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G-code interpreter/stepper controller
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At 07:30 PM 11/5/02 -0000, you wrote:
The missing part is how to handle endswitches.Usually the endswitch contact disables motion in that direction but leaves the remaining direction and all other axes active. That way you can back it off and remediate. You may choose to include an alarm, to notify the operator of the condition. Regards, Hoyt McKagen To prevent virus propogation, don't put this addy in your book Belfab CNC - US Best MC - Camping/Caving - Two-Wheel-Tech List - Never trust a fat man |
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Hi everybody,
I am in the finishing/debugging stages of a 3 axis stepper controller/ G-Code interpreter. The missing part is how to handle endswitches. My assumption is that hitting an endswitch is a catastrophic failure, and it should never happen; therefore I was going to have the controller freeze all movements, signal the error (a big red LED) and let the operator shutdown the system, manually back off the tools, etc. and restart. I think that trying to have the tool be "smart" and back off the tool itself, etc. could possibly lead to damaging the machine and or part being machined. Does this make sense ? What is usually done, or expected in such a case ? Please let me know what you think is the best way to handle endswitches, and if you have experience with other systems or software, let me know how it is done. BTW, this system has the following features: - communicates with the host computer through a serial RS232 port (the host could be a palm pilot :-) ), use of hardware (RTS/CTS) flow control to ensure dataflow integrity. - embedded basic G-Code interpreter that supports linear and circular interpolation in all axis - extensible to up to 8 axis (through an extension board, to be designed) - automatically goes to low-current (holding) setting for a given axis if that axis has not been active for 100 milliseconds - active current control through integrated chipset, thus very little wasted power. Running and holding current are configurable through separate potentiometer, up to 3 amp per axis (although I have not tested this much power lacking the needed power supply...) - each axis can be configured as to what the positive or negative direction is (to accomodate for different machine configuration) - configurable "rapid transverse speed" (G00 code) - configuration settings are saved in permanent memory (eeprom) so they remain between shutdown/reset. - up to 10'000 steps per seconds (is this overkill ? my steppers stall after 900 steps/sec...) Currently supports unipolar steppers, in full-stepping mode. A bipolar stepper power board will come next. All feedback much appreciated, thank you. bruno |
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Luc Vercruysse
On most CNC machines there are 2 switches on each side of the axis. One is a
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limitswitch , the other one is a security switch. The limitswitch can be handled within software. Once a switch is hit, the motor decelerates and stops in a normal way (the same as you hit the stop button). The security switch disables all drivers and must be " hard wired ". very good specs. Is the system based on some microcontroller ? Is the interpreter running on the host computer ? Is software based on EMC ? Luc ----- Original Message -----
From: "bschwand" <bschwand@...> To: <CAD_CAM_EDM_DRO@...> Sent: Tuesday, November 05, 2002 8:30 PM Subject: [CAD_CAM_EDM_DRO] G-code interpreter/stepper controller Hi everybody,aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if you have trouble. sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........ bill |
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Hi,ok, but why the difference between the limit switch and the securityswitch ? if the limit switch is hit at one end of the axis, isn'tthat the same basically as hitting the security switch on the otherend ? Or is the limit switch actually used to reset the machineinitially only ?--- In CAD_CAM_EDM_DRO@y..., "Luc Vercruysse" <luc.vercruysse@p...>wrote:> On most CNC machines there are 2 switches on each side of the axis.One is a> limitswitch , the other one is a security switch.> The limitswitch can be handled within software. Once a switch ishit, > > very good specs. Is the system based on some microcontroller ? Istheyes, atmel avr at90s8535> interpreter running on the host computer ?no, on the microcontroller> Is software based on EMC ?no, completely written from scratch. EMC is much more sophisticated.My interpreter is quite limited, it only supports a very minimal setof G-codes, sufficient however to remove any hard real-timerequirements on the host. With this and a dallas semiconductors TINI,you could have a simple CNC or router, or multi-axis robotmanipulator on an ethernet network for a very low cost.brunobruno> Luc> > > > ----- Original Message -----> From: "bschwand" <bschwand@y...>> To: <CAD_CAM_EDM_DRO@y...>> Sent: Tuesday, November 05, 2002 8:30 PM> Subject: [CAD_CAM_EDM_DRO] G-code interpreter/stepper controller> > > > Hi everybody,> >> > I am in the finishing/debugging stages of a 3 axis steppercontroller/> > G-Code interpreter.> >> > The missing part is how to handle endswitches.> >> > My assumption is that hitting an endswitch is a catastrophicfailure,> > and it should never happen; therefore I was going to have the> > controller freeze all movements, signal the error (a big red LED)and> > let the operator shutdown the system, manually back off the tools,> > etc. and restart.> >> > I think that trying to have the tool be "smart" and back off thetool> > itself, etc. could possibly lead to damaging the machine and orpart> > being machined.> >> > Does this make sense ? What is usually done, or expected in such a> > case ?> >> > Please let me know what you think is the best way to handle> > endswitches, and if you have experience with other systems or> > software, let me know how it is done.> >> > BTW, this system has the following features:> >> > - communicates with the host computer through a serial RS232 port> > (the host could be a palm pilot :-) ), use of hardware (RTS/CTS)> > flow control to ensure dataflow integrity.> > - embedded basic G-Code interpreter that supports linear and> > circular interpolation in all axis> > - extensible to up to 8 axis (through an extension board, to be> > designed)> > - automatically goes to low-current (holding) setting for a givenaxis> > if that axis has not been active for 100 milliseconds> > - active current control through integrated chipset, thus verylittle> > wasted power. Running and holding current are configurablethrough> > separate potentiometer, up to 3 amp per axis (although I havenot> > tested this much power lacking the needed power supply...)> > - each axis can be configured as to what the positive or negative> > direction is (to accomodate for different machine configuration)> > - configurable "rapid transverse speed" (G00 code)> > - configuration settings are saved in permanent memory (eeprom) so> > they remain between shutdown/reset.> > - up to 10'000 steps per seconds (is this overkill ? my steppersstall> > after 900 steps/sec...)> >> > Currently supports unipolar steppers, in full-stepping mode. Abipolar> > stepper power board will come next.> >> > All feedback much appreciated, thank you.> >> > bruno> >> >> > Addresses:> > FAQ: > > FILES: > > Post Messages: CAD_CAM_EDM_DRO@y...> >> > Subscribe: CAD_CAM_EDM_DRO-subscribe@y...> > Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@y...> > List owner: CAD_CAM_EDM_DRO-owner@y..., wanliker@a...> > Moderator: jmelson@a... timg@k... [Moderator]> > URL to this group: > >> > OFF Topic POSTS: General Machining> > If you wish to post on unlimited OT subjects goto:> aol://5863:126/rec.crafts.metalworking or go thru Google.com toreach it if> you have trouble.> > > >> > I consider thisto be a> sister site to the CCED group, as many of the same members arethere, for OT> subjects, that are not allowed on the CCED list.> >> > NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BYPOSTING THEM.> DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........> > bill> > List Mom> > List Owner> >> >> >> > Your use of Yahoo! Groups is subject to > >> >> >
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50'000 ?at 200 steps per turn that's 15'000 rpm ! do steppers capable of that rate exist ?I guess I'll have to scale some values here and there...thanks for the tipbruno--- In CAD_CAM_EDM_DRO@y..., Art <fenerty@h...> wrote:> Hi:> > Take it from me, really, if theres one thing I KNOW its that10,000 steps> a second will never be overkill. 25000 seems acceptable to most,but to> really please most, you'll need about 50,000.> ( Took me a long time to get that one down... :)> > Art> www.artofcnc.ca
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Dan Statman
Since most people run in half-step mode or microstep mode the stepper
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equates to 2000 steps per revolution in 10X microstepping mode. This is a much slower 1500 RPM. Since this is an upper bound it is rarely needed, but nice to be able to achieve. If you are running in full step mode you will have other problems long before your maximum speed is an issue. Generally resonance problems are greatest with fewer microsteps. Daniel J. Statman, Statman Designs www.statmandesigns.com dan.statman@... ----- Original Message -----
From: "bschwand" <bschwand@...> To: <CAD_CAM_EDM_DRO@...> Sent: Wednesday, November 06, 2002 12:26 AM Subject: [CAD_CAM_EDM_DRO] Re: G-code interpreter/stepper controller 50'000 ?at 200 steps per turn that's 15'000 rpm ! do steppers capable ofthat rate exist ?I guess I'll have to scale some values here and there...thanks for the tipbruno--- In CAD_CAM_EDM_DRO@y..., Art <fenerty@h...> wrote:> Hi:> > Take it from me, really, if theres one thing I KNOW its that10,000 steps> a second will never be overkill. 25000 seems acceptable to most,but to> really please most, you'll need about 50,000.> ( Took me a long time to get that one down... :)> > Art> www.artofcnc.ca aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if you have trouble. sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........ bill |
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Ok, I understand. I was only considering full step. I should probably
go to half step at least. I read a lot about the physics of stepper motors and the way to drive them, about the advantages of microstepping, etc. but I am designing a simple, versatile and affordable system (well... compared to $150 per channel for a gecko drive); so I decided to forego microstepping in favor of simplicity of design for now. It should already have some applications as is. Current tests are very encouraging, and I think that there is a use for a small, programmable and self-contained stepper controller. At least for my personal use :-) My design is modular, so I will make sure to develop a microstepping option next ! Thank you for your feedback, bruno PS: the rings you make are really cool. --- In CAD_CAM_EDM_DRO@y..., "Dan Statman" <dan.statman@r...> wrote: Since most people run in half-step mode or microstep mode thestepper equates to 2000 steps per revolution in 10X microstepping mode.This is a much slower 1500 RPM. Since this is an upper bound it is rarelyneeded, but nice to be able to achieve.long before your maximum speed is an issue. Generally resonance problemsare greatest with fewer microsteps.capable of that rate exist ?I guess I'll have to scale some values here andone thing I KNOW its that10,000 steps> a second will never be overkill. 25000seems acceptable to most,but to> really please most, you'll need about50,000.> ( Took me a long time to get that one down... :)> > Art>www.artofcnc.ca reach it ifaol://5863:126/rec.crafts.metalworking or go thru Google.com to you have trouble.be a sister site to the CCED group, as many of the same members arethere, for OT subjects, that are not allowed on the CCED list.THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........bill |
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JJ
I would have the machine disable all drives, turn off all accessories
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(spindle, etc.), and signal the condition (turn the light on, maybe a beeper too). After that, allow the operator to do anything they want, enable the drives, move (under program control) any axis away from the crash direction, ignoring the limit switches until they close/open again. E.g. the machine crashes moving -Z, stops and alerts, operator enables drives and moves +Z. At this point the program begins checking the Z limits again. The spindle, etc. remain off, of course, until the operator turns them on. You also might want to use a distinct key in your program to turn the spindle on/off. For example, if you have a message box that says "Enable drives? Y/N" and one that says "Turn spindle on? Y/N" the operator might not be looking at the screen and press Y, thinking he can back the Z off, but forgetting he already did, and turn the spindle on. Regards, JJ Be Kind, Be Careful, Be Yourself -----Original Message-----I consider this to be a sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list. NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........ bill List Mom List Owner Your use of Yahoo! Groups is subject to |
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