Thread: help needed 8' x4' cnc

Alen,

Max current draw depends on everything you will end up hooking up but as a guide, 15A should be enough. At maximum draw, each of those PS pulls roughly 1.5A, a 2kw spindle is roughly 8A and the misc ps (5v/12v etc) wont be much so say maybe 1 amp. With these alone at max pull would be roughly 13A. Very rare that any of these would be at maximum so it should be well below during normal operation. Startup will be different as there will be inrush currents but worst case these may just trip the breaker.

Also just a note, your steppers only require about 66% of their actual current requirement do to design. See the gecko website for theory on picking the correct voltages for steppers and current requirements.

I would love one of those nice looking square spindles, like you say the mounting is alot easier.

I work daily with solidworks and autocad and having access to them will help greatly depending on your needs. These are CAD programs. Mach3 is a control program, you will still need a CAM program to convert these CAD files to a code that mach3 is capable of using to control the motion controllers through the BOB. The CAM program depends on what you will be doing. I'd recommend vectric or artcam products. Again depending on your needs there are variants or their software or other programs out there too. Yet more decisions to be made....lol. At least alot of them have demos to try. I prefer artcam but then again i cannot afford to buy it as its expensive but alot more powerful however probably not as user friendly as vectric products.

Daniel
****Sorry didn't read above post correctly so missed that you were looking at CAM software too*****

Hi Daniel
Thanks for the info

It's good to know the amperage.. I might need to run another cable from the main box for it... Shouldn't be a biggie...

Regarding the cam software.. I've got the access to CamBam plus
That should sort out conversion for the time being..
For the longer run.. will need to invest into purchasing either CamBam or equivalent...
But for now.. I should have software sorted...

Will need to pick Peter's brain about connecting proximity switches to his Bob... hopefully it should be fine... Are they hard to calibrate???
Reading through some info.. they seem to have a bit of issue with interference... Is that true or just a bit of exageration??

Daniel raises a point about the inrush current.
On my machine I had to put in switches to turn on the various motors separately as otherwise the circuit breakers would blow every time.

I too run individual switches(push button switches controlling contactors) to turn on the spindle, electronics etc. This also helps when i am running the diamond drag tool as i don't have to power up the spindle to run it. I also run off a dedicated 20A circuit after the inrush currents kept popping the circuit i was on so if your close to the max current on a circuit speak with a sparky and see about getting a dedicated line put in for the CNC. Sometimes it might be as easy as supplying a case of beer.

Proximity switches are quite easy to run, they act very much like a normal switch and easy to work with, only difference is they normally get supplied a voltaege, normally 5v-30v to run them. Other than that the operation is quite easy to understand with basic knowledge.

Daniel

Also proxy interference isn't an issue really unless you run non shielded wiring, have ground loops in the system or running high frequency equipment aroudnt he machine at that time. When it comes to wiring, you can buy from places like DKSH who sell LAPP brand shielded multicore control cabling at a good prices.

Thanks Daniel and Bob
Great info

Was planing of getting about 20 mtrs of shielded cable from Peter...
Haven't investigated shielded cabling properly yet...
Peter's cable seems to be affordable... not sure about how good is insulation on it.. especially on such size table..
(It does seem to be a bit thin though.... at least from the photo... )
Will check out DKSH as suggested..

Good idea about switches to start everything separately.. Since I'll be putting electronics into the full tower.. I might use its front 5.25" bay and put switches for everything into it (altronics has some nice looking switches )
Well money saving is getting cloe to the target figure required for electronics.... Once I get that.. that's it .. fully commited then.. otherwise some good hard earned $$$ would go to waste... which will put me in bad books with SWMBO for a long time.. and we cannot allow that can we...

hmm through my hommans page browsing came accross those relays which I think I need to add to the electronics list...
Any suggestions???

Alen,

again its great to see your setting goals and researching lots.

The DKSH website is a bit of a pain to browse but there are heaps of nice pieces throughout their site from connectors and cable chains etc but i haven't compared their prices on them yet. Here is a link to a search for the olflex cabling. Stick witht he olflex classic and it will be fine, although if still too dear, the cabling from peter is not too bad at all, but as you can imagine there is a fair difference between the two.

And no you cannot get SWMBO on the bad side.....not until the machine is built anyway...lol. Then its just a matter of doing some nice stuff for her and it will keep her happy.

Thanks Daniel
had a look through DKSH site..
Got the right cable.. but wondering what gauge to get..?? What would be recommendation...
Considering it is fairly low voltage but current is a bit of a pain..I definitely don't want to run it too thin of a gauge for the wire.. and off course trying not to go too thick .. so I can save bit of $$

Good thing is they are approx 20 km from me.. yeeey... lucky me.. just hope they are open saturdays...
I need 4 core one for steppers don't I ?? (just making sure... )

Originally Posted by Prle77

I need 4 core one for steppers don't I ?? (just making sure... )

4 core for the steppers plus the outer shield so that you can shield and earth it all. (One end only)

We used the following cable from DKSH Stock Code 0026232 - 4G1mm OLFLEX FD810CY it was about $4.50 a metre but it is nice cable and designed for automation purposes.
Looking back at the pix for the table looks ok but is it going to be easier to start a fresh than to modify it to what u want, any other thoughts people?

But if you are using those switches from Altronics, for extra cool factor* you can also add these to them:
Altronics - S1036 Switch Cover Missile Style Red

*or extra "Damndamndamndammit it's not gunna stop on the soft limits" insurance!

Regarding the table.. Agree with Chris...
Will pretty much start from scratch...
But will use those I beams for sides...
The measurement of the I beams:
Overall beam 96mm
Top bar 98mm
Thickness of material 5mm
Overal length 3540mm .. usable length 3150mm (there is some L profile welded on one of the ends..)
Since top has been machined I would expect fairly level surface...
Underneath the top bar there is approx 44mm of space.. (ideal for mounting rack)
Re-checked the spacer bars between I beams... even if they are stretched to the max.. I still won't get the desired width of 1500mm .. (max is 1400mm) which won't leave me with enough space to cut width of standard sheet..

Whole CNC design steps would be..
Deciding on parts (electronics, linear bearings, spindle)
Get the parts.. (that way i can measure exactly for mounting holes, positions etc..)
Do the proper drawings...
Go see my steel guy and start spending weekends at his shop putting everything together...
Dismental the whole thing.. move it to my place.. put it together, make sure it is alligned properly and start playing with mach 3 and see if I can get something out of it