Announcing the ORDuino !

Topics Related to the ORD Bot Printer

Re: Announcing the ORDuino !

Postby Zat German » Wed Mar 07, 2012 7:14 pm

An E-stop is different from a Reset, which is what you are describing. In the case of an emergency stop, you need to reliably kill everything without depending on the CPU to do it(it might not be in any state to process such a command or input), that means it has to be hardwired. An E-stop could also be tied directly to the CPU's reset pin but then you lose state(even if it is a crazy one) which interferes with trying to debug stuff. An emergency stop is an emergency, recovering the build or losing sync is secondary to to getting the machine off and in a safe(ish, since we are dealing with hot things here too) state.
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E-stop input? what do you think?

Postby frob » Wed Mar 07, 2012 8:05 pm

Zat German wrote:An E-stop is different from a Reset, which is what you are describing. In the case of an emergency stop, you need to reliably kill everything without depending on the CPU to do it(it might not be in any state to process such a command or input), that means it has to be hardwired. An E-stop could also be tied directly to the CPU's reset pin but then you lose state(even if it is a crazy one) which interferes with trying to debug stuff. An emergency stop is an emergency, recovering the build or losing sync is secondary to to getting the machine off and in a safe(ish, since we are dealing with hot things here too) state.


Ok i hear what your saying -
I'm just wondering which is safer - letting the motors coast, or doing a hard stop (motors coils need to stay driven for this ) and possibly retracting to a "safe" home position immediately after that. Personally, i would vote for the latter.

Here's what the Allegro datasheet says about the enable inputs:
"Enable Input . This input turns on or off all of the FET outputs.
When set to a logic high, the outputs are disabled.
When set to a logic low, the internal control enables the outputs as required.
The translator inputs STEP, DIR, MS1, and MS2, as well as the internal sequencing logic, all remain active, independent of the Enable input state."


So my feeling is if you want to do this in a way that directly bypasses the CPU, the best way would be to override the STEP input instead, so the motors immediately and forcefully lock up with their full holding torque to instantly stop all movement.

And if i was to really get fancy, after that i'd drive the printer to a safe home position (or at least kill the enables, lock down reset, (or more likely the main power), so you could then do it by hand) when the E-stop button is released - and then automatically shut off the power source. which would need a little more circuitry to accomplish.

Considering that the current RAMPS and ilk don't have any E-stop connection at all (as far as i know), this would likely be the first ever Arduino derivative 3D printer controller that supports any kind of E-stop function. I''d like to believe others would find this desirable, but there cant be that much demand for it, otherwise current controllers would already include it. Its certainly not nearly as hazardous a system as a large CNC or laser cutter.
So i'm not really convinced how much of this, if any, is really called for in a 3D printer.
Whats the worst case scenario you envision where such an E-stop would make a difference?
Do you envision using this on a laser too? why not i suppose! :D

Anyone else want to chime in on this?
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Re: Announcing the ORDuino !

Postby Zat German » Wed Mar 07, 2012 8:18 pm

Well, I plan on adding the ability to cut foam with a spindle(probably a Dremel MiniMite in a custom housing) to my ORD so that is one reason. Another is that the ORD bot seems to move pretty fast from what I have seen, compared to RepRaps and other 3D printers. The Ultimaker which is of comparable speed is basically in an enclosure, where the ORD bot is very open. I consider it a safety requirement for any machine I run, even if others may not. Since this is a prototype, I might as well ask for it now so it can be considered rather than after it goes into production. :)
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E-Stop (the feature creep)

Postby bdring » Wed Mar 07, 2012 8:26 pm

The current e-stop is flip the power switch or hit the reset. The software has a pause that halts the print where it can be restarted. That means it does not loose steps from a fast stop. You flip the switch when the software is not responding to the pause. I think flipping the power or hitting the CPU reset is the only way. Emergency means stop now, forget the print. I had a software lock up with the extruder heater on. E-Stop should be software independent and shut it all off.

I am concerned about the amount of custom programming that is going to be required to get your board running. Reprappers love to try new firmwares. I asked Jeremy to try out Repetier the other day and he had it going in minutes. You adjust configuration.h and you are ready to go. Having to hack in digital pot settings for motor current, special e-stop routines means hacking a lot of files. New firmwares and revs come out every day. The same configuration.h usually works.

I think you have a lot of coding ahead of you to get all the features running.
Bart
"If you didn't build it, you will never own it."
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Re: Announcing the ORDuino !

Postby frob » Wed Mar 07, 2012 8:33 pm

Zat German wrote:Well, I plan on adding the ability to cut foam with a spindle(probably a Dremel MiniMite in a custom housing) to my ORD so that is one reason.
Cool - (me too , but with an RC BLDC motor) - either way the spindle + end mill is the most dangerous part, and that which i'd most urgently want to shut off with the E-stop.
How do you envision handling that part of it?
Zat German wrote: Another is that the ORD bot seems to move pretty fast from what I have seen, compared to RepRaps and other 3D printers. The Ultimaker which is of comparable speed is basically in an enclosure, where the ORD bot is very open. I consider it a safety requirement for any machine I run, even if others may not.
I don't disagree with that either, mostly because i admittedly have an irresistible urge to over-engineer everything i touch, as you may have noticed... :roll:
Zat German wrote:Since this is a prototype, I might as well ask for it now so it can be considered rather than after it goes into production. :)
Absolutely! and I'm glad you did, now I'm seriously considering it - as long as there's room and it doesnt significantly increase cost & complexity - I'm just trying to decide what the right way to do it and how much is enough? If i am to add it it has to be decided quickly. Thus a little discussion & friendly debate goes a long way to answer that :D
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Re: E-Stop - last call for feedback :)

Postby frob » Wed Mar 07, 2012 8:46 pm

bdring wrote:I am concerned about the amount of custom programming that is going to be required to get your board running. Reprappers love to try new firmwares. I asked Jeremy to try out Repetier the other day and he had it going in minutes. You adjust configuration.h and you are ready to go. Having to hack in digital pot settings for motor current, special e-stop routines means hacking a lot of files. New firmwares and revs come out every day. The same configuration.h usually works.
I think you have a lot of coding ahead of you to get all the features running.

That's part of the reason i decided to revert to the allegro drivers and leave in the motor current pots - and use mechanical switches for the motor step modes. So all the existing stuff from the RAMPS has the exact same pin-outs and should work exactly the same out of the box, with the standard RAMPS config.
Only to use new features will it be necessary to splice in new code. And really there isn't that much to write to support those.
I expect it will take more time to get familiar with the compiler and existing open-source code that it will to actually write the code itself.
And since the existing RAMPS code should load and work fine out of the box, there's not as much urgency to get all those mods done and tested (for user's benefit) since the board is already functional without it. The urgency for me is mainly to fully test the prototype board to make sure there's no latent hardware bugs (which would only appear after the advanced features are enabled later) before i order the first large production batch.
If Reprappers love to try new firmwares as you say, then surely they will be thrilled when new versions appear that unlock the advanced features already built into this board ;) :D
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Re: Announcing the ORDuino !

Postby Zat German » Wed Mar 07, 2012 9:01 pm

frob wrote:Cool - (me too , but with an RC BLDC motor) - either way the spindle + end mill is the most dangerous part, and that which i'd most urgently want to shut off with the E-stop.
How do you envision handling that part of it?
That would just be a straight up power cut to the spindle when the e-stop is hit. I have some really nice and quiet 36v spindles but they are pretty heavy and not really needed for the EVA foam I am going to be cutting. I picked the MiniMite because it is extremely light at 4.8 ounces without the battery where my other spindles weigh more than a pound. That means I can do really quick jogs when not cutting and harness the speed of the ORD.
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E-stop spindle control?

Postby frob » Wed Mar 07, 2012 10:06 pm

Zat German wrote:
frob wrote:How do you envision handling that part of it?
That would just be a straight up power cut to the spindle when the e-stop is hit. ... I picked the MiniMite because it is extremely light at 4.8 ounces without the battery where my other spindles weigh more than a pound. ....


Question: is an E-stop usually a latching switch or a momentary one, and just simple spst or more poles? just trying to figure out how that would be wired.
interestingly it looks like the MiniMite would be happy with 5V like you would get from an ATX supply so you could just pull out the motor and scrap everything else and just switch that using the extruder heater output-
i don't know it it would b worth trying to override that on the board or if you could just run the motor leads through the E-switch itself on another pole. The KISS principle says do the latter if the switch will support it.

The MiniMite seems like a good idea so out of curiosity i found the user manual and seeing the exploded view of the parts, it is a bit disappointing to find it looks like a cheap toy DC motor (bushings) with a collect chuck adapter pressed on to the 2mm motor shaft.
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Re: E-stop spindle control?

Postby Zat German » Wed Mar 07, 2012 10:32 pm

frob wrote:Question: is an E-stop usually a latching switch or a momentary one, and just simple spst or more poles? just trying to figure out how that would be wired.
All the ones I have seen latch when you press them and you have to pull them out or twist them to reset. The ones I have ordered have separate NC and NO blocks so you can wire it for either or both.

The MiniMite seems like a good idea so out of curiosity i found the user manual and seeing the exploded view of the parts, it is a bit disappointing to find it looks like a cheap toy DC motor (bushings) with a collect chuck adapter pressed on to the 2mm motor shaft.

It is extremely cheap, so I am not that surprised. Where did you find an exploded diagram for the MiniMite? I even contacted Dremel after looking on their site but could not find one. They told me they did not have one.
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Re: E-stop spindle control?

Postby frob » Thu Mar 08, 2012 12:38 am

Zat German wrote: Where did you find an exploded diagram for the MiniMite? I even contacted Dremel after looking on their site but could not find one. They told me they did not have one.

here it is :
from here:
http://www.dremel.com/en-us/Tools/Pages ... x?pid=7300
DOWNLOADS
7300 MINIMITE CORDLESS OWNER'S MANUAL
https://mdm.boschwebservices.com/MDMCac ... 725v-1.pdf

7300 MINIMITE CORDLESS PARTS LIST
https://mdm.boschwebservices.com/MDMCac ... 310v-1.pdf
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