On Thursday 28 January 2021 16:05:05 John Dammeyer wrote: > Hi Gene, > I understand that. But I also know I bought the expensive and > theoretically high quality US Digital encoders 10 years ago for my DC > servos. Ultimately they were way to sensitive to noise and in fact US > Digital discontinued that line for that reason. So I have two useless > encoders. I replaced them with CUI and they work better. > > My point is what you see on EBAY and AliExpress are not all created > equal. The US Digital encoders appeared to work but eventually the > UHU Servo drive reported a difference in counts and a move to home was > off by a number of encoder edges. Enough to count to a few thousands > of an inch. > > The UHU CPU replacement from Sweden (Henrik Olsson) was a dsPIC and > had better encoder support. Even then it still had problems with the > US Digital. Not with the CUI. > > What I'm saying is that when you order an AC servo c/w drive you may > find that because they had the lowest price it was low because they > used the cheapest encoder. Or maybe the cable they supplied was lower > quality. Whether the product is from China, Japan, USA or Germany for > example, lower price doesn't equate to the same quality as higher > price. > > The best example so far for me was the stepperonline.com 6A driver > that had a 3.6kHz whine on two different stepper motors. Loud enough > to be a pain in the ear and cost with PRIME shipping from Amazon was > $80 Cdn. A unit from Bergerda with the same specifications and close > to the same look ended up with FedEx and Canadian taxes to be $82 > each. (I bought 2 for the two motors I had here). No whine. Ribs on > the heatsink were twice as high. A few extra features and a metal > cover rather than plastic which might even help with electrical noise > suppression. And a different size connector for the control signals > verses motor/power so no chance of accidentally plugging in the wrong > one. > > So though a lot of units look the same, unless you are buying a STMBL > with full source code and schematics and have control over everything > including the encoder on the motor the lowest cost unit isn't always > the best. > > I'd still rather buy a MESA board than some cheap clone from China for > example. Or if I needed something Jon Elson sold I'd buy from him > rather than lowest cost from China.
I hear that. Loud and clear although I can sometimes argue a bit. For starters both are right here and answers to any problems with their stuff are generally same day answers. You, I, nor Mastercard, simply cannot put a price on that. > John Dammeyer. > > > -----Original Message----- > > From: Gene Heskett [mailto:[email protected]] > > Sent: January-28-21 12:31 PM > > To: [email protected] > > Subject: Re: [Emc-users] Fanuc Servos? > > > > On Thursday 28 January 2021 12:09:00 John Dammeyer wrote: > > > Just be careful and ask the supplier what type of encoder is > > > mounted on the servo. There are encoders and there are encoders. > > > My http://en.bergerda.com/ servos use a Japanese brand which they > > > claim are better than some of the Chinese ones out there but are > > > also considerably more expensive. Differential output from the > > > encoder is a must have to reduce the effects of electrical noise. > > > > > > John > > > > True, but Omron makes differential encoders with up to 1024 ppr, for > > a $21 price on ebay. > > > > I have one with 1000 ppr on the rear of my GO704's spindle motor, > > turning faster by 3 or 4x than its rated for, currently driven by a > > piece of heat shrink tubing as the elastomer coupling has gone away > > two years ago. > > > > The diff signals are made single ended to drive a 5i25's inputs by a > > pair of rs-485 to ttl boards at nominally $2 each on ebay. I had to > > program them for 1 way traffic though. So my spindle scale is a bit > > over 7,000 in high gear, and a bit over 14,000 in low, and I can use > > PID_S.Pgains of 20 or more. > > > > To say my speed control is stiff is the understatement of the month, > > I only know the spindle load is high by the chirping iron in the > > motor at around 1.8x its nameplate 9.7 amps courtesy one of Jon's > > pwm-servo's set for around 17 amps. Up to that point, no change in > > the machines noise as a tap digs in. > > > > I get my spindles index from a screw silly glued to the side of the > > drawbar retaining cap by way of an ATS-667 watching it go by. > > > > > > -----Original Message----- > > > > From: andrew beck [mailto:[email protected]] > > > > Sent: January-28-21 1:14 AM > > > > To: Enhanced Machine Controller (EMC) > > > > Subject: Re: [Emc-users] Fanuc Servos? > > > > > > > > You can buy Chinese yaskawa copy ac servo drives 2.4kw for like > > > > 260usd. So it's just not worth it now. I just sold my fanic > > > > drives in the end. Its so nice to just bolt on some matched > > > > servo drives that just work out of the box. > > > > > > > > On Thu, 28 Jan 2021, 14:20 Jon Elson, <[email protected]> wrote: > > > > > On 01/27/2021 11:35 AM, Todd Zuercher wrote: > > > > > > How useable are Fanuc's servos and amps with Linuxcnc? My > > > > > > understanding > > > > > > > > > > is that it is very involved to try to force them to work with > > > > > anything other than a Fanuc control > > > > > I make converters for the two most common types of Fanuc > > > > > encoders used on brushless motors. > > > > > I also make a digital servo amp for them that can be used > > > > > with my PWM controller. > > > > > The older "red cap" motors had encoders with standard > > > > > quadrature plus index output, but the commutation signal was > > > > > proprietary. I have a board that converts the commutation > > > > > to industry-compatible "Hall" signals. > > > > > > > > > > The newer type is serial, but my converter produces > > > > > industry-compatible quadrature plus index, plus the "Hall" > > > > > signals. Note there are absolute and incremental versions of > > > > > these encoders. > > > > > The problem with the incremental versions, like (alpha)I64, > > > > > is that they are lost when power is applied, so they need > > > > > you to crank the motor past the index location by hand after > > > > > every power on, before commutation is available. So, these > > > > > encoders need power-off brakes and battery backup if the > > > > > control is ever turned off. > > > > > The absolute version have additional low-res data tracks > > > > > that allow the encoder to know the angle immediately at > > > > > power-on, so no battery is needed to have commutation > > > > > immediately on power on. > > > > > > > > > > Now, the Fanuc servo amps are more difficult, as about 1984 > > > > > they stopped releasing any documentation on their > > > > > electronics. So, it is essentially impossible to find any > > > > > schematics or connection info for their amps. Most of the > > > > > brushless amps take SIX PWM signals per axis, so > > > > > the controller sends separate PWM to EACH transistor. This > > > > > moves all the smarts to the controller, but it complicates > > > > > things a bit. > > > > > > > > > > Jon > > > > > > > > > > > > > > > _______________________________________________ > > > > > Emc-users mailing list > > > > > [email protected] > > > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > _______________________________________________ > > > > Emc-users mailing list > > > > [email protected] > > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > _______________________________________________ > > > Emc-users mailing list > > > [email protected] > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > Cheers, Gene Heskett > > -- > > "There are four boxes to be used in defense of liberty: > > soap, ballot, jury, and ammo. Please use in that order." > > -Ed Howdershelt (Author) > > If we desire respect for the law, we must first make the law > > respectable. - Louis D. Brandeis > > Genes Web page <http://geneslinuxbox.net:6309/gene> > > > > > > _______________________________________________ > > Emc-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
