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Need some opinions!!! cnc conversion of a ZX7045
Hi guys, about 1 year ago I bought a ZX7045 machine, when I bought it already had plans to convert it to CNC now I'm really decided to go for it but I need a couple of opinions from the experienced guys...
well first I really want to make a precise machine so on ballscrews I'll go for TBI C5 rolled ballscrews probably with doublenut, I think 16mm for X and Y will do and 20mm for the Z what you guys think? about the pitch I'm thinking to go with 5mm, it's not a big big machine so I think 5mm will be good but I need your input on that too...
about motors, I decided to go with the Leadshine hybrids ES-MH33480+ES-DH2306, the drivers are direct AC connect and they look very beaffy for this machine, from the torque/speed curve I get the full 8Nm up to 300RPM that's about 1500mm/min on 5mm pitch and get half the torque at 900RPM that's 4500mm/min seems like more than enough for this machine...
I already bought a nice Lenze 2.2KW VFD motor rated for 3400RPM @ 120HZ for the spindle I get the full torque from 60 to 120HZ and 1700-3400RPM I'm thinking of using a 1:2 and 2:1 pulley ratio for high and low speeds I think it will be very nice this way what you guys think? I do mostly aluminum think 7000RPM will do or it's short?
I bought the machine with morse 4 tool holder (only one that my vendor had unfortunely) but I'll buy a BT30 spindle, already know where they sell them just need to replace the bearings for handle the max speed of at least 7000RPM...
now the crazy part... I don't like the dovetail ways of the machine very much... scratch that, I don't like them at all... and I'm seriously thinking to change the machine to go with some hiwin or TBI rails, here's where I need the most of your opinions... already made some draft's on this... has someone did this before? I'm seriously thinking about this...
I'll attach some sketches I made and I think it's very possible to do....
anyway about this subject, on the drafts I'm using 25mm linear rails, however I'm thinking to had 2 more carriers on the X axis, that table weights ALOT and I'm a bit scared to have it hold only by 2 (4) cars when it's all on one end...
about the Z axis, I don't think I'll manage to get those 25mm rails without significantly change the Z pilar, so will 20mm rails be enough? I also have to sketch the head so I can really look at this...
other thing, I'll have to make a new cross plate to hold the linear carriers and of course the ballnuts mounts, either I'll make it in aluminum 7075 (I was thinking on this about 40mm thick and I can make it myself) or using steel I'll have to ask on a CNC shop to make it to me... what do you guys think?
I won't write any longer since I want to know first what you guys say...´
best regards
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Re: Need some opinions!!! cnc conversion of a ZX7045
I converted a zx45 using 16mm ballscrews on X & Y and 20mm on Z .. if I were going to do it again I would probably do whatever it took to go with 25mm on all axis. I believe a larger (stiffer) ballscrew would help with precision.
My ballscrews are all 5mm pitch and that works fine with the servos I'm using .. I have my machine set up for 200ipm rapids and that's plenty fast.
I have also converted my machine to BT30 spindle & could not be happier. At the present time I'm also considering a switch to linear rails on my machine, but don't really want to get into such a serious rebuild right now. (maybe some day!)
I have a thread on the zone named 'Bolton ZX45' .. it's pretty long & covers most of what I did on my machine.
Cheers,
gd.marsh
Re: Need some opinions!!! cnc conversion of a ZX7045
Quote:
Originally Posted by
gd.marsh
I converted a zx45 using 16mm ballscrews on X & Y and 20mm on Z .. if I were going to do it again I would probably do whatever it took to go with 25mm on all axis. I believe a larger (stiffer) ballscrew would help with precision.
My ballscrews are all 5mm pitch and that works fine with the servos I'm using .. I have my machine set up for 200ipm rapids and that's plenty fast.
I have also converted my machine to BT30 spindle & could not be happier. At the present time I'm also considering a switch to linear rails on my machine, but don't really want to get into such a serious rebuild right now. (maybe some day!)
I have a thread on the zone named 'Bolton ZX45' .. it's pretty long & covers most of what I did on my machine.
Cheers,
gd.marsh
thank you for your input gd.marsh, I'll have your thread checked out! and I'll take your notes on the Z axis ballscrew also!
about the linear guides I'm really thinking about it it's driving me crazy specially because I might lose the head tilting capability... anyway this thing it's for working with the head straight anyway so... but I'm really thinking to get serious about the linear rails... I'd took some measurements across the table and I really don't like what I've seen... some almost for sure linear rails will be placed, and since I'm going to completely disassemble the machine I guess it's worth doing it all together than make the conversion now and later have to do it all over again...
Re: Need some opinions!!! cnc conversion of a ZX7045
If you're thinking of motorizing the quill & head tilt making it a 5 axis machine, you may want to first investigate which CAM software you will use, as most of what's available in the 'DIY' price range won't give you that capability.
Even though the free motion control software will handle multi axis, true 5 axis capable CAM is still pretty much big money stuff.
You would be much better served in the over-all usefulness of your machine by eliminating the quill (which gives you greater rigidity on z axis) and use the head swivel only for manually tramming the head to the table. (adding a 4th bolt to lock the head to the Z carriage also helps rigidity)
If I were to do it all over again, I would put more effort into building a stronger, more rigid, & more accurate machine & less effort into adding the 'cool factor' kind of stuff.
gd.marsh
Re: Need some opinions!!! cnc conversion of a ZX7045
Quote:
Originally Posted by
gd.marsh
If you're thinking of motorizing the quill & head tilt making it a 5 axis machine, you may want to first investigate which CAM software you will use, as most of what's available in the 'DIY' price range won't give you that capability.
Even though the free motion control software will handle multi axis, true 5 axis capable CAM is still pretty much big money stuff.
You would be much better served in the over-all usefulness of your machine by eliminating the quill (which gives you greater rigidity on z axis) and use the head swivel only for manually tramming the head to the table. (adding a 4th bolt to lock the head to the Z carriage also helps rigidity)
If I were to do it all over again, I would put more effort into building a stronger, more rigid, & more accurate machine & less effort into adding the 'cool factor' kind of stuff.
gd.marsh
guess I didn't made myself clear, I have absolutely no intention of motorize the head tilt, neither the quill, just said if I do as I'm planning I'll lose the tilt capability (manual tilt if I need it for something, honestly don't know what but...)
about the 4th screw also thought about it as well ;)
anyway I'll have to do some more modeling and see what I've got, I'm also thinking about get the table a bit more offset to get more area on the spindle working zone, like I said, need some more modeling...
Re: Need some opinions!!! cnc conversion of a ZX7045
I still didn't pull the plug on the cnc conversion since I'm still gathering materials, I'm going with linear rails on all axis for sure, still thinking on the ballscrews, for sure they will be TBI C5 grade with double nut just need to decide/plan the diameters... most likely 16mm on XY and 20mm on Z.
anyway need help on the spindle bearings. My next step is upgrading the spindle to a 30 taper (already on the way from Canada !YAY!), a Lenze 3400RPM motor, 120Hz 2.2Kw and of course a VFD, went to an Invertek Vector drive.Now I want to go with angular contact since I'm looking for 7-8k RPM belt driven.
now my mill originally has one 30206 (30*62*17) bearing on top and 32008 (40*68*19) at bottom. On top I'll go for the 7206 that's for sure, the bottom one I need your help since I either have to sleeve the spindle shaft from 35 to 40mm and go for a 7008 or enlarge the spindle cage (don't know the correct name) from 68 to 72mm and go for the 7207 bearing...
my mill needs 2*6007 beerings going to NACHI or SKF not critical since they are only for the spline guide, 1*7008 or 7207 for bottom and 1*7206 for top. these are going to be Nachi or NSK have to decide yet, now what angle to get, price is the same for 15º and 25º I just don't know which ones are better for this aplication... can someone help me here?
I'm looking to buy in qualitybearingsonline these things are not cheap... found some good prices on NSK super precision in Aliexpre$$ but honestly, too good to be genuine I guess... anyway, waiting to hear from you guys.
thanks in advance...
Re: Need some opinions!!! cnc conversion of a ZX7045
I was going to wait until somebody else responded but its been a day and nobody else has...
using angular contact bearing of different sizes and far apart isn't the best plan - it may work out in the end but from a design perspective its not ideal.
Most often angular contact are used in a preloaded back to back configuration, or in cases where the loading is predominantly from one direction they can be arranged back to front (both facing same way).
The long spindle creates an issue with the preloading as the head and spindle heat up and the preload on the bearings changes - this is due to the different rates of expansion of the head and the spindle - due to both the different materials (cast iron vs steel) and the source of the heat (bearings/gears/belts) and heat dissipation . The current tapered roller bearings are more tolerant of the variable preload than the angular contacts, and the angular contact has less load capacity compared to the the tapered roller bearing. You will gain higher rpm capability at the expense of losing high load capacity at the lower speeds. This might be OK as long as you are aware and operate accordingly. i.e. use low speed for large drills that won't present a high side loading to the shaft, not for large shell mills.
See if you can find threads on here of people who have done angular contact bearing conversions, there are a few and see if any have had longevity issues with the bearings - I recall reading of at least a couple who ended up replacing their angular contact bearings fairly quickly (don't limit your search to ZX7045 / RF45 machines, look at the G0704 too and other small mills - sieg X3 etc.)
Mike
Re: Need some opinions!!! cnc conversion of a ZX7045
yes, I see your point... I really need high speed since my main work is aluminum with 6 to 12mm end mills, I intend to do some occasional steel but it's really occasional and even when I do it will be small pieces so we're talking about 6-12mm mills, and always carbine so higher speed is required.
lower RPMs only just for drilling... don't get me wrong, I would prefer to use the roller bearings, I just can't find any rated for that kind of speeds, I mean, I've seen a NACHI 30207 rated for 7400RPM in oil lube (I intended grease lube but...) and an SKF 30207 rated for 7000RPM refference speed and 9500RPM limiting speed and these are really cheap bearings like 20-30usd... the smaller one 30206 from SKF is 8500RPM refference speed so they might be ok for me but I was really leaned for the AC bearings, and like I said I do not expect giant side loads... but I might get excited with this bigger machine tho XD
anyway besides the type of bearing what's your advice on spindle modification? go for enlarging the spindle cage from 68 to 72 and change the bearing from 7008/32008 to the 7207/30207 or sleeve the spindle from 35 to 40 and stay with the 7008/32008?
if I go to the AC bearings, which are best 15 or 25º?
Re: Need some opinions!!! cnc conversion of a ZX7045
You could look for a 7007 angular contact for the bottom (35*62*14), and put a sleeve in the housing to bring it from 62mm to 68mm. Might be the easiest route, don't need to machine the big head casting and you can play with getting the right fit of the sleeve in the casting. You can also check, there might be enough room for a pair of 7007's at the bottom. The higher the contact angle the higher the axial load and reduced radial load capability. As the application you are looking at running is predominantly high speed milling the 15 degree angle would probably be my choice, and I wouldn't run big drills.
Mike
Re: Need some opinions!!! cnc conversion of a ZX7045
Looking forward to your linear rail conversion on all three axis. Subscribed.
