What speed rapids can I do with the xylotex?

[lagfish]

Running on 425 oz-in steppers on the X3 mill running 5TPI (0.200" pitch) ballscrews? I know going with 269 oz will get higher rapids, but is the torque enough for the X and Y?
Here's my attempt to calculate force produced by the motors:

Torque=Force*pitch/(2*pi*eff)
Torque = 269 oz-in = 16.8 lb-in
Eff = 0.90 %
Pitch = 0.200 inch
Force = 475 lbs at stall.

If we estimate torque to be 70% at normal machining speeds, then force is 332 lbs.

To me, this doesn't sound enough, since cutting forces alone can be over 100 lbs for large cutters, plus friction of the ways, and the large inertia of the table.

Anybody tried using 269's on the X3?

[welderfabrod]

Hi lagfish I don,t normally post much to these sites because I now there are people out there with far more knowlege than I have, perhaps its that fear of making yourself look a dummy, probably completely unfounded but there we are.
The reason I ,m replying to yours is that I converted my X3 to 4 axis cnc using the Xylotex board back early last year and some of what I have learned may be useful to you.

My setup is this:- X Y & Z axis have 14mm dia. x 4mm pitch ballscrews, X & Y axis are direct drive to screws, Z axis is geared through toothed belt 2 to 1 and lifts the whole head not the quill. The fourth axis is a 110mm rotary table (90 to 1).
X & Y steppers are 180N.cm, (don,t know what that is in oz. in.)2.5amp, 4.5v. Z axis 220N.cm, 2.5amp 7.5v. This is controlled by an 800Mhz PC currently using EMC2 for control. I intially controlled this using an old Toshiba laptop that took most of the day to boot (it had Windows 95 on it!) using TurboCNC, great program relatively easy to setup for steppers pity its not been upgraded for a long while now.
My experiences are:- X & Y max feed is 1800mm p/min have set EMC2 to default at 1200, I can,t stop the table against the motors at 1200. Z axis max is set at 600mm p/min and this is marginal as it has locked the motor on the odd occasion, but I think that this is more due to the max output voltage of the Xylotex rather than the motor being under powered as this one is a 7.5v motor and would probably be happier at something over 70volts. I do intend to put a different driver on this sometime in the future as it has caught me out. but for now I ,ll just live with it and take care.
I found the X3 ideal for CNC conversion the only scraping I had to do to get the screws to run smoothly was a few thou. on the Y axis screw nut seating, nothing was done to the dovetails apart from taking time on setting the jibs. What I did find when I came to converting it, I had,nt noticed it while using it as a conventional mill, was that the the left hand column dove tail had been undercut for 5 or 6 inches from the top so inspect yours thoroughly if its new.
Am I pleased with the conversion? you bet I am, works for me.

I found EMC2 a bit more difficult to setup than TurboCNC, it took me longer anyway, but is a good program with a selection of GUI,s that should suite most people and has a number of setup configurations already prewriten including a couple for the Xylotex board, these do need tweaking for individual machines though.
For the future I,m looking at making an attachment to fit on the table to give me a 5th axis.
As an aside I have 2 Emco 5 CNC lathes one of which I have coverted to use other control software but retains about 80% of Emco,s hardware including power supply and spindle speed controler, but despenses with its cpu board and its horrible keyboard and makes it a much more useable machine. But I suppose thats for another topic if anyones thinking of going down the same route with their Emco lathe and is interested.

A bit long but hope it is useful.

[lagfish]

Hi welderfabrod,
Thanks for the lengthy reply. Converted to Imperial, that's 70ipm rapids with 250 oz-in motors on X&Y. When you say you can't stop the table while running at 1200mm/min, is that putting your weight into it? From the looks of things though, 250 oz-in motors may be enough to run the x and y on the X3. Infact, I think this close to what Syil uses on their X3 machines. This is good because going with Xylotex + smaller motors would save close to $200 compared to Geckos + larger motors.

[welderfabrod]

Yes lagfish with my weight against it. The other question is am I likely to need this sort of power, I doubt it after all this is a small mill with only a 600 watt motor, with a recommended max end mill of 25mm and face mill of 50mm, and I personnaly am unlikely to want to take 250thou cuts at high feed rates into steel on this particular machine, these small machines are not heavy enough for this sort of treatment I prefer to take lighter cuts at higher speeds and feeds. I would say that about 70% of my work is in aluminiums of one grade or another and I have had no problem at all with the X3 Xylotex combination apart from the Z axis restriction I mentioned. And as I am a hobbiest I,m not to concerened about production times. Your situation may be very different.

[kanton]

Hi welderfabrod,

I may do an X3 conversion and I would l like further information about yours. Is your setup from a kit you purchased or something you designed and built yourself? If its a kit, who sells it? If it was DIY is a writeup available with pictures?

Thanks

[welderfabrod]

Hi kanton I did mine myself although I will admit I used some idea's from other sources. My biggest worry was that most other conversions I had seen with this size motors were using 2mm pitch ball screws but I could'nt source these at the time so I plumpt for 4mm on the grounds that ball screws are about 90% efficient as apposed to lead screws which are about 30-40% efficient, and these have proved more than adequate for my purposes. Unfortunately I did'nt take any photo's at the time. One thing I did do was fit two adjustable gas struts, one either side of the head each being set at a bit less than haff the wieght of the head. My thought here was that I did'nt want a one sided support as it were on the head which may have put a twisting action on the head and possibly cause it to lock on the dovetails. Not sure wether this would have been the case or not as I know others have not done this and don't seem to have problems. And as my supplier only supplies these in pairs anyway it was'nt really an extra cost.
I will try to answer any further questions on my conversion but I'm going into hospital at 12 o'clock today for a small op so will be unavailable for about 3 days.

[kanton]

Hi welderfabrod,

I hope the operation went well. I would appreciate links to the "other sources" if possible.

Thanks

[welderfabrod]

Hi again kanton op went reasonably well thanks but still a bit sore.

As far as sources go the one I found very useful and convinced me that I could convert an X3 myself was a short series published in Model Engineers Workshop about 3 years ago which delt with the X3 specifically. Ashamedly I can't remember the authors name and I can,t get to my workshop at the moment to find the mags. However you can look this up on thier web site.
Athough I incorparated many of my own ideas the main idea that I took from the above article was that of glueing the bearing shafts for the ball scews into the end of the ballscrews using Loctite adhesive and this has proved extremely reliable as long as you respect fit and cleanliness during the process. But whatever you decide to do this article gives you a good overall idea of the whole process of the conversion.

[welderfabrod]

Kanton have just taken the plunge to go out in the workshop (withdrawl symptoms set in). refering to last post the mag issue No's are 102, 103 & 104.
the author is Dick Stephen. In issue No 113 there is an option by Tony Jeffree for an improved way of mounting and connecting the stepper motors to the ballscrews. I know there is also constuction details of an attachment using an encoder that allows you to control the axis with a handwheel as on many full size machines so conventional milling is also possible but I can't find that article yet if your interested in that let me know and I try to find it.

[kanton]

Hi welderfabrod,

Thanks for looking. Unfortunately, I don't have access to Model Engineers Workshop magazine where I live. Has any of this information been published on line? If so, where?

Thanks

[welderfabrod]

Kanton yes these articles are reproduced by ArcEuro Trade here in the UK on their website in pdf so can be downloaded. www.arceurotrade.co.uk, go to projects and articles. Although they do not use the Xylotex board but this is a matter of choice really.

Hope this helps.

[kanton]

Welderfabrod, yes it did help. Thanks again!