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2 axis CNC

edijse

Oct 3, 2013
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Oct 3, 2013
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Good evening.

I have a piece of equipment that just broke down and is no longer manufactured for over 10 years. In simplicity, it is 3 axis cutter. I have side to side Y movement, roller rotating for X axis and a knife up and down movement on Z axis. All of the motors, limit switches and encoders seem to be OK. I am getting a software fault and with machine that is no longer supported I am stuck with it.
I would like to get rid of the mother board and instead replace it with my own. I would like to be able to draw a 2D drawing, upload and fire up.

I am fairly familiar with electronics and mechanics.

Any suggestions on how to accomplish this under lets say $300? Getting a PC if needed is not an issue...

Any help is appreciated.

Best,
Edge
 

Gryd3

Jun 25, 2014
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Arduino and the Beaglebone are commone 'mother boards' for hobby CNC machines.
Alternatively, there is also EMC2 which is bundled with LinuxCNC.
It's an Ubuntu Linux operating system with some modifications and tweaks to allow it much more stringent control over the Parallel port on a computer. This can be installed on any number of machines, as long as they have a parallel port.

Regardless of the choice made, you still need drivers for the motors, as the computer, or microcontroller won't be able to do it...
I could be wrong though... when you say 'encoder' do you mean the device that provides positional feedback, or the device that controls the motor? You see, there is the brain that tells it to move, and the driver that controls the fine details about how to actually move it the distance requested.
I should also mention that if your machine uses servos instead of stepper motors... your going to have a 'fun' time getting everything tuned and ready.
Is it not possible to keep and repair or re-purpose the board? Without a complete list of the parts you have/need you will probably approach or exceed the $300 limit.

I would like to push the LinuxCNC project though, as it's been around a lot longer and has gained some very helpful tools, options, and configurations. It can operate CNC laths, 2.5, 3, 4, 5.... multiple axis machines and even things like scara arms and other articulated arms with its 'inverse kinematics' modules.
If you have pictures we can help ID what you may need, and what you should probably hang onto.
 

edijse

Oct 3, 2013
8
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Oct 3, 2013
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Great! thanks for responses. I do like the Arduino idea as I have a few sitting in my drawer waiting for a project.
I tried to upload pics. it did not work. I have the frame, two 12Vdc motors for x and y axis. the z axis is a short up and down movement with a knife blade. The X axis is basically a rotating drum that used to have a rubber material for cutting.
I believe that I can reuse everything, the power supply included. It does have a magnetic circular encoders for positioning attached at the ends of both motors. It has proximity sensors for home positions as well. Everything is functional except that once I power the machine it errors with an error that it could not reset the encoders. when it turns on, it is supposed to rotate the axis, determine home position and then wait for job upload. I know that the motors are not given power when machine starts up...
The boards were sent to 3rd party company for repair and got returned "fixed" so there is no faulty components on them. therefore, I think it is a software issue...

I think I'll give a shot for grbl and arduino. Otherwise, I also have a raspi laying around and all in all this should be quite exciting project..
 

Gryd3

Jun 25, 2014
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I would suggest you dig in a little more though first..
Are the 12V motors 'stepper' motors, servo's or just plain DC motors?

Steppers are easy to work with. Servos require a fair bit of tuning and research. Plain DC motors will need some kind of custom or 3rd party controller to work in tandem with the positional encoders to operate 'like' a servo.

I would hate for you to take things apart and dive in if it will require an obscene amount of work...

Some big key notes between the choice of stepper vs servo is:
Servo can typically run quicker, and is a closed-loop system. Meaning that the machine will pretty much ALWAYS move exactly where you tell it to. Closed-loop positioning systems like this can be pricey/time consuming/difficult to develop/build/repair.
Stepper motors typically run slower, and are an open-loop system. This means that the controller will 'blindly' tell the machine to move X amount of steps, and can't verify it's exact position without first moving to a 'home' or 'limit' switch. Missing steps causes the machine to loose it's position. The machine should only miss steps if it is heavily loaded, or if it is moved at such a speed that it begins to 'resonate'. These can be avoided by tuning the machine, and flat-out not pushing it too hard. Many many machines rely on stepper motors. (most 3D printers, and many entry level manufacturing CNC machines) They are much simpler to use and troubleshoot.

So.. you can trade simplicity for accuracy and speed. Given the budget of $300 I want to help you make sure you have all your ducks in a row before starting or your project cost could end up much higher..
Have you considered wanting to repair the board yourself perhaps? The error you are receiving could very well be one of the encoders and not the actual board.. Food for thought?
 

edijse

Oct 3, 2013
8
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Oct 3, 2013
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Gryd,

I probed the motors and their ecnoders. The X and Y axis motors have two power leads. I can move them with 12 VDC, I could not find specs for them but I suspect that they are supposed to have 15VDC as the power board has 15V power LED. The encoders for X and Y have two voltage level readings while turning, 0V and 5V. As to Z axis, it does not rotate as it is a stationary knife that lifts and lowers. it basically is an electro magnet that has a coil around iron core. the encoder on it has voltage from 0 to 5 in steps. Based on these findings, I don't think they are stepper or servo motors as per descriptions that I could find on google. However, the machine was very precise, even though it went trough homing procedure on every start up.

I checked all of the encoders and the motors, they are functioning correctly. all of the limit switches work as well. the board is getting power and receives inputs from keypad as evidenced by sound. I will send the boards out for repair one more time under warranty as they just got "repaired". Failing that, I plan to use the machine as a base for my own built CNC as in simplicity that what this thing is. The $300 is a very optimistic estimate. I'm don't know if you are familiar with Litho printing, but basically there is a certain coatings on paper that gives it shine after printing and keeps the ink better on paper. In certain applications the coating is not desired on parts of the print. this is achieved on cutting out parts of a rubber blanket. where there is a cut out, the coating is not applied. This machine was made in 2002 and we bought it in 2010. by now, the machine is no longer produced and only alternatives are small, 77"X155" CNC routers. At which point the price goes sky high and who is going to pay upwards of 20K for and application where the person could cut it by hand. Now, if the price stays below lets say $1000.00, I can justify on making one as it saves hours of labor for a person.

I wish I could attach pics, lets try this, here's a link to my GDrive: https://drive.google.com/folderview?id=0Bwnpt54LE0z3ZmdzY2RJVlBUc0E&usp=sharing. As you can see it is pretty simple machine.

The reason I would prefer Arduino method is that I am familiar with Arduino, they are cheap to replace and I have several laying around. Getting a PC to run software that converts lines to Gcode is not a problem as I have dozens laying around too. On LinuxCNC I don't even know where to begin...
 

Bluejets

Oct 5, 2014
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Linux cnc is good stuff, plenty of support etc.
Online searches should bring up what you want.
 

Gryd3

Jun 25, 2014
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On LinuxCNC I don't even know where to begin...
As Bluejets mentions, they have plenty of support.

Also, as mentioned above, the Arduino, RasPi, and Beaglebone solutions are usually used for small hobby machines. Typically 3-axis stepper based machines for 3D printing or small scale milling.

I'm certain you can get one of these solutions to work, but you may have a hard time getting them to work with that specific setup... Mainly because of how the encoders work.. It sounds like a very simple setup.
DC bi-directional motor with a very basic encoder... if you can call it that... it sounds as though there is a single output for an encoder... so the transition from 5V to 0V could be forward, or back. The controller would simply monitor the encoder as it drives forward and count the pulses to keep tabs on the current position of the machine. I'm willing to bet the accuracy of the machine is in large part due to the gearing of the motors. It looks to be setup in such a way as to require a lot of force on the X or Y axis to force the motor to move. Likewise the motor will most likely be operating with minimal torque.

Because of how this mechanism works... I think getting the microcontroller based solution will be difficult. I could be wrong... but that is not the norm when it comes to hobby machinery which is what the existing software for these things are based on.
Linux CNC however is used on multiple occasions on hobby and small scale industrial shops to retrofit and upgrade machines that are considered end-of life.
I'm not sure if it would have native support for monitoring and tracking the positions directly with the encoders though either...
I think in either case, you will need to build a controller that takes care of driving the motors. At the very least this controller will be able to sit between the microcontroller or the LinuxCNC and will make your life a little easier.. of course, swapping those DC motors out for steppers would probably be easier .

I know I've repeated a couple details already, but it's what I believe in.
Either approach you take will test you. Perhaps you should take a moment to google around and find the forum specifically setup for Linux CNC and one setup for the Arduino CNC controller.
Once found... as if there is any support/tools/information on using DC motors with a regular encoder. They may both have details already, in which case pick what you are more comfortable with. Otherwise, go with whichever one has the most details regarding your specific requirements.

(The DC motor + Encoder is your limiting detail... Steppers are easy on all fronts, and the Z axis you have will be easy on either system as well.)
 

edijse

Oct 3, 2013
8
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Oct 3, 2013
Messages
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sounds good. I'll start searching and see what I can come up with. At least, I know for sure that there is an application that I could use for this and would not have to dish out ridiculous amounts of money or just drop it and have someone to cut by hand.

Thanks for your help. I'll check out LinuxCNC and will compare with Arduino based setup. Either case, I might change the motors to stepper motors as I agree that they would work better with DIY set up.

Thanks.
Edge
 
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