Lead Screw upgrade

[MJ Designs]

I have started the upgrade to the x and y axis and thought while I was at it I would upgrade the lead screws to ball screws.
My question is - as long as I keep the same thread pitch as currently used all will still work, without changes to the controller.
Or how hard is it to change controller settings if pitch is changed.
And to confirm I have the pro plus and I think my current setup is
X axis 3/8 shaft RH thread and 12tpi
Y axis 1/2 shaft RH thread and 8tpi

One note while checking the above sizes I found that I had some significant play 1/16th or better in the stepper drive shaft. Rungemach / Bob has a post here some where about it and I will have a go at his fix if no one else has a better solution.

Micheal

[rungemach]

Hello Micheal

You can't go by the threads per inch as lead screws can be multi-start which means that there are more than one thread running next to each other rather than one continuous spiral thread.

Anyway, what counts is the full revolutions per inch, which is most likely 4 tuns per inch on your machine.

If you go with a ball screw, be sure you will need to keep it clean by using a dust shoe on the router etc.
The y axis under the table is somewhat protected but the x axis is out on the gantry where it can pick up lots
of dust that will eventually gum up the balls in the recirculating races

Using a ball screw also usually involves bearings at each end, which the shark does not have. The end bearings will eliminate the "motor shaft play" issue. Most stepper motors have bearings that are held against the housing by an initial press fit at the shaft end and a wave spring on the far end . if the motor takes too much axial force, the bearing gets pushed into the motor body and pulled back out when cutting the other way. After a while the bearing gets easier to move in and out and there ends up being axial play in the shaft during heavier cuts. That problem is very hard to discover unless you try pushing the lead screw into the motor and see the shaft move. It is a common problem with steppers as they are not made to push and pull things directly, they are supposed to deliver their power by rotation. The Shark, and other small cncs that drive the lead screw directly, saves costs by not having thrust bearings and flexible motor couplers to eliminate that play.

[MJ Designs]

Yes Bob on doing a little research I have now found that ball screws and dust are not good friends.
So now plan to just replace the worn T nuts.
Nextwave have them for $62 not bad - freight $117.72 not good
so have emailed support to try and get exact details about what leads are used so as to try and source them locally.
Micheal

[rungemach]

NWA's price for the replacement plastic lead screw nuts is right in line with what they usually retail for, about 20 dollars each.

Since they are so light, you should be able to get them shipped for a lot less that 117.72. The box to send 3 will most likely be under 2 lbs in weight. NWA may disclose their specs and supplier if you email them. Here in the US, Thompson and Roton are likely suspects. They may have distribution in your area.

[MJ Designs]

rungemach

I didn't think the price of the nuts was much out of line and have no problem paying that / but the frieght price of 117.17 is what came up on the nextwave site and for 3 little NUTS, I would be NUTS to pay that.

I did email support yesterday but as yet no responce, Hopefully nextwave will come through with the specs for me, or i will have to make friends with someone over there to post them on to me.

[Cory Newman]

one of my T-Nuts was broken when I received the machine. They send it to me for free and in came in one of those bubble wrap envelopes. Would be awful hard to justify $117 in postage on that.

[jeb2cav]

Hi MJ - are you in the US or shipping overseas? If overseas, you may want to email NWA directly for a shipping rate - their store may automatically provide some goober rate if shipping outside the US.

[MJ Designs]

Jeb i am in Oz and yes the frieght prise was an automated thing in the NWA sopping cart. I did contact support and the have come back with and offer to just post them to me for $30. Much better then the $117.17.

[baby15]

can the motors off the new shark be put on the shark hd to make it faster. I did notice tonydudes mako does run faster today.

[rungemach]

The newer machines have a higher top speed because the lead screws have a different pitch.
On the newer machines, the lead screw pitch is 2 motor turns per inch, whereas the older sharks were 4 motor turns per inch.

What that means is that for a given motor speed, the new HD sharks will move twice as fast, but with half the force, and half the resolution.
To try to recover some of that lost force, the motors need to get more powerful.

So just using bigger motors will not make an old machine faster, just more powerful. Also, the controller must be able to provide the power that the larger motor would require to develop its full power. Changing the lead screw pitch will double the speed at any given motor seed, but reduce the moving force available at the router.It is a lot like the gearing of a car, a higher gear gets you higher top speed, but with lower force.

The ability to go faster may not be a benefit if the machine can not keep the cuts accurate at the higher speeds.
IMHO , the best thing you can do with a non-HD machine is to make it stronger.