Generating a test writing file for first CNC test - stupid noob question

[Cret]

I've finally got my machine set up and running now in Mach3, it has soft limits, is calibrated and homed etc, so it's ready to roll basically (Estop installed!!), but I want to try making it just write something on paper with a sharpie pen first.

I'm trying to make a suitable file to test it with but getting nowhere.
Mach3 has a write wizard but every time I enter a value in a field like the 'tool n' or feed rate etc (as per a youtube video showing how to use this plugin) then move to a different field it zeroes the value of whatever I just added.

I tried instead to use a little text to gcode application I found which generates dxf files and it seems to create files of gcode ok from text you write but when I load & run in Mach3 I get a bad character error on the first line. I'm not savvy really with gcode but the first line of code is a zero, followed by 'section' on the next line.

If you got any suggestions, or know where I can just download an example file to make it write something with a pen it would be brilliant thanks mate. So close to using it but doing something stupid I guess!

Really appreciate any advice, thanks!

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[hoss2006]

There are sample files in the mach 3/gcode folder a lot of people use to test, the roadrunner is popular.
If your program saved as a dxf that won't work, Mach needs a txt file for gcode, several types will work, .tap, .gcode, .nc, .txt etc.
I have several samples too here that you can download, scroll down till you see calvin peeing.
Hossmachine_Cnc Conversion
Hoss

[RASPNC]

Ive used the circular pocket wizard in Mach 3 a few times, it works well.
One thing to check, make sure the tool diameter you set is smaller enough to machine the shape you specify,

Nikki

[LongRat]

When you enter the values in the wizard, you have to press enter before moving to the next field or your values will be deleted.

[Cret]

Thanks guys - that was exactly the problem!!

I was watching a youtube video for this seeing the mouse click from one field to the next so I was doing this but obviously the guy was hitting enter without it being visible! It's the simple things!

I need to work on the values used on this wizard though. X&Y are fine but I'm not 100% sure of the settings for 'Rapid Height', and 'Z Top' if I'm honest.
I got one letter written then the head ascended to it's home/zero position (top of its travel), before descending again for the next letter.
So I had a depth setting of 127mm to descend down from 0, and this works, but it tries to go back to the top between each letter and I'm not sure which is the right setting in order to make it move just off the paper before coming down again.

Sorry if I'm missing the obvious (and I think I am!).

Awesome to see it trying at least!

[LongRat]

Zero the Z DRO on the surface of the material and set Z Top to be zero. Rapid height is the clearance plane height above the material - 3mm would be a suitable normal value.
In your case it sounds like you have set a home switch at the top of the Z travel, which is fine, but then you are using the machine co-ordinates as the work co-ordinates. You would normally set a work co-ordinate system separately from the machine. So the machine zero is at the top of the column but the work zero is the top of the stock. The difference in these two zeros is known as the work offset.

[Cret]

Thanks for the info - it's really helpful and appreciated.

I did get it figured out in the end cheers, and here's an awful quality clip of the 'action':


Afraid I was holding the phone while hovering my other hand over the Estop and not really concentrating on making a quality video!

Am sooooo excited to have this working after years of wanting to have a machine like this.

My plan of attack now is the following:
1) Read up on tool auto zeroing, and make whatever is necessary for enabling this in mach3 (as I understand it I need a probe to touch the tool against, which complete continuity in a circuit and signal to mach3 that it should stop the z axis).
2) Read up on tool offset and how this fits in with gcode and a workpiece etc so that everything works as it should (I don't really yet have any knowledge on this).
3) Try then cutting some basic shapes in wood
4) Repeat with aluminium
5) Start making things, beginning with hardware to replace the printed plastic parts I made, and then hardware for limit switches etc.

I also need to find a suitable space for the electronics PC case, and replace some wiring and fit proper switches etc.

[LongRat]

Ah yes, what a great feeling it is when your machine moves for the first time. I remember it well and it doesn't get old! Well done.
If I remember correcty the Mach3 user manual PDF has some decent info about tool and work offsets you may find useful. You are right about the contact probe thing, that is how most of them work. A simple insulated contact pad. It's pretty easy to enable in Mach3 and does work very well. The Auto Tool Zero button is even there on the main Mach3 screen waiting to be used.

[Fastest1]

A simple piece of circuit board laid on the table with a wire going back to the BOB works great.

[Cret]

I've made a probe and wired ito to pin 15 on the bob:




I've enabled it as active low in the inputs screen.
I've set up one tool in the tools table, although I don't have all the values it needs - need to read the documentation properly about this.

Also, as I understand it I'll probably need to get some code and perhaps modify it for the functionality of the auto zero. I assume it has default code for this, but that it's limited in what it can do, thus its common to modify it to suit individual requirements.

[Fastest1]

That is correct in regards to the code. Are you also a member over on the Mach forum?

[Cret]

Thanks

No, I haven't joined there yet (at least I'm pretty sure I haven't yet!) but I'm sure I will be doing.

[Cret]

Had a fault with the auto zero with the height the tool was retracting after I put in the code from an instructable/youtube video.

I've sorted it and it was fairly obvious actually. I had a tool height set in the table of 50mm. Not even sure why that was there to be honest, but I think it was just an arbitrary number I put in so it had something in for one tool at least. Changed it to zero, changed the tool out and back and now it works perfectly.

After running auto zero, the tool sits at 9.44mm above the table, ie the probe's 7.44mm and 2mm extra. I'll change that to sit at 10 so it's a nice round figure.
Great!

Next up, I need to understand offsets I think before I try to do anything with the machine. I watched a video demonstrating a guy that makes guitar bodies on youtube, how he uses G54, G55 and G56 reference points or 'fixtures' to place his material in a known start point relative to the machine's zero. So I'll look into this a bit more, then maybe try doing some sort of cut into a soft piece of wood.

[Fastest1]

Hard foam insulation is good for testing and understanding too. If you break a tool in it, you are going way too fast! ;-)

[Cret]

Good idea thanks!

[Cret]

Well, I finally made the machine carry out its first cut just now and nothing went horribly wrong thankfully.

First things first, I made mounts for 3 home switches and fitted them to the zero positions for the machine on all axes. Wired them up and set them up in Mach3. They're currently set as active high because I didn't have any NC switches to use. Will get some though as I think it's a safer option in case a switch fails.
So they're set up, I have referenced all home on the machine co-ordinates, and nervously watched as each axis homed itself to the switch and settled just off them. Phew.

I did briefly confuse home switches with limit switches at one point, where the soft limits where switched off, an axis hit the home switch, and carried on, without me immediately realising why. I realised quickly that it was because the soft limit button was disabled. Is there a way for the home switches to also be physical limit switches as well, or would that not be a good idea?

Anyway, I fitted a 5mm mill attached a vise with some wood in it, and jogged the table over to the wood and the head dropped down until it touched the material, then zeroed the work co-ordinates.
Next, I opened one of the wizards - shape wizard, then set it up to cut a circle. I'll be honest that I didn't expect nearly so many settings for this, and wasn't sure what several of them were for as such, so I set very low figures and hovered over the Estop!

So I told it a 10mm radius circle, and the resulting circle is 25mm wide. It's using a 5mm end mill, so it seems the centre point of the mill is where the cut circle is measured from. I guess I've missed some sort of offset, or set it wrong to account for the diameter of the mill so that it ends up actually being a 20mm circle instead of the 25mm it came out as.

Also, I set the plunge and depth as 3mm but am not sure what the distinction is here? I also set the horizontal offset each as 1mm. I wasn't sure their purpose but when it cut into the wood it cut one shallow circle, then dropped very slowly lower & cut a second, then repeated this pattern for a third. I'd have to guess the vertical offset is like a divisor in this case for how it layers the 3mm plunge or depth into 3x 1mm deep cuts?
Not sure what the horizontal offset did though....?

But anyway, it worked nicely, even if I was ready to hit the stop! Video'd the second run of it once I realised it wasn't going to do anything horrible.

[Fastest1]

Yes you can use the switch for both limit and home. Both need to be enabled though they are the same switch.

It has nothing to do with soft limits.

The fact that the machine kept running after hitting the switch tells me it was only a home and not limit in the config.

Also til you know your machine inside and out, hover over the EStop. It will bite you as soon as you relax.

[Cret]

Thanks, I hadn't tried setting the home switches to also be limits, but when it occurred to me I wasn't sure if that's something people normally do?

I'll set them when I get home tonight though as I think it'd give a bit more peace of mind.

[Fastest1]

Of course this only works if the limit switch is at the end of that axis' travel (I think, as there are a few settings in regards to off home and the like I dont understand). The homing and limits section has the dialog as to which way the machine travels to find home (which it sounds like you have set up correctly). Once the limit and home is found, the machine references itself. Then if soft limits are set up correctly the machine will stop before reaching the end of its travel. It will also warn you prior to a file being run and where the violation occurred.