Who has lifted a 4.5kw Z axis with a Nema 23?

Im upgrading my machine. I bought a 4.5kw spindle - yep - looking forward to putting that baby on in place of the 2.2kw I have been using for years. My gantry is HEAVY. Gantry is made up of a timber beam 100mm x 300mm with a 6mm plate alloy on one side to attach everything too. And being careful I even balanced it. So the gantry being heavy and rigid is no problem. Its the Z axis with that weight and the Nema 23 I am wondering if it is too much.

What I am doing is installing another 8kg on my Z axis. Quite a lot really, and in that I have put 10Kg additional weight on top of the 2.2kw spindle to see if the Nema 23 will be able to lift it. And it did no problem. The Nema 23 is a closed loop stepper. Here are my questions:

1: I am building a new Z axis assembly, more solid, heavier linear guides, larger rails, larger plate alloy. I see there are heaps of calculations with ball screws. I am thinking I will just use the 1605 with a double ballnut. I wonder if I should look at the 1604 with the 4mm pitch to make it easier for the little Nema 23 to lift the additional weight? The double ballnut is twice the friction, but the 4mm pitch instead of the 5 is ummm 20? percent less to lift the extra weight?

Or am I putting too much thought into it and just stay with the 5mm pitch screw?

The only question is the speed and acceleration, if that is OK, then nothing needs to change. If the motor lifted the spindle without problems, then I would change nothing. You have already proved that it works. It's a stepper motor, so not really possible to overload it. It is already drawing maximum amps with no load on it.

Hi Boy - As Jim has said. You have proved the pudding so keep it simple. Otherwise do the maths for confirmation that it works on paper....You probably don;t need a double nut. Peter

Oh - update to this. It worked, and worked very well. I now have a 4.5kw spindle mounted on a Z axis that is heavy, rigid, and just eats 6061.The Nema 24 is not even struggling.

Hey - Boydage I'm keen to see pictures of your timber gantry. My next router will be all laminated plywood so looking for working examples. Peter

Sure thing. Its more alloy than timber the timber portion is just the meat of the gantry with the alloy being the base for more precise fitting. I am away on travel for work will snap some pics when home again. B

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Originally Posted by peteeng

Hey - Boydage I'm keen to see pictures of your timber gantry. My next router will be all laminated plywood so looking for working examples. Peter

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Hi Pete,

So the construction of my machine is timber/alloy. The Alloy is the longitudinal strength and the timber being the lateral. As its developed I have ended up putting more and more alloy into it. And the next step for me is to weld up a proper serious base out of something like 200 x 100 box section. You know, something that I will need to use a forklift to move. The table in the center of the table, is a cast iron top off a woodworking machine that I had spun up in a lathe to flatten. Its about 70kg and is there to hold my larger modular vice along with any other hold down devices for alloy. I have put a PVC wall around it, and there is a drain in the centre that accepts any runoff from mist/coolant. The timber beams underneath the table, are also sandwiched by alloy 6mm plate on both sides. Held on with lots and lots of screws.

I like bolts and screws and lots of them. Much prefer that way of attachment than welding. Cant take a weld apart as easy haha

The Z axis, is two 16mm plates of 6061 alloy holding the 4.5kw Spindle that was the best thing ever I purchased since the closed loop steppers.

Control box is, well, not much to say really. I have a decent size fan about to go in, was going to install it today but ran out of time. There are lots of little odds and sods jobs that I need to finish. One of them is sorting out my probing. Along with some new ballscrews that I am ordering tonight. The gantry is nice and rigid with the wings I added in a few months ago. And I am really happy with the accuracy of this machine. The modular vice in the pic, my boss purchased for me because i make things for him.

Anyways. I do like to hear comments about hoe I could have done something better. And am happy for input.

Hi Boydage- If the gantry is not stiff enough add a plate on the back. This will then make it symmetric and the timber will be like the web of an I-beam. The plates will provide the bending stiffness and the timber will transfer shear across the gap. If its stiff enough all good. Lots of screws... I'd epoxy it together. My thoughts are to build the gantry in timber but have plate front back top and bottom. I have modelled this and its very stiff. The timber provides the shear path. The timber also allows me to go around the corner and down to the bearings in one structure. The gantry needs shear stiffness at its ends not bending so AL not need around the corners. In this way the plates can be cut on a router then glued to the timber core. My next machine will be a lifting Z axis with moving gantry so a bit different. Good to see an alternative approach. Regards Peter

they are 12mm screws? what pitch? Just looking at that now. I'm using 1605 for Z and 1610 for trans gantry and long gantry

Hi. I have found my gantry is well supported and rigid enough for what I am doing. The only issue was prior to bolting the wings on the sides where it was prone to chatter laterally during the more aggressive cuts.

The screws are 1605. On the X, absolutely no problem and well proven although on my Y they are a bit prone to shake at 3000mm Min. I have actually bought some 2510 screws that are on their way soon. Along with some 2525 screws I will use in the future.

I wouldn't use timber again if you ask me. Various reasons. Sandwich them in alloy like you say is completely true nice and strong. But I would stop there. Now anything I build will be extremely heavy and totally overkilled on strength and rigidity. I would like to be able to machine steel one day. Have a proper coolant flush. Timber I can't do that. My only real reason for not using steel? I hate working with it. Its full of carbon, which is left behind after grinding. It rusts. It has its places though Eek lol

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Hi Boydage - Yes rusty steel is my lifelong hate. After I left school I built two steel bike frames then moved into aluminium so much nicer stuff to work with. So its got to be aluminium or titanium. I agree timber is a hurdle for coolant but then wooden boats get by. I intend to plasticise the timber in a vacuum process with epoxy. Shouldn't let coolant in then... I use stainless steel alot only issue is its hard to drill if you have to. So I make sure all the holes are correct before I send orders to the laser cutters. But I do drill SS when I have to. So sounds like an AL plate build mill is bubbling along somewhere... Peter

One word for drilling stainless steel. Well three.... oh.... more. Cobalt drills, slow, cutting oil, pressure. Yep. We use it all the time in my workplace. We manufacture operating theatre equipment.

Looking forward to seeing some build pics!

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Hi Boydage - Here's the design and build thread. I've finished the bench, now starting the machine base.

https://www.cnczone.com/forums/diy-c...neering-6.html Peter