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chuckknigh
08-30-2003, 09:38 PM
Well, I went to one of those tool sales they hold out in the country -- some little company (Homier is a common one) sets up in the local VFW hall, and sells tools to us country folk. Today, it was Cummins Tools.

Well, while I was there, today, I found a drill press vise. It is essentially an X-Y table. In fact, it reminds me of a crude version of the X-Y facility on the Harbor freight mini mills.

http://www.cumminstools.com/browse.cfm/4,92.htm

It has acme lead screws which move the table in 2 directions, and a built-in clamp on the top. Surprisingly nice, actually.

It's a fairly rough casting, but it has dovetail ways and a built in facility for shimming them to remove slop! The actual sliding surfaces aren't too bad, either. Once I take it apart, clean it *properly,* and hopefully finish a few of the surfaces it ought to even look good!

I've not measured its exact capacity yet, but just eyeballing it, it looks like it's about 4x6 inches of movement, or thereabouts. The vise capacity is 4".

Anyway, needless to say, for $19.99 I picked it up. I think it'll make a nice complement to my wooden router, if I convert it to CNC. Might even allow me to do some light metalworking!

A question, though. The ACME nuts are part of the castings, so I can't remove, replace, or upgrade them -- is there any way to add backlash compensation, or just generally "tighten it up," perhaps with an injectable polymer compound? Something to take out, or at least minimize the backlash?

I'd just *add* nylon nuts to it, but they'd take up a bit of room, and basically eliminate half of its travel!

There must be a way to upgade the hardware itself -- relying on software to compensate is not an ideal solution.

-- Chuck Knight

wms
08-30-2003, 10:28 PM
Chuck,

Run a search on this forum for "Moglice"

There are several thread that deal with just such a thing.

Ken_Shea
08-30-2003, 11:18 PM
Chuck you mentioned to tighten up the acme backlash by the use of a polymer injection. In the auto repair field for many years I have used this method with great sucess on king pins, tie rod ends etc. This of course was with a special polymer but you may find that even the use of glue gun polymer that it may do what you need.

Just drill a whole in the center of the threaded area and inject the glue gun polymer and see what it does, cost nothing, is reversable and may just be a simple solution.

let me know if you do it and how it turns out.

Ken

wms
08-30-2003, 11:25 PM
Ken,

That sounds like a good idea. Call the patent office.


And oh ya how about saw dust in the gear box?:D

Ken_Shea
08-30-2003, 11:40 PM
Ward,
I know it sound like a hoot, but I have injected a bunch of this over the years with really great success, especially helpful in antique cars where the original parts are not available. Glue gun is actually not a glue but simply cheap polymer.

Does saw dust works well in old gear boxes.:D
Man that really ages us doesn't it Ward?
No one under the age of 40 would know anything about that.

I still have some polymer left you need an injection? great for worn out joints, knees, elbows etc.
Oh, I forgot I do have to drill a hole!!

wms
08-30-2003, 11:57 PM
Ken,

I really do think that sounds like a good idea....


I just threw the sawdust part in for a laugh.

chuckknigh
08-31-2003, 01:00 AM
Hey, hot glue is nothing more than a medium temperature thermoplastic. Nice stuff for a lot of uses.

A couple of concerns, though. Would it resist wear sufficiently to function as a lining for a screw drive?

It's somewhat springy, so would it introduce backlash into the system? (Tiny layer shouldn't be too bad, but it's still something to consider)

Would it introduce a lot of friction into the system? And, on a related note, would use at a "normal" speed generate sufficient heat to melt the polymer, thus ruining any alignment I had beforehand?

Is there a release agent for it? I'd hate to inject it, and have it stick to the lead screw.

A consideration about its installation, too. I'd have to practically bake the vise in the oven to heat it up sufficiently...the part would have to be hot, as well as the glue, since the glue would freeze "solid" the second it hit cold steel. Might be a bit of a practical problem in this...

Still, overall a good idea. Is there not a nice polymer that cures chemically, that would do the same thing? If I have to, I'll just go get some JBWeld and tap a new hole...but there's no guarantee the tap will align perfectly with the lead screw. They're rolled, not ground...thankfully they're short!

-- Chuck Knight

P.S. Moglice is essentially a granite hard epoxy, isn't it? Somewhat like the JBWeld I mentioned before. If memory serves, it's used to rebuild bearings...a good suggestion.

Is it possible to get a TINY bit of this stuff? I don't want to rebuild 2 nuts, and have buy a pound of the stuff. Since it's for machine tools, I have the sneaking suspicion that it's rather expensive.

P.P.S. On a 60 degree thread, there is a thin "sliver" of a nut called a jam nut, that I can buy at my local hardware store. Looks like "half" a nut. Is something comparable available in ACME? If so, I might be able to use it to adjust out any backlash, using some of the split nut designs -- this option would take up the least space possible, I would think...short of modifying the existing hole.

-- Chuck Knight

NeoMoses
08-31-2003, 01:25 AM
you might take some all-thread and a cheap nut/bushing and try casting your own "moglice-like" nut out of JB-weld. Once cured, they both have very similar properties, so it just might work and be much cheaper.

Ken_Shea
08-31-2003, 09:07 PM
Chuck never really gave the hot glue any serious thought, it just popped into my head and I threw it out as food for thought. There have been many times something said that was nut usable but prompted ideas that were.

I would not think you could turn these fast enough to cause any friction heat.

I have some hot glue that actually kinda hard and most hot glue melts at very low temperatures maybe 200f?.

I like the idea of the JB weld mentioned by NeoMoses, you could call the company and ask them what a good coating would be so it would form to but not stick to the acme thread. Get a syringe minus the needle from a vet or doctor and use that to inject it . My guess is it would not take much. I have seen epoxy glues already in a syringe and it mixes as it comes out.

good luck, and let us know what you end up with.

HomeCNC
09-01-2003, 05:10 PM
I used HOT glue on both exposed ends of my home made pre-loaded ball nuts as a wiper to keep chips out. It works great! Forms to the screw but does not stick because of the thin layer of oil on the ball screw.

cbcnc
09-01-2003, 05:29 PM
Hi,

Polyvinyl Acetate or PVA is used when laminating with epoxy in molds. It might stick to a clean leadscrew and not allow the JB Weld to bond to it.

Chris

chuckknigh
09-02-2003, 12:31 AM
Well, I have an email in to the JBWeld people, to see if anyone has tried this before. Surely I can't be the first...

Turns out they're located in Sulphur Springs, TX...less than 100 miles from me. Who knew?

Anyway, I did a little digging on Moglice, and other than a friction reducing component, they seem to be essentially the same stuff. Same properties, and everything.

Hopefully it won't be too difficult to make this thing, successfully -- I really don't want to modify the original casting, if I can avoid it.

That way lies madness.

-- Chuck Knight

chuckknigh
09-02-2003, 12:52 AM
This is a picture of the unit in question. It's a fairly cheap ($20) cross slide vise, but it seems to work pretty well.

I saw instructions for "lapping" lead screws to fit better, so I may try that. I've adjusted the ways so they run true, now, and it seems to work pretty well overall.

Now, if I could just make the backlash go away, I'd have a good platform on which to build!

-- Chuck Knight

cbcnc
09-02-2003, 01:20 AM
Yup, just like mine that I have had for about 10 years now. Down to the "100" on the casting. It is a low precision drill press vice. If you tighten the gibbs to get rid of the slop the cranks become a bear to turn. The dials are graduated in 5 thou increments. The dials also function to hold the leadscrew to the plate. Watch out there as the leadscrew has a step in it and rides in a hole in the plate. That is the bearing, steel on steel. If filings get in there they will wear out both pieces. It happend to me.
You might consider fitting some bronze bushings and proper shaft collars.

Chris

chuckknigh
09-02-2003, 01:33 AM
Precisely -- it's not a bad unit, but it's a bit "rough."

The markings are in 5 thou increments? I did not yet know that...thank you for the information. It's not like it came with documentation!

The "hole in the plate" is for the upper section (haven't decided if it's X or Y, yet), and will be addressed soon. But, first, I want to get it running smoothly, overall.

It looks to be a pretty "modular" design, and as if it could be upgraded with relative ease. My primary concern is the lousy cast-in nut for the upper segment. I've gotten a few ideas from this site, and from the CAD_CAM_EDM_DRO list...we'll see if any of them pan out.

-- Chuck Knight

P.S. I figure that it's hard to go wrong at this price...even if I end up just taking it apart completely, for the fun of it all.

NeoMoses
09-02-2003, 10:55 AM
Yep, that's almost identical to the cross-slide vise I've got on my drill press. It works well for drilling, but I'm not sure if you could get enough of the backlash out of it for milling. Good luck!

anoel
09-02-2003, 11:39 AM
I've got one of those Cummins Cross slide vises. It's way crude... I had to take it apart and file the ways and do some major tweaking to get it to slide even remotely smooth. Honestly I can't imagine trying to adapt a set of motors to that thing. It's way too crude... I use mine for drilling on the drill press. it works OK for that. Now for a good deal on a pretty decent cross slide vise take a look at the Grizzy "Shop Fox" 4" model http://www.grizzly.com/products/item.cfm?itemnumber=H0967

One of my buddies has that one and it's very smooth out of the box, not at all crude.

chuckknigh
09-02-2003, 09:50 PM
Mine isn't very crude, really. I can easily turn the lead screw cranks with one finger, except at one point in its travel (needs lapping?)...shouldn't be too hard to make everything work. My example is not as crude as yours, apparently. Don't you just love Chinese quality control?

Someone on the CAD_CAM list told me that they had done such a conversion, and they used "accelerated wear" to adjust the fit. Basically they lapped the lead screw, and then used 500 grit abrasive inside the ways, and just ran it back and forth for a while -- once it was "worn" it worked fine.

Someone else sent me this video of their unit in action -- a good video, really. They used it as proof of concept for some steppers, and cobbled it together over a weekend, but it's the same idea. Notice, they also upgraded the lead screw.

www.electronicsam.com/video/VIDEO1.mpeg

On mine, the only real problem it has is the roughness and backlash in the lead screws. Apparently someone over at MaxNC has also done this conversion and even sells plans. The important part in their approach is to replace the lead screws...he used 1/4"x20 allthread, which surprised me, but it does give a lot of mechanical advantage. Apparently he made an "adapter" that threaded into the cast ACME nut, and which was held tight with a set screw.

I might try something similar with JBWeld. Cast nuts would be easier for me to work with, anyway.

-- Chuck Knight

anoel
09-02-2003, 11:20 PM
Your's must be a lot nicer than mine, I just got mine about 3 weeks ago. when the Cummins show came through Bloomington. I got my bottom slide to work decent. The top slide is still a little rough. The cast nut and leadscrew are the problem there. I'l get bored and take it apart.

The vise screw turns very nice though.

chuckknigh
09-03-2003, 12:44 AM
The first unit I got was even smoother, but when I took a good look at it, there were voids in the castings, ON the dovetail ways. Unacceptable.

I returned it and had the guy go through a couple of them, till I found one with some potential. Reasonably smooth action, etc...

Cummins, HF, etc may not have much in the way of QC, but I sure do. I picked the "best" one I could find, quickly.

-- Chuck Knight

samco
09-04-2003, 04:05 PM
Hey that is my video. It is kind of funny - I was looking at the webstats from my site and saw that my video was exterally linked from this site. Kind of cool.
This is a 15 year old vice - I don't know where it was bought. The lead screws are original. It is fun to play with.

here are some more videos.

http://www.electronicsam.com/video/VIDEO2.mpeg
http://www.electronicsam.com/video/VIDEO3.mpeg
http://www.electronicsam.com/video/VIDEO4.mpeg

some lower current steppers
http://www.electronicsam.com/video/MVC-341W.MPG
http://www.electronicsam.com/video/MVC-342W.MPG
http://www.electronicsam.com/video/MVC-343W.MPG
http://www.electronicsam.com/video/MVC-344W.MPG
http://www.electronicsam.com/video/MVC-345W.MPG

See if I can go over my bandwidth ;)

sam

chuckknigh
09-04-2003, 08:38 PM
Sorry, had I known you were on this site, I'd have mentioned your name.

It's a good video, and shows the unit in action quite clearly.

I'd like to know how you built the mounts for the motors, personally. It looks like about a 2" square tube, but it's the details I'm interested in.

-- Chuck Knight

lsfoils
09-04-2003, 08:45 PM
Hi Sam,

Looks like your using a drill press for this operation. Is that true? I have seen a few of your videos and always see the clear plastic, have you tried cutting other materials? I think its cool you have a set up which must have been fairly cheap to do. Good job!

samco
09-04-2003, 09:05 PM
Not mad - I thought it was neet. The perspective of the video is bad. The square tubing is actually 4"X4". The steppers are 4.25 inches in diameter. We did cut some washers out of aluminum and shimstock. It is bolted to the table of a small import drill press.

sam

chuckknigh
09-05-2003, 01:08 AM
So, they're just bolted onto it and cantilevered out, unsupported?

These are the kinds of details I need -- or I can just invent my own mounting system, independently. :-) I prefer pictures!

Did you also automate the Z axis, or just put in pauses, when you would move the cutter "down" by hand? There *are* some drilling machines that are operated in this way...

--------------------------------------------

Now, it's time for an update.

Spent some quality time with the vise, this evening, and took it completely apart. First time I've had a chance to do this.

I found one part was installed backwards (installing it properly improved its performance considerably) and I took the time to adjust the ways for, as far as I can tell, optimal performance. It works quite smoothly, now...in fact, surprisingly so. Don't you just LOVE Chinese quality control? ;-)

However, while taking it apart, I found something curious. The two nuts are of decidedly different designs and have distinctly different "problems."

The "lower" nut is of a removable type, and seems to have extremely little backlash when fitted to the screw. So little that I can neither see nor feel any, when engaging it by hand. BUT, it's mounted as a cylindrical nut in a receiving hole, held in by friction, and this hole has a rather sloppy fit. It lets the nut move quite freely... Assuming that what someone told me is correct, and the marking on the gauge are in .001" increments (it makes sense), the backlash afforded by the *mounting system* is around .02", or nearly 2/3 of a turn! I have a few ideas of how to improve this fit, and consequently minimize the backlash considerably. A trip to the hardware store, tomorrow, sould solve a few problems...and make a noticable improvement in that axis.

The "upper" nut is a different story. It's integral to the castings and can't be removed, reinforced, or otherwise improved without modification. But, it's fit is not too horrible -- the backlash is only about half of the other axis, and with a little "doctoring" it should be almost acceptable. I have some JBWeld, and I intend to try to "build up" the inside of the nut, to improve the fit. This nut, unlike the other one, is *securely* fastened to the vise. If building up the inside of the nut doesn't work, I should be able to compensate in software...

Regardless, I believe that knowing where and what the problem actually is, is the key to fixing it.

-- Chuck Knight

ToyMaker
09-05-2003, 08:26 AM
Chuck:
I saw one of these at Kobeys swap meet in San Diego last weekend - $20 new-in-box. The display sample had something between 1/8 and 1/4 inch slop in the top slide - I walked away.
Your tear-down and analysis have convinced me that with a little time investment this can be made into a serviceable tool. I'll go back tomorrow and get one. Thank You.

robotic regards,

Tom
= = = = =
"Some things have to be believed to be seen."
- - Ralph Hodgson

samco
09-05-2003, 08:27 AM
>So, they're just bolted onto it and cantilevered out, unsupported?

Yes, The only thing holding the motors are the two bolts that used to hold the tab for the leadscrew. It is actually quite solid. The mechanical tubing is now what traps the leadscrew.

>These are the kinds of details I need -- or I can just invent my own mounting system, independently. :-) I prefer pictures!

>Did you also automate the Z axis, or just put in pauses, when you would move the cutter "down" by hand? There *are* some drilling machines that are operated in this way...

The spindle is not automated and I don't think that I will. Like I posted on the yahoo message board I think I will buy an enco or other cheap x/y table to automate. This would then go on my craftman drillpress which I would then automate the z. and yes I did put m00 at the spots where I needed to raise or lower the spindle.

sam

MikeA
09-05-2003, 09:39 AM
I know you have only spent $20.00 on the vise, and I sure like the premise, but the amount of travel seems to small to mess with. Enco sells a compound table with 8" x 5" travel for less than a $100.00, labeled as a "milling" table. Just seems a better investment for the amount of time you will spend on the vise. Food for thought.

rcrabb
09-05-2003, 11:01 AM
I converted one of those enco slide tables. I works great. I ended changing the screws from 12-10 acme to 12-13 threaded rod.

chuckknigh
09-05-2003, 11:03 AM
Don't buy one of these just on my say-so. Remember, this is Chinese quality control, which means NO quality control. The one you pick up may actually have 1/2" backlash...you won't now till you open it and play with it. Your leadscrew may even be bent! I went through several before I found one with some potential, and even then, a part was installed backwards!

Having said that, the reason I bought this unit is that I needed a drill press vise. I've had more than a few uses for one, lately. I saw them in their ad, and all of their vises were under $20.

Well, when I saw one which was also an X-Y table, you can imagine my excitement -- if I could do a conversion, fantastic! If not, I'm still "stuck" with a drill press vise, which is what I needed in the first place! It's also the reason that I want all of my modifications to be reversible...and they will be.

Now, as to why I would do a conversion of something so small, it's not small! It's got just over 4x6 inches of travel, which for small parts (maybe even metal) is excellent. Remember, my intent for these routers is to cut out parts for clocks...most gears are small, and the case parts don't require the same level of precision.

I have a wooden router table with a capacity of 18x24" already, so this should complement it nicely. I hope I can get most of the backlash out -- in my experience big wooden parts don't require the same amount of precision as small ones, for most uses. And, comparatively speaking, this cast iron vise is MUCH stiffer than my wooden table, so it should be capable of higher precision.

Right now, I'm just waiting on my boards, so I can hook everything up to the big unit and see it come to life. In the meantime, this can be a nice distraction, and a potentially useful project.

I'll keep everyone updated as I progress.

-- Chuck Knight