CNC Starts Cutting a New Path Midway Through the Cut

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Bigjay
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CNC Starts Cutting a New Path Midway Through the Cut

Post by Bigjay »

I am trying to cut out some letters on a large sign using a pocket toolpath which is set to cut all the way through the material utilizing 6 passes. (.625") The toolpath has 3 components to it, a set of letters, a logo and another set of letters. The font has some small areas so I have utilized a .125 endmill. The cut went well until it moved to the second part of the cut and then it started cutting all over the place. Any ideas as to what may be causing this?

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martin54
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Re: CNC Starts Cutting a New Path Midway Through the Cut

Post by martin54 »

pictures help :lol: :lol: :lol:

From what you have said it sounds like you may have lost steps, there are quite a few different reasons for this, if you search the forum for lost steps you should be able to find info on the most likely causes :lol: :lol:
If it is a problem with lost steps then it will be a matter of elimination until you find the culprit :lol: :lol: :lol:

Bigjay
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Re: CNC Starts Cutting a New Path Midway Through the Cut

Post by Bigjay »

Okay so I went back and tried this again, slowed down the tool path feed rate and still have the same issue. I have included pics of what I am trying to build and the pics of what the machine is doing. It is a sign that has the words tilted tulip with the tulip logo in it. The word tilted cuts the way I expected but as soon as it gets to the tulip logo, I start to have problems.
Attachments
20210808_140751[6355].jpg
20210808_140757[6356].jpg
20210808_140802[6357].jpg
Capture.PNG

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Adrian
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Re: CNC Starts Cutting a New Path Midway Through the Cut

Post by Adrian »

You have to work your way through all the likely causes of lost steps as Martin says. Feed rate is only one of them. If your pass depths are too much then slowing the feed rate won't always help.

If you attach the CRV file then people will be able to look at it and make suggestions as to feed rates and whether there are any other issues. Generally if the preview is correct and you're using the correct post processor then, other than feed rates/pass depths/rpms, all the likely culprits lie outside of VCarve and will be physical machine problems or control software issues.

Looking at the pictures it doesn't look to me as though the positioning is correct before it gets to the tulip.

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martin54
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Re: CNC Starts Cutting a New Path Midway Through the Cut

Post by martin54 »

As Adrian has said sharing the file would be a good starting point, The toolpath preview is very accurate so is a good indication of what you should be getting when you actually machine the file but it has no idea what your machine is capable of so can't help with any of your settings, other users on the forum can often help with that sort of thing.
That then pretty much rules out some of the causes so you can start looking at other things like how you are sending files to the machine, dust extraction/grounding, electrical interferance, binding, loose components to name a few of the more common reasons :lol: :lol: :lol:

Bigjay
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Re: CNC Starts Cutting a New Path Midway Through the Cut

Post by Bigjay »

I am running a Mill right Mega V with an older laptop that is situated right beside my machine. I am using UGS platform for sending gcode to my machine. I tried it again last night and had good results but I homed my machine in between each new gcode file. I attached the gcode for the tulip logo for your review. I also tried to attached the crv file but it is telling me the file is too large. I really appreciate your help with this.
Attachments
tulip Logo Gcode.pdf
(103.83 KiB) Downloaded 62 times
Tilted Tulip Round.dxf
(1.08 MiB) Downloaded 56 times

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Adrian
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Re: CNC Starts Cutting a New Path Midway Through the Cut

Post by Adrian »

Bigjay wrote:
Mon Aug 09, 2021 5:58 pm
I am running a Mill right Mega V with an older laptop that is situated right beside my machine. I am using UGS platform for sending gcode to my machine. I tried it again last night and had good results but I homed my machine in between each new gcode file. I attached the gcode for the tulip logo for your review. I also tried to attached the crv file but it is telling me the file is too large. I really appreciate your help with this.
Are you specifying feed rates in mm/min?

If you're having to rehome the machine each time then it's definitely losing track of where it is which is lost steps.

You could try zipping/compressing the CRV file to see if that make it small enough to attach otherwise use a file sharing service such as Dropbox, OneDrive etc.

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martin54
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Re: CNC Starts Cutting a New Path Midway Through the Cut

Post by martin54 »

As Adrian has said you shouldn't be homing the machine between each toolpath, just a thought though if when you did this using seperate toolpaths & homed the machine each time everything seemed to be OK.
Does the job use the same tool for all the toolpaths & did you send the entire job as one file?
If that is the case then have you got all the power saving features turned off on the laptop? Not just the ones that are visable like the screen & sleep but the ones that need you to use the advanced option such as HDD & USB :lol: :lol: :lol:

Bigjay
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Re: CNC Starts Cutting a New Path Midway Through the Cut

Post by Bigjay »

Here is the crv file zipped. The original toolpath was one file but when I started having issues I changed it into 4 seperate toolpaths. All toolpaths are with the same .250" endmill. I have shutoff all power saving options for the laptop so I don't believe that is an option. As well I did a 10 hour 3D carve the other day and had no issues at all. I think the issues is related to the deeper cuts somehow. I am using 4 passes to cut .65" deep.
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Tilited Tulip Round.zip
(1.09 MiB) Downloaded 62 times

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Adrian
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Re: CNC Starts Cutting a New Path Midway Through the Cut

Post by Adrian »

You say in your original post that you're using a 0.125" tool but all the toolpaths are setup for a 0.25" bit instead? If you're using a 0.125" bit when the toolpaths are programmed for twice that you will get odd results especially given the pass depth you would be using for a small bit like that.

You're also using pocket toolpaths when a profile cut set to cut inside the vector would be quicker as you're cutting to the full depth of the material.

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adze_cnc
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Re: CNC Starts Cutting a New Path Midway Through the Cut

Post by adze_cnc »

Adrian wrote:
Mon Aug 09, 2021 9:11 pm
...as you're cutting to the full depth of the material.
Something that has bothered me from the first images posted: if you are cutting through the material how are you keeping the "islands" in letters such as "e", "d", and "p" plus the script loops in the "l" and "d" attached to the rest of the material? I'd have figured this wouldn't actually have been cut all the way through.

Bigjay
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Re: CNC Starts Cutting a New Path Midway Through the Cut

Post by Bigjay »

You are absolutely right, there are other ways I could have set this up but am learning as I go and have made some mistakes along the way. The concern I had was why my machine was experiencing lost steps. I think I have figured out the issue, there was a slight misalignment between the gear rack and the pinion gear which was causing the machine to bind on the x axis. looks to be working fine now. Thanks for the suggestions.

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