acorn and dmm dyn 4 losing steps

[martyscncgarage]

This is from your report you posted initially.
Where did you come up with the rev/in numbers? Especially that Y value....

Do as I instructed for the test. Set Gear/Line to 2000 in DYN4, Steps/Rev in Wizard to 8000, Overall Turns Ratio to 1
and test.


Axis Label Motor Encoder Lash Comp. Limit Home Dir Screw
revs/in counts/rev. (inches) - + - + Rev Comp
1 X 2.0000 4000 0.0000 0 0 0 0 Y N
2 Y 1.7500 4000 0.0000 0 0 0 0 Y N
3 Z 5.0000 4000 0.0000 0 0 0 0 Y N

[fozzyber]

marty,
I will do the tests you describe, but as far as my "paper arrow" it is made of .060 aluminum. it is not bending or moving.
I also use the dmm monitor to verify position (reading the encoder position) .
I did make a shielded cable for the step and dir last night and the problem got better on one drive
and seem to go away on another, so I think it is a electrical interference issue, between the acorn and dyn4s.
I have the dmm cables on order and will see how they do, are they twisted pair and shielded?
jerry

[martyscncgarage]

As I previously mentioned I don't know about the DMM cable construction other than I would expect them to make them to perform to the 400k requirements.

Please do the test.

Where did the 1.75 value come from as I previously asked for your Y axis?

[fozzyber]

the 1.75 gear ratio is from the gearing of the belt that drives the y ball screw.
I have a 16t pully on the motor and a 28 t pulley on the ball screw shaft.
same setup on the x except 16t and 32t pulleys. and the 4th axis is slaved to the first axis (x)
jerry

[martyscncgarage]

the 1.75 gear ratio is from the gearing of the belt that drives the y ball screw.
I have a 16t pully on the motor and a 28 t pulley on the ball screw shaft.
same setup on the x except 16t and 32t pulleys. and the 4th axis is slaved to the first axis (x)
jerry

That doesn't include the pitch of the ballscrew?
Calculate it with the ballscrew pitch or leave it to an even number and follow the procedure I attached for you.

[fozzyber]

ballscrew pitch is easy on this one 1 rev = 1inch.
jerry

[cncman172]

Jerry,
After you run Marty's tests and get the results, you might want to consider the following approach. The DYN4 amplifiers accept differential signals these are defined on your amp as inputs 11,23,22,10. The Acorn outputs singled ended signals, meaning Step and Direction for each axis. If you use the screw terminals on Acorn to access these signals they are Open Collector. This means when you use these signals you need to use a pull up resistor on each output and pull them up to 24V on Acorn. Normally any resistor from 1K to 2K will work fine.

You can convert the Acorn singled ended outputs to differential outputs meaning Step+, Step-, and Dir+, Dir- by using a differential driver module. These are dirt cheap about $9 per axis. The module then provides the exact outputs that the DYN4 were designed to accept. Differential signals are much more noise immune and are used in most commercial type machines for that reason. I put a few notes together in the attached PDF. I use this approach with Panasonic amplifiers as I also had issues with the singled ended inputs on those amps. After making this type of upgrade they are rock solid. Just a thought. You can prove it to yourself, just build one test cable with the module for say the Y axis and check your results. The fact you have played around and have partially convinced yourself you have noise issues might help you make the leap. Just my two cents.

Acorn-Diff-Driver.pdf

(165.95 KiB) Downloaded 157 times

Russ

[fozzyber]

cncman172 ,

thanks now we are cutting with carbide.
I just ordered 3 of them, does one unit do 2 axis or just one?
I think the issue you stated is the exact issue I'm having.

thanks

Jerry

[cncman172]

Jerry,

Each of those units will only handle one drive. So for example if you have a gantry that has two stepper motors that move one axis you would need two for that axis. I have attached the simple manual that shows you the board and the connections.

You do need to make sure you carry the ground from the Acorn and the 5V to the differential driver along with the X step and X direction signals. Very easy to hook up. The idea is to make the wires that go from Acorn to the differential driver board short so you mount them close to the Acorn and they are tiny you can build short cables. The Ethernet type cables that leave which should be shielded can be longer with no issues, those signals will me much more immune to EMI type noise.

Russ

[fozzyber]

I have looked at the manuals and I am unsure of how to wire this,
I started drawing this up but I'm not sure what to hook up tp INDEX+, Index- , A channel + and B channel +
can you look at my sketch and explain please.

jerry

Jerry,

Each of those units will only handle one drive. So for example if you have a gantry that has two stepper motors that move one axis you would need two for that axis. I have attached the simple manual that shows you the board and the connections.

You do need to make sure you carry the ground from the Acorn and the 5V to the differential driver along with the X step and X direction signals. Very easy to hook up. The idea is to make the wires that go from Acorn to the differential driver board short so you mount them close to the Acorn and they are tiny you can build short cables. The Ethernet type cables that leave which should be shielded can be longer with no issues, those signals will me much more immune to EMI type noise.

Russ