One interesting and fun option is to make your own cycloidical reduction. These are completely buildable on a CNC mill that can do 2 1/2 D machining on mild steel. Unlike most other gears, these can be cut from plate stock with just an end mill. THey can be 3D printed too.
See the wiki link below. In a real system, the purple and grey parts are made from sealed bearing units and you'd have two moving plates stacked 180 degrees out of phase so as to counterbalance each other. But the good points are (1) high torque, (2) very low backlash, (3) compact size, (4) very simple 2D geometry https://en.wikipedia.org/wiki/Cycloidal_drive There are 100 Youtube videos about people making these with 3D printers but they work better with metal. These have become popular with people building robot arms and robot legs but could also be driven with a servo motor and used as a rotational axis for a machine tool. In a machine tool application, you would place a rotational sensor on the axis and close the servo loop inside the controller. A cycloidal system can be back-driven (just like spur gears or timing belts) so they MUST be used in a closed-loop On Sat, May 16, 2020 at 10:45 AM John Dammeyer <jo...@autoartisans.com> wrote: > I agree with Lester. Searching for that description on the www.ebay.ca > eventually does bring up that particular supplier along with about 10 > others. All located in either China or Korea. Most of the motors are more > in the $800 range. It almost looks like various companies are all > sourcing the same images. > > Mine came through EBAY from the USA. And IIRC, was about $400 US. Not > only that the supplier provided drawings of how they had it connected to > their conveyor system. And the manufacturer supplied a few scanned > documents of the now discontinued B series. > > I've been bitten once by what I thought was a supplier in Italy that > suddenly had a UK company doing the shipping that ultimately shipped > something totally different from China. It took six months with carefully > documented emails with the Chinese company to get Mastercard to finally > issue a refund. The moment the refund came through the email address with > the Chinese con artist company vanished as not available. > > It started with our shipping company sent the wrong part. > Poor us, we had to pay shipping so perhaps we can refund 40% and you keep > the goods? > Poor us, perhaps 50%? > If you ship it back then when we receive it we can refund 80%. > When I asked for a name and phone number because Canada Post needs that > for tracking the replies became more interesting. > The address for return was incomplete and google maps showed it in the > middle of some sort of residence building in China. > > At that point the email records were complete enough that Mastercard was > able to reverse the charges but with a warning that it could be contested > for another 3 or 4 months. That expired a couple of months ago with > nothing else from the supplier. > > The point is. If you get taken be vigilant. Keep records. Don't be > nasty. And don't give up. They rely on you either being rude or just > taking your losses. > > John > > > > > -----Original Message----- > > From: Lester Caine [mailto:les...@lsces.uk] > > Sent: May-16-20 1:23 AM > > To: emc-users@lists.sourceforge.net > > Subject: Re: [Emc-users] Cheaper than normal FHA-25B > > > > On 15/05/2020 13:08, andy pugh wrote: > > > I have no connection with the vendor, if you order one and receive > > > dolls-house furniture instead don't blame me. > > > > As with many of these sellers it is questionable at times just what they > > do actually have and where the product IS actually located. This one > > does say shipping from China so why then is there a 'UK LocaL Warehouse' > > in big text, and is the "Our opening times are 08:00 - 17:00 Monday - > > Friday." UK time or Chinese time? They also obviously have no idea what > > they are selling, so no indication where it has been salvaged from or > > how old it's likely to be? > > > > When you see a nice 'UK Stock' flash actually on the images but the > > sellers details are in Chinese, it's a good indication of someone > > pulling the wool, but they are slipping up these days as they forget to > > fiddle the 'located' entry and THAT says China ... > > > > I'm trying to pick up a couple of bits currently to finish off a radio > > control car and hitting this problem. The parts ordered from a 'UK > > Stockist with Royal Mail Delivery' in early April are still waiting for > > tracking to update from a Chinese tracking number to the 'Royal Mail' > > one but at least ebay took one look at the tracking number and refunded > > me straight away saying 'the tracking number is invalid'. Problem now is > > finding someone who has the parts in the UK ... > > > > -- > > Lester Caine - G8HFL > > ----------------------------- > > Contact - https://lsces.uk/wiki/Contact > > L.S.Caine Electronic Services - https://lsces.uk > > Model Engineers Digital Workshop - https://medw.uk > > Rainbow Digital Media - https://rainbowdigitalmedia.uk > > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
