Planning for a CRP4848

[vbgraves]

Greetings all. I’ve been lurking about trying to learn a little first, but this is my first post. For several years I’ve wanted a CNC router but just never found the time or funds to pursue. I recently came across the CRP4848 machine and would really like to build one; my primary usage would be in wood, plastic, or MDF, but I might consider aluminum in the future. I plan on using a router with the system rather than an AC spindle.

To this point I’m leaning towards the CRP NEMA34 DIY electronics kit (just because I only want to build one machine, and I’d rather not wish I had the larger motors later), and my basic question has to do with power usage. The area in my shop where the machine would reside has 20A outlets, but they are on a single circuit. So I’ve got 2400W available. The 48V/21A power supply in the NEMA34 kit could use up to ~1000W, an 11-13A router could take over 1000W, and a future dust collector might also take a few hundred watts. To those of you who use the CRP NEMA34 kits, do you have separate circuits for the machine and the router, or am I worrying about something that in reality isn’t a problem?

On another electrical issue, I have a 60A subpanel in my detached workshop, which has been adequate up till now. Would that be enough to even consider using a VFD spindle with the machine (I currently don't have any central heat or air conditioning in the workshop, but that might also change) sometime in the future, or would I need to upgrade to a 100A panel?

Thanks,
Van

[ahren]

Van,

Glad you're starting a build thread! Assuming the 60A panel in your workshop is 220V, it should be adequate if you ever add a spindle. A 1.5 kW VFD will only draw ~7A or so at 220. You are close to budget on the single 20A circuit, and I don't think you'll be able to run a dust collector on it as well, but you should be able to run a router and the control box.

Best regards,

Ahren

[kinghong1970]

Van,

firstly, good choice... Ahren from cncrp has been amazing in support.
and for your needs, if you're able to work with a nema23, shouldn't it be easier for your current set up and budget?

rgds,

Al

[vbgraves]

So it sounds like the CNC machine needs its own circuit if NEMA34 system is used. I neglected to mention that adding a circuit is relatively straightforward for me since my interior walls are not covered yet. It might be a good idea in either case to isolate the CNC controller from other equipment that might be on the circuit, such as an air compressor starting up.

The real question then becomes whether to get a NEMA23 or NEMA34 system. Assuming I'm not planning on doing very much metal cutting with the system, is it really just a question of cutting time? The smaller motors will have to cut shallower or slower or both. I suppose for just a hobby machine, speed isn't a big concern, but I don't really have an idea of what to expect in either case.

It would be interesting to hear from those who have NEMA23 systems -- after using it for several months, do you find that you're always pushing its limits, and do you wish you'd have paid the extra cost for the NEMA34 system? And conversely, do many of the NEMA34 owners find that they rarely benefit from the extra performance? For the $1k cost difference I could buy a router and a dust collector and still have a high quality CNC machine.

Van

[ger21]

If your using a router for the spindle, either system should be able to overpower the router.

[vtx1029]

I've had my rapids up to 600 ipm and cut my spoil board at 300 ipm just for kicks. It did just fine, but I normally keep it at 400 rapids and limit the cutting to 100-150ipm. No regrets on the Nema 23's. With the gear reduction they do pretty well

Only thing I would maybe to different is buy the Kelling G540 nema 23 kit being it has lower inductance it should perform a little better. But when I was buying the convenience of CRP's kit (pre made cables) made me go that way instead. Either way I don't think you can go wrong.

[vbgraves]

Since I'm just starting down this CNC path, I think I'd rather keep it simple and get a machine running with a router rather than a VFD spindle. I can always upgrade the spindle later. But I hadn't thought about the router not keeping up with the NEMA23 drives, so I wouldn't be able to take advantage of the extra performance of the NEMA34 drives except during non-cutting moves, which isn't worth the extra $$ to me. Looks like I'll stay with a NEMA23 system and maybe get a SuperPID to go with it!

I'll look further into the Automation Technologies NEMA23 kits and compare to the CRP kits. Looks like a little more work with the AT kits but not too bad. Their enclosures also seem to be a better match for the smaller size of the G540 hardware.

Lots of choices to make!

[vbgraves]

So since my last post I added an ethernet port next to where I plan on locating the router in my shop. This will allow access to ngc files over my network. I considered adding a dedicated 120V outlet but decided it's something I don't have to do right now. If I ever get around to finishing my walls, I'll do it then.

I'm still thinking about the CRP4848, but at a somewhat slower pace. I have a desktop CNC mill that I've gotten to work with LinuxCNC, and now I'm finally adding a spindle so I can actually cut something with it. This is my CNC crawl before the CRP4848 walk. I want to figure out the software side of CNC programming with this system, what CAD/CAM software, etc.

I want to continue my plans for the CRP4848, and I'll keep this thread alive with design of the support frame for the router, which I'd like to have on hand before purchasing a CNC hardware kit. I'm sure there are lots of examples out there, so hopefully I can get some feedback. I've been thinking about using some oak 4x4s - there's a local pallet company around I can buy them from. However, they would be green, so warpage would be a problem. If I can't find someone local that could kiln dry them for me, I'm not sure I'd want to take a chance with them.

Van

[vtx1029]

If you want to do a wood base look at LVL beams or you could easily make your own beams like ger21 did by cutting down 2x4's and gluing them back together.

I was headed down the LVL route but found a guy that sells some used extrusion by me and it was about the same price for me to just go the 8020 route.

[vbgraves]

Thanks for the suggestion on the LVLs. I'll give that some thought and review some of the other LVL designs and will try to post some images for comment when I get that far.

[vtx1029]

Check out this thread
http://www.cnczone.com/forums/diy-cn...teel_base.html

Check out the first post of my build thread. I have some pictures of what I was going to do...

[brtech]

You can make the base out of cheap wood if you want to trade sweat equity for cost and you have a table saw and a bunch of clamps. Find a lumber yard that has real Southern Yellow Pine (SYP). SYP is strong and pretty hard for a softwood. Laminate a couple 2 x 4"s to make 4 x 4"s if you can't get SYP 4 x 4"s for the legs. Do the same with top and bottom stretchers, and either use cross braces or mid span legs. Best would be drawbored through Mortise and Tenon joints. Then make a torsion box top out of 3/4" MDF, screw some T track down, and fill in between the T tracks with 3/4" MDF strips held down with countersunk bolts so you can change them. Cheap, strong, effective.