I have just installed a DC-04 and got it working pretty well. I am not getting any response from Peter. Could be that I sent the mail on the weekend or could be computer problems as I have been experiencing all kinds of strange email problems. Almost no email for a week or more including no junk mails then a flood. Anyway, I can use the tach and in manual mode I can attain a 1450 rpm, however under automatic I can only get 1096-1100? I have tried changing the PID values and it did help me to understand what those settings were for, they didnt help. I had read about a trimpot adjustment but the way it was worded made me think it was for the manual setting. Anyone have an idea? I did get to do some threading and it is very close to correct and cool to watch without having to worry if you are going to engage into the correct location manually. Speed control matches the S command perfect until 1100 rpms.

I have just installed a DC-04 and got it working pretty well. I am not getting any response from Peter. Could be that I sent the mail on the weekend or could be computer problems as I have been experiencing all kinds of strange email problems. Almost no email for a week or more including no junk mails then a flood. Anyway, I can use the tach and in manual mode I can attain a 1450 rpm, however under automatic I can only get 1096-1100? I have tried changing the PID values and it did help me to understand what those settings were for, they didnt help. I had read about a trimpot adjustment but the way it was worded made me think it was for the manual setting. Anyone have an idea? I did get to do some threading and it is very close to correct and cool to watch without having to worry if you are going to engage into the correct location manually. Speed control matches the S command perfect until 1100 rpms.

Hi John,

Not sure what is going on with the emails. I'll go through the spam box and see if they are there.

Under automatic control, the max speed you can achieve is about 5% less than under manual control. This is because the DC-04 needs to steal a bit of the voltage for its own use. The trimpot allows you to decrease the max manual speed to match the max automatic speed if you desire that.

The closed loop control in Mach3 does not work unless things have changed . So I wouldn't bother using that. As to the linearity you need to keep in mind that the DC-04 is an open loop control system.  There are a number of things that influence the linearity of the spindle speed. I have done a lot of testing and can confidently say that the DC control voltage generated by the DC-04 (And the other Digispeeds) is linear with respect to the PWM signal it receives from Mach3.

With the DC motors, there is the initial friction of the spindle drivetrain to overcome. This will cause the spindle to turn slower than you would expect at low RPMs.

Then there is the DC motor characteristics at the top end. Once the motor gets to approx 95% of its max speed the response is no longer linear. For a machinist this is usually not as issue as at this stage you basically wantthe spindle to run as fast as possible rather than an exact speed.

Between 10% and 90% the DC motor should be very linear.

You also need to keep in mind that the spindle speed usually creeps up a bit once all the bearings are warmed up, so I suggest that any sspindle speed tuning should be done after the spindle has been run for 20 minutes.

For tuning, I do the following.

• In Mach set the max pulley speed to 1000 rpm.
• Turn on the spindle and set the speed to 1000 (maximum).
• Record what mach is reporting as the actual spindle speed and enter this into the pulley setting.
• Set the spindle speed in Mach to about 50% of the maximum speed.
• Tweek the max value in the pulley setting to get actual speed to mach the set speed.
• If 50% of max is not where you normally operate, then do the tweek at that speed.

Cheers,

Peter.

Peter
Thanks for the response. I have talked to my ISP but I guess asking questions here puts me on some kind of watch list! Email activations have been ignored also. Anyway I got it running pretty well today. I cut a thread at 20 tpi at 400 rpm on an old sherline with some backlash in x not compensated for and they turned out real well. Maybe not perfect but hell it was my first try and I using a piece of electrical tape across my pulley. I am thinking of using a thinner piece of tape but the indexing was spot on at 400 rpm indicated. I did try it with and without spindle feedback or averaging at different times. Seemed like it did work better without the feedback. Yesterday seemed like the opposite. Anyway it has been fun and I have an insatiable appetite for info when I am in the middle of something so patience might not be my forte. The delay caused me to read a lot of info on wikipedia and here. Nothing I didnt need to do. Do look into my email, it was thru your support on your website.

Hi John,

Good to see progress is being made. As to the index mark, Mach3 just looks for the transition edge so the width of the mark is not important EXCEPT that it needs to be wide enough. How wide depends on a number of things, including the spindle speed, Mach3 kernel speed, opto sensor sensitivity, etc.

If you are using 1/2" electrical tape, then just leave it at that. No need to make is thinner.

I'll look through my spam later tonight.

Cheers,

Peter.

Here is a pic of it. Of course the diameters are not relevant to anything. Just testing repeatability of the cutting tip to follow the previous path. Incredible, to me anyway. Obviously I need help in photography too!

Hi John,

That looks really cool. Even if there is no nut that will fit it.

Cheers,

Peter.

By tomorrow that will all change. I will either measure a bolt or look up the specs and make 1. Thanks for the new found possibilities. Of course I am still trying to find out why I am doing this. I think it is the challenge to say the least.

John,
You may want to take a look at the write up I did called Threading on The Lathe-Mach3 Turn.
It is located in Members Docs or via SUPPORT> Documentation  above. Covers a lot of info.
RICH

Rich
Do you see something blatantly obvious that is incorrect? I did read that write up more than 2 times. Some of the literature regarding this topic is difficult to read. I always doubted the A.D.D. or hyperactive label  but I am starting to have my concerns. At the time I cut those threads impatience had gotten the best of me and I just had to hit "cycle start".  You can only hope you are understanding it for so long then its time for action. I actually cut that set of threads many times at many different speeds with various features I didnt fully (or partially) understand and I  wasnt really getting the helpful responses to progress. I do find the results in aluminum were much better at 400 rpm than they were for 175 rpm. Also cutting fluid produced the best results. Even though the lathe is a Sherline it is so much more rigid that trying to thread via the mill.

John,
I don't see anything wrong just didn't know if you were aware of that write up.
What literature is difficult to read? In the write up?
If in the write up, can you be more specific or provide feedback on it.
RICH