Dyna DM2400 Conversion

[bjorn toulouse]

My advice, anyone wanting to to CNC a machine, find a CNC machine that has a bad control.

That is excellent advice!
Too bad more folks don't follow it.

Rex

[Dave_C]

Marty,

PID stand for Proportional, Integral and Derivative.

PID control has been used in the HVAC DDC industry for over 20 years. It works extremely well for most any type of control.

TO adjust:

The P value (proportional) is the response to the error from setpoint. IE: A large P value makes a large change even with a very small error from the desired setpoint.

The I value (Integration) is the timing part. How long before it makes its next adjustment.

The D value is the derivative value and it determined by how much did the last adjustment get close to the setpoint.

So they all work together. If your speed is searching up and down but settles closer to the desired setpoint with each up and down then put in a bigger P value. The I and D values can usually stay the same unless they were just way off to start with.

Hope that helps, I typed this from memory so I may have explained it a bit nontechnical.

Dave C.

[Marty_Escarcega]

Thanks Dave.
When PID tuning a motor a and its control from scratch, do you start with P to get close, then introduce I to incrementally sneak up on the set point? Does D fine tune?
Marty

[RET]

Hi Marty,

What Dave says is right. My experience with PID is in the temperature control field and a long time ago, but when the control is set right, for a step change, it should make about two rapidly reducing oscillations before arriving at the new set point (speed in your case). Just as an aside, the temperature controls I was working with could maintain 1,400 degrees Centigrade, measured with a platinum thermocouple; not 1,399 or 1,401, but dead on, and this was back in the 1970's!

If it oscillates about the new set point, or takes too long to settle down, the rate could be set too high. For most applications,the rate setting should be low. I would suggest you record the present setup so you can always go back to it, then make small changes and record the results. If you plan properly, it should take very few changes to see what needs to be done. Unless you are experienced, change one variable at a time, but I would start by reducing the rate.

Proportional changes can affect the other settings. Proportional gives a basic "correction" towards the new set point, but by itself will give a constant "offset" from the desired value. Integral gives a "nudge" towards the new set point and the timing and amount of the "nudge" are proportional to the integral setting.

Rate determines how fast the approach is; if it is much too high, you get into the situation where the speed will "hunt" around the set value and never settle down.

Hope this helps.

Richard Trounce.

[Marty_Escarcega]

Thanks Richard.
But can you define "rate"?
Is it P, I or D? Those are the only three I can adjust or tune.

[RET]

Hi Marty,

"Rate" is the "D" or derivative part of the PID loop.

As I said before, I hope this helps. The great thing about this website is that you can get help from anyone, anywhere. Of course, the corollary to that is that what you post had better be right or you can get "jumped on" from anywhere in the world.

Richard Trounce.

[RET]

Hi,

This might be a little off topic, but I very seldom see anyone using the Sherline computer and software for CNC milling.

I started off over ten years ago with a turnkey package from Sherline and I can certainly recommend their software. They wrote a very "user friendly" front end for the EMC and EMC2 control system. It is very easy to use and runs both lathe and mill front ends in both inch and metric. I use the inch mill version which has 4 axis capability (x, y, z and "A" which is rotary) and works to tenths.

A few years ago I rebuilt the Sherline mill into a much bigger and more accurate machine with 5/8" machine tool quality ballscrews and 1" dia. Thomson shafts on support rails. I kept the same stepper motors; with the reduced friction, I figured that I would get twice the effective power.

I also made a rotary headstock which takes all of the 2C collets I have for the lathe. That makes things that were hard to do before very easy.

I am very pleased with the result.

Richard Trounce.

[Marty_Escarcega]

Richard
Its very topical for the CNC forum but ya mixed it with the DM2400 subject.

[Mid Day Machining]

Here is what I have been doing for the last month or so. Just have the spindle to finish tuning.


Pictures:
https://plus.google.com/u/0/photos/1182 ... 2851643457

Still have covers and some loose ends to tie up.

Marty

Hey Marty, what did you end up using for controls on those machines? The one in the video looks pretty cool moving at 100 IPM.

With the original controls their rapid was only 30 IPM.

[Marty_Escarcega]

Here is what I have been doing for the last month or so. Just have the spindle to finish tuning.


Pictures:
https://plus.google.com/u/0/photos/1182 ... 2851643457

Still have covers and some loose ends to tie up.

Marty

Hey Marty, what did you end up using for controls on those machines? The one in the video looks pretty cool moving at 100 IPM.

With the original controls their rapid was only 30 IPM.

Hi Steve,
I wondered if you would notice. Take a close look at the stepper motors. I made new motor mounts, special oldham couplers. Screws are direct drive now. 48VDC power supply, Gecko G540, KBIC-120 DC Motor Controller for the spindle. Machine is now running Mach3. Adjusting backlash out of X & Y nuts as well as adjusting the gibs. I finished Z a bit ago. A bit more minor tuning and this one should be done.

Mach3 is the same control software running on your Tormach no?

Marty

[RichD]

Another DM2400 owner here.
Converted to PC & G-Code with Cnc-Pro as a controller.
Stepper drivers are Camtronics and a Dart spindle drive. All orig electronics removed.
Pic shows running a ball endmill profile around a loco boiler firebox firehole ring with a
Z axis extender accessory.
Great machine.
Also have a Sherline Mill CNC converted with many upgrade changes.

[Marty_Escarcega]

Very nice. I see you kept the original stepper motors? Do you have the covers for them? I still may have mine if you need them.