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Cut parts are wonrg size
« on: July 03, 2012, 07:41:43 PM »
I am new to this so hopefully the solution is an easy one.

I built my router and have it up and running just fine. I have had success tuning the motors and when I tell it to move a certain distance it does to within .001 inches, which is fine for what I use it for. The issue is that the parts I cut out look like they are right, but are off proportionally by a lot... sometime by more than an inch. I can repeat the part, and while all the parts are the same, they are all wrong by the same amount.

I am using AutoCAD, outputting a dxf to Lazy Cam, creating all of my tool paths and sending it to Mach 3 for cutting. My line of logic is that something is not translating right in one of these steps. I also think this is a software problem and not a machine problem because the parts created are all identical... meaning all sides are completely flush with one another. So repeatability is not a problem, I just need it to reproduce what I drew faithfully.

So if one of you more experienced (not necessarily older) CNC guys out there would be so kind as to point me in the right direction on correcting the error of my ways I would really appreciate it.

Thanks, Dave
Re: Cut parts are wonrg size
« Reply #1 on: July 04, 2012, 12:36:23 AM »
Hi Dave,
when you cut different parts and  they are all wrong by the same amount, it looks to me as it has to do with cutter compensation.
Look if the tooldiameter match the tool you use. look is the G code toolpath with or witout cutter compensation. G42 / G41
If that is ok then be shure scaling is set to 1 . When you import the dxf in Lazy Cam then measure it in  Lazy Cam  to be shure the size as you expect it.

Alex

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Re: Cut parts are wonrg size
« Reply #2 on: July 04, 2012, 02:40:31 AM »
Hi Dave,

Use your existing system to create the GCode for a square part.
When you load it into Mach check the Program Limits DRO's in the tool path window - do they indicate the correct size of the part ??
When you make the part does it come out to the correct dimensions ??

This will tell you if your problem is with your software or your Mach configuration (steps per unit).

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline ger21

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Re: Cut parts are wonrg size
« Reply #3 on: July 04, 2012, 07:30:42 AM »
Post your .dxf and the g-code and I'll take a look.
Gerry

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Re: Cut parts are wonrg size
« Reply #4 on: July 17, 2012, 03:35:53 PM »
Sorry guys,

I have been sick for the past week or so.

I would love to post the g code, but i do not know how to get it out of mach 3 in a manner that I can post it.

All of your replies gave me an ideas though... none of which worked.

Here is what I did... I went into autocad and made a part. I made sure that I was scaled 1:1 before saving as a dxf. The part still did not cut right after going through Lazy Cam, it ended up being 6-3/16" instead of 6" wide. I rechecked the calibration of the axis and they all check out. So, I went and got into v-carve pro and taught myself how to create a part in there and out put it... the damned thing came out at 6-3/16" instead of 6".

So, this tells me that the error is not in AutoCAD, or the Cam program. The axis calibration works out in Mach 3 pro and all of the axis move the designated amount... so where does this leave me??? is there a rogue tool off set that I have missed? How do I set all of Mach 3 pros offsets to a default 0 in a global manner to make sure this is not what is biting me in the butt?

Anyone have any other good ideas?

Thanks for all the help. I have dreamed of having my own CNC machine for more than a decade... I just need to get past this maddening part.
Re: Cut parts are wonrg size
« Reply #5 on: July 17, 2012, 03:45:35 PM »
Hi Dave,
is your scale set to 1.0 ?
Alex
Re: Cut parts are wonrg size
« Reply #6 on: July 17, 2012, 03:52:04 PM »
Yeah, I really don't mess with scaling features in mach 3.

Offline ger21

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Re: Cut parts are wonrg size
« Reply #7 on: July 17, 2012, 06:11:40 PM »
This would lead me to believe that the part is drawn wrong in AutoCAD.

Or, you're programming for the wrong tool diameter.
Gerry

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Re: Cut parts are wonrg size
« Reply #8 on: July 18, 2012, 06:44:13 AM »
I would love to post the g code, but i do not know how to get it out of mach 3 in a manner that I can post it.
You can have LC save the code as a file or when in Mach you can click Edit and then save the file.
That said, post both the gcode file and the dxf from ACAD, and we can have a look.
RICH
Re: Cut parts are wonrg size
« Reply #9 on: July 18, 2012, 09:05:04 AM »
Rich,

Well, duh that makes perfect sense. I have a few things to do this morning, but I will definately get that stuff together and post it later on this afternoon.