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Converting a printer to a CNC?

 
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LaughingCheese
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PostPosted: Fri Feb 26, 2010 2:13 pm    Post subject: Converting a printer to a CNC? Reply with quote

I have an old printer that I intended to scavenge for motors, but I thought what if I could use more than just the motors?


I was thinking if I was careful about the dissasembly I could possibly keep it in working order, and just reassemble it in CNC form with all 3 motors working together.

Its a Brother MFC DCP-120, meaning it prints as well as scans, so it has at least 3 motors.

Two in the scanner and one for the printer.


Is this doable? I was thinking maybe I could use the Ethernet or USB outlets to transmit G-code instead of having to build the drivers and use an LPT port.

In other words, could I reuse the electronics of the printer?



Obviously, that dinky little printer wouldn't be able to cut a whole lot, definitely not aluminum and probably not wood, I'm hoping it will just cut foam, that's all I really need right now.


EDIT: This is the printer I have:

http://www.brother-usa.com/Printer/ModelDetail.aspx?ProductID=DCP120C


No, its not in use anymore, obviously. Laughing
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coffeehedake
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PostPosted: Fri Feb 26, 2010 4:12 pm    Post subject: Reply with quote

LaughingCheese wrote:
Is this doable? I was thinking maybe I could use the Ethernet or USB outlets to transmit G-code instead of having to build the drivers and use an LPT port.


It's possible, but I think all of the software I have seen wants to directly output g-code to the controller. The logic board in the printer probably won't understand g-code. All of the sites I've seen seem to want to have you salvage the motors, guide rods, etc, and then slap in a new controller unit. (This guide has you build one from a design)

I was tempted to do something similar with a couple old plotters I had kickin' around. Yep, I said plotters. I haven't taken them apart yet, but I may just end up buying big steppers off the net, and a lead screw to drive the whole thing.

Both are expensive, and that's unfortunate. The controller is also expensive. I figure if I can actually build this thing it'll pay for itself in the aggravation I'd save trying to model the bucks for vacuum-forming out of clay. *shrug*
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LaughingCheese
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PostPosted: Fri Feb 26, 2010 4:54 pm    Post subject: Reply with quote

coffeehedake wrote:
LaughingCheese wrote:
Is this doable? I was thinking maybe I could use the Ethernet or USB outlets to transmit G-code instead of having to build the drivers and use an LPT port.


It's possible, but I think all of the software I have seen wants to directly output g-code to the controller. The logic board in the printer probably won't understand g-code. All of the sites I've seen seem to want to have you salvage the motors, guide rods, etc, and then slap in a new controller unit. (This guide has you build one from a design)



Quote:

Both are expensive, and that's unfortunate. The controller is also expensive. I figure if I can actually build this thing it'll pay for itself in the aggravation I'd save trying to model the bucks for vacuum-forming out of clay. *shrug*



I have seen a couple that use breadboard controllers for and one or two that use Arduino as the main controller board.

I was thinking if I could make it work using Arduino and breadboards that could cut the cost of the electronics considerably, and the remaining expensive parts would be the motors.

Here's a DIY controller [not Arduino]:

http://www.instructables.com/id/Easy-to-build-CNC-Mill-Stepper-Motor-and-Driver-ci/

Slightly unrelated, but pretty awsome:

http://cnczone.com/forums/showthread.php?t=100127&highlight=arduino+cnc
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coffeehedake
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PostPosted: Fri Feb 26, 2010 5:13 pm    Post subject: Reply with quote

Hmm... I seem to also remember a bread-boarded controller. I also remember seeing a book on Amazon, I think it was called practical Arduino, when I was looking for books on building a CNC machine. I don't know for sure if it happens to have the specifics for using the Arduino as a controller for a CNC machine, but Amazon seemed to think it was related. YMMV. Worth a shot though.

The funny part is, even if you only end up with a small CNC machine from the printer parts... you can use it to etch your controller for a bigger one. Wink

I like the Nintendo controller video... ha! That's awesome.

Let me know if you have any luck or progress in your research. Definitely interesting.
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LaughingCheese
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PostPosted: Fri Feb 26, 2010 9:54 pm    Post subject: Reply with quote

coffeehedake wrote:
Hmm... I seem to also remember a bread-boarded controller. I also remember seeing a book on Amazon, I think it was called practical Arduino, when I was looking for books on building a CNC machine. I don't know for sure if it happens to have the specifics for using the Arduino as a controller for a CNC machine, but Amazon seemed to think it was related. YMMV. Worth a shot though.


Thanks, I'll take a look!

Also, if you notice from my post, I couldn't actually find the thread about the Arduino CNC.

Guess I have some more searching to do. :p

Quote:

The funny part is, even if you only end up with a small CNC machine from the printer parts... you can use it to etch your controller for a bigger one. Wink


lol! True.

I think I need at least 2' X 2' tho, and I would preferably like a gantry type router that's 2' X 3'.

Obviously the rods from the printer won't be long enough, but maybe I could just use the motors.


Are the motors in printers all the same?

Like if its a multifunction printer, does the scanner part use the same motors as the printer part? And how can you tell?


Quote:

Let me know if you have any luck or progress in your research. Definitely interesting.


Will do; I may just end up using the motors tho.
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coffeehedake
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PostPosted: Sat Feb 27, 2010 10:17 am    Post subject: Reply with quote

LaughingCheese wrote:
Are the motors in printers all the same?

Like if its a multifunction printer, does the scanner part use the same motors as the printer part? And how can you tell?


I don't think so. There's different types of steppers, different amounts of torque, etc. (I believe it is measured in Oz/in) Some of the really old printers had surprisingly large motors in them. Some used timing belts to drive the print heads, and I think that's typically how most scanners work. (Small motor with a timing belt drive)

I stumbled across this page: http://insectphotos.net/tools/electronic/cnc/index.htm which may be of some help. Also this one gives a lot of background info on stepper motors in general:
http://www.omega.com/prodinfo/stepper_motors.html

You can see in the pictures there, that the drive motors are relatively small, though the engadget site shows some larger ones from an old AppleWriter printer.

One of the things I've noticed is that some of the stepper motors have a rating on them, once you have dissected the device. At least on the engadget page, the old AppleWriter steppers have a posted degree per step rating.

Culvan would probably know a lot more about this stuff than I do. My feeling, however is that for a large amount of travel on any given axis, you're going to need a pretty beefy motor. Ideally, looking for a motor from a really large format printer, scanner, or plotter would probably yield better results. That being said, the smaller motors in your printer may be just fine for the Z axis, as there won't be as much traveling for the motor to handle.

I'm going to take a look through my CNC machine book and see if there is any advice there. I'll let you know if I find anything useful.
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coffeehedake
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PostPosted: Sat Feb 27, 2010 10:58 am    Post subject: Reply with quote

Ok, I found some information that may or may not be helpful. The book I'm using tells you what motor to get, but doesn't say why.

Considering the motors are $50 each, I figured why not post the specs for these motors, and we can compare them to whatever info we can find out about what you have. Here's the spec sheet:
http://www.kelinginc.net/KL23H286-20-8B.pdf
The model number on the specific motor is KL23H286-20-8B, Kelig Inc is selling them for $49 each, and from what I'm seeing the have the same stepping rating as the AppleWriter motors, but probably more torque. (Guessing) The torque rating is 425 oz/in. (That's about 27 lbs per inch by my math)

I'm guessing that the torque has to be pretty high, as at any given time, one motor has to be able to move the whole gantry and the attached routing tool (which is heavy) all by itself. Unless you're using really lightweight materials, I don't know if a printer/scanner stepper is going to have the power.

The book I'm using has the entire structure built out of MDF, which is pretty heavy. They also used an off-the-shelf Bosch hand router, which is also pretty heavy. I'd bet that if you modified the design a bit, and used lighter body materials, and perhaps a Dremel or RTX with the flexible extension attachment, you'd be okay.
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Culvan
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PostPosted: Mon Mar 01, 2010 9:36 am    Post subject: Reply with quote

coffeehedake wrote:
LaughingCheese wrote:
Are the motors in printers all the same?

Like if its a multifunction printer, does the scanner part use the same motors as the printer part? And how can you tell?


I don't think so. There's different types of steppers, different amounts of torque, etc. (I believe it is measured in Oz/in) Some of the really old printers had surprisingly large motors in them. Some used timing belts to drive the print heads, and I think that's typically how most scanners work. (Small motor with a timing belt drive)


From the printers I've dissassembled, I usually only get one stepper motor. I can't remember which motor it is though. Usually I get a few DC motos out of them too. Stepper motors are the ones with more than 2 wires comming out of them. Stepper motors will have 4, 6 or 8 wires.

You can "feel" the strength of the motor just by turning the shaft by hand while it is off. Stepper motors will feel a bit rough since they tend to hold at the steps. A strong motor will have very defined bumps as it turns. All the ones I've gotten out of printers are don't seem to have much force to them. That's not to say they won't work, but it is a real design constraint.

coffeehedake wrote:

I stumbled across this page: http://insectphotos.net/tools/electronic/cnc/index.htm which may be of some help. Also this one gives a lot of background info on stepper motors in general:
http://www.omega.com/prodinfo/stepper_motors.html

You can see in the pictures there, that the drive motors are relatively small, though the engadget site shows some larger ones from an old AppleWriter printer.


Good sites. The only thing I'd bring up is that half-stepping isn't as powerful on the half steps. The reason it is used in CNC applications is usually to make the movement smoother and reduce vibrations that can cause errors.

coffeehedake wrote:

One of the things I've noticed is that some of the stepper motors have a rating on them, once you have dissected the device. At least on the engadget page, the old AppleWriter steppers have a posted degree per step rating.

Culvan would probably know a lot more about this stuff than I do. My feeling, however is that for a large amount of travel on any given axis, you're going to need a pretty beefy motor. Ideally, looking for a motor from a really large format printer, scanner, or plotter would probably yield better results. That being said, the smaller motors in your printer may be just fine for the Z axis, as there won't be as much traveling for the motor to handle.

I'm going to take a look through my CNC machine book and see if there is any advice there. I'll let you know if I find anything useful.


Unfortunately this is a mechanical question and I'm not that good with the mechanics. However I think I can frame this so it makes sense. The motor has to overcome friction and accelerate the gantry, cartriage or head. Friction will depend on the weight and how well constructed and aligned your sliders are. Acceleration is dependant on weight again and how fast you want it to accelerate. If you don't have enough force for the acceleration you are commanding it for then it will miss steps and it won't cut where you want it to cut. You can always slow the system down and reduce acceleration, but you must have a minimum amount of force to overcome friction or you won't move at all. There are also ways to gear the motors to increase the force they provide, but reduce the speed. One way is to use threaded rod instead of a timing belt. On my system, one rotation of the pulley on the timing belt produces about 1 inch of movement. Whereas 20 rotations on the threaded rod produces 1 inch. Friction is higher on the threaded rod, but the force to produce movement is geared up by a factor of 20.

The other thing to consider is what was the old stepper motor designed to do? Most of the time they are moving a print head that weighs a up to a few ounces. Typically early in the design, engineers will using much more force than they actually need. As they make later models they try to reduce the cost by bringing the components closer to the minimum values. This is combined with the fact that they are always finding ways to make everything lighter. The newer a printer is the lighter the components and the weaker the stepper motors. The older ones are going to be stronger because the materials were heavier and there was more "slop" in the designs. I'd look for old and heavy printers for salvage materials. I don't think you'll be able to move a 5 pound gantry with a salvaged stepper designed to handle a 2 ounce print head. If you plan to go with salvage, think lightweight, or at least similar weight to what you salvaged from. Using the rails from the printer/scanner seems like a very good idea since that's what it was designed to move.

Andy
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coffeehedake
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PostPosted: Mon Mar 01, 2010 10:03 am    Post subject: Reply with quote

Glad you dropped in for that Andy, good info.

I read this last night: http://buildyourcnc.com/torquemotion.aspx and it gives a little more information on Torque for the motors.

I don't think I'm going the salvage route, unless I can pull some really big motors out of something. I do have a few big plotters, but they are really old, and I'd be concerned that parts don't work, etc.

On top of that, I'm following relatively closely to the guide in the book, "Build Your Own CNC Machine" which is from http://buildyourcnc.com.

I've calculated out the major costs to build the starter machine, and it's about $480 so far, not including software and lead-screws, but including all of the steppers, the breakout board, drivers, cables, and MDF. This is a decent 3-Axis starter, with a 2'x4' table. I'm not sure what the Z-axis travel range is, however.

I would highly recommend the book. It is very detailed. However, a lot of folks can get started just by going to the site... he has the entire book on the site in a step by step process with videos, text and pictures, as well as free downloadable plans for the MDF parts.

This might be a good start for you Cheese. The Breakout board is actually cheap for this project too... $25! Steppers and drivers are about $50 each, tho, so watch out for that.
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