How to switch axis directions?

[juzwuz]

Hi! Hopefully someone will know....in EMC2 can I switch the direction of an axis? For example when I jog in the positive x-direction, the axis goes in a certain direction. Can I switch the direction in EMC2? Thanks!

[RandyO]

in the emc handbook it says in the part where you set up each axis for each stepper you have to put in a figure for the input scale go back and put a minus sign in front of your input scale number to reverse the direction.I hope thats it.

[juzwuz]

I just tried it and it worked fine. That was too simple! I guess I was looking through the manual for more explicit directions and I could never find them. Now I'm working on messing with some of the parameters because for some reason I'm only getting 10000 steps per second output from my parallel port. When I had 10 microsteps and 20 turns per inch leadscrews, I could only get 15 inches per minute travel. I turned the microsteps down to 5 and now I can get 30 ipm.

[samco]

base period is what is used to calculate maximum step rate. It is computer dependant. the default setting is 50us - in the ini file it is 50000 (50000 ns).

to calculate the maximum step rate

1/.00005= 20000hz - it take 2 periods to do steps. so..

20000/2 = 10000 steps per second.

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no lets calculate your maximim feed rate - this is dependant on your input scale... your input scale is 40000 if I calculated it correctly

((1/.00005)/2)/40000= units per second. = .25 in your case inches/sec.
.25*60 = 15ipm/.

If you lower the base period - depending on your computer - you may be able to get down to 20000ns or .00002. This is computer dependant - lower it and see if the computer is still usable. It will start to get sluggish the lower you go.

at .00002 you could run 37ipm - or if you change to 5 micro steps you could run 75ipm.

sam

[juzwuz]

Hey, I just came in from the garage after messing with the Base Period parameter and I noticed your post. Thanks for the explaination. I lowered the Base Period to 25000 with 5 microsteps, 200 steps/rev motors, 20 tpi leadscrews and I was jogging at 45 ipm. I could have gone higher but it seemed a bit scary fast since the machine is just a Taig mill with 12 inches of travel on the x-axis. I didn't notice any slowdowns with the PC (1GHz, Pentium 3, 256K RAM). I think I'll switch back to 10 microsteps, and adjust the parameter so that I can get around 30ipm.

Do you have any other tips on EMC2? I still need to run some sample gcode to see if everything works. Unfortunately I already missed my goal of making things for Xmas presents but maybe I can still cut something before the year is over.

[widgitmaster]

Hi JuzWuz!
Happy New Year!
I'm glad to see your machine is finally comming alive!
Have you added the 4th Axis to it?

Eric

[samco]

what are you using for the gui? tkemc, axis?

I love the axis interface.
http://www.electronicsam.com/images/KandT/Dapper.png
http://www.electronicsam.com/images/...axisubuntu.png

sam

[juzwuz]

Eric,

Been a while since I last talked to you. The harmonic 4th axis is still sitting on the shelf since I had to work out wiring issues. One of the first things to make is an adapter from the 4th axis support plate to the Taig mill table. Should be a nice introductory project to milling. I gotta figure out this software stuff though since I haven't done CAD for 16 years and I've never done CAM stuff or gcode. Then hopefully early next year I'll have my 22" by 24" CNC router built and working. I'll use the other 4th axis for the router. Should be cool!

When are you going to make your own large CNC mill? I bet it would be one of the more closely followed threads since you tend to document everything so well.

Happy New Year!

Justin

[juzwuz]

Sam,

I have the mini gui right now because it seemed the easiest but I haven't really settled on any gui. Axis looks good. I might mess with that one for a while.

Justin