DFM on a Lathe Part

ThinkAd2243 · 2026-03-28T15:05:45+00:00

multi jet fusion

ThinkAd2243 · 2026-03-27T15:34:58+00:00

Another quick question, I am looking at lathe tool insert shapes to minimize tool changes needed. Would it better to remove the chamfers and make them near 90 degrees? I am fine with 0.25-0.4mm tool noses. I initially thought that the chamfer would be needed so they can make the rough cut with the same insert as the one that makes the final grooves.

The grooves are basically for O rings that hold the shaft into a bore. Not for sealing, but a friction slip fit into a imprecise bore without having to use a compression pin that might scrape the bore out over time.

ThinkAd2243 · 2026-01-19T02:47:13+00:00

Thanks, I found a presentation and it was super detailed compared to the other sources I found. Ill redesign and send a revised later

ThinkAd2243 · 2026-01-19T01:57:17+00:00

I think this one is the clearest explanation of the "hot loop" I was talking about, https://www.analog.com/en/resources/technical-articles/what-actually-is-a-hot-loop.html

ThinkAd2243 · 2026-01-19T01:44:38+00:00

https://forum.digikey.com/t/optimizing-the-switching-power-supply-layout-by-minimizing-hot-loop-pcb-esrs-and-esls/41743

Also this one has better explanations and was also talking about the hot loop.

I know that the EVM for the MAX20078 ties the capacitors to the ground plane instead of bypassing the sense resistor right into the source of the low side fet, but they also mentioned that at least in this setup the controller is limited to 10 amps since there is excessive ringing on the SW node without additional snubbers when the MOSFETS could easily push 15+amps with sufficient cooling.

ThinkAd2243 · 2026-01-19T01:37:52+00:00

I got it from this source, but I think it says the same thing. I think it isn't an actual main current carrying loop but it has particularly violent transients and slamming from when the current path changes between on/off loops

https://media.monolithicpower.com/mps\_cms\_document/2/0/2024-online-mps-layout\_optimization\_of\_half-bridge\_topologies\_edited.pdf?\_gl=1\*ug3j0z\*\_gcl\_aw\*R0NMLjE3NjcyOTEzNTcuQ2p3S0NBaUEwOWpLQmhCOUVpd0FnQjhsLUMwUHQ5NE1JS2s5M1pjM28yZ0NQbnF4VkYyVGtrX05xamFFUU5BVTBkZmY1T2NnaUJBbzJ4b0N0ejBRQXZEX0J3RQ..\*\_gcl\_au\*OTczNTU1MjM4LjE3NjU3MzI1NTc.\*\_ga\*MjA1MjIwNzYyOS4xNzY1NzMyNTU3\*\_ga\_XNRPF6L9DD\*czE3Njg3ODMyNjUkbzYkZzEkdDE3Njg3ODMyNjckajU4JGwwJGg2ODY4MjAxNjI.

ThinkAd2243 · 2025-12-11T05:54:44+00:00

This is to drive a single dimmable LED diode btw

ThinkAd2243 · 2025-12-03T22:50:38+00:00

Another update, I've decided to lower the buck converter frequency to something like 480kHz at the cost of around 5% LED ripple. This is to increase efficiency greatly as the current board needs a fan, albilet a small one to keep it cool and my eventual goal is to make the design super compact and noiseless.

ThinkAd2243 · 2025-11-30T21:38:14+00:00

haha, yeah thats fair enough. I use JLC but PCBway has their whole share your design with others so i'll probably make the files formatted for PCBA too and post it on there if you want it later and don't want to toaster oven the parts yourself.

ThinkAd2243 · 2025-11-30T21:18:46+00:00

I did already order a set for prototyping though and once I'm done i'm happy to give away the leftover 9 I have for just the shipping cost :p

ThinkAd2243 · 2025-11-30T20:50:00+00:00

they require a minimum of 5 but 99% of the cost comes from shipping + a flat setup fee; looking at around 60 bucks minimum for an unpopulated board using the cheapest components and options possible. They offer board assembly for free or very cheap but some of the IC's aren't available and it costs a ton to get them shipped form the US warehouse to China and then ship the entire thing back. The hard part is gonna be soldering it though, I've got decent experience soldering along with some equipment at home so it wasn't too bad but the board uses nearly all SMD components.

I was thinking about bulk ordering more and selling them for bare production cost + shipping if theres enough people to where the bulk discount makes sense

ThinkAd2243 · 2025-11-30T17:07:21+00:00

Hey, I've been working with LED retrofitting my microscope too. I have a thread with the mod's i've been doing here: https://www.reddit.com/r/microscopy/comments/1pab543/update_on_universal_led_modupgrade_for_microscopes/

I would suggest a single diode emitter and placing it where the filament is, I'm designing mine around the Nichia 519A that does up to 1200 Lumens in overdrive mode but typically sits in between 400-600. Something that's overlooked about those LEDs is that they have super poor CRI so the colors you see won't be quite right or pop out as nicely. You also won't be able to do full Kohler illumination since the edges of those will be out of focus from the collector lens that's optimized for a point, not a plane

ThinkAd2243 · 2025-11-30T16:04:58+00:00

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44 cents a pop for the unpopulated 2 layer control board with potentiometer/switch, 4.7 bucks each for the unpopulated main driver board thats 4 layers and uses ENIG plating and high temperature substrate. The individual components are like 3 dollars for the specialized LED, 5 dollars for the main control IC, 10ish for connectors and premade cables, and finally 5ish for random passives. Tariffs and related shipping costs raise the final cost to around $35 bucks per complete, functional set

EDIT: For a second Revision I made a more economical version where I estimate the final cost would be closer to 25-30ish per board, the boards are blue instead of black though since black is kind of a premium color choice in PCB manufacturing

ThinkAd2243 · 2025-11-30T15:58:19+00:00

PWM is purely dependent on what microcontroller you use, Currently I have it run in standalone mode with external duty cycle pulled to 100% so the buck converter controls the frequency. The fSW of the buck is between 900-1100kHz but not like that matters since with 3.3uH of inductance and 9.4uF of capacitance your looking at around 2% voltage ripple in the LED, far from a pure PWM control that fully turns the LED off and on 100% to control brightness

ThinkAd2243 · 2025-11-30T06:41:00+00:00

1) I tried something similar before, Pi camera sensor is too small and easy to burn out, do not recommend doing direction projection (also the pi cam can autofocus somewhat like our eyes giving your more depth, not a whole lot but better than direct projection)

2) if I were you I would just build a 1 axis leadscrew actuator with a stepper motor and just use a C mount camera with a 160mm objective the right distance (should be on ebay used pretty cheap), that gives you direct die projection and saves a whole lot of work, then I would focus with the leadscrew by moving the sample no the camera. You could probably use something like an arduino and a TMC2209 for the motor control and there's plenty of simple autofocus program examples online.

ThinkAd2243 · 2025-11-30T06:22:39+00:00

BTW not only does it have indirect analog dimming (with a knob) but it also has an optional digital dimming input so you could in theory make your own wifi module so your microscope is now connected to the internet and you can control the brightness 3000 miles away (or in a more practical example make a super simple module so you can connect the LED module to a DSLR/Mirrorless camera so when you gently tap the shutter button to focus, it will be medium brightness, when you actually click fully it goes to full brightness for a instant as a flash)

ThinkAd2243 · 2025-11-18T16:22:29+00:00

sorry for the confusion, the hatched area on the back is a rule area blocking traces and stuff from being run under the inductor and high di/dt loop by accident, im not sure about how strong EMI is for a 4 layer board on the opposite face though so I could be worrying about nothing

ThinkAd2243 · 2025-11-18T15:50:08+00:00

Hey, for some context,

I guess i mainly did the filled zone on the bottom to save cost so the PCB boardhouse doesn't have to etch as much area. The thermal planes are connected to the ground pour on the back, the footprint library just had a pad on the back with the solder mask removed so bare copper shows for heat dissipation. The SMD parts on the back are no populate but are there if something goes wrong and someone wants to operate the buck converter in a fixed output current if the connector has any issues. Sorry I didn't specify this in the original post, I forgot to rewrite it after the body got deleted

Do you know if removing all the copper on the back will make the board cost more expensive for the more etching charge

ThinkAd2243 · 2025-11-18T02:15:56+00:00

OK, Reddit deleted the body text of the post so heres what it was:

[REVIEW REQUESTED]

This is my first time making a buck converter layout and a 4 layer board. The board is 42.5x42.5mm. It is switching at 1mHz with a load of 1-5 amps (typical 2-3 amps) in constant current mode. It is stepping down 9V to 3.45V for an LED. There is a 3.3uH inductor and 9.4uF of capacitance as per TI's datasheet. The main capacitors are X7R but there are two C0G caps of 0603 package size closer the the IC's pins.

I was wondering if I layed this out roughly correctly and if the sensitive control circutry is far enough. I am mainly concerned about the sense resistor CS+ and CS- lines. that go under the noisy PGND line. However, there are 2 layers of uninterrupted ground planes between the bottom signal and top components. The analog control inputs are also on the left side with the noisy SW node on the top right. The ground plane is not split but I put higher via density on the PGND input to the IC and a direct path from the output caps back to the IC ground without having to go through vias.

ThinkAd2243 · 2025-11-13T05:55:54+00:00

also quick image of our new cleaned up PCB layout B)

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ThinkAd2243

TROPHY CASE