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Scary depth
« on: August 03, 2007, 02:21:06 AM »
Hi guys,

Hope that someone can help me.  I have been having great difficulty getting true depth readings since beginning to use Mach 3.

For example when I do a carving and the depth is set to .15mm it will still cut down to more than a mm.

My latest problem really has me worried in that I am trying to cut some pockets for business cards .  I used vcarve pro to do the very basic design and then loaded it into Mach 3.

I set the depth of cut to 2mm because the timber I am cutting is pretty hard.

When I start the cut the router moves to the correct X,Y position to begin and then plunges down to anywhere between 6-10 mm.

I have had a look at the offsets screen and even changing values there makes no difference.  There was a thread about something similar here a while back but I can't find it now.  I presume that I am having some problems with either the tool or job offsets but my poor little mind is becoming swamped.  Hope someone can give me a bit of a hand.

Thanks in Advance.

Roly
Batlow NSW

Offline jimpinder

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Re: Scary depth
« Reply #1 on: August 03, 2007, 04:18:08 AM »
Can you read the G code and find out if the program as written is dong this or not. I assume this is your Z axis, and you should be able to decipher where it is told to move down to. Then you know where to start looking.

If it is not your program, then it must either be that your start position ( i.e. the starting height of your tool is incorrectly set or not zeroed, whatever, to match your program start position) or as you say, it is the tool offsets.

The tool offsets you can cancel and try again without them and see if there is any difference. Most of my difficulties have been - either the workpiece is not where the machine thinks it is, or my machine was not zeroed in before the start.

Not me driving the engine - I'm better looking.

Offline stirling

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Re: Scary depth
« Reply #2 on: August 03, 2007, 04:19:20 AM »
Hi Roly - sounds obvious but are you sure you've got your "steps per" set correctly for the Z axis in motor tuning?

Offline lemo

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Re: Scary depth
« Reply #3 on: August 03, 2007, 08:55:36 AM »
No problems whatsoever here. If you have 'random' depth when plunging then your drive/motor section is flawed. If you have a constant offset, then your parameters in Mach3 are flawed, or the generated toolpath has a problem. Toolpath is easy to check while looking at the generated code.
Lemo
Cut five times and still to short...

vmax549

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Re: Scary depth
« Reply #4 on: August 03, 2007, 01:05:28 PM »
A simple test would be to zero the z axis, then from the MDI line type in a z axis move of say 2mm. Did it only move 2mm?
(;-) TP

Offline mhdale

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Re: Scary depth
« Reply #5 on: August 03, 2007, 08:29:19 PM »
I have had a similar issue in the past and found it to be caused by selecting the right tool but the wrong offset... Not that it could not be anything else but look for an H in your gcode and make sure the number after the H matches the Tool you are using....

Mike
Re: Scary depth
« Reply #6 on: August 03, 2007, 11:33:58 PM »
Hi guys and thanks for the help.  I zeroed the z axis and then asked the x,y,and z axis to move ten mm.  the x axis moved about 8, the y axis about 6 and the z about 40.

I then went through the set up and configuration again and as my ball screws have a 4mm distance from crest to crest I worked out that the steps per should have been about 800 and they were set at 1800 odd. So I reduced them down and returned the motors as well.  Came up with different figures for each but they moved fast and smoothly.

I then ran the ten mm move program again and the x axis moved 35mm the y 26mm and the z 40mm.

Is it now a time for adjustment and tuning the motors again or should I just leave the motors at the old speed with the new steps per adjusted.

Any ideas would be helpfull.

Thanks again
Roly

Offline stirling

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Re: Scary depth
« Reply #7 on: August 04, 2007, 04:34:03 AM »
Your 800 steps per setting suggests you're using a 16 * microstepping factor and 200 steps/rev motors - is that true?. If you have 4mm screws and say 200 steps/rev motors then with no microstepping your steps per (mm) should be 50. If you're microstepping then multiply this by the microstepping factor e.g. for 10 * microstepping you'd end up with 500 for your steps per. This should be the same for all axes if your geometry and microstepping is the same for all axes. Hint: make sure when you set the value on the dialog you click in another text box otherwise Mach won't keep the value you've entered. Also remember to save the axis before moving on to the next.
« Last Edit: August 04, 2007, 04:37:54 AM by stirling »

Hood

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Re: Scary depth
« Reply #8 on: August 04, 2007, 04:19:19 PM »
Look on the settings page, you will see a button called Set Steps Per Unit, its just above the reset button. Press that, choose an axis, enter the distance you want to move then measure the distance it actually moves and enter it when asked. You should now have that axis set correctly so move on to the next axis and so on.
Hood
Re: Scary depth
« Reply #9 on: August 05, 2007, 12:58:57 AM »
Gentlemen to all who answered my queries I thank you very much.

I worked through all the suggestions but it was the advice given by hood to set the steps per unit that did the trick.  I managed to cut my business card holder and it wass great to see the machine do its 2mm steps into that beautifull ironbark.
I must be honest when I say I could not have done it without your help
Thank you again

Roly
Fro Batlow NSW