New Memeber and very new to CNC

Hi all,

I’m very new to the world of CNC. I’ve just built a CNC kit which I bought from ebay. It appears to be working (moving via the 'Grbl Controller' software) though, I have a key question. Hope this is not to daft and too funny, for you advanced users.
Here goes, I’m having trouble understanding the Z-axis and how this is initially set up when starting a new job. My worry is that the spindle will go straight through the circuit board I’m about to mill, breaking the drill the bit and damaging the board itself, and I guess not doing the CNC any good!? So, how to I prep the machine to deal with these possible situations?

Many thanks.

Not used the Grbl software. I use an smc4-4-16a16b controller unit for my machine and VCarve for design/gcode. I'm also no expert, but you should be able to move your spindle to where you want the job to start. Move your z so your tool bit is almost touching the PCB. In your software, you should then be able to reset the x,y and z co-ordinates to 0. This will be the start point for your job.

That's how I do things. If you are unsure though, best wait for someone who has experience with the software to make a post.

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Originally Posted by Rye

Not used the Grbl software. I use an smc4-4-16a16b controller unit for my machine and VCarve for design/gcode. I'm also no expert, but you should be able to move your spindle to where you want the job to start. Move your z so your tool bit is almost touching the PCB. In your software, you should then be able to reset the x,y and z co-ordinates to 0. This will be the start point for your job.

That's how I do things. If you are unsure though, best wait for someone who has experience with the software to make a post.

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Thanks for your quick reply - do you have/know of any more info/examples of setting up a new job/project on a cnc? This is the one I have (please don't buy from this users as they are very shoddy!!!)

Thanks again.

You could also set your Z 0 to just a fraction above your table, for example, stick a piece of paper on your table, bring your Z down till it just grips the paper and make this your Z zero. If your pcb was 3mm, then your starting height would be positive 3, and finishing depth would be 0. This would (should) then ensure there were no accidents.

Another thing to try is to raise the bit about 10mm above your PCB and set that to zero. Then do a dry run (also known as "cutting air") and make sure the tool path and speed looks as you were expecting. One thing to check is that non cutting moves are a few mm above the PCB, not at zero.

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Originally Posted by Fred

Another thing to try is to raise the bit about 10mm above your PCB and set that to zero. Then do a dry run (also known as "cutting air") and make sure the tool path and speed looks as you were expecting. One thing to check is that non cutting moves are a few mm above the PCB, not at zero.

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Hi Fred,
Ok sound interesting. So does that mean whatever software you use to run the *.nc file, the coordinates are offset from/to this? Would this be a rule of thumb procedure before each job?

Thanks

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Originally Posted by jamhot

Hi Fred,
Ok sound interesting. So does that mean whatever software you use to run the *.nc file, the coordinates are offset from/to this? Would this be a rule of thumb procedure before each job?

Thanks

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Before you start wrecking your machine have a good read through this :-
http://www.cnccookbook.com/CCDIYCNCBeginners.html

It will help you understand what you are trying to achieve

Brill - thanks Clive. I'll have a good read. :thumsup:

To save your bed and table like metioned always cut air but if you want to see the actual cut then buy some thick insulation Foam and cut that first. This way gives enough time to react without damaging tool if goes wrong.

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Originally Posted by JAZZCNC

To save your bed and table like metioned always cut air but if you want to see the actual cut then buy some thick insulation Foam and cut that first. This way gives enough time to react without damaging tool if goes wrong.

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Yeah good thinking - I thnk I need to get some blocks of wood or smilair material to test on (and use as a safty bed)! Thanks.

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Originally Posted by jamhot

Yeah good thinking - I thnk I need to get some blocks of wood or smilair material to test on (and use as a safty bed)! Thanks.

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wood will stick break tools soft but firm material is what you want.

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Originally Posted by JAZZCNC

wood will stick break tools soft but firm material is what you want.

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What material do you use, or would recommend? Thanks.

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Originally Posted by jamhot

What material do you use, or would recommend? Thanks.

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Re read post #9

Oops silly me, thanks I'll grab some of that - Cheers.

Go to Wickes and buy the floor insulation, about £5 for a 1200x400x50 piece I think. I use bits of packaging to practise if I'm not sure, like the below...

https://uploads.tapatalk-cdn.com/201...9b3aa615ff.jpg

Sent from my HUAWEI VNS-L31 using Tapatalk

Quote:

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Originally Posted by njhussey

Go to Wickes and buy the floor insulation, about £5 for a 1200x400x50 piece I think. I use bits of packaging to practise if I'm not sure, like the below...

https://uploads.tapatalk-cdn.com/201...9b3aa615ff.jpg

Sent from my HUAWEI VNS-L31 using Tapatalk

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Ok, I'm liking these ideas. Maybe I should buy something from Amazon, the packing should last me a while - thanks