3 Questions

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3 Questions

Postby Parkgrr » Wed Apr 14, 2021 7:58 am

Maybe you guys can tell me if I’m crazy or not or if any of these approaches are a bad idea. Also I am a dead-to-rights rookie, beware these may be very ‘dumb’ questions.

I'm finishing up a retrofit build and am doing calibration/setup for the first time. My goal is to establish enough constants that when I start a new cut all I need to do is home the machine, place the stock onto the bed, line it up against existing studs/dogs and press go.

1: This means that I would have a set constant machine origin for all projects which is just a set offset from the XYZ home coords. Note: I plan to calculate all tool paths with the origin being on the bottom of the stock. So assuming I set my machine Z origin correctly to spoilboard and I don’t have a radical gap in software-to-actual stock it should behave correctly without actually setting Z to actual top-of-stock every time. I recognize that this approach would be the less-accurate approach for Z, and that stock thickness can often be inconsistent, however in the work I’m doing even 2 or 3 mm of unexpected thickness in actual stock is not a big deal.

Q1: Is running a machine origin based on homing alone accurate enough for day after day consistency?

2: My machine has ATC and a fixed touch-off plate. I’ve considered if there is a way to do away with before-every-cut tool touch off. I’d like to set all Z tool offsets in the software in one go on the day I install tools and never after until the next time the tool in a tool holder changes.

Q2: Do you see an issue with doing away with touching off before every cut?

3: My machine is a Multicam MG whose X and Y are reversed from what you might expect. When standing at the ‘front’ of the machine (where branding faces you and the valves for the vacuum table are) X moves the gantry itself and runs away from you, and Y moves L and R in front of you (across the gantry). It makes sense to me to do away with this and change the gantry movement (away and towards you) to be Y and across-gantry movements (L and R) to be X.

Q3: Is there any reason you can think of that this would not be a good idea to change this? Is there a situation in which this original setup is beneficial for some reason?

That’s all. Any other first-time machine setup advice is very welcome!

Best
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Re: 3 Questions

Postby ger21 » Wed Apr 14, 2021 11:51 am

1) Depends on what you are doing, and what level of precision you need. But I've been working this way for over 25 years, both on big Italian routers ($150K+), and my DIY machine.

2) No, that's the proper way to use an ATC. You will need to write an ATC tool change macro.

3) It really doesn't make any difference. I prefer the long axis to be the X axis, as I find it easier to work that way in CAD and CAM software, with the long axis left to right on the screen. But I also like the X axis to be left to right when I'm operating the machine. In your case, you pick which one is more important. But it doesn't make any difference as far as how the machine operates.
Gerry
UCCNC 2017 Screenset - http://www.thecncwoodworker.com/2017.html
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Re: 3 Questions

Postby Vmax549 » Wed Apr 14, 2021 1:24 pm

#2 will depend on what type of tool holders your machine uses . IF it uses dedicated tool holders such as BT30,etc then you can do all tool offsets at one time and only update when a tool bit actually changes . IF your machine uses a tool changer then it should be using a dedicated tool holder.

Just a thought , (;-) TP
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Re: 3 Questions

Postby Parkgrr » Wed Apr 21, 2021 1:20 am

Ok got it. Mine uses HSK63F tool holders, so I'll plan to do one-time offset setting when I install tools. I'll plan to use homing to determine origin as well. I'll do some tests to check that it's accurate and repeatably accurate.

Good advice as far as treating X and Y. Sounds like I'll need to just do some work to see which I prefer. I suppose it's switched back and forth easily enough.

Thanks very much I really appreciate the input.
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Re: 3 Questions

Postby Battwell » Wed Apr 21, 2021 11:44 am

if you install a tool length setter i have a macro that probes and saves each length to tool number. so it only has to be done once.

i prefer the long axis to be x. (as it should be) this is easiest to draw in cad with screen oriented landscape so matches the bed properly!
(also allows wood grain direction to be left/right on all parts easiest)

once you have set up and saved a fixture. homing and running is fine and only has to be reset after a spoil board skim. this is the way i work.
g54 bottom left xy zero with z zero on spoil board.
g55 to g59 for any other fixtures on my table or odd jobs where i set z as material top etc.
Uc300eth on router and mill
If they say it can't be done- I find a way!
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