Messages

21

General Mach Discussion / Re: Using Mach as a camshaft measuring device

« on: October 20, 2010, 10:25:14 PM »

My first question is: Why is the 50 millionths degree of precison necessary, if you are looking at the cam lift/rotation parameters in Excell?  Perhaps you are making this more difficult than necessary.

I have made all manner of cams using 4-axis CNC machines, beginning in 1981. Once the cam is digitized, in a series of angle/displacement readings, you can import the csv file into Excell, and see the cam profile.

When taking/recording the readings, you must be sure to sync the angle value, and the displacement. It may seem simple, but unless you have built a fully automated machine, it is easy to get the number pairs out of sync.  For a simple setup, you can use a dividing head to hold one end of the camshaft, and set up a linear probe with spc output. Usually, a spc output has a two number output line, comma separated. The first one is a line count, and the other is the digital value. If you make note of the the start angle cam position relative to the starting line count, and advance the rotation exactly one degree at a time, you can edit the file when you are finished, and put in the correct angle values in place of the line count. One degree steps in an Excell file will give a very good picture of the cam. You will also have a table of offsets to whatever degree of precision your linear indicator reads to. Doing this by hand, you can digitize a cam lobe in about 45 minutes.

Making a dedicated machine would not be very difficult, and using Mach3 to do it is also not difficult. Mach could turn the rotary table in whatever increments you would choose, and operate a relay to clock the digital probe. The recording would not be done by Mach3, as it would be just stepping the rotary table, pause, clock the linear probe, step again etc.  The linear probe could be sending it's readings to your laptop computer, i.e. a terminal program.


Regards, John
 







   









 

 

22

dspMC/IP Motion Controller / Re: Buying DSPMC - Why would I need Analog Inputs?

« on: September 13, 2010, 01:58:49 PM »

Regarding analog input, I think the more expensive control is worth the increased cost. In the final machine modification total cost, the analog I/O controller is relatively small.
All commercial machines use knobs for spindle speed, feedrate modification, and analog motor load meters etc.

I have two commercially built CNC mills. When running a new program, you are always watching the cutting tool, with one hand on the feedrate knob, in case the cutter feed, or spindle speed is too high. You can tell a lot just watching and listening. A tool can break in an instant, if a particular spot loads up the tool. It is easy to just crank down the feedrate, and edit the program later. Much less effort, than installing a new cutter, cleaning out the broken tool bits, resetting the tool offsets, and going back to the beginning, and possibly having to reset the machine home position. All this if you did not scrap the part!!

Looking up at the screen, and using the feedrate jogs is way too cumbersom, and takes longer. Look at all the posts asking how to add a spindle speed, or feedrate and what hardware to use.

I own a dspmc controller without analog, and wish I had opted for it. The controller is absolutely amazing.  Plus, it is a great company always working to improve the firmware, willing to answer any question you may have. 


Regards,
John

23

General Mach Discussion / Re: wells index cnc 700conversion to mach3

« on: September 07, 2010, 10:25:57 PM »

Hello mpryne:

I have no experience with the Bandit control. It is a really old control. If it had DC servo's, with a +/- 10v signal output to the amplifiers, you could use the servo's and motors, and retrofit a new controller such as the Vital Sysems dspmc.

If it is stepping motors, I would suggest a total retrofit.

The Vital Systems controller is an excellent unit, and very capable, plus it has been engineered to work with Mach3.

That's all I can suggest at this time.

Regards,

John

24

General Mach Discussion / Re: wells index cnc 700conversion to mach3

« on: September 03, 2010, 02:22:43 PM »

What is the controller manufacturer? If it is a Sharnoa controller, I may be able to help.

regards,
John

25

General Mach Discussion / Re: BobCad w/ Mach ?

« on: September 03, 2010, 12:53:16 AM »

Last year I called to re-install a version ( I think v19) on my HP laptop. The lady on the phone was very polite, and after verifying my account, original purchase, etc., walked me though the codes to activate the program. A day or two later, I began to get calls from the sales department, trying to talk me into an upgrade which was somewhere in the neighborhood of $1500.00, and I declined, and said I did not do much machine work anymore, and what I had was just fine. The calls kept coming again, again, and finally I just hung up in their face! The phone call rang again immediately, and I hit the red button. The calls kept coming day, after day, after day.
After about a week, they stopped calling. I still get emails almost every week!

The learning curve is pretty steep! It does output good code, but today there are much better programs coming along, at very competitive cost.

26

dspMC/IP Motion Controller / Re: AxisWorks tuning

« on: April 01, 2010, 04:08:21 PM »

Hello Peter81:

I have not heard of any video for Axisworks, although that would be a great addition for getting through the learning curve. You might drop Rufi at Vital Systems a note, and ask him if he would have time to produce one. I know he is always busy writing better software, but it's worth a try.

Some further thoughts on tuning, after my last message:

The "S" curve you see on the screen is the acceleration of the motor, in graphical format. From the beginning of the S curve, to the end of the curve, just as it becomes a straight horizontal line is, "Time," in the horizontal axis of the graph.

The vertical height of the "S" curve is the motor acceleration from standstill, to full programmed velocity.

It is that acceleration within the "S" curve, that requires the most motor amps. So, the motor can only move so much mass (weight of gantry or table), to a given velocity, in a given amount of time. Remember, horsepower (or Watts) is "work per unit of time."

That "S" curve time period is in fractions of a second, or a few hundred milliseconds. This is far to little time to visually see what is going on. However, with Axisworks, you can now "see" what is taking place. When the velocity is set too high, for a given time, the motor servo "faults out" and never goes to it's programmed distance.

By playing around with the numbers, you can learn the motor maximum acceleration and velocity for a given mass.

Since you are using two motors to move the gantry, the velocity that can be achieved with one motor observed in Axisworks, will be less than what is achievable in real use, when the two motors are working in unison, moving the same mass.

So, if your single motor faults out at 100 i.p.m. (inches per minute), you can probably achieve 130, or 140 i.p.m. when using the machine with the two motors in unison. This limit can only be known by trial and error.  The maximum velocity will not be double, since all these relationships are NOT linear, but it will be somewhere above the single motor velocity for sure.

You cannot put the higher velocity factor into the Axisworks test cycle, since the motor will immediately fault out. You could try putting a slightly the higher velocity setting in the Axisworks program, and not giving it the run command. Save the parameters into the dspmc controller, for each motor individually, and then try it out in a simple test program, i.e., go 10.0" at feedrate X, stop, go to 0.000 at feedrate X, stop.

Alternately, you could just program higher and higher velocity feed rates in a program, and see where the motors fault out. The problem with this, is you might damage the gantry if one motor came to a full stop, with the other one going full power. Whatever you do, proceed in incremental steps, making one change at a time, going from the "known" to the "unknown."


Regards,

John
 
 

27

dspMC/IP Motion Controller / Re: AxisWorks tuning

« on: April 01, 2010, 12:03:13 PM »

Hello Peter81:

If the two motors are identical, and driving the same load at the same time, they should have the identical settings.

The numbers (parameter settings) are the PID coefficients you find by trial and error to produce "best motion". These numbers are part of a very complex mathematical algorithm, and are not by any means "linear" with respect to the motor behavior. It would be educational to read some of the explanations in Wiki, regarding PID calculations. There are several excellent tutorials on that subject, with great graphs, to help understand what PID is. "P" means Proportional; "I" means Integral; and "D" means Derivative. These are mathematical terms.   

When the two motors are driving the gantry, the load is less for each motor, than when one motor had to drive the entire load by itself. However, that does not mean the motor cannot operate under a smaller load.

When a single motor axis is tuned for its best capability with Axisworks, it often will be used at a low speed, and be producing less horsepower.

The "best fit" PID settings will allow the motor to perform in its most efficient format, in real time. The servo motor is capable of working at low through high speed ranges, and the current draw will vary depending upon the demands at the moment. The greater the "load", the higher the current. This factor is the Kilowatt rating of the motor.

Any servo motor has a Kilowatt rating by design. This means it is capable of doing a measurable amount of "work."

Work or the term "Horsepower" is mathematically a function of.....force per unit of time. The mathematical equivalent of 1 horsepower, it "raising 550 pounds 1 foot in 1 second."  In Kilowatts, 746 watts equals 1 horsepower, or about 3/4 of a Kilowatt.

When Axisworks produces a graph, it is measuring a complex series of factors; amps, velocity, time, all at once, and showing you in graphical format, in REAL time, this action. Not a trivial problem, to say the least.

At initial start-up, the the motor cannot achieve the programmed speed instantly, thus the acceleration/deceleration "curves generated by the PID algorithm, and finally stored into the memory of the dspmc controller. It is this complex series of outputs, that make the PID servo motor motion so superior to other kinds of motion systems.

Hope this helps.

Regards,

John

   

   

28

dspMC/IP Motion Controller / Re: AxisWorks tuning

« on: April 01, 2010, 04:04:05 AM »

Hello Peter81:

Could you clarify the motor setup? Are you using two motors with 2 separate drives?

As far as I have experience with Axisworks, it will drive a single axis motor, and allow you to set the best timing parameters based upon your visual feedback from the graphical screen. The dspmc manual gives the basic starting settings for the inputs, and then you can play with different numbers, and find the maximum accleration, and smoothest response. The motor will also sound quite different at different settings. The sound itself is a good indicator that you are getting bettor or worse with the numbers. At some settings the motor will sound bad, and other settings it will default, and stop suddenly. You can set the motor to drive the table for a given distance and stop, or reverse each time you give the go command. You can check the exact distance traveled vs. your input command distance. It is a great program to arrive at that mysterious mix of timing numbers, and acceleration rates. You will find what is the absolute limit in acceleration and speed, because when you set too high, the motor will start to accelerate, and just quit.  Once the best numbers are deduced by trial and error, you can save them to the controller memory. Those parameters will remain the outputs that will be used for that particular axis servo amplifier.

If your two motors are driving a common load through a solid connection, yet using separate amplifiers, you could just save the same settings to the second amplifier. However, Axisworks must have an axis designation, i.e., X,Y, Z, A, B,C, to save the tuning parameters to.

If so, you can disconnect the power leads to one motor, and tune one axis at a time. Then, disconnect that axis motor power, and connect the other one, setting the same parameters, try it out, and  save to  A, B, or C, whatever axis name is slaved to the X axis.

I do not believe Axisworks can read two motors powered from one amp. The dspmc controller is not at all like stepping motors, using pulses from the PC.  The dspmc receives direction, distance to go, and feedrate from the PC, and drives the motor based on the internal PID settings stored in the dspmc memory, and the feedback from the motor encoder.
Each axis has it's own PID settings in memory, saved from Axisworks.

The maximum speed possible with the dspmc is only limited (within common sense reason) by the power, and quality of the motors and servo amplifiers used. Unlike the pulse train output for stepper type drives, which are tied to the pulse output from Mach3. There are some very superb motors now available, that will give fantastic machine speed using the dspmc, but at a cost.

Regards,

John

   

29

General Mach Discussion / Re: Cincinnati Sabre 750 retrofit to Mach 3?

« on: March 21, 2010, 09:04:07 PM »

Greetings KEFAFU:

I am retrofitting one of my early 1980's 4-axis mills, using the Vital Systems DSPMC controller. They (Vital Systems) worked with Art developing the firmware to run with Mach3. The manual and related software AxisWorks (motor tuning, PID graphical interface) is very well written, and thorough. The controller interfaces with the PC through an Ethernet crossover cable.

The old proprietary controls are not worth spending the money to repair; (1) Parts are hard to find, (2) the circuit boards costly if you can even get them, (3) they are really ancient technology, (4) the controls are filled with zillions of wires that have become frayed, insulation in doubt, and generally a nightmare to figure out, (5) even if you could get the original schematics and prints. which more often you cannot, (6) the screen is an obsolete, bulky CRT, with a crappy visual look, (7) and a nice color touchscreen is out of the question! ( and the lack of memory was a joke, and the "drip-feed" involved special boards and connections.

The PC, and the evolution of electronic micro-circuitry has revolutionized the machine tool industry. The big, corporate proprietary controls are all gone bye bye, along with their super costly maintainence and ridiculously expensive parts. Good riddance!!

Mach3 is a constantly evolving control interface, with the very writers often on this forum answering questions, and helping to make the solutions. Mach v.4 is in the near future, and the network of professional users/experts/ worldwide is the icing on the cake.

Regards,
John

30

General Mach Discussion / Re: How to attach 24v relay to mach3

« on: February 04, 2010, 06:22:24 PM »

CNC4PC sells a board that takes 5v. ttl signal input, and will output a 24v. signal.

John