Mach3/PC Steps Per Inch Set Up Advice

Has anyone used a PC with a CNC Controller along with Mach 3? I just completed my build and am trying to zero in on what microstep settings to use and steps per inch calculations. If you have a 1000mm machine working in this way - I would love to see your settings.

I am using the figure of 126.9999 steps (127) per inch at full step. Double at half step, etc. That is with the 20 tooth pulley and 2mm pitch. Does that sound right? How far are you going with your microstepping?

Yes that is correct. I downloaded the same numbers/formula from somewhere else just last night - I think it was from a shapeoko wiki. I was gathering up the numbers to have them ready since I’ll be using my own breakout board and drivers with linuxcnc. The same page had the answer for the Z if you’ve got the 12tpi acme screw.

I didn’t bookmark the page, but if you google this phrase (in quotes) it should be easy to find:

“and now combine them together in the only way that gives microstep/mm:”

That page is doing the math in metric. Multiply by 25.4 to get the result in inches.

Thanks for the link. That helps. It looks like the standard set up is 1/8 microstepping for x and y and 1/2 for z. This will give me a place to start. I have 36 volts and 10 amps of power so I might try to push it to 1/16 if I can and 1/4 for the z. I have VCarve Pro and I want to take advantage of the new 3d model capabilities.

Please let me know how it works and what stepping you end up at. 1/16 might be pushing it - torque goes down as steps go up - but it would be nice. My X-Carve should ship this week and it looks like I’ll be using something close to you, but with LinuxCNC instead of Mach 3 - separate board and drivers, NEMA 23 270oz motors for the X/Y and 140oz for the Z, 36V power supply.

The X and Y figures were dead on. I used a dial gauge and full rapids back and forth several times and each time was within 2,000th of an inch. I ordered the Acme screw and delrin nut. I had to set it at 1/8th. My steps per inch after dial gauge for a half hour were: 38412.88746 (using “set steps per inch” on Mach 3).
x and y velocity are set at 199.98, acceleration 40. For z I used 49.998 V and 30 accel. All axes can go faster but I toned it down because the default spindle is a worthless piece of tin. It self destructed with a 1/4 end mill… bit flying out, smoke, etc. Even with an 1/8th inch end mill traveling at 10 inch per min and a dept of cut in MDF of .05, it chattered like crazy. It just doesn’t have the mass and horsepower to cut anything but modeling foam. I will try to attache pic and videos.

Thanks for the numbers. My X-Carve arrives Tuesday but I’ve got all my electronics wired except limit switches on XLR connectors, so it’s just a matter of assemblng the machine and hooking up those ends of the wires to the terminal blocks. I was worried about that spindle because of all the conflicting info and unanswered questions about it here in the discussion boards. I suspect I just flushed 60 bucks down the drain on it, and wasted the last month waiting when I could have been out buying something better suited to the machine. Is there any data printed on the spindle itself that you could take a picture of?

Nothing I can see. I think I can crush it like a tin can. Do you have a Dremel? My Dremel fits perfectly into the default spindle holder. Flip the the spindle holder upside down so the delrin nut mounts on the bottom. The Inventables logo will be upside down. Use a flat blade screw driver to pry open the older and slide it in. My protrudes from the bottom of the holder just enough to reach the power switch. It is very close to square and works like a beast. I am using this until my chinese 600 watt spindle and 48 volt power supply arrive - then I will have to build a spindle mount… or order that generic spindle mount.

So… Would the tpi for the z acme screw be 94.5 with no micro stepping? Havnt set up anything using belts before.

Excuse me… I mean steps per inch, not tpi

I think it would be closer to 4,800. And this brings up a good point - why even use micro stepping on the z axis when you get 2 ten thousands of an inch resolution without it.

On x and y, I believe it is 127 steps per inch at 1/8 stepping and those axes use belts, not the z,

What’s neat about the drive I’m using is it uses a “morphing” micro stepping automatically so I just need to figure out the base steps per. Just havnt had a chance to sit down and do the math yet

I know. I want one. But mine is just fine. These “Sain Smart” generic drivers have been chugging along for years. But - even the HOUSING is cool on the Gecko. On the other hand, if you do the math:

3 x Stepper Drivers @ $35 = $105
1 x Generic BOB @ $20
TOTAL: $125 vs. $300 for the Gecko.

Maybe my system will burn up soon.

Because I have 2 Gecko G540s and 4 280 oz nema 23 stepper motors sitting around doing nothing they are going on my machine when I can get started assembling it.

I’m also considering building reduction gears for the X and Y axis.


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Update: G540 is on its way! Also, I upgraded the Z stepper to the Nema 24 425 oz/inch motor and it was very easy. The motor just mounts on TOP of its original mount with spacers between the motor and it’s mount plate. I am going to upgrade the X-axis motor as well, but not the two Y-axis motors.

@TimothyTruex - let me know if you have any set up advice for the G540. I downloaded the manual and the Mach3 xml file so it seems pretty straightforward - other than the steps per inch calculations using the morphing. What did you end up with?

Sorry I didnt see this till now. My steps per unit for x/y are 1276.399 and the Z is 24372.181. Let me know how yours is running. I am very happy with mine.

Same. I actually now have two! One smaller, ultra-rigid, dedicated metal and plastic machine in addition to the 1000mm. Thanks for the reply.

Awsome, glad to hear that!