What would be your view on simply holding the gantry against the stops when switching on?

Having a z-zero touch plate, do you see a zero-ing purpose for a proxy on the z-axis?

My view is that using the hard stops is just as valid an approach, although slightly less sexy. With the proxies, the process is:

1) one double click, two keystrokes, one push button to turn on machine.
2) safety check for possible collisions with anything on the bed
3) four keystrokes to start the X and Y axis homing. Max execution time is about 20 seconds.

Is it worth the extra $$ and complexity just for this feature? For many, I suspect the answer is no from a logical viewpoint, but yes from a satisfaction standpoint. It's definitely more in the cupholder category than the rearview mirror category.

I do note that at least in my EMC2 based world, running past a proxy limit allows recovery purely in software, because the computer still knows where the machine is. Once you hit a hard stop, you're recalibrating.

I don't have a proxy on my Z-axis, and I see no purpose for one.

I think the common setup operation is to get a specific location in 3D space zeroed so that the physical machine and the program agree. Using the touch-off capabilities of a Z-zero circuit against one or more of three dimensions is a very nice way to do this, and it doesn't involve the proxies.

Brad, I was playing a bit of devil's advocate by bouncing those questions off you :)

One might have to move the gantry, y-car and z-slide a long way to get a home position before switch-on, so the switches would be a lot more convenient, no doubt about that. However, in our situation, the loss of a home reference is extremely rare, so the gantry moving is around about 3 times a year. I think the guys with switches do a homing at every day's switch on.

As far as Andy's question goes here in his thread, I would suggest that one mustn't see proxies as a very complicated hurdle. It is something that can be figured out a bit later.

I have bought the proxy`s but never installed them,when I am finished for the day I go to my 0 points and switch the machine off next morning at start up I just make sure that my z -axis hight is what it was the day before.

Thanks all for the info,
I think i will get her cutting and then see how i get on.
Thanks Andy

She Moves
 

Well i have finally got her to move :).
Its a nice feeling after all that hard work to see it working.

I have the pk296aesg7.2 motors with the power supply supplying 75vdc to the geckos. I have wired them Bipolar series and they seem to be getting very hot. Do i need less voltage to wire them diffirently?.


I think now the learning starts!

Gerald, Thank you so much for making this machine a joy to build. It looks very daunting in the begining but once you study the plans and break it down it is very straight forward. Two months ago i had never welded, tapped a hole or knew what n/c or n/o meant!.

Thanks Andy

Well done Andy - it is the Industrial Revolution all over again! :)

What resistors did you fit to your Gecko's and did you double check the resistance values with a meter? They should be 20 kiloOhm for that motor as bipolar series.

Thanks Gerald, Eye sight is not what it used to be!

Andy,

Good work and the machine looks great.

That's a beautiful looking piece of machinery. Very well done!

Andy,
Very Nicely done!

Thanks all of you, i am really pleased with it.
I am having some problems trying to set the steps per mm in mach3?
The steppers say 0.25 step so 360/0.25 = 1440 x 7.2 = 10368 steps per rev of pinion?
Pinion dia = 30 x 3.14159265 = 94.2477795
10368/94.2477795 = 110.0078967
I have entered this but it is not to scale? Have i missed something?
Thanks Andy

The pinion diameter is measured at half of the tooth height - it is not the outside diameter of the pinion. The accurate way is know the module number and the tooth count. See: Understanding & Selecting gear pinions - setting the steps per mm[inch]

That thread is thoroughly confusing at first, but there is a calculator at about post #27.

http://www.worldofcnc.com/images/Com...e%20Pinion.pdf
Thanks Gerald for the quick reply, The pinions im using are the snb1030 in the above link, sorry didnt know how to put page in.
Measurement Do = 30 which is what i calculated?
Thanks Andy

Ah got it now,
0.25 is the output shaft,
so 1440 steps per rev x 10 for gekcos =
14400/ 94.2477795 =
152.78874554
Thanks Andy

If you are feeding that motor/gearbox full steps, the output shaft would turn 0.25 degree for one full step. (The gearbox ratio factor is included in the 0.25 degree marking). (the error here is that the 7.6 factor should not be considered)

However, your Gecko does 10 microsteps for the motors one full step, so Mach has to feed 10x more steps to get the right movement. (a factor of 10 should be included)

Therefore:
The steppers say 0.25 step so 360/0.25 = 1440 x 7.2 x 10 = 10368 14400 steps per rev of pinion
Pinion dia = 30 x 3.14159265 = 94.2477795
1036814400/94.2477795 = 110.0078967 152.789

It me much longer to get it! :)

Setting step/unit
 

Hi Andy,

On the settings page of Mach (Alt-6) is a button above the reset button called 'Set steps/unit'. Click this button and you don't have to worry about any of the maths, Mach does it all for you.:o

Greg

Thanks Greg, That is really usefull.
Andy

My First cuts
 

Pics of my first cuts:)

Well i have finally managed to make my first cuts.
I was very nervous but all went well and i am pleased with the results :)

I think i need to play with the speed settings as it was great along the straights but when it got to corners it seemed to me that it was moving too fast?
This is the first time i have operated a cnc so its hard to know what is the norm.

Thanks Andy

Sorry the pics arnt great.

Andy,

Wonderful!

The pictures give the impression that the areas around the letter "B" are raised. Is this an illusion? What ever it is, these are the best "first cuts" I've seen.

Nice work. Congratulations.:)

Now, slap some Logo's on her and request a Serial Number!:D

Thanks John, logos on the way.

Afew more pics this time painted mdf white so it shows up better.

Last photo shows a few flats on "B" i think it should of been cut with two passes as when i cut the smaller version it came out perfect.

Thanks Andy

WOW!!!! Beautiful graphic design. First class work.

Thanks Doug, Beautiful but unfortunatly not designed by me - free in v carve pro demo.

I was just reading your post in the motor tuning part, What did you mean by g's?.
When you set the velocity and acc in mach do you use this to control the speed or the feed speed on the main page?.

When i first set them i tuned them so they sounded good, when i jogged the amber leds on the geckos would light up but since i have set the settings slower as it seemed too fast.
Should i set them so they sound good then adjust the feed speed to the job im doing?
Thanks Andy

I believe Mach3's use of the term "G's" stands for gravitational pull. I didn't come up with it. Mach 3 has a window on the motor tuning screen that shows the Gs. You don't set the G's, I believe Mach3 calculates the G's based on your settings.

It has been a while since I tinkered with this stuff and hopefully someone will correct me if I'm wrong but I think those velocity and acel settings are for jogging. Jogging is when you aren't cutting but only performing a rapid move through the air. You set the feed speed with your CAM program and it is contained in the G Code you are using for your particular workpiece being cut. At least I set mine that way.

I left the X and Y axis jog speed settings as fast as the machine could handle. They will actually go a little faster than I have them set. Unfortunately, at the fastest settings, when I tried to jog the gantry from one end of the table to the other, after about four feet the motors started losing steps so I reduced the velocity setting. For the Z axis, I had to slow it down because I was having trouble accurately zeroing the Z axis. It moved too quickly. No matter how quickly I tried to press and release the page down button on my keyboard, the Z axis would jump down too far. Slowing down the velocity fixed that.

I hope I answered your questions. If I misunderstood you or failed to answer completely, let me know and I'll take another stab at it.

Doug

Thought i would update as i havent for a while.
I have been really busy at work so havent had much time to spend on mechmate but yesterday had time to cut this.

It is 250mm dia cut in 18mm mdf and took 2hr 20min.