Newbie questions with Sieg KX3 Mach3 and CNC in general

[trialanderror]

I have had my Sieg KX3 Mach3 for about a week now and have a few questions and concerns. I am really new to CNC. Hope someone here can answer whatever possible.

1. I am trying to tune the X and Y axis motors in Mach3. I am using Metric. The defaults settings in the KX3 profile are the following:

Steps per: 500
Velocity: 1999.8
Acceleration: 300
G's (uneditable): 0.0305928
Step Pulse: 2
Dir Pulse: 0

I am using a $25 .01mm tolerance dial indicator attached to a $25 magnetic stand. I lined it up with my eye as good as possible so when the Y access moves so does the dial indicator.

I assume 1 step is supposed to represent 1mm. When I move 1 step, I am getting fluctuating results. For example: I move 1 step forward and the dial indicator will go 1 rotation, I would then go one step back and it would go .98 of a rotation (.98mm). I would then go forward and it would move .98 of a rotation and it keeps varying + or - up to .05 mm from where it should be. Could this be the dial indicator not secure enough or good enough quality or not 100% straight? Or could it have something to do with the machine. I have tried "Set steps per unit" and still having the same issues after it changes the Steps per. I also played around with the accelleration, velocity, and feed rate and still getting the same misc readings.

Also, should I be touching the steps per unit or should I keep it at 500 as set by Sieg? What settings are other KX3 users using for this?

2. Should I be turning off my machine if I am not going to use it for say 10 or 20 minutes or should I just leave it running? Kind of thinking it may be like a computer or lightbulb that is good to keep on.

3. I bought SAE30 Hydraulic Oil (can't yet find way lube) as recommended by Sieg. They didn't mention in the handbook if I am supposed to use this lube for the auto lube system as well as the table and misc parts, they just mentioned to replace the red waxy stuff I took off during the initial cleaning with this.

4. What would be the fastest spindle speed and feed rate combo recommended to end mill 6061 aluminum at .5mm depth with lube and a 4mm HSS end mill? I have been experimenting with this a bit but seem to get chips building up above the surface (to the sides of the tool path) as well as a lot of grinding noise which doesn't sound too healthy (have to plug my ears). Tried 750 FR at 4500 spindle speed and 500 feedrate at 2000 spindle speed. Just looking for some recommendations.

Hope someone can help

[Memran]

Hey

1) This sounds like you have some backlash.

Typically, you will see this when changing direction, eg, X moving right 10mm, and moving left 10mm, and not ending up exactly where it started, but moving left another 10mm (past the starting point), then back to the right 10mm, and will (probably) be where it started.

Backlash is commonly caused by some slack in either the leadscrew bearings or nut, and less commonly caused by slack in the gibs.

Mach3 has backlash compensation, where you can can tell it how much backlash your machine has, and it will adjust. Note that this will never be as good as removing backlash from the machine.

If you are moving in one direction (eg +x) as follows g0 x1 and actually move 0.98mm, followed by g0 x2 and are actually at 1.96mm, then you probably have an incorrect number of steps per unit.

If you find it is more "random", you may be experiencing missed steps. Listen to your motors while they move. You should not hear any "jumping".

2) I leave my machine on for long stretches. A lot of drivers have idle power settings for the motors, where they will reduce power by 50% for example.

3) Don't know. Sorry

4) This is a huge subject, and requires someone smarter than me to answer

[trialanderror]

Thanks for the reply Memran, I was thinking it was the dial indicator all along.

I did your up down down up test and it seems to always go back to where it started. I am using a .01mm dial indicator and start it at 50 and get the following results

Starts at 50
Y+ 1 step ends at 47.9
Y- 1 step ends at 48.9
Y- 1 step ends at 46.5
Y+ 1 step ends at 50

Always does this so its not random. How do I figure out and set the backlash compensation in Mach? Fixing the machine itself seems a bit complicated, will have to check on the Sieg forums if there is a post about it.

[Memran]

To measure the backlash, user your dial indicator as you have been doing and do some similar moves, like this:

1. Begin with any positive direction move. This is make sure that the axis is already at one side of the "backlash zone".
2. Reset the dro to zero, and zero your dial indicator.
3. Move positive by a known distance, (eg G0 Y10)
4. Move back to zero (G0 Y0)
5. The reading on your dial is your backlash measurement.
6. Repeat a few times to confirm.
7. Repeat for other axis.

In Mach3 the backlash setting is in the first menu and is called 'backlash compensation'. Just enter your readings in there, and also tick the box to say it is enabled.
Restart Mach and run the same test above, and if all went correctly, you should be reading zero on your dial.

Hope that helps

[trialanderror]

Thanks I will give this all a try. For the backlash setting, what is a good "Backlash speed % of max" to set? The default is 20.

[Memran]

Maybe someone else will correct me, but I can't see that setting being very important. Default is probably fine.

[diyengineer]

I set the steps per inch using mach. 500 was no where close to where it should be. Mine operated @ 500, but after using the calculate steps per inch on the x,y, and Z axis in mach 3 i ended up in the neighborhood of 10,000-12,000 steps per inch.

Setup your dial indicator, click calculate steps per inch (or millimeter), watch how far it travels, enter that into mach 3 and it will do the math for you. Test the axis after its complete and it should be pretty dead on.