In-time your zero plate will be peppered with little indentations, especially if you use fine pointed bits. I just replace the AL. plate when it gets bad. Setting your feedrate to 30ipm or less will not give the Z axis the shock it would receive if hitting the plate at 180ipm 

Putting foam or rubber pad under the Z plate usually gives false readings due to inconsistent compression. If you mic the plate including the pad it will not be the same reading as when compressed by the Z axis during a zeroing routine, you would also get different reading with different feedrates in this scenario.

I do not use a plate to touch off so this is just my 2 cents. I agree with ronginger. I would think that you would allways want to touch off at the same rate for consistency. Do any of you guys doing this use carbide bits, cutters? Does this not chip them? Has anyone tried a spring loaded plate? I thought of a base plate with a shoulder bolt in each corner. A top plate with bronze bushings to slide on the shoulder bolts. A spring on the shoulder bolts in between the two plates. Would this work?


Ignorant on the matter but wanting to learn.
Brett

I (and I'm pretty sure this goes for Gary also) use carbide tooling all the time and if you use a slow probe feedrate and an aluminum or brass plate, you should be fine.  I've never had a chipped cutter (yet).    I use a strip of flexible adhesive backed non-ferrous magnet on the back of my plate which allows me to stick it to the side of the machine when done with it.  I just add the total thickness of the plate and magnet strip to the plate thickness setting.

Yep same as Scott run run 100% carbide bits and never broke or chipped one yet on the zero plate.
As Scott stated slow feedrate and a soft aluminum or brass for the plate, when it gets too much pitting I just replace the plate, cost about 35 cents for aluminum (buy it by the lb $3.00 worth will last a couple of years).

Brett, you idea may work but myself personally would not use any plate that has any physical movement or cushioning due to the chance of error, just a couple of thousands will show up after a bit change and cause grief for additional sanding and clean up.
Another thing you might note is that quite often when using a touch off plate the area under the plate may be very small, I have had to zero out on a 1/2 x 1/2  area within the relief on many occasion, (due to material movement after an area clear)
Just for your info I have another very small plate with a gator clip to fit into detail areas when needed, I just clip it onto my existing plate and run the zero routine.

Seems to me that you could just jog it very close then insert the plate. Set the feedrate slow and touch off on alluminum, it should be soft enough to not hurt the tooling. Does this sound right to the people who know?

Dwayne

Thanks for the Input guys. At what rate are you jogging into the plate? .5 IPM?

Brett

Dwayne, if you set your feedrate in your touch off script as in Scott's example above then there's no need to jog close to the plate, just put the plate under your bit and run the routine.

Brett, don't know what the other guys run at but I use 30IPM for my touch off.

gary

Thanks Gary.

Brett

This is a very interesting thread. I had no idea you could make such a simple touch off plate. Im just getting started cncing. built my first mill this fall. was wondering. I dont know a damn thing about using macros. where do I look to even begin figuring out how to set something like this up. I get the basic of the plate. its setting up the program to perform the operation that Im unclear on.

GNBG,

You can do it a couple of ways, with a button placed on your screen or by making a .m1s file containing the macro and calling it up with a M(file number like 301, etc.) in the MDI line.  The variables in the macro will have to be changed to suit your needs, settings, and screen.

The easiest is to place a button on your screen (along with a DRO for the plate thickness and the feed rate at which to measure at) with Screen4 and edit the script for the button in Mach3.  Take a look at the script behind some of the other buttons and also look at the settings for some of the buttons in Screen4 (the exe for that is in the Mach folder).  The Screen4 video will help to understand that part a bit and as far as macros, looking at what's behind some of the buttons in Mach3 and the wizards are a good place to learn by example.  The DRO, Button, and LED lists on the Wiki are a must to have in front of you too.

If it's all more than you want to mess with, send me the screen .set file that you are using and I can place a button (with script) and a DRO on it for you and you can then dissect it to see how it works. 

It's best to test this with a junk bit or a broken off one chucked upside down just in case. 

Regards,