How to Build a Plasma Z-Drive?

[tof1]

Could someone please explain or link me to how I can fabricate a Z-drive? I get the basic idea of it but I'm not too sure when it comes to the anti backlash lead screws, couplers, and nuts? Also the floating head with electrical hook up (homing switch?) for CandCNC's electronics?

Thanks in advance for any help!

[millman52]

I don't know oe a specific set of plans being posted online here. The things you need to concider is: How much stroke do you need? If using a THC like Candcnc's MP3000 it needs to be able to travel somewhere in the range of 150 IPM.

for 6" travel or so your lead screw needs only a bearing (best to use a double row angular contact bearing) on 1 end usually the top to limit endplay of the screw. Screw/bearing assembly will beanchored to the back or base plate along with the motor. Flexable coupling between motor & lead screw is common. You can find them from almost any CNC parts vendor. Check out the various parts vendors advertising here on the zone. (TEA come to mind right off but there are many others as well as EBAY)

Ball nuts usually have a threaded or flanged end to mount them to your moving part of the Z. A couple small pieces of linear rail & a couple bearings makes up th sliding surface between the base plate & the movable plate. of course the center of the ball nut & center of the lead screw must be centered between the 2 plates.

The floating part for the torch mount only needs about 1" of movement & a secure, safe plase to mount & operate a limit switch.

Here is a very good example in pictures. Look specifically at posts 1, 16, 18, & 29 : These picture shuold pretty much explain everything.: My 4X4 table build

Go through the build logs of plasma machines & router machines as well. You should find something to meet your needs. There is everything from entirely home made using pipe & skate bearings to any kind of linear rail out there.

[tof1]

Thanks Millman! It actually doesn't look too complicated. The only electrical part looks like the Z home switch, correct? I'm still not 100% sure how the Z acme screw gets put together...

The bearing blocks are basically just aluminum blocks machined for a press fit bearing that will slide over the acme screw?


What is the black plate bolted to this block? Does it also have a bearing? On the end of the acme screw, a coupler clamps the machined part of the acme screw and the motor shaft together but what does the threaded part mount to?


So the bearing blocks on the left and right do nothing but house a bearing to keep the acme screw from moving side to side, correct? I know the middle block mounts to the floating head but I need the block explained (what goes into it & in what order).


Thank you!!

[millman52]

BigToy, I hope you don't mind me using your photos as an example. Your design I feel is very good & about as basic as you can get

This picture should tell the story.
tof1, I have added some text to the picture to help clear your questions. Only reason I suggest mounting the microswitch somewhere around the top of the floating torch holder is to get it a bit farther away from possible heat & sparks.

The acme screw is turned on a lathe at each end to fit the ID bore of the bearings. BigToy shows the top portion in the second picture down in your previous post. The bearing fits tight against the end of the acme threads & is locked in place with a standard nut above.

[Weldtutor]

C how I can fabricate a Z-drive? I get the basic idea of it but I'm not too sure when it comes to the anti backlash lead screws, couplers,

Interesting to note the extreme similarity to the picture posted above by millman52.

With my system the Acme screw has a bearing at the top only.
The nut that the screw runs in is toward the lower area of the assembly, which is guided by the side rail bearings.

Additional pictures are HERE in my project log.

Any Z axis backlash you might have would tend to be controlled by gravity, acting with the weight of the torch & Z components.

[millman52]

In Big toy's case he has used a bearing at the top for thrust in 1 direction & then 1 at the bottom to limit thrust in the other. In other words the 2 bearings are preloaded against each other. This limits any backlash to what is in the motor coupler & the nut to acme screw only.

In my very first reply I suggested using 1 bearing only at the top & use a double row angular contact bearing. which effective dose the same thing as 2 bearings preloaded toward each other.

On this short of an axis & especially at stepper speeds there is no need for shaft(screw) support on the bottom end of the Z screw. The "ball nut" or in the above pictures acme nut is support enough

[millman52]

Hopefully within the next couple weeks I will be building a 2nd Z axis to allow me to add plasma to my existing gantry. This will allow me to leave both ox/fuel & plasma mounted all the time.

I am going to use a 2 start ball screw 1/2" travel per rev of motor. If my plans work as my barnyard engineering skills have it planned. The ballscrew & nut will be sealed inside a telescoping tube to keep contaminates off the precision surfaces of the assembly. Will only use 1 linear rail for the Z & a second small rail for the floating head.

I'll post pictures & text of my progress on my build log.