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- CAD-CAM-EDM-DRO
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Re: DRO
Joe Landau
Art,
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I am starting to build a DRO for my mill--have bought motors and encoders from Goldmine, and am planning the setup. I'm curious how your wire loop worked out, --what path did you use, and what kind of wire. I remember reading that Steve was worried about slippage. Have you experienced any, and how have you prevented it? Intuitively, I'd think a steel wire on a very small steel shaft could slip very easily. --Joe Landau "A. G. Eckstein" wrote:
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---------------------------------------------------------- Joe Landau jrl@... VersaForm Systems Corp. (408) 370 2662 591 W. Hamilton Ave., # 201 Campbell, CA 95008 Excellence in Medical Software www.versaform.com |
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(No subject)
Joel wrote:
I'm working on a chopper drive for the motors. I have a prototype up andI'm sure I'm not the only one who'd be interested in hearing what you chose for a drive circuit, if you'd be willing to briefly describe it. Chris -- Christopher C. Stratton, stratton@... Instrument Maker, Horn Player & Engineer 30 Griswold Street, Cambridge, MA 02138 (617) 492-3358 home/shop |
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Re: CAD Question
hansw
Bill,
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Could you please un-subscribe me from the list. I'll be back late in the year. I don't want people to think I don't appreciate the list; I do, but just can't afford the time at the moment. Thanks Best Regards Hans Wedemeyer WAnliker@... wrote: From: WAnliker@... |
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Re: Interface update
Harrison, Doug
As a consulting engineer, I'm above actually doing any real work;) And my
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wife, an electronics tech who does all my circuit board work, gets $32 an hour. The boards could be offered assembled and tested if one wishes to pay for it. $32/hr for an experienced board builder might be a good deal for some. -----Original Message----- |
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(No subject)
Joel Jacobs
Greetings.
I've been on this list for a couple weeks now and thought I should give an intro. First, I gotta say this list is really exiting - I can't believe how much 'good stuff' has come through in the short time I've been on. I'm working on a CNC mill project. It's one of those Taiwanese mill/drill's. I have 300 oz/in steppers mounted and geared 2:1 to the ACME screws via tooth belts. I think I'll need to do some work to reduce friction, I'll probly need to install ball screws. Has anyone ever tried Teflon bearing engine oil additives i.e. 'slick 50' for lubricating the slides? I'm working on a chopper drive for the motors. I have a prototype up and running. So far I've got the current up to 3 amps/phase. With two phases energized it's drawing less than 500ma from my 40 volt supply. It's designed to go up to 5 amps but I'm stopped here till I get some instability issues worked out. It seems to have some problems at certain motor speeds - I believe it's caused by the physical resonance of the motor armature. I have an eval copy of cncpro I'm using to get things running. The EMC stuff looks real good too though. I installed Linux on a computer to play with - not sure what to think about it yet - still trying to get the RT kernel installed. Joel Jacobs (Central Ohio USA) |
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Re: Interface update
Jon Elson
"Harrison, Doug" wrote:
From: "Harrison, Doug" <dharrison@...>I have a design for a bus interface adaptor that I have used with a number of different instruments. It is designed to communicate with up to 256 instrument 'modules' with up to 256 registers in each module. It uses a 26-pin rippon cable interface. The design for the adaptor was made for the original PC parallel port, so it can only read back 4 bits at a time through the control bits. I have made PC boards for this. With all the pull-up resistors, it draws a bit of power, and is powered by a 'wall-wart' power supply, and a 7805-type regulator. If people want to use this design, I could make it available, and/or have a run of PC boards made, for a group project. I have a sort-of driver program written in Turbo Pascal for DOS/Windows. I don't have anything currently for Linux. Jon |
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Re: Interface update
Harrison, Doug
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-----Original Message-----Most, but not all step motor drivers have optoisolated inputs. It's those exceptions that I want to accomodate here. The auxillary outputs, 3 in all so far (CNCPro at least) go throughI though CNCPro had 4 aux outputs. Also, the homing inputs are hooked up to IR switches with their ownIt would also be nice to have the ability to use 120VAC for the homing inputs. I know this sounds strange, however, some of my industrial applications require long wiring runs that would be succeptable to noise if 5V were used. Here again, I'm talking about an option made available by careful design of the PCB. Populate as needed. Are you sure you need optoisolation on the board too? I can add themAgain, these would be a populate as needed option. Possible enhancements: On board 5V power supply(otherwise supply externalAgreement. About using the parrallel port for drive LED's....you should sink them ofAlso agreed. This newsgroup is made up of enthusiastic, knowledgable people. We share a personal interest in what we do. However, I have industrial applications for this board. Industry is heavily populated with disgruntled workers that seem to enjoy trashing things. Having built test equipment for production workers I can tell you that idiot-proofing (they call it industrial hardening) is an absolute must. I see an all-in-one wonder board with lots of holes in it. Some of us want optos. Some want on-board power. Etc - etc. Let's design a PCB layout that will provide all of this in any combination the builder desires. More of us would build things if we didn't have to fiddle around with all those darn wires. I'll put up the money for the boards and parts because I have industrial applications for it outside of CNC. Then if anyone on this list wants one I will pass it on at my cost. Sound fair? Doug |
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Re: Ballscrew bearings
Jon Elson
stratton@... wrote:
From: stratton@...This is the best, but use it only at ONE end of the screw. Use a simple ball bearing at the other end to prevent vibration of the free end. On short screws, there is no need for that, either. But, you don't want to constrain the screw between two sets of angular contact bearings, as it would either bow the screw, or whatever the screw is attached to. You put the bearings into a block with a shoulder in between the bearings. Then, you have a collar that squeezes the inner races together, providing whatever level of preload you need to remove backlash. I used this approach in the Z axis on my mill, and it has been working very well. A normal ball bearing and a needle thrust bearingYou'd really need two thrust bearings, and they are not the best for this application. A tapered roller bearing (if I can find one with a 1/2" bore)These are generally not available in small sizes, although some do exist. In the smaller thrust ranges, angular contact bearings provide much better performance (ie. less drag). Jon |
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Re: Stepper Drivers
Jon Elson
Ian Wright wrote:
Oh, now we're really going off the deep end. We were talking about aPS -anyone know a cheap source of big transformers?Try a scrapyard and look for old industrial welders. suitable transformer for some 24 W stepper motors. Yes, if you use a 5 KVA transformer, you will have no trouble providing 75 Watts to 3 motors, and you will also prevent thieves, tornados and tsunamis from stealing/blowing/washing away your CNC control! Jon |
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Re: Stepper Drivers
Oh, now we're really going off the deep end. We were talking about aI'm not sure they are 24 watt motors. They may be rated to dissipate 24 watts as heat, but how much electrical energy can they convert to mechanical energy? I suspect more than that. Chris -- Christopher C. Stratton, stratton@... Instrument Maker, Horn Player & Engineer 30 Griswold Street, Cambridge, MA 02138 (617) 492-3358 home/shop |
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Re: Old CNC controls
D.F.S.
Boy, that is quite a range, I didn't know that much was of a change was possible. Thanks. I'm going to look at going that route with my lathe. Marc |
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List problems
Onelist is experiencing some problems for the last few days, I have had
problems reaching the list at there URL. they are aware of the problems and hopefull they will soon be repaired, and then I will repair any of the list links that do not work. In the meantime send me mail if you require changes in your list membership. There are 430 members tonight. bill List Manager |
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Re: CAD Question
In a message dated 2/23/00 8:12:47 PM Mountain Standard Time, hansw@...
writes: << Could you please un-subscribe me from the list. I'll be back late in the year. I don't want people to think I don't appreciate the list; I do, but just can't afford the time at the moment. >> It was with sorrow that I unsubscribed you. I have appreciated your input to the list, and look forward to seeing you come back on. Onelist is making changes and until they get it all straightened out, I can't straighten out any problems. I have not been able to sign on a couple of times, and got the same, no group comment, this is why I had a couple of tests last week. Looking forward to having you back in the future. Bill |
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Re: Quiet spindle motor?
Craig C Chamberlin
You can buy the current Sherline motor and control box separately...Price is $US150-175. It is very quiet.
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Craig [I was wondering if anybody knew where I could get a 1/10 hp AC-DC |
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Re: Interface update
Dean Sala
Doug,
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It's real great that you are trying to resolve this problem. I completely agree that we need some sort of breakout box that could get us up to speed faster. With an on board 5vPS, relays, screw in terminals and such. It just so happens that I have already designed a proto type of this board to work with CNCpro. Except that it does not use optoisolation on the board. I already have optoisolation on board my step drivers. The proto type plugs into the parrallel port via cable. It has it's own DB25 connector on one side and has a series of screw terminals on the other. It consists of a SN74S244 hex schmit trigger driver to drive the step and direction data (3 or 4 axis or whatever)into the Step motor drivers. The auxillary outputs, 3 in all so far (CNCPro at least) go through ULN2003a's (that can be parralleled for more current) to drive 1amp 5v relays. Also, the homing inputs are hooked up to IR switches with their own terminal block. The other inputs are just tied high through 4.7ks. I am still working on the design and am thinking about making it more universal for other parrallel port NC programs that aren't as configurable as CNCpro. But first I'm keeping it simple. I'm sorry for not getting ideas from you guys but now I have a feeling what you want. Are you sure you need optoisolation on the board too? I can add them right to the output of the SN74S244 but then the opto isolators would be driving opto isolators. Maybe I can put a switch selector to bypass opto isolation if the step drivers have them. Possible enhancements: On board 5V power supply(otherwise supply external 5v PS). Connectors to connect 120v to stepper power supply with fuses etc. Diagnostic LEDs connected to various outputs. Connectors for main power switch and power light. Oh, limit switch connectors tied to turn off stepper PS. There you have it! All-in-one wonder board! About using the parrallel port for drive LED's....you should sink them of course but it's always better to put a buffer inline like an S series TTL driver which can source 28ma and sink 64ma perfect for this situation, more noise resistant and just what their made for. This way you don't have to worry about how much power the parallel port can provide. Good luck Dean ----- Original Message -----
From: Harrison, Doug <dharrison@...> To: <CAD_CAM_EDM_DRO@...> Sent: Wednesday, February 23, 2000 9:31 AM Subject: RE: [CAD_CAM_EDM_DRO] Interface update From: "Harrison, Doug" <dharrison@...>reviews. Based on your opinions and some new revelations, I am now leaning toward aetc. A separate card would definitely be better here. Those of us who want toit does not limit us to a particular class of MB's.dirt cheap DC-DC isolators, which would eliminate the need for an external 5Vindustrial strength.encoder interface, on-board timer and 8255 I/O. This might be feasible if theboard went into a PC slot. Adding these to an external board would necessitatewith the machine. I believe other software uses this same approach. It is thefor, fewno myof them for my own applications. A little profit from the sale of such releaseddecision to do the design. At the very least, the plans could be toto public domain. thatfeed the 5V isolator. there.will give a good clean pulse at 100khz? Perhaps a good representative discussion of shop built systems in the above catagories.For the FAQ, go to------------------------------------------------------------------------ To Unsubscribe, read archives, change to or from digest. |
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Re: Quiet spindle motor?
[I was wondering if anybody knew where I could get a 1/10 hp AC-DCI've got a sherline with the older AC motor, that is also on the noisy side. Contributions seem to come from the fan, brushes, relatively low switching rate of the control, the fairly high RPM you find on these small machines, and the fact that they vibrate a lot more for a given imbalance than a heavy cast iron machine would. Could you just put it in a foam-lined plywood & plexiglass box with isolation feet (machine-box and maybe box-table)? Chris -- Christopher C. Stratton, stratton@... Instrument Maker, Horn Player & Engineer 30 Griswold Street, Cambridge, MA 02138 (617) 492-3358 home/shop |
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Re: Stepper Drivers
From: "Harrison, Doug" <dharrison@...>With optocouplers on the inputs and the box closed up it should work.Sometimes it gets tempting to just buy IRF640's rated for 200 voltsDepending on what kind of isolation your amps have, this might work But dangerous to work on - need a floating scope or an isolation transformer on the amp (a safer bet in general but back to the $$). Also the wires to the motors are then more dangerous - fine use 4-conductor line cord. But how about the insulation in the motors themselves - what is that good for? I suppose I could ground the lathe and design in a fuse that would blow if one of the windings shorted to the frame. It would be the way to squeeze every last inch per minute out of the steppers though! Chris -- Christopher C. Stratton, stratton@... Instrument Maker, Horn Player & Engineer 30 Griswold Street, Cambridge, MA 02138 (617) 492-3358 home/shop |
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