CNC Bridgeport with Heidenhein control



You remember when you made printouts of coordinates and then turned the handles to those positions to make shapes? That is what CNC control does, but it will do it on all 3 motors at around 1000 times per second depending on controls. The double loop, for example, is when the control gets a feedback from the motor and also gets feedback from the scales on the axis. The motor feedback is used to sense what the motor is doing, the linear scales sense the actual table position. These could be the same but if your ball screws get a tiny amount of backlash, the motor will try to make up for it.
The servo motor gets power to run forward or backward and has something to sense turning so it can be controlled, usually through a Proportional, Integral, Derivative (PID) control loop.
My system uses motor feedback to the motor amplifiers and uses encoder or scale feedback to the CNC control. So, if my position is off a move is required, my control will send out a signal to tell the drive to move the motor at a speed and direction. The amp will send power to the motor and sense the motors movement, as the position error is smaller, the controller sends a smaller signal until the motor stops at the correct position.
RogerN
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OK, I think that I understand that. I will look for some webpage that described architecture of a CNC system. I already have all the manuals in my possession.
i
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Ignoramus21067 wrote:

Load up and run EMC2 or Mach3 in demo mode with no machine. I use Mach3, mostly because it was ready for prime time before EMC2 was. When I started with CNC I tried EMC (EMC2 wasn't out then) and Mach3 side by side on identical PCs controlling the same machine (at different times) and chose Mach3 as the more polished solution. EMC2 should be more on par with Mach3, but I haven't tried it since I already have Mach3 and the hobby license is unlimited.
CNC controls are a *lot* simpler than you might think, and a little fiddling and you should have it figured out very quickly. The G code that CNC controllers operate on is nothing more than simple positioning commands for the most part. Where is gets complicated is in the CAD/CAM end and generating code for full 3D work, and you really don't need to get fully into that for hobby work. Most hobby work tends to be 2.5D, not full 3D and that makes it quite a bit simpler. Look at SheetCAM for an example of a decent 2.5D CAM package.
For hobby work, you'll find that the few things you really need 3D moves for are usually ones that are easy enough to hand code. There are specific G code commands for arcs and stuff which are useful if you're hand coding, but they aren't typically used by CAM programs which mostly generate the code as line segments since code length isn't a concern on an modern CNC control.
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Thank you Pete. Are there some provisions for using this mill in kind of manual mode. Let's say that I just want to drill a hole in a part and mill off a corner, something that is easy to do with a manual mill. How much harder would it be to do with CNC. Maybe with keyboard arrows or some such. The question probably shows my ignorance, but I want to know how much I am giving up by switching to CNC.
i
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Ignoramus26960 wrote:

Two "manual" functions:
MDI - Manual data input, basically a CLI interface to the G code interpreter. You just enter a single G code command at a time like "G01 X4.5 Y3.7 F150" which moves to the specified X and Y position at the specified 150 IPM feed rate.
Jog wheel - You can manually move one axis at a time using the jog wheel and you can set the jog steps to increments like 1", .1", .01", .001".
Once you get familiar with G code, jog will only be used for "touch off" functions to establish your zero, and then you'll use MDI input for anything manual, or just pop up a text editor and write a quick chuck of G code then load and run it.
I haven't looked at the EMC2 docs, but I know there is a decent G code reference section in the Mach3 docs you could download and look at. G code is a standard, so it's pretty much the same for any control (they do have custom extensions on some).
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wrote:

Mach 3 has "Wizards" included in the licensed version that will allow you to simple code very quickly for mill drilling, pocketing and surfacing.
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On Feb 24, 10:46am, Ignoramus26960 <ignoramus26...@NOSPAM. 26960.invalid> wrote:

I use an EZ Trak Bridgeport manually when reworking a part to scribed lines and punch marks. The Jog knob substitutes for the table cranks. After a little practice to remember the button sequences it isn't that much different from using a manual DRO machine.
The CRT died on that one too.
An example of an EGA to VGA adapter: http://www.controlcable.com/custom.asp?i=65033
jsw
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Jim, sorry for a dumb, repetitive, redundant question, but I just want to make sure. This thing converts incoming EGA signal to outgoing VGA signal. So I can plug in a regular 15 inch VGA monitor (which I have) into the EGA output of the Heidenhein control, using this converter int he middle? Right?
i
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Ignoramus26960 wrote:

It's not clear what it does really. From what I've found, the VGA RGB signals are .7V p-p, and sending raw TTL 5V RGB signals to those lines probably would be bad. Of course there could be little resistor ladder D/A converters molded in there somewhere, but I wouldn't count on it.
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On Feb 24, 7:37pm, Ignoramus26960 <ignoramus26...@NOSPAM. 26960.invalid> wrote:

That is a question for the older smart guy at the local computer store where you buy it. They do exist and aren't expensive.
Go when they aren't too busy and leave yourself some time. My last simple question lead to a story about back when he worked at Intel. Another one talked for an hour past closing until his worried wife called.
jsw, who practiced looking attentive for long periods for this: http://en.wikipedia.org/wiki/The_Milk_Train_Doesn 't_Stop_Here_Anymore The hard part was keeping my eyes up on her face.
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On 2/24/2010 8:17 PM, Jim Wilkins wrote:

Nice figure, Hmm?
Kevin Gallimore
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    Assuming that the monitor supports the scan rates (and thus the resolution) that the EGA connector produces. I think that pretty much any multisync monitor can go down that far. Double check for LCD monitors, as not all will support all lower rates.
    If you can find a LCD screen which will handle the proper rates, that strikes me as the one which makes sense to use in a shop environment -- less surface area of ventilation holes for chips to fall into -- and less power consumption as well.
The pinouts for the two interfaces are:
    <http://www.allpinouts.org/index.php/EGA     <http://www.allpinouts.org/index.php/VGA_15_Pin
    Note that the EGA output is at TTL levels, while the VGA is 0.7 V P-P at 75 Ohm impedance, so a voltage divider on each color signal will be needed -- and perhaps another divider for the secondary color outputs on EGA to give differing intensities. I haven't bothered to check whether there will also need to be inversion of sync signals. For that -- if needed -- you would need some active circuits and thus a power source.
    But since the converters are available for not much money, that strikes me as the way to go.
    Good Luck,         DoN.
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Don, so, if I can get a NEC MultiSync monitor and that EGA to VGA cable, I could then see the EGA image? Did I get that right?
i
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Ignoramus2215 wrote:

No, nothing to do with NEC Multisync monitors, they just happen to use that name. Pretty much all current monitors are multisync, the days of monitors that only handled one specific scan rate are long gone.
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    [ ... ]

    Not just NEC MultiSync, but any other which can handle the needed scan rate. I was using "multisync" as a generic term, not a brand name. Note that I used lower case in the term.
    The converter card which you posted a link to (or someone else posted the link) looks as though it will also handle scan rate conversions -- so that and a LCD monitor looks like the best bet in terms of surviving shop conditions -- with a sheet of Plexiglas or Lexan to protect the screen from hot chips and coolant splatters.
    Good Luck,         DoN.
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It seems to me that you might be asking if there is a manual mode, similar to using a pendant control on a robotic machine, that allows the operator to take control of the robot's motion capabilities. With some robots, there is a "teach" mode, where the operator can save the motions of a task.
I don't know that answer, but I'm curious if any home shop machines have a pendant mode.
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WB
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Mach 3 registered has a learn mode in the collection of Wizards. Also, you can use keyboard controls to directly control the machine. I use both of those things. I'm curious how you thought us home shop guys zeroed the machine to the work piece?
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I am reading the EMC2 manual, it has a nice jog mode, I can run everything with keyboard arrows for X,Y and PgUp/PgDn for Z.
i
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Thanks, Bob.. the jog function was previously discussed, so I assumed that an operator had control capabilities, but I was curious about teaching/learning feaures.
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Ignoramus26960 wrote:

Some of the old tape-NC controls were not at all set up for manual machining. Later CNC controls with CRTs were not too bad, and your TNC-151 should be in that era. They have jog buttons and maybe even an MPG to crank like a manual machine's handwheels. Pretty much all PC retrofits will also allow you to do that. I used the jog keys on the keyboard for a while, but put MPGs on my two machines now and find them to be a great addition. But, when manually facing off a surface or something, I still use the jog keys to get a constant feed rate.
My tabletop milimill has handwheels, and EMC works as a DRO when it is in E-stop, so I could use it completely manually, but I never seem to do that. I run it with the jog pendant instead. (I bought this machine for on the road demos, and never did any real machining on it until I put a spindle encoder on it, now I use it for rigid tapping 4-40 holes on some of my parts. So, that is pretty much its only actual machining it gets.)
Somebody mentioned putting a spindle encoder on your BOSS, but the way Bridgeport built their machine heads, if it didn't come with a spindle encoder, you will find it difficult to install one. That's why I don't have a spindle encoder on my Bridgeport. I think the only clean way to do it is to put a pair of gear tooth sensors through the side of the housing to pick up quadrature off the bull gear, and add a magnet sensor for the spindle index. The way the spindle slides in the spline, and the back gear and direct drive clutch all nest together, there just isn't any place to add a sprocket to pick up the direct spindle position for an encoder. I suspect you have a 4-J head on that machine, it may have a little more room in it than my 1-J head.
Jon
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