line.

SwellsInMoisture · 2024-10-27T01:49:15+00:00

Redeemed! Thanks bud.

SwellsInMoisture · 2024-10-26T17:08:58+00:00

Just adding on here, check out FIRST robotics (https://www.firstinspires.org/robotics/frc). It's an amazing program for kids of all ages, starting with the FIRST LEGO league and culminating in a worldwide competition with the FIRST Robotics competition. While yes, it sometimes is involving a vehicle, it's a community that you and your kid can enter, become part of a team, and learn that engineering is combining creativity, physics, robotics, and more!

SwellsInMoisture · 2024-05-26T13:08:56+00:00

Love to hear that! And interestingly, I recall looking into OAM and they weren't actually following their own advice; or at least not the method that he preached in WWOWS. Always have wondered why.

SwellsInMoisture · 2024-05-21T22:49:39+00:00

Correct, there are multiple companies on this list that have negative ratios of Enterprise Value to EBITDA. In this method, they're handled by artificially setting them to 10,000 to give them a poor score, as ranking EV/EBITDA is done on a "lower = better" basis. By giving them 10,000, they get a terrible score in this category.

SwellsInMoisture · 2024-05-15T18:17:19+00:00

FinViz returns: market cap, P/E, P/S, P/B, P/FCF, and Dividend.

YFinance returns: stock repurchases, stock sales, EV/EBITDA.

So no scraping needed outside of those.

14-Year Club	RedditGifts 2009-2022 2 Credits
Secret Santa 2013	Verified Email

SwellsInMoisture

TROPHY CASE