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LaughingCheese
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PostPosted: Wed Mar 10, 2010 1:21 am    Post subject: Tool Agnostic Designs? Reply with quote

I was wondering if I could just slap a Maker Bot Plastruder on the CNC gantry to make it a 3D printer as well?

Or would the electronics need to be different?

I don't see why anything would need to be changed really, unless you wanted more Z height, but then, the Maker Bot doesn't have a whole lot of Z height to begin with anyway.
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coffeehedake
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PostPosted: Wed Mar 10, 2010 11:45 am    Post subject: Reply with quote

Well... that's a more loaded question than I thought, after looking into it.

#1 issue, is what are you going to use to control the CNC machine?

If it's a Sanguino / Arduino, you're basically designing your own MakerBot / RepRap, but well beyond the physical design of what currently exists.

MakerBot uses ReplicatorG to run GCode and SkeinForge / SkeinFox to generate the G-Code for ReplicatorG. I don't know a whole lot about either, but I think the challenge here would be to calibrate ReplicatorG to understand the physical size of the CNC machine.

I can't offer too much help with the Sanguino / Arduino, as my knowledge with them is extremely limited. I've seen some awesome projects built with them, but that's pretty much all I know.

If you use a different controller, say a pre-built one on one of the CNC DIY sites, and build the whole CNC machine to spec, but just want to swap out the Router for a Plastruder, I think the only thing stopping you is figuring out how to get the software that controls the CNC movement to also run the Plastruder. The guys over at the MakerBot site are working on that too, but I don't see a definite solution right now.

Really need to know how to control the Plastruder to get anywhere, since whatever control software you're going to use has to be able to talk to it. CNC4Linux might be able to help, but I'm at quite a loss, not sure if Mach 3 could handle it or not.
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LaughingCheese
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PostPosted: Thu Mar 11, 2010 1:29 pm    Post subject: Reply with quote

coffeehedake wrote:
Well... that's a more loaded question than I thought, after looking into it.

#1 issue, is what are you going to use to control the CNC machine?


Are you talking software or electronics?

If software, I was going to go with EMC2.

Quote:

If it's a Sanguino / Arduino, you're basically designing your own MakerBot / RepRap, but well beyond the physical design of what currently exists.


I was thinking Arduino because it sounded cheaper than an electronics kit.

If I have to buy an electronics kit, I don't think I can afford it and I may spend my money elsewhere, at least until I get a job that can support my hobby. Laughing



Also could you elaborate a little more on what you mean by going "beyond the design of what currently exists"?


Quote:


If you use a different controller, say a pre-built one on one of the CNC DIY sites, and build the whole CNC machine to spec, but just want to swap out the Router for a Plastruder, I think the only thing stopping you is figuring out how to get the software that controls the CNC movement to also run the Plastruder. The guys over at the MakerBot site are working on that too, but I don't see a definite solution right now.


That's basically what I was thinking, swap out the Router for a Plastruder.

Basically you would just need software that could do both right?

The problem you are describing is probably because those machines are generally separate devices, and here I'm trying to make it 2 in 1, but there currently isn't any software for that.

I dunno tho, that's just my theory.

Quote:

Really need to know how to control the Plastruder to get anywhere, since whatever control software you're going to use has to be able to talk to it. CNC4Linux might be able to help, but I'm at quite a loss, not sure if Mach 3 could handle it or not.


That's a good point, I hadn't thought of that.

I guess I was assuming the control software would also be able to control the Plastruder.

Again tho, I will be using EMC2.
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coffeehedake
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PostPosted: Thu Mar 11, 2010 2:05 pm    Post subject: Reply with quote

Quote:
Are you talking software or electronics?


Actually both, but if you're going with EMC2, you're likely to be in better shape than with some of the other options for software. With EMC2 I think you can set the controls manually (you can with Mach3 as well, but I've never seen someone try it with a plastruder).

Quote:
I was thinking Arduino because it sounded cheaper than an electronics kit.


Actually, the controller boards aren't that expensive. The one I'm looking at will do a 4 axis for $25. The expense is the stepper motors and drivers, which are about $50 for each. The question then becomes though, how do you issue commands to the plastruder without a driver unit that the breakout board can understand? There's a lot about the plastruder that I don't quite understand, and also I'm not entirely sure how the Arduino talks to it as well. You may want to see what the folks over at MakerBot's forum have to say, they may have the opposite advice to give: use the arduino, and build a bigger MakerBot.

Quote:
Also could you elaborate a little more on what you mean by going "beyond the design of what currently exists"?


Sure, I basically just mean the physical construction of the machine. The makerbot / reprap is made on a very small chassis. You're building a big one, but how the physical design changes might impact the electronic functions, is unknown. Sorry, I realize I was very vague about that. (it sounded better in my head)

Quote:
The problem you are describing is probably because those machines are generally separate devices, and here I'm trying to make it 2 in 1, but there currently isn't any software for that.


Yep, that's exactly it. Although, considering you're thinking about using EMC2, you actually may have eliminated that issue. I also seem to remember someone over at the EMC2 forums posting about doing something VERY similar to what you're doing. I can't recall for sure, as I basically just skim through the forums there now and again, but it might be a good place to research too. Smile

I definitely like the idea though, don't get me wrong.

My ultimate dream has always been to have a Stereolithography machine, and I guess this is pretty close. (Though the ones I have seen in action use lasers, a big vat of resin or some kind of thermo-reactant semi-liquid, and a Z axis plate that moves up and down)

Either way you decide to go with the physical construction, and the electronics, the common denominator is the Plastruder. I'll look into it, and see what I can dig up. The best thing that could be discovered, is if it is simply analog on and off for it's functionality, because I think you could manage to get it to work.

Culvan might know a little more about this sort of thing with his robotics background, but I think he's going to be looking for the same type of information... How does the Plastruder handle a signal, what makes it work?
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LaughingCheese
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PostPosted: Thu Mar 11, 2010 3:12 pm    Post subject: Reply with quote

coffeehedake wrote:


Actually both, but if you're going with EMC2, you're likely to be in better shape than with some of the other options for software. With EMC2 I think you can set the controls manually (you can with Mach3 as well, but I've never seen someone try it with a plastruder).


Kewl.

Although I've heard its harder to use than Mach 3, what with it being Linux and all.

Quote:

Actually, the controller boards aren't that expensive. The one I'm looking at will do a 4 axis for $25. The expense is the stepper motors and drivers, which are about $50 for each. The question then becomes though, how do you issue commands to the plastruder without a driver unit that the breakout board can understand? There's a lot about the plastruder that I don't quite understand, and also I'm not entirely sure how the Arduino talks to it as well. You may want to see what the folks over at MakerBot's forum have to say, they may have the opposite advice to give: use the arduino, and build a bigger MakerBot.


$50 a piece!??!

What if I get these?

http://store.makerbot.com/nema-17-stepper-motor.html

There $15 a piece.

Underpowered?


I guess what I'm getting at, is what calculations do I need to make in order to find out which motor I need?

I'm no engineer. Sad


Quote:

Sure, I basically just mean the physical construction of the machine. The makerbot / reprap is made on a very small chassis. You're building a big one, but how the physical design changes might impact the electronic functions, is unknown. Sorry, I realize I was very vague about that. (it sounded better in my head)


No problem, thanks for clearing that up.

Also, as far as my build platform, theres a difference between total footprint of the machine and actual buildable area.

I think the dimensions I gave were for total footprint, I have no real clue as how to calculate actual buildable area.


Quote:

Yep, that's exactly it. Although, considering you're thinking about using EMC2, you actually may have eliminated that issue. I also seem to remember someone over at the EMC2 forums posting about doing something VERY similar to what you're doing. I can't recall for sure, as I basically just skim through the forums there now and again, but it might be a good place to research too. Smile


Cool, I'll check it out then.

I definitely like the idea though, don't get me wrong.

Quote:

My ultimate dream has always been to have a Stereolithography machine, and I guess this is pretty close. (Though the ones I have seen in action use lasers, a big vat of resin or some kind of thermo-reactant semi-liquid, and a Z axis plate that moves up and down)


Oh man, that would be truly epic! :p


Quote:

Either way you decide to go with the physical construction, and the electronics, the common denominator is the Plastruder. I'll look into it, and see what I can dig up. The best thing that could be discovered, is if it is simply analog on and off for it's functionality, because I think you could manage to get it to work.


Thanks!

Quote:

Culvan might know a little more about this sort of thing with his robotics background, but I think he's going to be looking for the same type of information... How does the Plastruder handle a signal, what makes it work?


He has a robotics background?!?

Awesome!
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coffeehedake
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PostPosted: Thu Mar 11, 2010 4:21 pm    Post subject: Reply with quote

Quote:
What if I get these?

http://store.makerbot.com/nema-17-stepper-motor.html
There $15 a piece.

Underpowered?


Here's some easier to understand specs:
http://reprap.org/bin/view/Main/StepperMotor

I dunno why MakerBot has them listed as "Holding torque: 260mM*m" everyone else I've seen uses Newton Meters or Ounce-Inches, but I'm also not an engineer either. LOL!

The spec sheet lists it at 100 oz-in. (however Keling sells the same motor, and claims it to be a 62oz-in) However to really figure it out you need to know the weight of your moving parts.

Patrick Hood-Daniel has a good explanation of how to figure out the necessary torque here: http://buildyourcnc.com/torquemotion.aspx However, the spec sheet won't really help us here, since we don't know the weight of your gantry, or the diameter of your lead screws- err... Wait a minute... I just realized something.... let's back it up for a second:

The MakerBot actually isn't driven by lead-screws like most of the DIY CNC mills. From what I've read, it rides a rail, but is driven by pulleys and belts.

This actually makes things sort of difficult. Here's the deal:
The lead-screw we use in a CNC provides a LOT of torque, at the cost of speed. Having a pulley or a chain as a direct-drive for the gantry would give you (usually) a 1:1 ratio for speed and torque on the movement of the gantry by the motor. For the MakerBot, this is probably fine, since it's very light. My guess would be that the little NEMA17 will push / hold around 5-6lbs (give or take) being directly driven, without a lead screw (or a worm gear, whatever). Versus 20-25lbs on a slightly larger motor with a lead screw.

Considering their size, and price, those are pretty decent motors. But you have a lot of planning to consider, even down to the materials you end up using. For me, $50 per motor, isn't that bad considering they're 425oz-in motors turning a screw, but there are smaller motors as well.

The Motor's I'm actually talking about are NEMA23's, but there are a bunch: http://www.kelinginc.net/StepperMotor.html


Here's what I would do in your situation:

I would design, and build my machine chassis, first. Figure out how much the gantry is going to weigh, and buy motors that can move it. Whether you use a lead screw or belts/chains is up to you, but planning before-hand will save you a gigantic headache, because converting the machine back to use the other drive method if it doesn't work out, may be difficult. (Depending on your design)

Besides, the whole point of this machine is to make it build something the size that you need. The bigger the workspace, the heavier the gantry is going to be to be able to cover that area. If you decide you need a certain size object created, then everything else has to be designed back from that point, so that you get what you need out of the process.

Anyway...

Quote:
I think the dimensions I gave were for total footprint, I have no real clue as how to calculate actual buildable area.


Are you working from certain plans? (I think you told me this already, but I didn't get any sleep last night, so my memory is completely shot) Maybe we can figure out about how large your work area will be.
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LaughingCheese
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PostPosted: Thu Mar 11, 2010 8:09 pm    Post subject: Reply with quote

[quote="coffeehedake"
Here's some easier to understand specs:
http://reprap.org/bin/view/Main/StepperMotor
[/quote]

Got that site bookmarked, guess I should poke around a bit more lol. Razz

Thanks for the link tho.

Quote:

I dunno why MakerBot has them listed as "Holding torque: 260mM*m" everyone else I've seen uses Newton Meters or Ounce-Inches, but I'm also not an engineer either. LOL!


Interesting.

Off topic note, if Maker Bot is open source, why can't I find the blueprints anywhere??

Rolling Eyes

Quote:

The spec sheet lists it at 100 oz-in. (however Keling sells the same motor, and claims it to be a 62oz-in) However to really figure it out you need to know the weight of your moving parts.


Uh oh.

Kind of hard to do that without buying the stuff and weighing it.

I'm trying to get all the planning done BEFORE I buy. Confused

Quote:

Patrick Hood-Daniel has a good explanation of how to figure out the necessary torque here: http://buildyourcnc.com/torquemotion.aspx However, the spec sheet won't really help us here, since we don't know the weight of your gantry, or the diameter of your lead screws- err... Wait a minute... I just realized something.... let's back it up for a second:


Oh man! Another site I've bookmarked!

I guess I already have the info under my nose then!

But thanks for reminding me.

Its tough doing your own research, especially when you don't know anything! Razz

Quote:

The MakerBot actually isn't driven by lead-screws like most of the DIY CNC mills. From what I've read, it rides a rail, but is driven by pulleys and belts.


Funky. Interesting how open source stuff is always doing something weird and non-standard.

I would probably be using a design with lead screws.

Quote:

This actually makes things sort of difficult. Here's the deal:
The lead-screw we use in a CNC provides a LOT of torque, at the cost of speed. Having a pulley or a chain as a direct-drive for the gantry would give you (usually) a 1:1 ratio for speed and torque on the movement of the gantry by the motor. For the MakerBot, this is probably fine, since it's very light. My guess would be that the little NEMA17 will push / hold around 5-6lbs (give or take) being directly driven, without a lead screw (or a worm gear, whatever). Versus 20-25lbs on a slightly larger motor with a lead screw.


So.....is 5-6lbs enough to cut MDF?

Laughing

Quote:

Considering their size, and price, those are pretty decent motors. But you have a lot of planning to consider, even down to the materials you end up using. For me, $50 per motor, isn't that bad considering they're 425oz-in motors turning a screw, but there are smaller motors as well.


Ok WOW.......I probably don't need 425oz, is that enough for aluminum?

Quote:

Here's what I would do in your situation:

I would design, and build my machine chassis, first. Figure out how much the gantry is going to weigh, and buy motors that can move it. Whether you use a lead screw or belts/chains is up to you, but planning before-hand will save you a gigantic headache, because converting the machine back to use the other drive method if it doesn't work out, may be difficult. (Depending on your design)


Well, you know way more than me.

Dude, I know zip, I would probably not be able to design my own machine. XD

I'd love to tho...



Quote:

Are you working from certain plans? (I think you told me this already, but I didn't get any sleep last night, so my memory is completely shot) Maybe we can figure out about how large your work area will be.


Sort of.

I'm still trying to decide if I want to build this machine:

http://www.instructables.com/id/How-to-Make-a-Three-Axis-CNC-Machine-Cheaply-and-/

Or go with the McWire model:

http://www.instructables.com/id/Easy-to-Build-Desk-Top-3-Axis-CNC-Milling-Machine/

There's just too many gaps and questions on the McWire build though.


However I've stared at the pictures long enough to where I think I could just go to Home Depot and pick them up.


The reason I haven't bought the parts yet is because I'm still trying to figure out what motors I will need, and whether or not I will need a gantry type.

McWire said you could build his design for around $200, but it may be too small for what I want to do.


I dunno, I feel I'm going in circles. XD

Maybe you do need to be an engineer??
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coffeehedake
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PostPosted: Thu Mar 11, 2010 8:49 pm    Post subject: Reply with quote

LaughingCheese wrote:
Off topic note, if Maker Bot is open source, why can't I find the blueprints anywhere??


Ya know, I was thinking the same thing myself! lol They sell the kits, all cut out and everything, but they're out of stock. I didn't look very hard, but I couldn't find the plans either.

LaughingCheese wrote:
Uh oh.

Kind of hard to do that without buying the stuff and weighing it.

I'm trying to get all the planning done BEFORE I buy. Confused


Yeah I hear ya. The other thing that I keep hearing a lot of, is that people are generally building a sloppy CNC first from easy to make, free, plans, and using that machine to build another one, sometimes retaining the original electronics, motors, and motion mechanics.

I don't think you'll have too much trouble designing a machine based on existing plans. The machine in the instructables how-to is a pretty good one, and I think that's the one Culvan ended up building. (I only switched to the BuildYourCNC.com model because it was a little bigger, and I had already bought the book). My recommendation would be to start with that design, and modify it to fit your needs. Even if you end up having to shell out the extra cash for heftier motors and drivers, you can use that machine to build a cheaper one, and sell the motors and such on ebay. I have a feeling though, that once you have the first machine built, you'll want to stick with the big motors, and just swap out the MDF parts with machined parts to make things more accurate. (That's what I'm aiming for)

LaughingCheese wrote:
Oh man! Another site I've bookmarked!


Yeah, that site is awesome. The book is very good too, and my only real gripe with it is that it doesn't have an itemized parts list. The author instead tells you what to buy at the end of each chapter, which is a pain in the butt. On top of that, he doesn't say "buy 4 feet of angled aluminum," he tells you only what you need for that chapter. I hate that, because I might need 8 feet of angle for the whole machine to be completed, but I only bought 2 feet at a time, and the very next chapter might need 2 more feet of angle. Other than that, the instructions are extremely detailed, the pictures are great, and he's got companion videos on the website that walk you through the whole construction.


At the moment I'm itemizing everything I buy, and tossing it into an excel spreadsheet, to help the rest of the community members, that are looking to modify the plans, and try to save more money. This way you can figure out what you can't skimp on, and what you'll need to change a little easier.

LaughingCheese wrote:
Its tough doing your own research, especially when you don't know anything!

Totally. I'm right there with ya too man. I've spent all of my time thus far doing research, and I'm not trying to make anything new... I'm just trying to follow the instructions. I have materials collected, power tools, etc, and I haven't built a thing. Doing further research to modify the plans means much more time. I do plan to change things, but not until I have the machine working as it does in the book.

LaughingCheese wrote:

Funky. Interesting how open source stuff is always doing something weird and non-standard.

I would probably be using a design with lead screws.

Well, I've seen a few that use the chain or belt design. (Toothed belts with drive gears are pretty popular in the DIY circles, especially when converting a pre-built Mill to a CNC one) I just tend to lean towards the lead-screw design out of opinion, but I'm fairly certain you could make one work equally well with gears and chains.

Quote:

So.....is 5-6lbs enough to cut MDF?


Haha! No, I don't think so. The stepper there is only moving a part, not drilling. Both the instructables design and the one I'm using incorporate a high-speed rotational tool (dremel, RTX, router, etc) as the cutter, not using a stepper to do the cutting. Not sure about the RepRap or the MakerBot, but I would imagine that's just using the Plastruder to do the work.

Anniversary tonight, so I gotta cut this short... I'll post some more later. Hope that was at least a little helpful!
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LaughingCheese
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PostPosted: Thu Mar 11, 2010 11:12 pm    Post subject: Reply with quote

coffeehedake wrote:


Ya know, I was thinking the same thing myself! lol They sell the kits, all cut out and everything, but they're out of stock. I didn't look very hard, but I couldn't find the plans either.


Quote:

Yeah I hear ya. The other thing that I keep hearing a lot of, is that people are generally building a sloppy CNC first from easy to make, free, plans, and using that machine to build another one, sometimes retaining the original electronics, motors, and motion mechanics.


My whole problem is I don't have the funds for all that.

Man I really need a job. XD

Quote:

I don't think you'll have too much trouble designing a machine based on existing plans. The machine in the instructables how-to is a pretty good one, and I think that's the one Culvan ended up building. (I only switched to the BuildYourCNC.com model because it was a little bigger, and I had already bought the book). My recommendation would be to start with that design, and modify it to fit your needs. Even if you end up having to shell out the extra cash for heftier motors and drivers, you can use that machine to build a cheaper one, and sell the motors and such on ebay. I have a feeling though, that once you have the first machine built, you'll want to stick with the big motors, and just swap out the MDF parts with machined parts to make things more accurate. (That's what I'm aiming for)



Quote:

Yeah, that site is awesome. The book is very good too, and my only real gripe with it is that it doesn't have an itemized parts list. The author instead tells you what to buy at the end of each chapter, which is a pain in the butt. On top of that, he doesn't say "buy 4 feet of angled aluminum," he tells you only what you need for that chapter. I hate that, because I might need 8 feet of angle for the whole machine to be completed, but I only bought 2 feet at a time, and the very next chapter might need 2 more feet of angle. Other than that, the instructions are extremely detailed, the pictures are great, and he's got companion videos on the website that walk you through the whole construction.


Its really well laid out but yeah not having a parts list is a MAJOR oversight. XD

Quote:

At the moment I'm itemizing everything I buy, and tossing it into an excel spreadsheet, to help the rest of the community members, that are looking to modify the plans, and try to save more money. This way you can figure out what you can't skimp on, and what you'll need to change a little easier.


That's awesome, thanks!


Quote:

Totally. I'm right there with ya too man. I've spent all of my time thus far doing research, and I'm not trying to make anything new... I'm just trying to follow the instructions. I have materials collected, power tools, etc, and I haven't built a thing. Doing further research to modify the plans means much more time. I do plan to change things, but not until I have the machine working as it does in the book.



Quote:

Well, I've seen a few that use the chain or belt design. (Toothed belts with drive gears are pretty popular in the DIY circles, especially when converting a pre-built Mill to a CNC one) I just tend to lean towards the lead-screw design out of opinion, but I'm fairly certain you could make one work equally well with gears and chains.


Interesting. Probably easier to come by.

Quote:

Haha! No, I don't think so. The stepper there is only moving a part, not drilling. Both the instructables design and the one I'm using incorporate a high-speed rotational tool (dremel, RTX, router, etc) as the cutter, not using a stepper to do the cutting. Not sure about the RepRap or the MakerBot, but I would imagine that's just using the Plastruder to do the work.


OH

Yes, I was aware that I would have to buy a Dremel or something as the cutting tool.

Part of the reason I want to keep the cost of the CNC around $200. Dremels are like $65.

But if the Dremel does all the work why do I need strong motors??

I'm not making the connection. Sad



I'm still pursuing other avenues of thought as to how I might build this stuff.

I'm thinking of a process involving paper patterns where I'd cut directly on the surface.

Or putting the pattern onto foam, strengthening the foam, then vac forming it.

That would make me a sculptor tho...

Quote:

Anniversary tonight, so I gotta cut this short... I'll post some more later. Hope that was at least a little helpful!


Wedding anniversary I assume? Razz

Congratulations!
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Culvan
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PostPosted: Fri Mar 12, 2010 11:17 am    Post subject: Reply with quote

LaughingCheese wrote:
Quote:

Culvan might know a little more about this sort of thing with his robotics background, but I think he's going to be looking for the same type of information... How does the Plastruder handle a signal, what makes it work?


He has a robotics background?!?

Awesome!


That may be overstating it a bit. I've been mentoring high schools in a program called FIRST. I have a degree in Electrical Engineering, but I don't do much with it for work. Robotics is really a hobby for me.

LaughingCheese wrote:
I was wondering if I could just slap a Maker Bot Plastruder on the CNC gantry to make it a 3D printer as well?


You seem to have identified my eventual goal. I believe that it is possible. I have not done the research to figure out all the details yet though. After reviewing all the parts in the plastruder assembly: http://wiki.makerbot.com/plastruder-mk4-assembly I believe that it's a fairly simple design. It looks like there's a DC motor that drives the pllastic into the heater. The heater is nichrome wire wrapped around a brass(?) threaded tube and there is a thermistor to read the temperature. That probably allows it to know when it's hot enough to start and control the temperature to keep it in some ideal range. This is intended to connect to a reprap motherboard and I haven't been able to find the protocol it uses. The thermistor/heater combo would need some sort of control loop. This will require an extra chip that has a Digital to Analog converter. That's probably where the Arduino comes in, but there are many microcontrollers that could work. Although I've only looked into this for about 20 minutes. I'm guessing the DC motor is just on/off so it can be driven by a relay, and best of all, many CNC machines and software have controls for turning the cutter on/off so there is a parallel in the software already. Assuming you have a microcontroller managing the temperature control algorithm then either Mach3 or EMC2 could run the plastruder. The microcontroller would probably also have to feed some signal back to Mach3/EMC2 to give it a "ready" indicator.

I suspect software will be a problem though. CNC software is designed to cut material away. Speed isn't a big concern, repeating an area isn't bad either. That's not true for a plastruder. I'm sure there's software that does that, but how do we get from that software to something that controls a CNC gantry? I won't know that till I get in much deeper.

Quote:

Actually, the controller boards aren't that expensive. The one I'm looking at will do a 4 axis for $25. The expense is the stepper motors and drivers, which are about $50 for each.


That's a good price. Can you share information on that 4-axis driver. What sort of current capacity can it handle? The current/power is very important for the driver circuit. While I was looking up info for the makerbot I stumbled onto a discussion about cheap stepper motors. They suggested the NEMA23 that has 60-70 oz-in torque (about double the NEMA17). http://www.alltronics.com/cgi-bin/category.cgi?category=55
There are some available for $10.

Quote:
I guess what I'm getting at, is what calculations do I need to make in order to find out which motor I need?

I'm no engineer.


Wish I had one that was easy. I used timing belts and pulleys on mine. The force applied by the motor is applied at the radius of the pulley. So the force for the gantry is = motor torque / pulley radius. That force has to fight mass, friction and resistance of the material you are cutting. Foam will have very little resistance. Friction can't be calculated, you have to measure it. You could estimate it with a coeficient of friction. Not sure what a reasonable estimate would be but the equation is Force of Friction = Weight * coefficient of static friction. You can estimate the weight of your gantry by the material you are using. Engineers use swags all the time. If you are guessing, you may want to double your figures just to make sure that you are looking at worst cast numbers.


Sorry I don't have time to go through more of this thread right now. I'll try to catch up and answer some more questions.

Andy
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coffeehedake
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PostPosted: Fri Mar 12, 2010 3:36 pm    Post subject: Reply with quote

Culvan wrote:
That may be overstating it a bit. I've been mentoring high schools in a program called FIRST. I have a degree in Electrical Engineering, but I don't do much with it for work. Robotics is really a hobby for me.


Whoops. Sorry about that Culvan. I am, however, glad that you dropped in again and saved the day, despite that.

Culvan wrote:
That's a good price. Can you share information on that 4-axis driver.


Well... I think I may have misled you. The drivers are $50 each. The 4-axis breakout controller is $25. Pricing for the breakout is here. Specs here.

Pricing for the drivers are here. While the specs are here.

Keling sells a 4 axis kit altogether with that exact breakout, 4 drivers, 4 (much bigger) steppers, etc here. Here's a parts list:
    NEMA 34 1200 oz-inSteppper Motors 4 Axis CNC Kit: $1239
  1. : 4 PCS KL-9082, 24- 90VDC, 8.2A Driver
  2. : 4 PCS EMA 34-1200 oz-in Stepper Motors
  3. : 1 PCS KL-7220, 72V(No load), Max 20A,Unregulated Power Supply,
    110V/220V
  4. :1 PCS C10 Breakout board, E-Stop or Limit Switch can be wired
  5. : 5V Power Supply for Breakout Board


LaughingCheese wrote:
But if the Dremel does all the work why do I need strong motors??

Because that dremel, router, or whatever, plus the gantry, electronics, and bolts to hold it all together, is wicked heavy for a tiny motor to move.

Hmm. I know for a fact that this particular machine I'm working on, will cut MDF. So I'm going to plod ahead, and aim to make MDF molds, bucks, and reverse molds. The thing I'm not seeing much of, is cutting MDF in 3 Dimensions. We'll see about that.

I think no matter how you look at this, you're still a sculptor. Whether it's in gMax and Poser, or with clay or powertools. It's all just different methods to get to the same end.
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Culvan
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PostPosted: Fri Mar 12, 2010 5:37 pm    Post subject: Reply with quote

LaughingCheese wrote:
But if the Dremel does all the work why do I need strong motors??

I'm not making the connection. Sad

Actually a very good point. It's easy to forget how much force we put on a tool when we are cutting something with it. However the bigger issue is being able to move the tools at all. If you don't have enough strength to overcome friction then your Dremel can't do any work. Your dremel will also kick while it is cutting and if your motors aren't strong enough it could move your gantry.

I do have to point out that all methods of moving an axis are not the same. Timing belts with timing pulleys is the fastest but the weakest. Lead Screws use a massive mechanical advantage. You can get much more force out of a lead screw than you can a pulley system like mine. Of course the trade off is that it is slower. I should also point out that a Lead Screw and Ball Screw are different from the threaded rod you buy at the hardware store. Although they are metal rods with thread that something nut like rides on, there are differences. Lead Screws and Ball Screws are designed to bear loads like this. They are very smooth and present very little friction. Threaded rod with a nut is not designed to move so freely as it's usually designed to hold something in place. The TPI (Threads Per Inch) is usually much higher on threaded rod (i.e. 20 threads per inch). That is not to say that threaded rod won't work. I used it to drive my Z axis and I'm very happy with it. However it has more innate friction. The large steppers I use overcome the friction, it's probably capable of moving way more weight than I'm using it for.

LaughingCheese wrote:
I'm still pursuing other avenues of thought as to how I might build this stuff.

I'm thinking of a process involving paper patterns where I'd cut directly on the surface.

Or putting the pattern onto foam, strengthening the foam, then vac forming it.

That would make me a sculptor tho...


Interesting. Im making a DC-15L (the Clone Trooper's long rifle). I printed out paper and glued it to 1/4" particle board. I cut it out on a jigsaw and I'm assembling it now. Perhaps when I'm a little further along I'll post some pictures of the build.

LaughingCheese wrote:
Off topic note, if Maker Bot is open source, why can't I find the blueprints anywhere??

http://www.thingiverse.com/thing:457
They have the part diagrams at the bottom of the page. I should take a closer look at them I could probably cut them on my CNC machine. Still trying to decide what way to go with the plastruder.

Quote:
The spec sheet lists it at 100 oz-in. (however Keling sells the same motor, and claims it to be a 62oz-in) However to really figure it out you need to know the weight of your moving parts.

I don't have my references in front of me, but the NEMA17 looked like it was capable of 36oz-in and the NEMA 23 was capable of about 70oz-in. That works out to 2 / 4 pounds of force if your moment arm (i.e. pulley radius) is 1 inch long. The stepper motors I'm using are 130oz-in. I'm pretty happy with them. I think I'm using them below their rated current because they don't warm up as much as some of the reports I've read. That probably means I'm not getting 130oz-in.

I guess what I'm trying to say is that if you can lubricate a hardware store threaded rod enough then the NEMA17 motors would probably be able to move a whole lot of weight.

Quote:
I'm still trying to decide if I want to build this machine:
http://www.instructables.com/id/How-to-Make-a-Three-Axis-CNC-Machine-Cheaply-and-/

That is the machine I built. One of the strong reasons I choose that was because the assembly instructions were increadibly simple. They're based off of legos. If you haven't done so already, download the assembly instructions and look through them. They're not perfect, but the simplicity gave me a lot more confidence. Which was critical since I failed on my first attempt to build it. (apparently I couldn't cut a straight line with my jigsaw.) I knew it wasn't the assembly that has failed and I could focus on correcting my tolerances.

Andy
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LaughingCheese
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PostPosted: Fri Mar 12, 2010 7:28 pm    Post subject: Reply with quote

Culvan wrote:
LaughingCheese wrote:
But if the Dremel does all the work why do I need strong motors??

I'm not making the connection. Sad

Actually a very good point. It's easy to forget how much force we put on a tool when we are cutting something with it. However the bigger issue is being able to move the tools at all. If you don't have enough strength to overcome friction then your Dremel can't do any work. Your dremel will also kick while it is cutting and if your motors aren't strong enough it could move your gantry.


Well thanks! Razz

Quote:

Interesting. Im making a DC-15L (the Clone Trooper's long rifle). I printed out paper and glued it to 1/4" particle board. I cut it out on a jigsaw and I'm assembling it now. Perhaps when I'm a little further along I'll post some pictures of the build.


Oh DUDE...that would be AWESOME!!

Sounds like I may not need a CNC machine after all. Razz

Although do you think you can make RC aircraft with your method?

Either flying wing zaggy types or symmetrical types which I could cut two halves of and vac form them?

Quote:

http://www.thingiverse.com/thing:457
They have the part diagrams at the bottom of the page. I should take a closer look at them I could probably cut them on my CNC machine. Still trying to decide what way to go with the plastruder.


Oh man, thanks!

I would never have thought to check that site lol.

Quote:
The spec sheet lists it at 100 oz-in. (however Keling sells the same motor, and claims it to be a 62oz-in) However to really figure it out you need to know the weight of your moving parts.



Quote:

I guess what I'm trying to say is that if you can lubricate a hardware store threaded rod enough then the NEMA17 motors would probably be able to move a whole lot of weight.


Interesting.

Quote:

That is the machine I built. One of the strong reasons I choose that was because the assembly instructions were increadibly simple. They're based off of legos. If you haven't done so already, download the assembly instructions and look through them. They're not perfect, but the simplicity gave me a lot more confidence. Which was critical since I failed on my first attempt to build it. (apparently I couldn't cut a straight line with my jigsaw.) I knew it wasn't the assembly that has failed and I could focus on correcting my tolerances.

Andy


Did you say LEGOS?!

You just gave me an idea!

Lego Mindstorms CNC? Wink

Ok, the plastic probably couldn't withstand the power of the motors, interesting thought tho.


I think I get what you mean though about the instructions being like legos.

I'll give it a look.
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Culvan
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PostPosted: Thu Mar 25, 2010 9:27 am    Post subject: Reply with quote

I've been looking into plastruders a bit more. It looks like Reprap and Makerbot/Cupcake originated from the same electronics and plastruder. The chassis are different and I can't tell if they are diverging as development moves forward. A few people have made CNC machines and attached a plastruder to that. Some of these people have documented what they did and published additional drivers to make this work in EMC2.
http://reprap.org/wiki/EMCRepStrap

The downside is there seems to be some sort of production issues for the Reprap/Makerbot/Cupcake parts. The build here requires an Extrusion Controller that appears to be out of stock. There should be an open source version of the plans for one, but I don't really want to put in that much time and effort right now. Some of the discussion I've read seemed to indicate that new electronics are being developed and should be available in the next 12-24 months.

A link at the bottom of the EMCRepStrap page mentions an inexpensive CNC machine. It looks like the price is up to $340 now and is missing a few parts that are cheap and easy to find locally and expensive to ship. Possibly of more interest is the 3-axis stepper drive for $50. The current (amps) specs are a little low, but are perfect for NEMA17 motors. I've seen some CNC stepper controllers on E-bay, they have better current capacity but run around $80-90 at the low end.
http://bluumaxcnc.homestead.com/BluumaxCNC.html

His website is worth looking around because it's geared towards the hobbyist. He uses plain(er) language than a lot of other sources I've read.

Andy
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LaughingCheese
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PostPosted: Thu Apr 08, 2010 11:50 am    Post subject: Reply with quote

Thanks for the bluumax link, he does have great info.


Apparently the RepRap Mendel version can have different tool heads like CNC Routers.

http://objects.reprap.org/wiki/CNC_Router


Perhaps I'll be building a Mendel? Laughing
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