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thoughts on a some used/ project cnc knee mills im looking at

Threephase

Plastic
Joined
Sep 24, 2016
Hello im new here. i read and get lots of info from this fourm.

My question is. im looking at buying a cuple cnc knee mills for at home. the mills are projects and eventually make parts with them. i was thinking of converting them to pc based system useing the steppers/servos that they already have.

The catch is there at a salvage yard and were bought for scrap and they know nothing about them, i may have already told them more than they needed to know lol.

what im looking for it some knowlage or insight into these two units,and what would be better for a cnc knee mill project.

#1 1985 Tree journeyman 325 with what looks like a delta 20 cnc controller?

#2 is a mid 1970s shizuoka missing controller and a lot of the electronics but all the hard parts are there.


thanks in advance look forward to chating
 
Thanks for the link to the videos iv been watching that guys vids,there good.

Also thanks for the opinion on them being in right place. But can you give me some reasoning? I could understand if I had thousands of dollars...but that's not the case. I can get these units for scrap prices and luckily for me scrap is only at 50.00 a ton.

I already have phase converter and tons of tooling and 40 taper....
 
Don't know either machine, but the PT job retrofitted a boss(?) bridgy when the control went out with a Centroid. I think he had something like $7-8k + into the control, plus the labor, which he did himself. The centroid is a sweet control, no complaints, but just to maybe give you some reference of what this will cost, EVEN if you get the machines for scrap price....
 
I've got some thoughts:
1. What's your budget on this?
2. Space limitations?
3. Compressed air requirements?
4. Have you ran a CNC?
5. Have you programmed a CNC?
6. Did you know that steeper motors suck?
7. Why do you want a POS conversion instead of a real CNC?
8. Have you ever ran a manual mill before?

It's fairly obvious that you are a hobiest. Nothing wrong with that, but you're kinda on the wrong board for what you're seeking approval of. Most of the guys/gals here either make money doing this or have made money doing this.
Just askin'
JR
 
I've never seen the logic in using stepper motors on a cnc, but then, I always cared about the parts I was making.
There is a lot of good used cnc out there. 25 years ago, pretty good cnc stuff started to be sold, stuff that wasn't broken down half the time with circuit boards going out of commission. Knee mill retrofits at that time allowed you to get into cnc and dabble with it, it still cost $15 to $20k to retrofit. If you want to modernize an old machine, you need new servo motors and drives, that is likely $5k to $10k, a new VFD, Why new? So you've got some documentation to go on to hook it all up. The machine had better already have ball screws. Look critically at the Z axis (quill). A lot of retrofits did a poor job of the quill hookup.

Add on the fact that the machines may not have a full enclosure, max rpm is not very fast, max rapid rate is not very rapid, no tool changer (if it has, that is another nightmare to hook up). A small Haas would beat any of these old things, and would certainly be my first choice to shop around for.
 
If not mechanically trashed the Tree isn't that hard or expensive to fix... but it's too steep a learning curve to fix an unknown machine. You could find a known runner for about that price, I've sold one.
 
You should probably give us some info on why you think you're qualified to do a retrofit. Assuming perfect hardware/iron, and only electrical and programming work, its still a lot bigger task than most people assume, unless you're willing to shell out the $ten large+ for a centroid retrofit that is supposed to "just work" right out of the box with a minimum of install time, integration, programming or wiring.

Having done a retrofit on a similar vintage machine (1979 Lagun knee mill / Former Bandit control) and currently bringing a 1984 Okuma Millac back to life I can suggest a few things I'd be concerned about before moving forward:

1) Does the either mill have steppers or servos? If steppers, rapid speed is going to be terrible and there may be no feedback to let you know that steps were missed (= scrapped parts). If Servos, whats the feedback mechanism (encoder or resolver? Maybe even scales?). If anything but encoder its going to be expensive and a PIA to integrate with modern motor drives. Even if they do have encoders they will likely be a lower bandwidth/count given the age which means less-fine control of the motors.

2) Are you prepared moneywise to throw out all electronics? Given that they're sitting in a scrapyard I can only assume they've been rained on a couple of times.

3) Given that they're in a scrapyard do you think there's a good likelihood of getting things like wiring diagrams or ladder info?

4) Can you properly assess the quality of the iron and other mechanical bits where they are sitting?

5) Have you any experience with motion control outside of this project?
 
$3-5K should get you a reasonably nice and running Tree 325.

I've put Centroid controls on both a 325 and a 425. I upgraded the encoders on the 325 axis motors to 2000L (you need a mill to do that)and replaced the OEM spindle drive (took up most of a cabinet) with a CT Emerson unit. Many other parts were reusable. The surplus Dynapath/Yaskawa control/drive parts were sold as spares to someone else. The 325 went from 2 cabinets to 1, the old stuff was miles of wires and multiple boards.

The 425 replaced the 325 and was unused but largely stripped (I wish I knew why that happened) so I bought new servo motors w/encoders prewired from Centroid, but kept the OEM Yaskawa G5 VFD (I did add a NOS board and an encoder for spindle motor feedback which helped a lot at lower RPMs after changing to the 6K pulleys).

The Trees fit into my garage with an approximate 8' ceiling. A bed mill may want more ceiling height (at my house that would mean extending into the bedroom above). I use a 10hp Phase Perfect to power the machine.

It would have been nice to have gotten an enclosed VMC with toolchanger but for a hobby CNC mill the Tree (especially the 425) seems very nice. I'm not trying to run multiple machines so I can babysit the mill and change tools now and then.

If you are wanting to do production something like the Tree can work (I cleaned a LOT of aluminum chips out of the 325 which had a busy life before I got it) but a VMC would make a lot more sense and free you up to run other machines.

cheers,
Michael
 








 
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