Messages

4651

General Mach Discussion / Re: Confused about Steps, Pulses calculations

« on: April 27, 2010, 09:23:57 AM »

Similar to marking your stepper shaft you can mark you hand wheel. Your just magnifying movement.

If the handwheel is say 3" dia then circum is 9.424". So you wrap a piece of tape around the hand wheel and then with a razor blade cut it. If you remove it and put a mark say every .050" along the tape then relative to a stepper ( 9.424/200=.047"  dosen't take into account the screw ) but you get the idea. Thus you can see steps roughly or linear movement depending on how you mark the tape. You can even make a big paper circle wheel.
For backlash rough check, you just tighten the gib and rotate the handwheel one way and then the other and you are seeing the backlash from the screw and bearings with the pointer set on mark. If you tighten the bearings / add preload and there was play due to them then you can see the
the adjustment affect of preloading the bearing. Idealy you would be checking the torque while you turn the handwheel but it's a poor mans way
for isolating things and seeing what is influencing the lack of movement.


Here is another example:
6" disc=18.85" circ  
18.85 / 200=.09425" one step of motor on the disc
Thus you can see affect of one step to movement.
You can put one on the motor and one on the handwheel and compare them if you wish.

Probably clear as mud....FWIW,

RICH

4652

General Mach Discussion / Re: Confused about Steps, Pulses calculations

« on: April 26, 2010, 06:55:53 PM »

Try 4us and check the x and y axis. Say the x axis steps per unit work out to be good and are repeatable, then swap the cable from the x axis to the y axis and see if the y axis movements are ok. ( do that when everything is turned off )
I will assume that the steps per unit are the same for the x and Y and that the accel and velocities are fine for both axis.
What you are doing is checking the BOB and drive to see if you are loosing steps by using the known good pulse path to check a possible bad one.
If the y axis is still no good then it may be mechanical.

One thing at a time .......
RICH

4653

Show"N"Tell ( What you have made with your CNC machine.) / Re: My first finished project on my new lathe

« on: April 26, 2010, 09:05:57 AM »

Looks good YuDoug. Glad the lathe is working well for you.
RICH

4654

General Mach Discussion / Re: Confused about Steps, Pulses calculations

« on: April 26, 2010, 09:02:55 AM »

Should be rather constent. A few thou i would expect but .022" is like a 1/3 of a turn of the screw. Sherline screws are 20 tpi and are made rather well
but even with anti-backlash device on them you still have backlash. The screws though are quite accurate in their travel and hold within about .001" for travel when new. Just giving this as something to gauge your screws to.

Not knowing the quality of your screws ( ie are they threaded rod? )
I would slow the velocity and acceleration down and run some more movement tests and see if the results are within some range.
Also check movement for 1",2", and 3" starting from the same spot to see if they are gaining consitantly or whatever. The caliper should work fine if held nicely and assume you checked it.

The kernel speed is ok. Have a look at your driver info to see what pulse width they recomend.

If the Y axis is fine,  you may want to just swap the x with the y and see if that causes any change to the Y movement ( off course use the Y settings when you do that).

RICH

4655

Screen designer tips and tutorials / Re: Can anyone make a "normal" windows screen design please? 0:-)

« on: April 25, 2010, 08:04:48 PM »

Jerry,
Maybe you want to hold off some until Mach 4 along with the new screen design comes out.
Or now is your chance to influence the new screen design......
RICH

4656

General Mach Discussion / Re: inconsistant dial gauge readings on axes

« on: April 25, 2010, 10:28:07 AM »

How much non-movemnet are you talking about?
How small of a step move are you talking?
What is the resolution for that axis?

Do you have an idler on the belt to keep the tension rather consistant?
I say this because we did some testing some time back ( actualy when were doing thread testing ). We were checking the mechnical part of the system and trying to compare physical movement to steps actualy sent from the pp as compared to what the stepper recieved. He could follow the
electrical signal path anywhere along the pulse path. BTW, the pulse counter was custom made for the company. So each electrical component  was isolated and related to each mechanical part or combinations. It was interesting to find that we could actualy find the number of steps " seemingly lost " due to varying belt tensions. Now we were cutting hairs, but never the less, interesting.

In fact we found that not all steppers are created equal such that when microstepping some steppers did better than others.

So large non-movements as they relate to the system can be measured conventionaly, but as you try find what part of the system contributes what fraction of the non-movement it can become very time consuming and difficult. You need to be meticulous as hell when measuring. Dial indicators
are calibrated ( we measured small distances opticaly/ eliminates the non movement of the indicator or non liner movement).

It is very easy to have backlash just do to bearing mounting and bearing preload can add to backlash. The screw can be non linear, the preload on the
nut can add backlash, inaccuracies in the belt ( inclucing timing belts ), lets not forget the gearing, etc, etc. So there are a lot of things that come into play and cumulatively they add up.

So i will not guess at your problem.
FWIW,
RICH

4657

Machscreen Screen Designer / Re: MachScreen releases

« on: April 24, 2010, 03:41:24 PM »

Klaus,
Appreciate the work you put into the screen deisgner for making it easy.
Even i may get dangerous and start fooling with screen designs.
RICH

4658

General Mach Discussion / Re: mach's rounding of measurements?

« on: April 24, 2010, 10:56:10 AM »

So perhaps this whole thread is just an issue with terminology.

Think you got it right Gerry.

410 steps per unit is just the # of steps as they relate to the mechanical movement over a unit of distance.
Resolution is just the inverse (1/410 ) or the mechanical movement for a single step. The calculated resolution is just a
an "ideal" Reference NUMBER.

There is a practical side of interpreting the resolution. Mechanical, software, and electrical ( system ) come into play as all is not perfect and influences
the accuracy. Accuracy defined as to how closely the "system" is to the ideal. The only way to improve resolution is to increase the steps required for the movement. Each of the above three has an effect on the actual accuracy of movement as it relates to the reference number and are related. Thus one would use the calculated resolution and then measure the actual. The user can make improvements but must keep in mind the practical influences of the above and the individual limitations associated with them.

RICH

4659

SmoothStepper USB / Re: Whats the current developement state of the SS?

« on: April 24, 2010, 09:58:34 AM »

There are two threads on the Warp9 site were discussions about BC has been going on. Here is Greg's latest response and why i say in the near future.

Thanks for keeping the discussion productive and civil. I think have decided to make it work the best and I will continue on my plans to make it stop whenever there is a reversal. It will be fun to see it working. I will work on it this weekend, but I wouldn't count on me finishing it this weekend. I'll keep you posted however.

There is difficulty in implementing BC to satisfy say CV mode. I would suggest that folks post to the Warp 9 site if they have some constructive  suggestions for Greg.

In a general, good components for the "machine system" are required to eliminate BC, using BC will help in achieving improved machining accuracy
but there will be trade offs in using it.

RICH

4660

Feature Requests / Re: G-code line limit in the demo versions

« on: April 23, 2010, 06:19:27 PM »

It may be even less as i remember if you did a loop via a subroutine it could end up being just a few lines