Milling Table Stepper Motor

[cfellows]

I have an Enco Mill Drill that I bought 16 years ago. Long ago I fitted a DC gear motor to the X-Axis with an additional gear set that can be connected or disconnected by loosening a setscrew and sliding the big gear back, disengaging from the dogs on the screw.

I've been slowly collecting parts to convert it to CNC and while I have most of the mechanicals, I've yet to get stepper drivers and controller box. So, in the meantime, I'm thinking it might be interesting to go ahead and swap out the DC gear motor for one of my steppers. An arduino powered stepper motor on the X-axis could be handy. I'm thinking a keypad to input numbers and decimals and a left and right cursor button.

So far, from a functional standpoint, I see being able to input a decimal number, then each time I press the left or right cursor key, the table would move in that direction the distance indicated by the number I input. It would speed up gear cutting even more with my electronic dividing head. Now I have to see what other functions might be easily implemented..

Chuck

 

[petertha]

Look forward to what you come up with. I think it would be great.
And how about feed rate input too?
Out of interest, what kind of motor torque is required for that application? What are typical input voltage & current requirements?
(I'm cnc illiterate)

 

[goldstar31]

As a follow up from Petertha's comments, I wonder if you will be good enough to suggest what stepper motor you would recommend.

I think that two issues come up. I am 83 and clearly from a generation who were not only cnc illiterate but computer illiterate. Again, for the literate, many have what appears to be a fairly common mill or mill/drill.

The second is that many of us reach a physical state where we lose mobility and dexterity-- before we lose - our marbles.

Putting some 'plain words' onto things like what the h*** is a shield? The last shield for me was something that the Vikings wore.

Meantime

Thank you

Norman

 

[RonGinger]

Several years ago I built a BASIC Stamp controller to drive the table on a surface grinder. That didnt support any display or key pad, so I set it up with a direction toggle switch, and a jog button. Click the direction and press the jog button and it ran that direction until you let go. Kind of like a power feed.

When you reached a spot at one end you pushed a 'remember' button. Then you flipped the toggle, jogged to the other end and pushed 'remember' again. Then there was a Start/stop button, one push and the motor started to oscillate from one remembered position to the other, the obvious motion for a surface grinder. I was going to add a Y stepover function, but lost interest. That would have made it a good mill program for gear cutting.

Ill bet the Arduino takes more programming to setup and calibrate the inch to step values, than to run.

Sounds like a fun project.

 

[cfellows]

Thanks, guys. Here are the most likely candidates from my collection.

The big motor on the left is a NEMA 34 (frame size) and has 1600 Oz In of torque. It's rated at 3.5 amps and I would use a 24 volt power supply with it.

The box in the middle is an IB104 stepper driver made by IMS. It will supply up to 4 amps with input voltages of 24 - 80 volts. It has a current limiting function which limits the amount of amps supplied to the motor. I bought it used on Ebay, and as you can see, I had to add all new connection points since the previous connections had simply been clipped off. This type of stepper driver use direction and step signals from the Arduino and controls all the proper sequencing of voltages to the coils of the stepper motor.

The motor on the right is a NEMA 23 and has 396 Oz In of torque. It's rated at 3 amps and I would also use the 24 volt power supply to run it. This motor is arguably on the small size for milling operations, but if geared down 3 or 4 to one, I think it will do the job, however slowly! That's why I bought 3 of these for the CNC conversion.

When using a stepper driver, all the old Ohm's law formulas kind of get tossed out the window. Normally, the number of amps would be the supply voltage divided by the coil resistance of the motor. Both of my stepper motors have a coil resistance of around 5 ohms, so a 24 volt supply is going to try to ram nearly 4 amps through the motor. However, the stepper driver has a current limiting function which will restrict the number of amps to a smaller, adjustable value no matter how high the input voltage is, up to 80 volts. This let's you have a higher torque (and higher speeds) without exceeding the current rating of the motor.

Chuck

 

[dman]

Thanks, guys. Here are the most likely candidates from my collection.

The big motor on the left is a NEMA 34 (frame size) and has 1600 Oz In of torque. It's rated at 3.5 amps and I would use a 24 volt power supply with it.

The box in the middle is an IB104 stepper driver made by IMS. It will supply up to 4 amps with input voltages of 24 - 80 volts. It has a current limiting function which limits the amount of amps supplied to the motor. I bought it used on Ebay, and as you can see, I had to add all new connection points since the previous connections had simply been clipped off. This type of stepper driver use direction and step signals from the Arduino and controls all the proper sequencing of voltages to the coils of the stepper motor.

The motor on the right is a NEMA 23 and has 396 Oz In of torque. It's rated at 3 amps and I would also use the 24 volt power supply to run it. This motor is arguably on the small size for milling operations, but if geared down 3 or 4 to one, I think it will do the job, however slowly! That's why I bought 3 of these for the CNC conversion.

When using a stepper driver, all the old Ohm's law formulas kind of get tossed out the window. Normally, the number of amps would be the supply voltage divided by the coil resistance of the motor. Both of my stepper motors have a coil resistance of around 5 ohms, so a 24 volt supply is going to try to ram nearly 4 amps through the motor. However, the stepper driver has a current limiting function which will restrict the number of amps to a smaller, adjustable value no matter how high the input voltage is, up to 80 volts. This let's you have a higher torque (and higher speeds) without exceeding the current rating of the motor.

Chuck

i had a spread sheet to do the calculations, basically that 1600oz inch motor if it is what i think it is is, may be ideal for a full size bridgeport with direct drive, no gear reduction.... that is as long as the inductance is low. i have some nema 42 motors that i chose with a short case and low inductance because they were cheaper than a comparable nema 34. the advertised torque on my motors is 1700oz/in and i figured that to be like putting a 40lb weight on the milling handle and trying to turn it. it's about all i'm able to put on the handle with one hand smoothly without leaning into it and would never do that in a milling operation.

now that's if "lost step" is a big concern and it is for cnc but not nessesarily for a power feed, you'd probably have torque for power feed with less but may lose steps when the motion starts due to acceleration.

the thing with stepper motors is the they need to energize the coil and discharge it 100times per coil per rev. a dc motor or ac motor only does this 1-5 times. the inductance of the coil determines the impedence curve. more frequency makes for more impedence. more inductance makes it climb faster.

the supply voltage makes current at higher frequencies (rpm) when the amps would otherwise start to drop from more impedance. you need a certain supply voltage for a certain torque requirment at speed. the voltage would regulate the top speed in this regard.

they may actually both be good choices for a power feed. a smaller motor may need gear reductions but the inductance may also be lower so they can run at higher speeds.

if you have the inductance specs i'll dig up the spread sheets, the only thing i didn't like was there was no way to set the acceleration rates in the spread sheets only velocity, the g-forces were preset and i don't know what the values they used were.

 

[Draw-Tech]

Hi All

Check out this site.


http://www.automationtechnologiesinc.com/

Jack
Draw-Tech

 

[cfellows]

I've had a change of heart. Rather than waste time hooking up a single stepper to the X-Axis, I'm moving ahead with converting the whole thing to CNC. Rather than use Mach3 and a breakout board, I'm going to use GRBL which runs on an Arduino UNO. It's free and reviews are rating it pretty good. There's any number of free g-code streaming programs which run under windows and connect to the Arduino through USB. Still looking for an inexpensive or, better yet, free CAM program.

I think I have all the mechanical stuff for the mill/drill. I have ball screws & nuts, 3 NEMA23, 370 Oz In steppers and the Arduino. I'm going to use the GRBL shield which is about $70, connects directly to the Arduino, and has three 2.5 amp stepper drivers built in.

I'm really in this more for the experience of learning and building a CNC machine. I don't really have any plans for mass producing parts with it, but once it's finished, I'm sure I'll find lots of use for it.

One thing I've learned is that the mechanical part, including the steppers is only half the cost. The CAD, CAM, and motion controller can easily add up to another $500 - $1000. And the fact that many of the systems still require a computer with a parallel port just doesn't seem right!

Chuck

 

[dman]

I've had a change of heart. Rather than waste time hooking up a single stepper to the X-Axis, I'm moving ahead with converting the whole thing to CNC. Rather than use Mach3 and a breakout board, I'm going to use GRBL which runs on an Arduino UNO. It's free and reviews are rating it pretty good. There's any number of free g-code streaming programs which run under windows and connect to the Arduino through USB. Still looking for an inexpensive or, better yet, free CAM program.

I think I have all the mechanical stuff for the mill/drill. I have ball screws & nuts, 3 NEMA23, 370 Oz In steppers and the Arduino. I'm going to use the GRBL shield which is about $70, connects directly to the Arduino, and has three 2.5 amp stepper drivers built in.

I'm really in this more for the experience of learning and building a CNC machine. I don't really have any plans for mass producing parts with it, but once it's finished, I'm sure I'll find lots of use for it.

One thing I've learned is that the mechanical part, including the steppers is only half the cost. The CAD, CAM, and motion controller can easily add up to another $500 - $1000. And the fact that many of the systems still require a computer with a parallel port just doesn't seem right!

Chuck

many compters still have parallel port headers on the mother board. especially the cheap atom and amd apu systems. $60for a board with integrated cpu +ram +a case with built in psu and you have a system for about $150. but thanks for turning me on to this. i always knew it was posslble considering the early systems out there. i would have other wise suggested rtstepper which uses a lot of linuxcnc on a pc then buffers the moves on a pic you can buy for $80 from the developer. rt stepper can run on just about any computer out there including mac and windows.

i'm gonna look into this grbl and who knows. it may power my lathe, or some version of it may power my mill but the mill isn't gonna run on a 2.5 amp stepper driver.

 

[geoff p]

I used to use Mach2/Mach3 for a home-built router, until I moved house and at about that time my computer died. The new computer doesn't even have a parallel/printer port and I couldn't justify the cost of USB-to-parallel adapters.

So the whole router concept died - well it was NOISY and I didn't really want to upset my new neighbours.

Nowadays I content myself with an X~Y table on a totally cr*p Chinese bench-drill, using the steppers off my router. They are 200 oz-inch but only require about a half-amp, so the Pololu A4988 drivers are adequate, sort-of.

GRBL is amazing! Even on an Arduino UNO with its limited processing power, GRBL can achieve very smooth running up to adequate (for me) stepping speeds. Its main beauty, though, is that it stores nothing - the received code is pre-processed, processed, outputted and then forgotten! Which means a file of many thousands of lines of G-code can be sent, so long as WinSlop maintains a USB-connection.

The only thing I miss from Mach3 is sub-routines, which are not covered by GRBL. Pity but not the end of the world.

I use Zapmaker's "Grbl Controller 3.4.5", to send my hand-written code to Arduino/GRBL through a USB-port.

I recommend it to anyone.

So far as CAD/CAM programmes I haven't a clue - my experience was limited to 'playing' with graphics-conversion type programs, and none did true curves - rather a series of (very) short linear cuts each a few micro-gnat's-cock in length.

Geoff
www.purpletiger.com

 

[DICKEYBIRD]

The only thing I miss from Mach3 is sub-routines, which are not covered by GRBL.http://www.purpletiger.com

I really love the Arduino CNC concept but the lack of Wizards would be a deal breaker for me. Almost all of what I do on my lathe & mill are done with Mach Wizards....writing code gives me the willies. You guys are clever though and probably won't miss a beat.

Thanks for the post Chuck; I'll be watching all the way!

 

[cfellows]

Another thing I'm learning is the output file capabilities of the CAD program is important if you want to 3D print or CNC cut your 3D model. This morning I was experimenting with Design Spark, a free 3D modeling program from DS Mechanical. The user interface is pretty straight forward although a little different from Alibre, the program I've been using.

I used DesignSpark to draw the attached drawing of a flywheel center which can be cut out of aluminum and inserted into a steel pipe section to make a complete flywheel. This cut-out is a pretty good design test for any CAD program. Bottom line is that DesignSpark has several good output file formats including the following:

PDF - Good for documentation and also a useable input format by several 2.5 & 3D CAM programs. If you click on the drawing and move the mouse around while holding down the left mouse button, you can change the viewing angle.

DXF - Also used by several different CAM programs.

STL - Good for some CAM programs and most 3D Printing slicing programs.

I would recommend DesignSpark to anyone wanting to learn a CAD 3D modeling program. Don't know the future of the software, but for now I think learning it would be a good investment of time if you also want to output your drawings to CNC or 3D printing.

View attachment FlywheelCenter.pdf

 

[Wizard69]

GRBL is a fine controller, but last I knew it didn't support an MDI mode. Maybe somebody has an interactive user interface for it now. If you are building a machine without an MDI mode you will be very limited with respect to interactive use. I see this as important because sometimes you want to leverage a CNC machine without the struggle of doing full up CAD/CAM work.

I've had a change of heart. Rather than waste time hooking up a single stepper to the X-Axis, I'm moving ahead with converting the whole thing to CNC. Rather than use Mach3 and a breakout board, I'm going to use GRBL which runs on an Arduino UNO. It's free and reviews are rating it pretty good.

It does have a good reputation.

There's any number of free g-code streaming programs which run under windows and connect to the Arduino through USB. Still looking for an inexpensive or, better yet, free CAM program. I think I have all the mechanical stuff for the mill/drill.

Streaming G-Code is fine if you have a good G-Code programs to run on the machine and have the intention to develop those programs as needed. But that isn't all there is to running a CNC. I can't imagine not having some sort of interactive capability on a CNC machine. Especially on a mill.

Now there may be programs out there that give you interactive capabilities with GRBL but I just don't know about them. Hopefully the hive mind will turn up something.

I have ball screws & nuts, 3 NEMA23, 370 Oz In steppers and the Arduino. I'm going to use the GRBL shield which is about $70, connects directly to the Arduino, and has three 2.5 amp stepper drivers built in. I'm really in this more for the experience of learning and building a CNC machine. I don't really have any plans for mass producing parts with it, but once it's finished, I'm sure I'll find lots of use for it. One thing I've learned is that the mechanical part, including the steppers is only half the cost. The CAD, CAM, and motion controller can easily add up to another $500 - $1000. And the fact that many of the systems still require a computer with a parallel port just doesn't seem right! Chuck

These costs do add up over time and that is why I'm a ways off from my own CNC equipment.

 

[cfellows]

Wizard, what are you thoughts on LinuxCNC?

Chuck

 

[Wizard69]

Wizard, what are you thoughts on LinuxCNC? Chuck

I have LinuxCNC installed on a virtual machine to play with, but I have yet obtained a machine to actually implement a CNC system on though. That being said I like the system but it is a complex package to set up. Then again so is Mach. LinuxCNC reminds me of older CNC controllers in some ways, but yet it is also very capable. Running on PC hardware means there are few limitations to program size. Back in the day I use to do a lot of work on Bandit systems and custom CNC systems built off DSP chips sitting in old 486 class computers, I think it is fair to say that LinuxCNC is light years ahead of those systems in many ways. Probably its only shortcoming with respect to those custom machines I worked on is system resolution, but not many do diamond turning in the home shop.

By the way both Mach and LinuxCNC are far easier to work with, set up wise, if you can use canned configurations. So with basic 3 axis milling you should be good.

By the way your post caused me to look again at GRBL last night. Well at least until they closed the library. 😜😜. I even downloaded the recent versions and did a little research. It does look like the developer is working on a GUI interactive interface for GRBL! However I did not get a chance to investigate in depth, nor do I know the features of the app. Interesting times here, it just looks like you are a bit early.

One thing to consider, GRBL or similar solutions will likely be required in the future as the cheaper PCs delete parallel ports and even slots to plug a parallel port into. Long term this is where I see LinuxCNC having problems, they will likely have to move the software to embedded platforms.

Gotta run!

 

[RonGinger]

GRBL is interesting, but it is really aimed at 3D printers, not CNC milling. It has lots of functions that have to do with setting up and controlling the extruder, which are of course useless for CNC. It lacks many things that CNC mills need, like all the drill cycles. I am not sure how it handles circles and arcs. Most important is its lack of a control interface. The 3D printer world wants to generate a file and just send it to the printer,like you do with a paper printer. For CNC you need functions like touch off to setup the tools and jog functions, and MDI is very handy.

When you are starting out to learn something new. like CNC, why use a tool not designed for that use? You will have enough to learn when you use a system aimed at CNC. Certainly GRBL can be made to do some control of a CNC mill, but its kind of like buying a garden tractor when you want to start farming 100 acres. Wrong tool for the job at hand.

On file formats, dxf is a 2D format, stl is 3D. For startup Im sure you will be doing 2D milling for a while, 3D has lots more complications you dont need when you are learning the basics.

 

[dman]

Wizard, what are you thoughts on LinuxCNC?

Chuck

if you want a compromise between grbl and linuxcnc and are afraid of linux then check this out.

http://www.ecklersoft.com/

 

[idahoan]

One other thing on the file formats; STL files are fine for rapid prototype machines and is usually what the system want to see. But an STL file is probably the worst 3d file of the bunch for 3d surfacing in a CNC mill.

An .XT or .STP would be my first choice; some CAM programs will also accept native files directly from the CAD program.

Dave

 

[Wizard69]

I think it is best to describe GRBL as a works in progress. As you note currently it functions best in printer mode, that isn't completely unusable on a mill but is extremely limited. The developer is working on a more interactive user interface but I'm not even sure what that provides in the way of user control. So one has to repeat we have a works in progress here!

GRBL is interesting, but it is really aimed at 3D printers, not CNC milling. It has lots of functions that have to do with setting up and controlling the extruder, which are of course useless for CNC. It lacks many things that CNC mills need, like all the drill cycles. I am not sure how it handles circles and arcs.

GRBL supports enough to be very useful for a number of milling uses.

Most important is its lack of a control interface. The 3D printer world wants to generate a file and just send it to the printer,like you do with a paper printer. For CNC you need functions like touch off to setup the tools and jog functions, and MDI is very handy.

Without a doubt this is the biggest concern with GRBL, without a GUI interface of some sort supporting MDI, it becomes very difficult to do what should be simple things. I don't think it is ready for prime time CNC milling. However it may work very well for running a router or similar process that can get buy without the extensive setup sometimes needed with a mill. The reality is you are working with Alpha/Beta software that is under active development. If somebody is up to the challenge of helping a developer out it is certainly worth investing some time. After all the more low cost CnC solutions the better. However if you want to setup and run a mill as trouble free as possible there are better solutions. Especially if the intent is to use the mill in an interactive manner doing one off parts.

When you are starting out to learn something new. like CNC, why use a tool not designed for that use? You will have enough to learn when you use a system aimed at CNC. Certainly GRBL can be made to do some control of a CNC mill, but its kind of like buying a garden tractor when you want to start farming 100 acres. Wrong tool for the job at hand.

That might be going overboard a bit. The key point here is that if you go Mach or LinuxCNC, they both have canned 3 axis mill solutions.

On file formats, dxf is a 2D format, stl is 3D. For startup Im sure you will be doing 2D milling for a while, 3D has lots more complications you dont need when you are learning the basics.

 

[blighty]

been having a look at cad/cam stuff as i was going to point in the direction of Alibre for cad and visual mill for cam. both very good and wont cost the earth.

then found this on there web site

http://mecsoft.com/freemill/

so that's the cam sorted....... if its any good.