[vtx1029]

I keep loosing steps what can I check? its happening mostly when switching from going in Y direction to a X axis move. both the x and y steppers stop in one spot but mach 3 thinks its still moving. I know I'm not stalling the steppers because I'm taking a light cut .020 with a 1/2 bit 50% step over at 20 ipm. At first I thought it was because I had my cam program open along with the internet so I thought it was maybe my computer being bogged down. So I closed everything, restarted Mach 3 and watched my processor while running and it never went over 25%.

Here's my what I have for steppers and control
# 3x ProboStep Uni-polar Stepper Motor Chopper Driver
# 3x HT23-280-8 Stepper Motor
# PBX-2 Parallel Port Breakout Board
# 24Volt 6.5Amp Switching Power Supply


My drivers are set at a 1/4 step

[vtx1029]

anyone?

[acondit]

You say it is not stalling, but that is the obvious thing that appears to be happening. You are running a 24v supply. That may be all that your driver will handle but it is probably not optimum voltage for those steppers. Additionally you are running unipolar, again not optimum for steppers.

You didn't tell us: the tpi of you leadscrew, the size and weight of the various axis. 20ipm could be right on the edge of the motors going into resonance with one gearing set up or it could be fine with another.

You are trying to drive a 1/2" bit. It takes more power to drive a 1/2" bit through material than a smaller bit. What happens if you try a 1/4" or 1/8" bit?

If you try cutting at 10ipm does it still stall?
What is your acceleration set at? (Could it be too high?)

What are you trying to cut? It takes more power to cut aluminum than MDF.

Just some things to explore.
Alan

[Fish4Fun]

vtx,

prolly the first thing to try is a "dry run", ie try running the g-code without the bit engaging the work (move your Z up 1"). If it still stalls in the air then you know it has nothing to do with cutting forces and can focus on other things, if it doesn't stall in the air, you can try it with a 1/8in Bit, then a 1/4in bit, if still no stalling then you need to look carefully at your 1/2in bit and depth of cut.

You might also check your rails for a "sticky spot". Try moving "home" +/- 1in in both X & Y and see if the "freezing" occurs in a "new spot".

I had a TON of problems with Mach3/LPT Port/Windows config and NEVER did solve the issue (I finally gave up and bought a USB based motion control board,WOW what a difference!).

Fish

[vtx1029]

You say it is not stalling, but that is the obvious thing that appears to be happening. You are running a 24v supply. That may be all that your driver will handle but it is probably not optimum voltage for those steppers. Additionally you are running unipolar, again not optimum for steppers.

They reason I say they were not stalling is because they make any noise or oscillate. I fairly new to cnc so you could be right. The drivers can handle up to 44v. My plan is to build a bigger router so this one will go down the road once that is built so I don't plan on upgrading this one any more.

You didn't tell us: the tpi of you leadscrew, the size and weight of the various axis. 20ipm could be right on the edge of the motors going into resonance with one gearing set up or it could be fine with another.

I believe its 1/2-10. My machine is a microcarve A4. Fixed gantry table top cnc. So the y is only moving the z axis and a bosch colt so maybe 6-8lbs, X axis is about the same. Cutting size is about 10 x 11 x 4

You are trying to drive a 1/2" bit. It takes more power to drive a 1/2" bit through material than a smaller bit. What happens if you try a 1/4" or 1/8" bit?

If you try cutting at 10ipm does it still stall?
What is your acceleration set at? (Could it be too high?)

What are you trying to cut? It takes more power to cut aluminum than MDF.

Just some things to explore.
Alan

It stalled when I was using a 3/8 90* v bit taking a .030 cut at 20 ipm as well. But ran a 1/4 bit at .125 at 23ipm just fine. I was cutting walnut. I reduced the acceleration from when I first got the machine its pretty mild. I don't remember the numbers of the top of my head but I'll look at all the above. Thanks for the response. I did try it again last night and was able to cut my piece without any missed steps but I reduced the feed rate to 70% of what it was. Had about an hour and 20 minutes of different tool paths :cheers: The only thing running on my machine was mach 3, not sure if that made the difference or not. Once I'm done with this job I can throw some mdf in and run the same tool paths to see if I can duplicate the problem I was seeing.

[vtx1029]

UPDATE -

Well worked on trying to duplicate the problem and I as able to with just cutting air. After trying a few things I lowered the X and Y motor velocity and acceleration a little and I was able to run the same g-code cutting air at 48 ipm with out any problems. Then I when t back and finished cutting, over an hour run time with no missed steps :cheers:

Thanks all!

[Fish4Fun]

vtx1029,

I had a TON of problems with my A4 and "missed steps" using Mach3 @ anything over 30ipm. I purchased a KFlop motion controller and took my LPT "out of the loop", and I now have no problems cutting @ 90-120ipm! Your problem is almost certainly in your PC//Mach3.

BTW, John uses 3/8" x 12tpi acme screws on most of his "A4's". This means 24,000 steps to the inch if you are using a 10 uStep/step driver & 200 step/rev steppers. So, @ 24,000 steps per second you should be getting 60ipm. I had a TON of problems with this speed attempting to use Mach3. With the KFlop I have played around with "jogging" @ up to 240,000 steps per second (600ipm)! In "real use" I limit the KFlop step rate to 90,000 steps per second (225ipm), and typically "cut" @ 90ipm and use 120ipm "rapids", this is plenty fast on my little A4.

Fish