Mechanical Design: Trapezoidal Motion

[@3dkiwi920]

Super helpful man! this is one area I was cloudy on :/ Videos in this format are great because of the visual simplicity coupled with the in depth explanation, and you're not treating the viewer like a moron, keep it up!

[@TabletopMachineShop]

Thanks! I certainly wish I could animate better:P

[@Blacktronics]

keep in mind this is missing thread pitch if you take a biggo stepper and stick it on a multistart leadscrew with ridiculous pitch (igus makes some with up to 10cm/rev) you can have some very high speeds at very high acceleration with low overall torque

[@TabletopMachineShop]

Yep true, I didn't really address mechanical power transmission in general. I was sort of getting at different motors with all other things being equal.

[@nerferfan]

Excellent video Greg. Simple, effective graphics. No flashy annoying things. Excellent pacing and very well explained.

[@TabletopMachineShop]

Thanks a lot!

[@Ed_Stoddard]

Excellent description of Stepper motor size and their strengths and weaknesses. I have a couple of designs I'm working on and chose motor sizes based on what I observed and read about each motor. I chose well according to your video and now I know 'why' there were good choices.. Thanks

[@TabletopMachineShop]

Good work! It's certainly not very intuitive... It took a bit of time for me to wrap my head around it when I first heard about it

[@stjinks]

Very well explained :) funny timing in the video. I had originally planned on using steppers for a machine function, but found clearpath motors, and have been busy trying to pair with a gearbox for my application. Fun stuff!

[@TabletopMachineShop]

They're pretty amazing, I use them whenever possible :P

[@joshwarner5676]

Cool to see some motion on the 3d printer. Can't wait to see it in action. I wasn't aware how superior bldcs are to steppers, definitely something to consider for future builds.

[@TabletopMachineShop]

They're definitely expensive, but they can do pretty amazing things. I think they're becoming a lot more viable for the hobbyist now that they controllers are becoming more accessable. I know Phidgets (a favourite supplier of mine) carries them now, though they only sell their controller which is a bit of a bummer

[@danharold3087]

Very informative. By reading the comments it seems we want more tech info. Thanks.

[@TabletopMachineShop]

I think a Part 2 is incoming!

[@ROBRENZ]

Enjoyed! ATB, Robin

[@Billystone90]

I really like this style of video great information and very well explained. Keep up the great work

[@TabletopMachineShop]

Thanks!

[@sallerc]

Great video, looking forward to the next one

[@TabletopMachineShop]

Thanks!

[@shawnlund]

Awesome as always.

[@beachboardfan9544]

This channel is gunna be awesome! 👍

[@mannycalavera121]

Great video, love it. Nice clean explanation.

[@DUIofPhysics]

Great video, I would suggest maybe making an addition to this video of S-Curve motion. We need more hobbiest motion controllers with s-curve motion control / jerk control.

[@TabletopMachineShop]

I was trying to decide whether or not to include that. Some hobby controllers have jerk limiting but it's not true jerk limiting. Perhaps I'll do a part 2!

[@DUIofPhysics]

I was looking into developing a proper controller, turns out the maths is kinda a pain in the butt. I've concepted a unit using NCOs and Integrating Jerk -> Acc -> Vel -> Pos in FPGAs. Wish we could find more of a team to work on such a thing.

[@pauldevey8628]

Keep up the amazing work!!

[@EmperorDevilhunter]

Steppers are basically BLDCs. They are usually limited by the max voltage that the stepper drivers can withstand. I have done some tests on my CNC mill and increasing the voltage in less than 50% I got three times more speed and acceleration without stalling.

[@TabletopMachineShop]

Yep steppers are basically two phase BLDCs. Higher voltage lets the current stabilize more quickly so the torque drop off is lessened and you can maintain motion at higher speeds. I remember moving from 24V to 48V on a build and i was blown away by how much better it was!

[@CraigLYoung]

You do a good at explaining things.

[@TabletopMachineShop]

Thanks!

[@JonFehr]

Great Video keep up the good work.

[@Anonymouspock]

My standard 3d print speed is about 200 inches per minute (100mm/s) which is a reasonable feed rate for a big CNC mill. A Tormach on the other hand...

[@TabletopMachineShop]

wow thats pretty solid... i don't think a Tormach can quite manage that :P

[@beerco667]

Nice video but I'll pick a nits - What you're describing is a Trapezoidal velocity curve, not trapezoidal motion. S-curve is the other velocity profile that's common but it's not so common on hobby controllers. I believe there was a version of Mach3 called "tempest" or something like that which had an S-curve velocity profile. Trapezoidal motion would be what your printer is doing when printing a trapezoid ;^)

[@TabletopMachineShop]

Fair point... I think we kind of abbreviated the concept at work down to "trapezoidal motion", but yep its technically a trapezoidal velocity profile. Some controllers imply they have an S curve velocity profile by saying they use jerk limiting, but it's more like acceleration-limiting-limiting. I may do a second, followup video on S-curves

[@beerco667]

Cool - you might want to even get into the acceleration profile as well - S-curve velocity profiles have a trapezoidal acceleration profile. As I was thinking about it, I think that Kmotion CNC/Kflop has S-curves with adjustable jerk.

[@daskasspatzle2396]

Nice explanation. If you take also the transmission and the price in account, maybe a stepper motor with a high torque can be as fast as something else, while the shaft rpm is still not that high.

[@TabletopMachineShop]

You could probably get better torque-speed characteristics than a smaller motor simply because you're using more power, although gearboxes add all kinds of new complications like inefficiencies and backlash!

[@daskasspatzle2396]

For sure. I thought more about with how many teeth you connect your Motor to the belt or similar, not about gear boxes.

[@madsighntist14]

Great Skill in discussing the topic, & for this Old (manual Mill/Lathe) Man, a very Helpful Production! I already had Subscribed to your "old channel" name But I think this Name Changes a Viewers ~Potential Interest~. Me: 2 TAIG Lathes, One (hand cranked) TAIG CNC MILL, and a Micro Mark "True Inch" 7X14 lathe. BUT wanting to go CNC!

[@TabletopMachineShop]

Ah, a true tabletop machinist! I'm certainly planning on getting back into CNC when I wrap up a few other projects!

[@jozlong2519]

Stepper motor is usually powered using 24V DC If you use 80v DC, acceleration can be increased But buy expensive stepper drivers

[@ethanmye-rs]

Can you make a video about bearing choices?

[@TabletopMachineShop]

It's on my list. It's a big topic and I really want to do a good job so it's spending a lot of time in the planning phase. Are you most interested in rotary or linear bearings?

[@katawatenshu]

"Are you most interested in rotary or linear bearings?" Yes :D

[@somebodyelse6673]

I would say no. I am interested in rotary AND linear bearings. Every machine I am interested in has both.

[@ergohack]

Tabletop Machine Shop which one do ballscrews count as? :P

[@HoY_82]

Less than an hour ago I literally just setup my trapezoidal on my cnc router after its rebuild. Weird timing! (new gantry with more than 5x the mass, but infinitely more rigid. was able to increase acceleration from 6 to 20, and top speed from 90 to 200ipm)

[@TabletopMachineShop]

I've been playing with it on my 3D printer trying to optimize my speed, so I was kind of in the mood to do a video about it :P

Excellent one, maybe a little, well, speedy for us non english speaking natives

[@TabletopMachineShop]

Good to know, I'll keep that in mind for next time!

[@katawatenshu]

Also the motor driver is about as important as the motor itself for acceleration, don't buy the very cheapest you can find. The third cheapest is probably pretty good though.

[@TabletopMachineShop]

Third cheapest is about right. They come out with new stepper driver ICs all the time that are actually getting quite impressive. I'm excited for BLDC driver prices to drop down to where stepper drivers are!

[@hdheuejhzbsnnaj]

Love your stuff, but I have to say you should really take a second to post some more vids of yr little CNC lathe making chips.

[@TabletopMachineShop]

Yeah I'll definitely have to do that :P

[@hdheuejhzbsnnaj]

Tabletop Machine Shop also report on design flaws that you wish you had done differently. I'm planning long term on scratch building something similar.

[@neiljborja]

I get what you're saying, but honestly the slightly more theoretical nature of this channel is what sets it apart for me. Maybe in the future hhlaps 1990 will help me get over my fear of PID control and I'll pass my controls class :p

[@hdheuejhzbsnnaj]

neiljborja I'm not asking for CNC porn, I'm asking to see how theory performs in the real world. There is a lot to learn from that.

[@miguelsal3000]

Gearboxes on Large Steppers? its a thing I swear :'D

[@TabletopMachineShop]

Yeah it totally is! You can get insane torque when you add a step down gearbox. If you add a step up gearbox, you're just trading your torque for speed and "squishing" the torque speed plot vertically.

[@PriestGreyRaven]

You are a younger version of Uncle Bumble F#=;! Or AvE as he's also known.

[@TabletopMachineShop]

hahaha thanks

[@CalvinoBear]

First

[@TabletopMachineShop]

Consistently so!