Enco Bridgeport clone conversion?

[beez9]

Is this the right place for a thread about converting an Enco 9x42 milling machine?



I rebuilt the head that had a couple of "issues" and now I'm beginning the CNC conversion. I'll be going 2 axis and then hoping to use the 2 axis to cut the parts to the quill conversion.

I've gotten started with a ballscrew kit from Broussard enterprises. So far it looks good, it comes with X, and Y ballscrews and the replacement yoke.

[HimyKabibble]

This is as good a place as any, or, perhaps, the "Knee Vertical Mill" group. But either is good. You'll find lots of nice conversions here.

Regards,
Ray L.

[beez9]

[79TigerPilot]

As Ray indicated there is a lot of good stuff here, I spent hours and hours reading posts before I started my BP conversion, couple years back. Ray did a very nice conversion on his clone. Do a search for "Vince's BP CNC conversion", Vince posted a lot of stuff. Vince also has a thread about a CNC lathe rebuild. Folks are doing some amazing things these days.

I think your ball screws from Broussard are the same ones I put on last year. My screws were manufactured by LeadTeam in Taiwan but they came from the retired previous owner of Broussard. Only issue I had was, I think my Y axis screw was for a 9" travel table and I managed to run the nut off the end of the screw and lost all the balls when I sent the table to the full rear stop. Just watch for this. I managed to fix the screw and get it working again. I have no backlash and the accuracy is just amazing. Also I replace the old BP bearings with a set of angular contact bearings for both the x and y.

My web album: Picasa Web Albums - Craig - CNC Mill Project

Craig

[beez9]

Thanks for the warm welcome guys! I've been lurking here for quite a while and have read all the threads cover to cover in this section of the forums. You guys both impressed me with your design and build skills, patience and ingenuity.

I'm a bit of a newb but I catch on really fast. Have been making chips for a couple or three years now. In my second semester at community college taking manual machining class. Will start CNC there next semester, they have four CNCs! Two brand new HAAS VMCs, one older VMC and a HAAS CNC lathe.

Craig, I have encountered the same problem with the Y axis screw but I detected it on the bench instead of in the mill. Its too short! I spoke to Jeff about getting a longer one but he says the supplier is quoting zillion week lead times and thus seems not to want to do business any more. I was planning to install a longer Y stop in the machine to prevent running the nut off of the screw. How did you deal with this after you re-balled your nut?

Here are some progress pictures. I pulled off the table and saddle:


Then I installed the Y axis lead screw:

[79TigerPilot]

As much as I can remember on my set I could see no way of fitting the Y-nut into the yoke at least not without some significant machining of the yoke. So I just mounted the flange on the rear of the yoke. Of course this set the nut back a few inches and increased the problem of running the nut off the screw.

The sound of little balls droping all over the place is something you don't want to experience, never did find all the balls. I gathered up what I could, measured them and ordered some new ones from Bal-Tek. Turns out there were two different ball sizes. I took a guess that each track got a single size and that's how it was preloaded. In the process I put the nut back on the screw the other way around with the flange facing the rear and the body facing forward. This maximized the travel on the screw and I now get about 11.8" of travel. I had to make a .4" thick spacer/adaptor that went between the nut flange and the face of the yoke. This centered the fore and aft travel and repositoned the mounting bolts. At full travel I allowed screw to just go through the nylon wiper ring to recover another 1/4-3/8 inches of travel. I figured there would only be a very limited need to use the table at its maximum and this would be ok.

I still want to try and get some raw lead stock from LeadTeam to make a new screw. I sent them an email a couple years back but only got a limited response and never followed up.

When I was doing my conversion, Ray suggested I add a key way for the pullies. After I had one of the pulley set screws loosen up I took his advise and added the key ways. Something to think about before you take your machine apart.

Craig

Craig

[beez9]

First real problem and I have to punt! The yoke doesn't even come close to reaching down far enough to bolt up with the Y nut. And it looks like the X dimension is off as well. And the mounting holes and pin holes don't line up either. Other than that it's perfect!







So, I'm putting the mill back together so that I can mill another yoke that fits! The yoke in the pictures is a replacement yoke from ENCO that I got so that I could take measurements without pulling the nuts out of the working item. I considered machining it to take the ball nuts but it looks much more flimsy than the CNC style yoke, and there's not enough meat around the Y nut area to drill and tap for the bolt holes.

IIRC there was a thread where someone else had to make a yoke, or have one made. Anybody remember which thread that was?
Thanks!
Beez

[beez9]

Well, I found the thread I was thinking of. Only took a few hours of searching.

http://www.cnczone.com/forums/bridge...54_mill-5.html

What are the pros and cons of making a yoke out of steel as described rather than cast iron?

Can I find a piece of cast iron to make it out of? All the online metals suppliers seem not to list iron.

Thanks!
Beez

[79TigerPilot]

Looks like there is quite a difference between the centers of the X and Y screw compared with the BP. You are lucky to have a yoke available to look at while you make a new one. I would think CR or even HR steel would be fine for something this short. I suspect the reason the current one is cast iron is because its easier and lest costly to cast the thing. You could always look into making a foam or wood pattern and finding someone to cast it for you. Even bronze would be hard enough. Even some of the high strength aluminum alloys would most likely work fine especially if you increase the section sizes a little.
Just a quick check of cast iron vs 7075-T6 aluminum:

Tensil Yield Modulus of Elasticity
steel low c 60k -100k psi 45-50kpsi 29000 kpsi
cast iron 25k to 60k psi ---- 11500 kpsi -20000 kpsi
7075 T6 74k-78k psi 83k psi 10400 kpsi
6061 T6 45k psi 40K psi 10000 kpsi
As long as you are under the yield point the Modulus is what governs the flex.

[beez9]

Well, it's been less than a year!
I've been out of the shop for quite a while but now I'm back.
I changed jobs and now, finally, I'm getting some time to work on my own projects. This project has moved back near the front burner.

Anybody care to quote on making me a new yoke? It can be steel, that would be fine. I've been contemplating making it myself but am not sure my 2.5 semesters at trade school machine shop have taught me enough yet. If it's affordable I think I might throw money at it.

The drawing from Robhrzic's thread quoted below will work with a couple modifications, I spent a bit of time working it over today to check all the dimensions. Here it is for quoting purposes: