Initial workpeice tooling set-up instructions using a pendant controller type machine

[Nthkentman]

Using an eMach EM900 machine with the pendant controller

Can anyone improve the route below ?

I'm trying to remember how to set-up the work and axis before starting cutting, watched a few U Tube clips and have decided on the route I have written...



In VCarve (Or your program for designing etc) set machining datum to TOP of workpeice for eachmaterial at material CENTRE for X & Y for all work designs
Insert pointer rod into tool collet to use as alignment tool for workpieceedges along X axis, mark workpiece centre using lines across from corners with a pencil.
Align workpiece edge along X axis using pointer and handsetrapid along workpiece edge and move work to align with x Axis before clampingetc
Clamp, stick, or whatever the workpiece to wherever requiredon table/platen
Using handset find drawn centre marker, jog to exactly the centreof the X marked on job eyeing up the cross lines.
Remove pointer after zeroing WORKPIECE axis X & Y todatum centre drawn lines in your pendant or software
Fit required cutting tool for the job into collet ready for Z Axissetting
Using handset set tool to “Touch Off” at job top face. Justkissing the top face
Zero Z axis using pendant or your software. Axis setting is now complete.
Ensure workpiece is fixed ready for use.
Reduce feed rate, start machine after loading required G code/Design and watch for issues, increase rate whensatisfied all is Ok.

[EddyCurrent]

That's fine for jobs that work about a centre line e.g. guitars, but I would think most jobs are referenced to the bottom left corner, the X0,Y0 corner
If you are doing repeat work you might want to think about 'fixtures' using G55 - G59 coordinate systems.

[JAZZCNC]

There's not right or wrong way or better or worse it's all down to preference.

My setup is mostly done from lower left corner but in the case of a circle I may use the centre it all depends on the job and material it's coming out of. Often i'm cutting parts out of existing sheets and with a circle working from centre is easier regards waste and fitting into available space etc.

If your mostly using square sheet material then I'd setup reference bump stops or edges along each axis so can work from same X0 Y0 WORK coordinate and cut this process out. Only needing to set the Z ZERO. (if using same thickness material won't even need to do that.!)
You should be able to set the G54 WORK OFFSET in the control. G54 is often the default OFFSET and will be the last place you set the WORK ZERO if the OFFSET was saved before closing down the control. So you can predefine a spot on the table and save as G54 default which will always be the same unless explicitly changed by you or G-code.
On first startup you should always HOME the machine first before doing anything. Then after this the Control nows the OFFSET's and because G54 is the default then it will be set to the spot on the table you designated ZERO for G54. Which is be the corner of the material when against the bump stops.

Even if you change the G54 OFFSET in g-code while working so long as you don't save the WORK OFFSET when finishing cutting session the machine will start backup at the spot you selected after homing.

One thing I will mention with smaller jobs is not to work on the table in one spot all time but to move the smaller stuff around the table to lower wear on the ballscrews in one area.

[Nthkentman]

Thanks Jazz for the advice.

I set a 19mm sacrificial board on the machine today and on top of that I set a small 200 x 120 x 13mm thick piece of ply

After setting the machine to "HOME, I then, using my procedure above, brought the arm axis's to the centre of my workpeice. Positioned the cutter to the correct marked centre and zero'd X & Y.

Then I brought the head down and jogged until the cutter (A 3mm dia single flute end mill) just touched the surface and zero'd Z

In my V Carve software I set the XY to centre of the work, and the height of the material as 13mm. Reference start for Z axis was top of workpiece at centre.

When I started the machine and set it all in motion the X & Y axis travelled to the exact set point in the middle of my piece as expected, but the Z rapid plunged into that point to the collet nut depth ! (Until I hit the E Stop button)

What did I do wrong? I'm missing something here and feel a little dumb.... Newbie cock up I know... Loooong time since I did this and it's a fun learning curve again

[Clive S]

By default V carve sets the material z position to the bottom of the job. Did you change it to the top?
Also did you have the "model in material" set to "gap above model". .. Clive

[Nthkentman]

By default V carve sets the material z position to the bottom of the job. Did you change it to the top? Clive

Hi Clive, yes I did change it to the top. The diagram shows as you say the default at the bottom of the workpiece, (Which I also tried) but irrespective of how I set it the Z axis is wrong... I'm wondering now if I am sending the wrong G code to the machine.
The PP asks for a file with extension .nc
So I use the first available .nc choice as my machine is not listed.
Perhaps I'm doing that wrong ?

[JAZZCNC]

What did I do wrong? I'm missing something here and feel a little dumb.... Newbie cock up I know... Loooong time since I did this and it's a fun learning curve again

Don't feel dumb we have all been here in some form or another.! . . My first attempt with G-code ended thumping a perfect square hole thru 40mm of MDF after sending Z axis wrong way. . .Lol

I don't use V carve but If it's not that you have set the Zero point at bottom of material and you can't find any obvious reason then it could be the Control as a TOOL offset set.
Just like WORK OFFSETs you can have TOOL OFFSET's so your control could have TOOL OFFSET's entered into it.?
So when your G-code calls for first tool it applies the OFFSET set in the control. This could give the trouble your seeing.

If you open the G-code file you look for G43 H# with the number being the tool number probably 1 in this case. It will be some where near the top and probably will be near the tool number IE:
T1
G43 H1

If so then chances are you have TOOL OFFSET applied. Just remove the G43 H1 or put G49 straight after it.

[Nthkentman]

Thanks Jazz, I actually believe it's me getting it wrong tho... I only have the facility for XY offset in V Carve,
I wonder if plain G Code in txt will work, even though the PP program suggests .nc extension... Not sure why there is a difference....
Looks like I'll be installing Mach3 and getting someone clever in to convert the machine board otherwise