Dual ballnuts for the X3, limiting travel?

[phantomcow2]

I've been milling parts for my CNC conversion of my X3 these past few days.
I was wondering if anybody here with a CNC converted X3 could chime in, particularly those with dual ballnuts like from Syils conversion. I made myself a 15/16"-16 tap and tapped holes for my ballnuts. I was lucky enough to have a few pieces of 15/16"-16 stainless rod around!
The blocks I made have enough room for the thread of two ballnuts, I was only going to use one. BUt I am thinking for 75 dollars more I can go dual, It may be worth it. My concern is with travel. Wouldn't this limit the travel a bit, particularly with the Y axis? How have people gotten around this, or do you just deal with it?

[FPV_GTp]

hi

I'm no expert on CNC and ball screws , but the double nut ball screw means 2 nuts on the shaft .

What is the purpose of two nuts on a shaft ? if your X3 mill will be using the slides to guide the table travel and the ball screws will only be moving the table on the V groove or dovetail guides on the mill.

I just purchased some big 40mm ball screws cheap and 3 out of 4 of them the are new , but one of the 4 ball screws had a double nut arrange and this unit was used and need cleaning.

The new ball screws i unwrapped and it still takes a bit of hand power to turn them , my point being if u have two nuts on one shaft u will ne more power to turn them.
so what is the advantage of having two ballscrew nuts on one shaft , if the milling table slides will be the guideing the X,Y,Z travels ???

I'm in the learning phase of CNC.

from what i can see on the twin nut ball screw i have the mounting points on the nuts would occupy space when there mounted to what ever they have to move , so i would imagine they will limit the travel of a table , i might be wrong

cheers

[phantomcow2]

Its only 2 more letters to turn u into you .

Do you understand what backlash is yet? This is the enemy of CNC, or any motion control at that. Using two ballnuts which are preloaded, eliminates this backlash. By preloading I mean they are pushing against eachother. It is possible to get a ballnut with larger balls "stuffed" inside, and this can mean zero backlash on ground ballscrews. But I already have 3 ballnuts, so Its not worth buying all new ones to me.

[FPV_GTp]

Originally Posted by phantomcow2 Its only 2 more letters to turn u into you . Do you understand what backlash is yet? This is the enemy of CNC, or any motion control at that. Using two ballnuts which are preloaded, eliminates this backlash. By preloading I mean they are pushing against eachother. It is possible to get a ballnut with larger balls "stuffed" inside, and this can mean zero backlash on ground ballscrews. But I already have 3 ballnuts, so Its not worth buying all new ones to me.

hi phantomcow2

LOL sorry about the "u" but you are using secondhand ball screws ? yes or no

backlash i understand the concept as i setup differentials and build race engines , but the ball screw i held in my hand yesterday that i purchased the new one in my hand had no backlash that i could detect held in my hand , i will on monday at work measure the backlash on the new ball screw using a dial indicater and securing the ball screw and shaft properly as all the documents are in German that come with the ball screws .

The second hand unit with the twin nuts i have to dismantle and clean and measure it for run out and wear , i hope i can salvage this second hand unit.


But you mention less back lash with a twin nut setup , how accurate do you want to make ur mill as im sure from what i have uncounted in different mills out there the table slides are accurate to a certain degree when milling on a table in the middle and when the table is move either left/right or forward/back in its X and Y movements the accuracy of the mill changes quite a bit. so my point being you have other issues to worry about rather than a twin nut setup but if you are trying to get zero backlash or correct a worn shaft by tightening up the wear facter thats a different story

I'm still learning here so don't take offense what i say and the "U' is not meant as a insult, it is just me being lazy typing the extra letters , if u see my other postings in here and other forums i do it quite a lot .

can you post some pictures doing your conversion and maybe document it please


cheers

[phantomcow2]

I will take some pictures of the hardware I've made tomorrow. I need to start turning down the ballscrews ends and then I can really get the show rolling. Got my motor driver kit coming in monday (hopefully).

THe ballscrews you have may be ground, are they shiny looking? Also, do they have little grooves on the peaks? THis is an indication of rolled ballscrews. YOur ballnut may have been preloaded. I have nearly 25ft of 16mm ground ballscrew stock in my basement, but no nuts for it. Damn. Also, be careful when disassembling those ballnuts! There will be over 100 balls coming out, and can easily get lost.

I've found the X3 (as well as other Sieg products) to be very accurate where it matters. Nothing was deburred on this mill, I got my fair share of cuts when I was cleaning it. BUt all the components were a dowel fit, very nice. Using my screwless vise as a guide I checked for perpendicularity of the X and Y axes using my screwless vise as a reference. Well I got the vise square to the Y axis (over a 3" travel) to within .0001". Used my DTI to test this.
Then checked the X axis, not even .0001" of deviation. Spindel runout was under .0002"
Mill was trammed pretty well, not perfect. I will correct this before I get the CNC all up and running.

Also, its not that I am offended by using U, or "ur". But its distracting. I've found high quality forums tend not to have much of this.

[Ron111]

Phanromcow2,
You are a good man for making your own 15/16 tap. Like you I did not like th$50 price tag from McMaster carr. Did you just put a slow beginning taper, mill three longitudial grooves and then thread it with a 60 degree cutter. Mr. cow are you a real machinist ?(I hear there are some on this forum)

Good Job man!!!!!!

(I wish you lived next door, I could borrow your 15/16-16tpi tap)

Ron

[Ron111]

Phantomcow,
Forgot to add that I finally got on a computer with dsl and was able to see the cncfusion videos. It was pretty wild when it snapped off that end mill. On my Shop master my machine would only bog down.
So, that machine is only using around 200in/oz steppers?
Can't wait to see you PIC's. What kind of travel are you looking at. You have been following the post about Greolt getting a longer ballscrew from syvil (bad spelling), any have you been following that post? May give you some ideas.
Travel limitation on Syil X3 conversion

This tread is from the last week or so.

Ron

[FPV_GTp]

hi phantomcow2

Just held in my hand a double nut ball screw now i understand the difference between a single and double

Yes on the double zero backlash as compared to single nut which just has a very tinny weensy little bit of backlash

phantomcow2 what stepper motor, stepper motor drivers, power supply and software do you plan on using ? and who are your source where you have purchased these items from ?

That link Ron111 interesting just curious where you purchased your ball screws and nuts from and what was the cost ??

and once again phantomcow2 I'm very sorry , I'm new to cnc-ing and keen to learn more so you guys that are more advanced in knowledge than us beginners be patient please

cheers

[phantomcow2]

Thanks. I will take pictures of the tap. Its very basic, I did not even bother to turn it down. Consider it a bottoming tap . I do work in a machine shop, not sure I would call myself a machinist though.
In all actuality, its just a 1" long piece of thread that came off a thrust tube. I milled 4 flutes into it with my 1/4" EM. I used the mill to start the threads perfectly straight and square. Its not as good as the real tap I bet, but hte threads cut fine into aluminum. I meant to take pictures of my stuff today, never got around to it.
Got drivers coming in tomorrow, 6ft of 1/2"x1/2" aluminum, and an extra stepper motor from home shopCNC sometime soon also. Off hand, thats everything else I need for the conversion. Besides some misc. stuff. I am going to try to get everything to fit inside the X3's electrical cabinet, It will be pretty cramped!

Read this post:
http://cncfusion.com/phpBB2/viewtopic.php?t=7

As for travel. I should get 6" of the Y, and a little over 16" of X. Also, I dont think I am going to bother with dual ballnuts. I want all the travel in X that I can get, and I think it will be okay since my backlash is consistent. If I find it to be a problem, I will add more nuts.

[phantomcow2]

FPV-

You can buy regular old 5/8-5TPI ballscrew from Industrial Hobbies and HOmeshopCNC. HomeshopCNC sells it for $1.25 per inch + 25 per nut.
Industrial Hobbies sells for 52 or something for a 6ft length, and the nut is something like 23 dollars.

No need to apologize for asking questions

I purchased a nice Coutant Lambda power supply from mpja.com a while ago, September I think. It is 28v and 15A, with another output of 14V and 6A. I might use this to supply my fans with power.

Steppers motors are a mixed bunch. One is a LIN engineering motor, another is a 34 frame IDC motor. Not sure where I got these ones, I've had them sitting around for a while. I had a good 12 motors sitting around, they just seem to come in. One stepper is from HOmeshopCNC Like I said. They seem like a pretty good source by the way.

Stepper drivers are a DIY kit. Here is the URL:
http://www.bright.net/~agarb/STMD/AVR_STMD.html

The 3 amp 55v max fits my needs. A lot of people get Geckos, but I did not see the need for a 7 amp driver where I will not even be using 3.

As for software, I run Linux now on my PC. So I will likely run EMC. I have an old Pentium II downstairs that has TurboCNC on it though, this software worked well. Mach seems to get fantastic reviews, I may buy a used laptop with windows on it to run Mach 3.

[Ron111]

Phantomcow,

Looked at the driver that you are going to use. Do you have to burn your own firmware on a prom or pal oe what ever now or is the firmware already burned on the device. I ask because I see where you can download the source code. But maybe that's where you buy the board from them and everything else from digikey.

Ron

[phantomcow2]

Actually you can buy a kit, everything all set to go, for 65 dollars. This includes a programmed chip, and all the parts. He says its cheaper to buy his kit than the parts from Digikey, which I understand.