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papermaker said:
Now I waiting for some new fans to cool the drivers. I have a heat shrink connected to the drivers but they sure do get quite warm. I'm still trying to figure out how I'm going to power these. I had two fans installed and powered from a 12v power supply.
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Congrats!

The two main things to remember about cooling are:

1. Drivers are going to get hot - let them
2. Orient the fins for the most efficient convection cooling

You probably don't need cooling fans - not that there's anything wrong with that. I build power amplifiers for radio that get extremely hot. Most folks would think that this amount of heat will destroy the devices. Not so. Just stay below 100°C (212°F) and you should be fine. Some devices can even operate up to 450-500°C.

The most effective thing you can do is provide the proper ventilation for the cooling fins. If you orient the drivers properly, the heat will dissipate. The only time you'll need fans for cooling is if you run the drivers very close to or at their maximum rated power, which is a bad idea to begin with.

The drivers should be mounted such that the fins and the spaces between the fins are oriented vertically so that the airflow is from bottom to top, since heat tends to rise. Also, they should be mounted so they are outside of the enclosure you're using. That way, convection will take over and you should be good to go without the need for fans. Again, that assumes you did not pick out drivers that are going to be stressed near their design limits. Convection works by heat rising and creating a slight vacuum under it, which will pull in cooler air from underneath. It actually creates a moving airflow, similar to a fan.

If you're going to block the airflow in any way, such as mounting the drivers internally or pushing the assembly against a wall or other obstruction, then you should consider extra cooling techniques.Another thing to consider is, if you've mounted the drivers internally, you might just be blowing hot air right back onto them, severely diminishing cooling efficiency, if you haven't created a reliable way to circulate outside, cooler air throughout the enclosure. So make an effort to mount them - the fins, that is - externally to the enclosure, in open air, or punch many holes in the enclosure, bottom and top, in line with the fan(s), to create the necessary ventilation for proper airflow.

None of this is to discourage you from cooling things the way that feels most comfortable to you, rather, just some info to set your mind at ease. Also, keep in mind that powering fans is going to put stress elsewhere in the system, so understand all of the parameters before you start buying and building.
 
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I'm trying to get the gibs adjusted on the mini mill and there seems to be a fine line too tight and binding and too loose and getting a choppy cut. If I snug them up the stepper motor doesn't have enough power to overcome the friction. I'm running about .25 Vref. Will adjusting this up apply more power to the stepper.
I should have waited until I was smarter before I started this project but at 55 I doubt that will happen!!
 
Don't wait, stuff like this is how you _get_ smarter. Before you start thinking you don't have enough torque, play around with your acceleration. More often than not that is the issue. Steppers don't like rapid acceleration (it takes a lot more torque than "cruising"). If you push them too hard, they can lose step, and that's no good. It is always possible that you are setting your gibs too tight, but I would check your acceleration first.

The practice I used to adjust my jibs was this

1) Loosen all the set screws
2) Tighten just the middle one _slowly_ while moving the axis back and forth until you just feel some drag
3) Do the set screw in front of the middle in the same manner, then the back.
4) Lock them all down, and check your drag again. There should be some drag, but it shouldn't be "hard". Run it the full length of travel, just to make sure you're not binding somewhere.

This worked well for me. Also make sure things are oiled. IIRC you purchased a ballscrew kit; did it come with ball-bearing mounts? The stock mounts are pretty high friction, if you are still running those, that may be part of the issue.
 
I know its a matter of tinkering to get it "zeroed in". I bought the CNCFusion ballscrew kit and have had some issues with binding but I seem to have that under control. I will try some tuning of the acceleration rate and see what that does for it.
 
This afternoon I ran the Mach 3 test G-code and everything went through the motions fine. It wasn't set to cut anything but I guess it is to test each axis. I'm getting braver and hopefully I will I can start cutting something soon.
 
MDF makes mills pretty well, and is not too hard on cutters if you crash. Good starting material, and relatively cheap. Only problem is, it generates a lot of dust. I also recommend turning your feed rate _WAY_ down (like, 50%), and keeping your hand poised over the ESTOP button as you get started. Things get exciting fast ;).
 
MDF sure is cheaper than aluminum. I think that there are wizards in Mach 3 Demo that can be used until I get the license activated. I hope.
 
You can't use the NFS wizards without a license. And you're limited to 500 lines of gcode without Mach itself being licensed.

But that's more than enough to test your machine, then decide to get it.
 
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