Harmonic Drive's design on HPG, HPGP & HPF Series allows the internal gear to elastically deform, accommodating the operational stresses that might otherwise lead to increased backlash. This elastic deformation is specifically intended to maintain consistent backlash levels, compensating for the wear and tear that might typically lead to increased backlash in a traditional gear system. HPG-20A-45 Permissible Radial Load 1,890 N, Permissible Axial Load 2,830 N.
Great video. The effort you put into framing the shots and capturing clear audio really shows. Not something you see very often in young RUclips channels. Maybe consider doing a quick shop tour video some time. It's always interesting to see other hobbyists setups. Keep it up!
Glad you liked it. I will do a shop tour video eventually, but at the moment my shop is in chaos as I'm rearranging tools and installing compressed air lines. Some people might find it more interesting this way, but I'll wait until things are a little less chaotic.
Great minds think alike! I wish I saw this video earlier. But we basically did the same thing. I have a Chinese mill and I did this gear reduction for both A and B axis. You can see in my A axis upgrade video that I had to machine down the OEM mounts too.
Before watching the 2nd episode to this and you explain it in there; if you were wanting to mount something larger in the 3 jaw chuck, yet keep it mounted close to the table, you could invert the jaws.
To be fair, it's a simple planetary gear reducer, it has nothing in common with harmonic drives . It's just a company that makes them is called Harmonic Drive LLC.
Thanks for the brilliant rich video. It rarely happens that I don´t find a British or American video worth being praised. They are absolutely well done. Perfect explanations, perfect in all the audio-visual aspects. Just cool. Very entertaining. Great show. Perfect to learn English engineering terminology. From Berlin: Happy New Year.
Thank you for the video. I'm making one my self after your Idea. BTW, this actually is planetary gear with super small backlash. I looked up the data sheet 😉. What is misleading is the company name "Harmonic Drive"
Glad you found it useful. Yes the company name has sort-of become synonymous with a strain-wave gearbox, which they also make, but this one is planetary.
That’s probably the smallest harmonic drive id consider using. The 32’s seem to be better suited for 4th axis work if you intend on doing any heavy cutting or metal work. For wood, plastic, I see no reason this wouldn’t work fantastic. Nice assemblyz
FWIW, the HPG series is a planetary gearbox not a harmonic drive, it is just made by Harmonic Drive Inc. I had one of the same series gearboxes and thought the same thing until I pilled the gearbox off the servo it was attached to.
Yes the Harmonic Drive web site has been updated since my initial research and they make the difference a bit more clear, i.e. it's not a strain-wave drive (commonly called "harmonic drive") but it does have continuous backlash compensation whatever that means. I plan to measure the backlash soon, so we'll see if this particular unit comes close to the manufacturer's specs.
We've found these to be one of the best gearhead mfg's on the market in their class. The backlash should be around 3 arc-min for the model you have unless it was abused. More that likely, you can expect a long life in your application.
Nice work! the unit used is a planetary reduction, not a strain wave gear, right? the brand is 'Harmonic Drive' but they have a few versions of the reducers, where the lower ratio planetary versions have a lower backlash than the (
Thanks for the brilliant video and excellent explanation. Don't you need a mechanism to avoid unwanted rotation during machining, for example a brake machanism. Also i want to know why would you use stepper motor instead of the servo ones.
Glad you found it useful. The stepper motor's holding torque is multiplied by the gear ratio of the gearbox, so the motor makes an effective brake provided that one doesn't try to cut too aggressively. A servo motor definitely has advantages but it adds cost and complexity, and the rest of my CNC machine uses steppers so it would not be a major advantage to have a servo just in the 4th axis. A servo may support greater acceleration and can be pushed harder since it doesn't suffer from lost steps, but I think steppers are a good choice for low-volume hobby work like mine where slowing things down is not a major disadvantage.
I think the HPG-drive you have is actually not a harmonic drive internally. (meaning the strain wave gear.) I have one just like it and I believe the hpg is a planetary drive, but a really good one. Made by Harmonic Drive company though. :)
I think you're right that it's not a strain-wave drive, which is often inaccurately called a "harmonic drive", but it's a Harmonic Drive brand planetary gearbox with "continuous backlash compensation". I see that the Harmonic Drive website has been updated recently and it's a bit more explicit about the difference now. It will be interesting to measure the actual backlash of this unit, which I plan to do soon.
There's nothing impressive about it. you can get the exact same thing on EBAY for less than 200 For the WHOLE THING!!! (and free ship! to boot!) This guy paid 200 bucks just for the Harmonic drive. plus motor, Chuck, chuck plate, adapter, etc etc. and all the LABOR.........Tsss I rather Click twice on Ebay and get it, ready-make..... (I made my own using using COG PULLEYS and BELT type. In fact I used to sell them on Ebay. they're too cheap now. NOT WORTH my time to mess with)
I really like your project and appreciate the delivery and production quality, you clearly have many talents. I'm reviving a small CNC mill at the moment and would like to add a 4th axis after getting the core functions working. I found the harmonic/planetary drive you're using and requested a quote, they came back with $905 each. Is that right?? I really like the idea of having a quality tool and the DIY path usually keeps the price down. Maybe I don't know what a good commercial tool costs?? Most of the commonly available items are around $500.
Sorry I have to correct you - one info is misleading. HPG doesn't stand for High Precision although it could be. Instead it stands for Harmonic Planetary because this series of HD gears are not harmonic drives but really really high standard planetary gears with backlash below 5 arcmins. Its really good among the planetary gears. One of the best it can get with that transmission type.
The manufacturer's website harmonicdrive.net/ has changed quite a bit since I made this video, and they previously used the term "High Precision Gearbox" (they still have it in the HTML page title, maybe an oversight). It looks like that's been replaced by "Harmonic Planetary Gearbox" which is a more descriptive term and also trademarked. Honestly I'm not sure I would have chosen this gearbox if I had understood that it was planetary and not strain-wave but that distinction was a bit muddy on the Harmonic Drive website and documentation at the time. I plan to make a video measuring the actual backlash and torsional stiffness of my gearbox, but alas it hasn't made it to the top of my to-do list yet.
Using the same 4th axis setup on my Shapeoko for mainly wood, but nothing harder than 7075, can you see any issues with milling the housing and plates from 6061 that will be heat treated afterward as opposed to steel? The only 'special' tools I have at my disposal are a Shapeoko 3 XXL and drill press so milling this much steel is a bit out of my reach. You're awesome by the way, a real kick up my ass to try harder. Thank you for sharing.
Very cool CNC interfaced index. How is that indexed? Do you use a secondary program with the number of degrees you want to move and an M23 in the program to trigger the move, or does it use an "A" then the number of absolute degrees in the main program to index? Nice job !!!
I can hear the differences too so I know what you mean, but it's all my voice. Some of it is due to using different recording setups, and probably some due to allergy season starting here so my voice sounds different depending on the pollen level. No idea about different dialects but now I'll be thinking about it.
Great explanation. I`m new to the robotics field. I`m designing a 6-axis robot with harmonic drives. I`m planning to implement the robot as a hand guiding for position teaching. Since harmonic drives has high torque, is this possible to do with stepper motors? If someone has an idea about these things, please leave a comment.
It is certainly possible to make a robot using stepper motors and harmonic drives, but whether it will meet your requirements is another matter. A gearbox such as this has a high reduction ratio, meaning that it multiplies the torque but divides the speed. So with a modest stepper motor you can get a lot of torque but the output won't rotate very fast. And the torque of a stepper motor decreases as its speed increases (look up the torque curve of any motor you are considering) so there's a limit to how fast you can step it and still get enough torque for your application. Just off-hand (no pun intended) it sounds like you may not need much speed or torque so it may be suitable for you, and you can get *less* torque if desired for safety by reducing the motor drive current. You might want to look for stepper or servo motors with an integrated gearbox and if a stepper, a position encoder.
@@BrainRight Thank you for your quick response. I`m considering steeper motor with absolute mechanical encoder. But my problem is will I able to teach the position to robot arm using hand guide due to the high torque of the harmonic drives?
Thanks. The main reason I used this chuck is that I already had it for use with my metal lathe, where the 3-jaw works well for round stock. I find it very useful to be able to move the chuck between machines while keeping the workpiece mounted. For square stock a 4-jaw chuck would be better and it would be easy to swap chucks if a need arises.
When can we expect to see the 4th axis in use on the Shark? I have a 4th axis from another CNC. I never thought I could use it on the Shark. I guess now that the speed is determined from the controlbos and the stepper motor doesnt really matter? The shipping on the original 4th axis to Australia would be a killer. Cheers
My next video is a project made using the 4th axis on the CNC Shark and it is in progress, should be ready soon. You should be able to use most any 4th axis with most any controller as long as the stepper+driver are compatible. The original Shark controller is set to drive 2.8A steppers so don't use a stepper rated for much less current or it can damage the motor. A stepper rated for more current should be okay, but wouldn't put out its max torque. The speed is determined by the pulses-per-degree (or pulses-per-mm) setting of that axis in the controller. With my DDCSV1.1 controller it's easy to set that on the settings page. The original Shark control panel lets you set it in a settings page, and offhand I don't recall the secret control key and password to bring it up but you can find that on the cncsharktalk forum.
Hey there! I am making a robotic arm with 5kg payload capability. From my calculations (worst case scenario), I would need about 100Nm of torque and I had chosen Nema 23 (holding torque 1.9Nm) & harmonic drive gear from HDsystems which are the same as yours! However, I have a question as to what specification should one look for while looking for a harmonic drive? Is it just solely the reduction ratio?
That's the main thing but also check the maximum rated torque and the specified backlash, which causes angular positioning error. You can't get it to zero but it's typically very low for drives like this.
Dear Friend, i would like to have your advice on milling machine. I'm about to buy one but i don't know what kind i need for my sign shop, I don't want to bay cheap that i will regret in next year and I don't very expensive one. i need one that will stay minimum 5 year doing things until i thing about expensive one (name and model)
Excellent, thank you, sorry this is a bit off topic but I'm really impressed with how you made this but especially on the adapter plate, how do you transfer the location of the holes from the motor and the chuck assembly AND still keep it all in alignment? Is it just measuring with calipers or using transfer paper, could you please make a video on how you marked it out? I'm new to machining, got a little mill and lathe and am trying to pick up as much information as I can from watching great videos like these but I know I'm missing some basic techniques to build on! I've built a furnace and am making some castings in aluminium and brass, and when the mounting holes are on the top I can transfer punch through a location hole to the drill out but when the part is 'facing' (sorry I can't describe this any better) the holes are then covered so I cannot see where to mark. Hope that made sense? Any help appreciated, thanks
I used the drawings of the motor output flange and the chuck mounting from the manufacturers to get the hole spacing, and I also double checked them with calipers. Just using calipers would be good enough because these holes don't have to be super-precise. The lathe-turned and 4th-axis-turned shoulders on the plate are what keep the parts concentric, and the bolts just keep them together so it's desirable to have a little extra clearance on the bolt holes. If they're off by a little bit it won't matter as long as the bolts don't bind. You could make the holes any number of different ways but I used trigonometry to calculate the X and Y offsets of the holes, multiplying the radius times the sin() and cos() of the angle for each hole. Then I zeroed out the dials on my mill at the center of the plate, drilled a reference hole there for later alignment, and cranked the table the required distances in X and Y in order to drill all the holes in the proper locations. It would be much easier with a DRO or better yet a rotary table but this is the old school way and works fine. As a sanity check, I first laid out all the hole locations physically using dividers and a protractor, so that I could easily see any gross error in my calculations and table-cranking. You could do it all that way, scribing layout lines with dividers and such, and it would be close enough for this if you're careful. Worst case, if a bolt ends up binding then you could just enlarge its hole a little because the bolts only hold things together and don't maintain the parts' concentricity. When I made the back plate to mount the 3-jaw chuck to my lathe, after turning it to size I used a simple transfer punch (off the lathe!) to transfer the chuck mounting holes onto the back plate. That would also have worked in this case but it was easier to do it on the mill. As you observed, that wouldn't work for the blind holes on the output flange of the harmonic drive. There are blind transfer pins that would work, and you could make your own, but I think it would be easier to use X-Y coordinates on the mill or to scribe layout lines with dividers.
BrainRight Thank you so much for your reply, very clear, shame you mentioned using math though, ( ha ha) I've not had to use it like that since school, a long time ago! 😪. It may sound daft to you or others but I did not know the expression 'blind hole' but now that makes perfect sense. I like the idea of making various size transfer pins to help with that. Really appreciated your video and reply! Cheers
In my next video, about making a faceplate, I show 3 different ways of laying out the hole locations including the trigonometry to calculate the X and Y offsets.
BrainRight Your a gentleman! Thank you! I'm done in after spending all day packing up my little workshop, ready for a house move and that's just put a smile on my face 😀. Cheers
Hi Brainright, Very nice videos and good workmanship. I am planning to use the same controller for a router project. I don't like Mach3 because of it's crashes and stuff here and there. This tiny little controller is powerful enough i guess. Seems stable too. BTW did you experience any crashes/hangs/bugs while using it? And another question is, "How did you manage the tool wear/offset at 11:14? I guess you would have taken the usb out and redone the Gcode. I will be happy to know if the controller can handle tool offsets/tool wear compensation. Eagerly waiting for your reply. Again , Nice work. Cheers. Jas
Thanks Jas. So far the controller seems stable and hasn't crashed but the most I have pushed it is in the micrometer dial project I did, and that was not really stressing it in terms of program size or driving all 4 axes at once. The controller does not support cutter compensation, so you're exactly right that I had to modify the toolpath and regenerate the gcode in order to compensate for tool wear or deflection. I don't find that a major inconvenience because I mostly do one-off projects and I usually have to tweak the toolpaths multiple times anyway. It would be a more significant limitation in a production environment, and especially in cases where cutters have been resharpened. So far all my end mills are relatively new and very close to nominal size, but their sizes will be more variable once I have set up a system for sharpening them. I think most of the offsets I see are due to deflection because the CNC Shark router's gantry is not very rigid, as it was designed mainly for woodworking. You can see some of that at the end of the micrometer dial video, where I think deflection caused the slight asymmetry visible at the top of the index marks. I could beef up parts of the router to make it more rigid, which I've already done to a degree, but I think the effort will be better spent doing a CNC conversion on my milling machine. Cheers, Jay
ahh, good to know that i am right about few things in the world. Another question- Is there a Gcode limit on it? like maximum number of lines etc? Also if you can share a list of g/m codes supported, i will be thankful. I have found a pdf manual but i don't know if it is written by the manufacturer or by some reseller. Thanks a lot for your reply. Good luck for your future projects. regards, Jas
There's no limit on G-code lines as far as I can tell. It reads the code from the USB stick as it is running. On my web page at brainright.com/Projects/CNCController/ I put a copy of the PDF manual, which may or may not be the one you already have, and it has a list of all the G-codes that are supported.
Hello again mate, I have just bought this controller and it looks fairly easy to setup and operate, but i am afraid if there are still major bugs in the firmware. Something suspicious happened on the very first day when i was trying to configure the settings (I.e parameters). I started with just one axis (X). Did the steps calculation, figured out the direction high/low and everything on the x started working. I wired the home switch and it worked as configured with "5mm move back" after homing. But now it is going crazy. While homing, it moves the x axis towards the home switch and just when the home switch breaks (it is nc i guess), rather than going 5mm away from the switch, it goes into the same direction as the switch, hitting the mechanical limits (missing the steps). I have tried changing the "x axis back distance after homing parameter-83" to a negative 5mm (-5mm) but it doesn't allow the + sign to be changed in the parameter. Any guess about what's happening? If i set the back distance to 0, homing works perfectly fine. I am worried why a thing will work one day and won't work the other day? I have played with the settings for a long time but no luck. The biggest worry is that the controller also shows the "-5mm value" in the machine coordinates after homing. So it is the controller driving the axis across the home switch. It is not that the direction pin is not working. It is something else in the parameters or a bug in the firmware. Also please let me know if you know a way to hard reset this controller or delete the settings file in the hard memory it has. The chinese website they have up is in chinese, and guess i need to find a chinese friend if i need to use help from the official website. :D Thanks.
Hi Jas, I have not used the home functionality but according to the manual (picture 2.19) the home and limit switches should be normally open, not normally closed. That might be the problem. I would recommend wiring up the limit switches too, so that it stops before reaching the mechanical limits and that way it should not lose steps even if the home function fails to work as it should. I expect that you could reset the controller by upgrading firmware. I think it is also possible to delete the settings file using the file management page. I would copy it first, using the copy/paste operations in the file management page, pasting it onto a thumb drive so you have a backup of it. Then if you delete the settings file and restart, I would expect it to reset to all defaults and create a new settings file. Warning, I have not personally tried this so I cannot guarantee that it will work, but that's what I would try first I wanted to reset everything. I think you can also create multiple settings files, and just load the one you want using the file management page. Again, I have not tried it yet but I plan to do that when I move the controller among multiple machines. Regards, Jay
In response to my faceplate video (ruclips.net/video/XvSZ1PYEcmY/видео.html) I received this question from Nicholas Miller, which I am reposting here: _Have you had any problems with lack of holding power using the nema 23 and planetary reducer. I purchased one and am now at the stage of buying a stepper, curious if you have any insight.... thanks - Nick_ The needed holding torque of a 4th axis depends a lot on what you want to do with it, i.e. how much torque is likely to be applied. Light cuts with a small tool and a small radius from the axis (such as my micrometer dial engraving, ruclips.net/video/3g9IFnVDOTo/видео.html) would impart far less torque than heavy roughing cuts at a large radius from the axis (such as rounding the edges of the backplate as I showed in the 4th axis build part 2). It also depends on the consequences of slippage, e.g. lathe-like cutting operations might not suffer at all from some slippage, and it's quite possible that some slippage or lost steps occurred as I was rounding the backplate edge but it would have gone unnoticed. I don't know how to calculate the exact torque imparted by a particular end mill when it's cutting at a particular rate, but as a simple worst-case calculation we could suppose that it digs in to the part and engages like a gear. With a 1/4" cutter at the perimeter of a 4" diameter part (or 6mm cutter at 100mm diameter), that's equivalent to about a 16-to-1 gear ratio so it could impart roughly 16x the torque of the mill into the 4th axis. Going through my 1-to-45 gearbox that's about 0.35x the mill's torque at the stepper motor shaft, so the stepper needs to provide about 1/3 the torque of the mill in order to resist slippage under these conditions. My mill has a 1 HP motor and turns the spindle at 1250 RPM in low range, which (pulling up an online torque calculator here) should give a max torque of about 5.69 N-m. The stepper needs to provide 1/3 that much torque to resist slipping, so we'd need a stepper motor with 1.9 N-m holding torque rating. As it happens that is exactly the max holding torque rating of my stepper motor, and it is pure coincidence that it worked out that way just now because I didn't do this calculation ahead of time and I just picked arbitrary numbers for the part and cutter diameters in this example. I chose 1.9 N-m steppers for a much simpler reason - it's the size that my CNC router uses and I wanted to have similar motors on all the axes. The holding torque is not the whole story though, because stepper torque drops off as the speed increases. You can find torque curves for specific stepper motors, and for mine it typically drops by about 50% at 1000 RPM. So while my stepper should be able to resist the torque of a heavy cut under conditions described above when it's stationary, it would be prone to losing steps if such a heavy cut were taken with the axis rotating moderately fast. I wouldn't worry about it at all for things like engraving, but for roughing especially I will make sure to take relatively light cuts.
@BrainRight WOW! thank you so much for the wonderful / detailed response I really appreciate it! It gives me a direction to go as far as research / picking a motor! I'll let you know what i come up with, I have a pretty cool harmonic Rotary / indexer build in the works! Thanks again - Nick
Slightly tangential, but on the Fusion 360 channel is a video from Pier 9 of some exotic tool that measures load and I assume torque on the tool as the tool is running. (Probably costs more than all my tools combined.)
My gearbox is made by the Harmonic Drive company, which is well-known for its strain-wave gearboxes so the name is often used synonymously, but this particular model uses a low-backlash planetary gear train. I got mine on eBay, where you might be able to find one for $100 or so.
For machining the aluminum adapter plate I used a 6.35mm/0.25" diameter 2-flute spiral carbide end mill in a router at approximately 20,000 RPM. The cutting feed rate was 600 mm/min, max horizontal stepover was 3mm and max vertical stepdown was 0.5mm. These parameters may be far from optimal due to my limited experience cutting aluminum on this machine, but they gave satisfactory results and in general it requires very light cuts to minimize cutting forces that will deflect the cutter due to the limited rigidity of the machine.
I'm sorry but I do not sell these, or anything else for that matter. This is just a personal project that I published for others to learn from. There are some commercially available 4th axis units that may be similar but I don't know what is available in Brazil.
I do own the same plc controller. I am trying to collect all the people that have this plc (ddcsv1.1) to a facebook group called ddcsv1.1 plc controller. search for it.
I like it very much that you explain your thoughts and reasoning. This is so much more valuable than just showing the build process.
I would've never imagined I'd encounter mechanical engineer Bob Ross.
Bob: There are no mistakes, only happy little accidents.
Me: Bob, you ever been in a machine shop?
Harmonic Drive's design on HPG, HPGP & HPF Series allows the internal gear to elastically deform, accommodating the operational stresses that might otherwise lead to increased backlash. This elastic deformation is specifically intended to maintain consistent backlash levels, compensating for the wear and tear that might typically lead to increased backlash in a traditional gear system.
HPG-20A-45 Permissible Radial Load 1,890 N, Permissible Axial Load 2,830 N.
Great video. The effort you put into framing the shots and capturing clear audio really shows. Not something you see very often in young RUclips channels.
Maybe consider doing a quick shop tour video some time. It's always interesting to see other hobbyists setups.
Keep it up!
Glad you liked it. I will do a shop tour video eventually, but at the moment my shop is in chaos as I'm rearranging tools and installing compressed air lines. Some people might find it more interesting this way, but I'll wait until things are a little less chaotic.
Great minds think alike!
I wish I saw this video earlier. But we basically did the same thing. I have a Chinese mill and I did this gear reduction for both A and B axis.
You can see in my A axis upgrade video that I had to machine down the OEM mounts too.
sounds interesting. I'll be checking out your channel.
you machining styles are wild.
Before watching the 2nd episode to this and you explain it in there; if you were wanting to mount something larger in the 3 jaw chuck, yet keep it mounted close to the table, you could invert the jaws.
Fantastic build. Thanks for the detail info!
Its all over my head but still like watching your video thks
There's nothing wrong with enjoying projects vicariously; I do it all the time.
To be fair, it's a simple planetary gear reducer, it has nothing in common with harmonic drives . It's just a company that makes them is called Harmonic Drive LLC.
I love watching this types of videos, now I must finish my last year in college and start doing my DIY tech hobbies :D
Thanks for the brilliant rich video. It rarely happens that I don´t find a British or American video worth being praised. They are absolutely well done. Perfect explanations, perfect in all the audio-visual aspects. Just cool. Very entertaining. Great show.
Perfect to learn English engineering terminology. From Berlin: Happy New Year.
Thank you for the video. I'm making one my self after your Idea.
BTW, this actually is planetary gear with super small backlash. I looked up the data sheet 😉.
What is misleading is the company name "Harmonic Drive"
Glad you found it useful. Yes the company name has sort-of become synonymous with a strain-wave gearbox, which they also make, but this one is planetary.
That’s probably the smallest harmonic drive id consider using. The 32’s seem to be better suited for 4th axis work if you intend on doing any heavy cutting or metal work. For wood, plastic, I see no reason this wouldn’t work fantastic. Nice assemblyz
you are very technical person and I like your cnc controller a lot .I like to have one of that .
Very nice job on those face plates! Looks like I am going to have to build a 4th axis now!
Congratulation my friend good work.
Thank you! Cheers!
Excellent and helpful for me
Amazing job and wonderful explanation of the process. Thank you!
no biggie. Any 9 year Old can do this.......
FWIW, the HPG series is a planetary gearbox not a harmonic drive, it is just made by Harmonic Drive Inc. I had one of the same series gearboxes and thought the same thing until I pilled the gearbox off the servo it was attached to.
Yes the Harmonic Drive web site has been updated since my initial research and they make the difference a bit more clear, i.e. it's not a strain-wave drive (commonly called "harmonic drive") but it does have continuous backlash compensation whatever that means. I plan to measure the backlash soon, so we'll see if this particular unit comes close to the manufacturer's specs.
We've found these to be one of the best gearhead mfg's on the market in their class. The backlash should be around 3 arc-min for the model you have unless it was abused. More that likely, you can expect a long life in your application.
Nice work! the unit used is a planetary reduction, not a strain wave gear, right? the brand is 'Harmonic Drive' but they have a few versions of the reducers, where the lower ratio planetary versions have a lower backlash than the (
Thanks for the brilliant video and excellent explanation. Don't you need a mechanism to avoid unwanted rotation during machining, for example a brake machanism. Also i want to know why would you use stepper motor instead of the servo ones.
Glad you found it useful. The stepper motor's holding torque is multiplied by the gear ratio of the gearbox, so the motor makes an effective brake provided that one doesn't try to cut too aggressively. A servo motor definitely has advantages but it adds cost and complexity, and the rest of my CNC machine uses steppers so it would not be a major advantage to have a servo just in the 4th axis. A servo may support greater acceleration and can be pushed harder since it doesn't suffer from lost steps, but I think steppers are a good choice for low-volume hobby work like mine where slowing things down is not a major disadvantage.
I think the HPG-drive you have is actually not a harmonic drive internally. (meaning the strain wave gear.)
I have one just like it and I believe the hpg is a planetary drive, but a really good one.
Made by Harmonic Drive company though. :)
I think you're right that it's not a strain-wave drive, which is often inaccurately called a "harmonic drive", but it's a Harmonic Drive brand planetary gearbox with "continuous backlash compensation". I see that the Harmonic Drive website has been updated recently and it's a bit more explicit about the difference now. It will be interesting to measure the actual backlash of this unit, which I plan to do soon.
Great job sir thanks 😊
Glad you liked it.
OMG! It's Bob Ross reincarnated! We are all saved!
Very nice work! For larger diameters the jaws in that chuck might be reversible.
Yes the jaws are reversible but I would also need to elevate the unit on a spacer so the protruding jaws clear the table.
I think you are AWESOME.
sub'd
Very impressive design, craftsmanship, and description! Off to part 2 :)
There's nothing impressive about it. you can get the exact same thing on EBAY for less than 200 For the WHOLE THING!!! (and free ship! to boot!)
This guy paid 200 bucks just for the Harmonic drive. plus motor, Chuck, chuck plate, adapter, etc etc. and all the LABOR.........Tsss
I rather Click twice on Ebay and get it, ready-make.....
(I made my own using using COG PULLEYS and BELT type. In fact I used to sell them on Ebay. they're too cheap now. NOT WORTH my time to mess with)
@@jesscast5122 try pricing it today....
Great vid, Dave Letterman guest spot at 7:16
thank you tecnology man
I really like your project and appreciate the delivery and production quality, you clearly have many talents. I'm reviving a small CNC mill at the moment and would like to add a 4th axis after getting the core functions working. I found the harmonic/planetary drive you're using and requested a quote, they came back with $905 each. Is that right?? I really like the idea of having a quality tool and the DIY path usually keeps the price down. Maybe I don't know what a good commercial tool costs?? Most of the commonly available items are around $500.
Great video! Subscribed
Good work 👏
Sorry I have to correct you - one info is misleading. HPG doesn't stand for High Precision although it could be. Instead it stands for Harmonic Planetary because this series of HD gears are not harmonic drives but really really high standard planetary gears with backlash below 5 arcmins. Its really good among the planetary gears. One of the best it can get with that transmission type.
The manufacturer's website harmonicdrive.net/ has changed quite a bit since I made this video, and they previously used the term "High Precision Gearbox" (they still have it in the HTML page title, maybe an oversight). It looks like that's been replaced by "Harmonic Planetary Gearbox" which is a more descriptive term and also trademarked. Honestly I'm not sure I would have chosen this gearbox if I had understood that it was planetary and not strain-wave but that distinction was a bit muddy on the Harmonic Drive website and documentation at the time. I plan to make a video measuring the actual backlash and torsional stiffness of my gearbox, but alas it hasn't made it to the top of my to-do list yet.
Ha ha! Well, rats. I just ordered one of these. I'll give it a go anyway. :-)
Excellent
Excellent work
Using the same 4th axis setup on my Shapeoko for mainly wood, but nothing harder than 7075, can you see any issues with milling the housing and plates from 6061 that will be heat treated afterward as opposed to steel? The only 'special' tools I have at my disposal are a Shapeoko 3 XXL and drill press so milling this much steel is a bit out of my reach.
You're awesome by the way, a real kick up my ass to try harder. Thank you for sharing.
Very cool CNC interfaced index. How is that indexed? Do you use a secondary program with the number of degrees you want to move and an M23 in the program to trigger the move, or does it use an "A" then the number of absolute degrees in the main program to index?
Nice job !!!
good work
Quite funny to notice different voices and different dialects. ;-)
I can hear the differences too so I know what you mean, but it's all my voice. Some of it is due to using different recording setups, and probably some due to allergy season starting here so my voice sounds different depending on the pollen level. No idea about different dialects but now I'll be thinking about it.
would you say using aluminium instead of steel for the faceplates would be fine?
Aluminum deforms more easily but it probably wouldn't make much difference, assuming that this axis would be subject to relatively low cutting forces.
Well done!
great~
Does this work with the post processor from your website?
Great explanation. I`m new to the robotics field.
I`m designing a 6-axis robot with harmonic drives.
I`m planning to implement the robot as a hand guiding for position teaching.
Since harmonic drives has high torque, is this possible to do with stepper motors? If someone has an idea about these things, please leave a comment.
It is certainly possible to make a robot using stepper motors and harmonic drives, but whether it will meet your requirements is another matter. A gearbox such as this has a high reduction ratio, meaning that it multiplies the torque but divides the speed. So with a modest stepper motor you can get a lot of torque but the output won't rotate very fast. And the torque of a stepper motor decreases as its speed increases (look up the torque curve of any motor you are considering) so there's a limit to how fast you can step it and still get enough torque for your application. Just off-hand (no pun intended) it sounds like you may not need much speed or torque so it may be suitable for you, and you can get *less* torque if desired for safety by reducing the motor drive current. You might want to look for stepper or servo motors with an integrated gearbox and if a stepper, a position encoder.
@@BrainRight Thank you for your quick response.
I`m considering steeper motor with absolute mechanical encoder.
But my problem is will I able to teach the position to robot arm using hand guide due to the high torque of the harmonic drives?
hi brainright , thanks for video , please to explain difference beetween harmonic drive and planetary gears , thanks
This is a great build. I’d love to know why you choose to use a 3 Jaw chuck instead of a 4 jaw?
Thanks. The main reason I used this chuck is that I already had it for use with my metal lathe, where the 3-jaw works well for round stock. I find it very useful to be able to move the chuck between machines while keeping the workpiece mounted. For square stock a 4-jaw chuck would be better and it would be easy to swap chucks if a need arises.
@@BrainRight I know it was a while ago, but any chance you have the model number of the Harmonic Drive you got? Or at least what you searched for?
When can we expect to see the 4th axis in use on the Shark?
I have a 4th axis from another CNC.
I never thought I could use it on the Shark.
I guess now that the speed is determined from the controlbos and the stepper motor doesnt really matter?
The shipping on the original 4th axis to Australia would be a killer.
Cheers
My next video is a project made using the 4th axis on the CNC Shark and it is in progress, should be ready soon.
You should be able to use most any 4th axis with most any controller as long as the stepper+driver are compatible. The original Shark controller is set to drive 2.8A steppers so don't use a stepper rated for much less current or it can damage the motor. A stepper rated for more current should be okay, but wouldn't put out its max torque.
The speed is determined by the pulses-per-degree (or pulses-per-mm) setting of that axis in the controller. With my DDCSV1.1 controller it's easy to set that on the settings page. The original Shark control panel lets you set it in a settings page, and offhand I don't recall the secret control key and password to bring it up but you can find that on the cncsharktalk forum.
What is the average backlash of a harmonic drive?
Hey there! I am making a robotic arm with 5kg payload capability. From my calculations (worst case scenario), I would need about 100Nm of torque and I had chosen Nema 23 (holding torque 1.9Nm) & harmonic drive gear from HDsystems which are the same as yours! However, I have a question as to what specification should one look for while looking for a harmonic drive? Is it just solely the reduction ratio?
That's the main thing but also check the maximum rated torque and the specified backlash, which causes angular positioning error. You can't get it to zero but it's typically very low for drives like this.
What is the maximum diameter workpiece can this drive and Chuck support?
dumb Q
Great!
Dear Friend, i would like to have your advice on milling machine. I'm about to buy one but i don't know what kind i need for my sign shop, I don't want to bay cheap that i will regret in next year and I don't very expensive one. i need one that will stay minimum 5 year doing things until i thing about expensive one (name and model)
Excellent, thank you, sorry this is a bit off topic but I'm really impressed with how you made this but especially on the adapter plate, how do you transfer the location of the holes from the motor and the chuck assembly AND still keep it all in alignment? Is it just measuring with calipers or using transfer paper, could you please make a video on how you marked it out? I'm new to machining, got a little mill and lathe and am trying to pick up as much information as I can from watching great videos like these but I know I'm missing some basic techniques to build on! I've built a furnace and am making some castings in aluminium and brass, and when the mounting holes are on the top I can transfer punch through a location hole to the drill out but when the part is 'facing' (sorry I can't describe this any better) the holes are then covered so I cannot see where to mark. Hope that made sense? Any help appreciated, thanks
I used the drawings of the motor output flange and the chuck mounting from the manufacturers to get the hole spacing, and I also double checked them with calipers. Just using calipers would be good enough because these holes don't have to be super-precise. The lathe-turned and 4th-axis-turned shoulders on the plate are what keep the parts concentric, and the bolts just keep them together so it's desirable to have a little extra clearance on the bolt holes. If they're off by a little bit it won't matter as long as the bolts don't bind.
You could make the holes any number of different ways but I used trigonometry to calculate the X and Y offsets of the holes, multiplying the radius times the sin() and cos() of the angle for each hole. Then I zeroed out the dials on my mill at the center of the plate, drilled a reference hole there for later alignment, and cranked the table the required distances in X and Y in order to drill all the holes in the proper locations. It would be much easier with a DRO or better yet a rotary table but this is the old school way and works fine. As a sanity check, I first laid out all the hole locations physically using dividers and a protractor, so that I could easily see any gross error in my calculations and table-cranking. You could do it all that way, scribing layout lines with dividers and such, and it would be close enough for this if you're careful. Worst case, if a bolt ends up binding then you could just enlarge its hole a little because the bolts only hold things together and don't maintain the parts' concentricity.
When I made the back plate to mount the 3-jaw chuck to my lathe, after turning it to size I used a simple transfer punch (off the lathe!) to transfer the chuck mounting holes onto the back plate. That would also have worked in this case but it was easier to do it on the mill. As you observed, that wouldn't work for the blind holes on the output flange of the harmonic drive. There are blind transfer pins that would work, and you could make your own, but I think it would be easier to use X-Y coordinates on the mill or to scribe layout lines with dividers.
BrainRight Thank you so much for your reply, very clear, shame you mentioned using math though, ( ha ha) I've not had to use it like that since school, a long time ago! 😪. It may sound daft to you or others but I did not know the expression 'blind hole' but now that makes perfect sense. I like the idea of making various size transfer pins to help with that. Really appreciated your video and reply! Cheers
In my next video, about making a faceplate, I show 3 different ways of laying out the hole locations including the trigonometry to calculate the X and Y offsets.
BrainRight Your a gentleman! Thank you! I'm done in after spending all day packing up my little workshop, ready for a house move and that's just put a smile on my face 😀. Cheers
wow.
Muito bom
Prices only
Hi Brainright,
Very nice videos and good workmanship. I am planning to use the same controller for a router project. I don't like Mach3 because of it's crashes and stuff here and there. This tiny little controller is powerful enough i guess. Seems stable too. BTW did you experience any crashes/hangs/bugs while using it? And another question is, "How did you manage the tool wear/offset at 11:14?
I guess you would have taken the usb out and redone the Gcode. I will be happy to know if the controller can handle tool offsets/tool wear compensation.
Eagerly waiting for your reply.
Again , Nice work.
Cheers.
Jas
Thanks Jas. So far the controller seems stable and hasn't crashed but the most I have pushed it is in the micrometer dial project I did, and that was not really stressing it in terms of program size or driving all 4 axes at once. The controller does not support cutter compensation, so you're exactly right that I had to modify the toolpath and regenerate the gcode in order to compensate for tool wear or deflection. I don't find that a major inconvenience because I mostly do one-off projects and I usually have to tweak the toolpaths multiple times anyway. It would be a more significant limitation in a production environment, and especially in cases where cutters have been resharpened. So far all my end mills are relatively new and very close to nominal size, but their sizes will be more variable once I have set up a system for sharpening them.
I think most of the offsets I see are due to deflection because the CNC Shark router's gantry is not very rigid, as it was designed mainly for woodworking. You can see some of that at the end of the micrometer dial video, where I think deflection caused the slight asymmetry visible at the top of the index marks. I could beef up parts of the router to make it more rigid, which I've already done to a degree, but I think the effort will be better spent doing a CNC conversion on my milling machine.
Cheers,
Jay
ahh, good to know that i am right about few things in the world.
Another question- Is there a Gcode limit on it? like maximum number of lines etc?
Also if you can share a list of g/m codes supported, i will be thankful. I have found a pdf manual but i don't know if it is written by the manufacturer or by some reseller.
Thanks a lot for your reply.
Good luck for your future projects.
regards,
Jas
There's no limit on G-code lines as far as I can tell. It reads the code from the USB stick as it is running. On my web page at brainright.com/Projects/CNCController/ I put a copy of the PDF manual, which may or may not be the one you already have, and it has a list of all the G-codes that are supported.
Hello again mate,
I have just bought this controller and it looks fairly easy to setup and operate, but i am afraid if there are still major bugs in the firmware. Something suspicious happened on the very first day when i was trying to configure the settings (I.e parameters). I started with just one axis (X). Did the steps calculation, figured out the direction high/low and everything on the x started working. I wired the home switch and it worked as configured with "5mm move back" after homing. But now it is going crazy. While homing, it moves the x axis towards the home switch and just when the home switch breaks (it is nc i guess), rather than going 5mm away from the switch, it goes into the same direction as the switch, hitting the mechanical limits (missing the steps). I have tried changing the "x axis back distance after homing parameter-83" to a negative 5mm (-5mm) but it doesn't allow the + sign to be changed in the parameter. Any guess about what's happening? If i set the back distance to 0, homing works perfectly fine. I am worried why a thing will work one day and won't work the other day? I have played with the settings for a long time but no luck. The biggest worry is that the controller also shows the "-5mm value" in the machine coordinates after homing. So it is the controller driving the axis across the home switch. It is not that the direction pin is not working. It is something else in the parameters or a bug in the firmware.
Also please let me know if you know a way to hard reset this controller or delete the settings file in the hard memory it has.
The chinese website they have up is in chinese, and guess i need to find a chinese friend if i need to use help from the official website. :D
Thanks.
Hi Jas, I have not used the home functionality but according to the manual (picture 2.19) the home and limit switches should be normally open, not normally closed. That might be the problem. I would recommend wiring up the limit switches too, so that it stops before reaching the mechanical limits and that way it should not lose steps even if the home function fails to work as it should.
I expect that you could reset the controller by upgrading firmware. I think it is also possible to delete the settings file using the file management page. I would copy it first, using the copy/paste operations in the file management page, pasting it onto a thumb drive so you have a backup of it. Then if you delete the settings file and restart, I would expect it to reset to all defaults and create a new settings file. Warning, I have not personally tried this so I cannot guarantee that it will work, but that's what I would try first I wanted to reset everything. I think you can also create multiple settings files, and just load the one you want using the file management page. Again, I have not tried it yet but I plan to do that when I move the controller among multiple machines.
Regards, Jay
I would like to buy a 3rd party 4th axis do you have the wiring diagram for the 4th axis shark Controller card?
No, sorry I never used my 4th axis with the original Shark controller and never had the 4th axis card for it.
COOL
In response to my faceplate video (ruclips.net/video/XvSZ1PYEcmY/видео.html) I received this question from Nicholas Miller, which I am reposting here: _Have you had any problems with lack of holding power using the nema 23 and planetary reducer. I purchased one and am now at the stage of buying a stepper, curious if you have any insight.... thanks - Nick_
The needed holding torque of a 4th axis depends a lot on what you want to do with it, i.e. how much torque is likely to be applied. Light cuts with a small tool and a small radius from the axis (such as my micrometer dial engraving, ruclips.net/video/3g9IFnVDOTo/видео.html) would impart far less torque than heavy roughing cuts at a large radius from the axis (such as rounding the edges of the backplate as I showed in the 4th axis build part 2). It also depends on the consequences of slippage, e.g. lathe-like cutting operations might not suffer at all from some slippage, and it's quite possible that some slippage or lost steps occurred as I was rounding the backplate edge but it would have gone unnoticed.
I don't know how to calculate the exact torque imparted by a particular end mill when it's cutting at a particular rate, but as a simple worst-case calculation we could suppose that it digs in to the part and engages like a gear. With a 1/4" cutter at the perimeter of a 4" diameter part (or 6mm cutter at 100mm diameter), that's equivalent to about a 16-to-1 gear ratio so it could impart roughly 16x the torque of the mill into the 4th axis. Going through my 1-to-45 gearbox that's about 0.35x the mill's torque at the stepper motor shaft, so the stepper needs to provide about 1/3 the torque of the mill in order to resist slippage under these conditions. My mill has a 1 HP motor and turns the spindle at 1250 RPM in low range, which (pulling up an online torque calculator here) should give a max torque of about 5.69 N-m. The stepper needs to provide 1/3 that much torque to resist slipping, so we'd need a stepper motor with 1.9 N-m holding torque rating. As it happens that is exactly the max holding torque rating of my stepper motor, and it is pure coincidence that it worked out that way just now because I didn't do this calculation ahead of time and I just picked arbitrary numbers for the part and cutter diameters in this example. I chose 1.9 N-m steppers for a much simpler reason - it's the size that my CNC router uses and I wanted to have similar motors on all the axes.
The holding torque is not the whole story though, because stepper torque drops off as the speed increases. You can find torque curves for specific stepper motors, and for mine it typically drops by about 50% at 1000 RPM. So while my stepper should be able to resist the torque of a heavy cut under conditions described above when it's stationary, it would be prone to losing steps if such a heavy cut were taken with the axis rotating moderately fast. I wouldn't worry about it at all for things like engraving, but for roughing especially I will make sure to take relatively light cuts.
@BrainRight WOW! thank you so much for the wonderful / detailed response I really appreciate it! It gives me a direction to go as far as research / picking a motor! I'll let you know what i come up with, I have a pretty cool harmonic Rotary / indexer build in the works! Thanks again - Nick
Slightly tangential, but on the Fusion 360 channel is a video from Pier 9 of some exotic tool that measures load and I assume torque on the tool as the tool is running. (Probably costs more than all my tools combined.)
Planetary gear or harmonic drive?
How can I buy it, how expensive
My gearbox is made by the Harmonic Drive company, which is well-known for its strain-wave gearboxes so the name is often used synonymously, but this particular model uses a low-backlash planetary gear train. I got mine on eBay, where you might be able to find one for $100 or so.
@@BrainRight that's nice I already designed 70% of my cnc. 1m*1m*1,5m.
I found some Harmonic drive units.
hippie genius
Nice job I like
greaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaat
Hi Sir. Good work.
Can you tell me what feed rate, DOC, tool diameter, nº of flutes and RPM are you using in mim. 11:07?
Thanks.
For machining the aluminum adapter plate I used a 6.35mm/0.25" diameter 2-flute spiral carbide end mill in a router at approximately 20,000 RPM. The cutting feed rate was 600 mm/min, max horizontal stepover was 3mm and max vertical stepdown was 0.5mm. These parameters may be far from optimal due to my limited experience cutting aluminum on this machine, but they gave satisfactory results and in general it requires very light cuts to minimize cutting forces that will deflect the cutter due to the limited rigidity of the machine.
thanks
OLÁ BOM DIA MUITO LEGAL ESTA OPÇÃO DO EIXO GOSTARIA DE SABER O PREÇO PARA VOCE ENVIAR PARA O BRASIL ABRAÇOS
I'm sorry but I do not sell these, or anything else for that matter. This is just a personal project that I published for others to learn from. There are some commercially available 4th axis units that may be similar but I don't know what is available in Brazil.
OK OBRIGADO POR SUA ATENÇÃO CURTO SEUS PROJETOS ABRAÇOS DE RICARDO
I do own the same plc controller. I am trying to collect all the people that have this plc (ddcsv1.1) to a facebook group called ddcsv1.1 plc controller. search for it.
your hair is not real. haha