[alpinasjofallet]

Hi, I am planning to convert an Emco Unimat PC (the last of the Unimats that also has stepper mounts). I have bought the original Emco shaft encoder for the main drive (5volt optical sensor) and was planning to also buy the original Emco CNC conversion kit (still available for about 820€, although it is almost 20 years old). However I am now thinking of instead going for a more flexible set-up with Mach3. I therefore, search advise on:

1. Were to find low-height steppers. They need to have a torque of 20 oz inch and can not be much bigger than 60mm in diameter and 30mm in height. Any tip on were to find such steppers in Europe is appreciated.

2. Advise on driver boards for these steppers. I need a portable compact solution (my kitchen-table is my workshop...). I was thinking of HobbyCNC or the cheap eBay DB6560´s - but after reading about the 6560's it seems that they are a no-go. Other advises?

3. How do I hook up my shaft encoder, is it possible to use the homing pins/function, in for example the HobbyCNC board?

For those not familiar with this Unimat, more info is available at:
Page Title

Best regards

[LUCKY13]

It would be much easier to do away with the setup they have on that machine ( stepper mounting and belt drive).


This way you could use a very small Nema 23 stepper, remove the crank handle instead of using it for a pulley, then mount the stepper dirrect drive to the screw. Easier, maybe cheaper, and performance would be much better.

This would allow you to use a G540 driver from Gecko which will be a lot better than any of the cheaper drives your looking at. Its self contained, has its own breakout board and spindle controller built in. It does have four axis though which you dont need but two. The other two could be used to add a nice little milling attactment. Its a very small driver/breakout board package that performs very good with small motors. It might even fit under the lathe or on the back side of it.


Now not knowing the real size of the parts of this lathe I may be suggesting something that doesnt have a chance of fitting, but it should ( the Nema 23 steppers).


This is the smallest stepper I have found that might work with the factory mounting. The propblem with a lot of the small can type stepper is they are 7.5 degree steps. IDK that may work anyway with the belt drive though. ANyway here is a 31.74mm long stepper that is 1.8 degree steps that might mount with the factory setup. If it will fit the G540 should run them quit well.

10.8V, 1.8 DEG. STEP MOTOR-MPJA, Inc.


I just did a quit look at one of the elctrical surplus stores and found this stepper. I am sure many more can be found. They have many cheap Nema 23 steppers also if you did go the other mounting I suggested. You could even get a double shafted stepper and mount a handcrank on out backside if wanted but when you have CNC there is no real need for Handcranks. BTW the G540 is on sale right now for $200.00 and maybe even free shipping from Keling.

Jess

[alpinasjofallet]

Thanks, that made a few things more clear. I plan however to keep the original belt drive system. So using can type steppers with 7.5 degree resolution should not be a problem - since they have a 1:5 ratio through the belt drive.

Unfortunately, the Gecko 540 is 299€ here in Europe (almost 500 USD) so it seem to be a little overkill. However, using two Gecko 250's seems to be a very neat solution - but can they drive can type 7.5 degree steppers?

Lastly, is it possible to use the homing pins/function of a breakout board to connect main spindle shaft encoder (sending 5 v pulses)?

[LUCKY13]

I think the 250's should drive a can type stepper just fine, but you need to ask at Gecko to make sure. Really I think you can find the G540 for 200.00 US dallors if you keep looking, but maybe not. Heck I seen a deal on three 250's for 169.00 us dollors, but maybe not in your area.


I did find some normal steppers that would fit last night but I wil have to find them again and I didnt see a price. SO given time you should be able to find a 1.8 steppper that can work.


7.5 + 1.5 ratio will stilll only give you a 3.25 stepping. Although if using micro stepper form a driver that may work out. I have never used stepper to know how all this micro stepping works.


I have one Nema17 stepper here that is almost small enough to fit so it may not be as hard to find one, just need to keep looking. I feel like they would be better than a can type if you can find them.


You might be able to use a breakout boards homing pin for a encoder for the spindle. It would probably leave that axis on the board unusable for a axis but it should work. Most of the breakout boards have a setup for a spindle if you buy the right one. I guess this is needed for threading on a lathe. Again this is where the G540 is so good because it has all this built in. Let me look around again. If nothing else I feel sure some of the dealers here would ship a G540 to you. Its so small it could be sent through the mail also. They are so good it would be worth doing what it takes to get one. I will post back tonight and see what I can find with a 540 and some steppers.


Jess

[LUCKY13]

BTW, measure and see just exactly what the longest motors you could use would be. It might even be possible to shim the nrackets out some so look at that also.


Jess

[alpinasjofallet]

Thank you so much for the tips. I think I have my set-up clear now!

The gecko 250 is reasonable cheap here in Europe so I will start with two of these and prepare cables and space for a future third one. I will mount drivers, breakout board and power-supply together with a mini-ITX motherboard into a single case to minimize the cable mess. I guess it will need some extra work to keep it cool + some work to keep the electrical noise down from the drivers, but I think its worth the hassle.

For steppers I will use 7.5 degree stepper in original mounts (some stepping as the original Emco steppers) , they have a 1-to-5 ratio, so I will get 1.5 degree step at the leadscrew. The biggest problem with the lathe is the pathetic main drive of 80 watts (yes, thats correct!), so the feedrates and cutting depth will be very low anyway. The biggest problem will probably be that the rapid traverses is going to be anything but rapid - however its a small lathe, and its only a hobby for me.

As I can see I will be able to drive 3 axis and still have a few lines left empty on the parallel port for input on a breakoutboard. Looking forward to post the results.

[LUCKY13]

Here you go, I found so many steppers that will work you can take your pick. If the link doesnt take you right to the motors just go to the listings on the left and click motors, then steppers.


Normal built steppers, plus can stepper and each have 1.8 or other degree stepping.

Lin Engineering 4018X-07-04 bipolar stepper motor | Alltronics


You should be able to get a nice stepper that will giev you all the power and accuracy you can use. WIth a 1.8 degree stepper and the 250 Gecko drive you will have extreem resilution, plus the speed to have good rapids with the extreem res ( it want be real fast but faster than it was with three times the res and accuracy).. Even with a very fast pulse rate with the belt drive you will still be limited on rapids, but again much fatster than you was.


You said 80 watt main drive. I am guessing you was talking about the spindle itself. It would be very easy to use a small servo and driver, or even just a good DC motor with controller, or even a servo with a DC controller plus a encoder to give it threading. You can get a good DC motor as cheap as 15.00 dollors that would feed this. I found some nice ones in the top of a printer that had a document feeder that is good enough for continues duty or servo use. The thing about a good DC motor is you can run it what ever RPM you want and with the encoder it can even index plus threading. I dont know what RPM the original setup uses but you can run faster than it came originally. You just want to use your head with it and watch for over heating. It basically will go as fast as it can without getting hot or out of balance. WIth small work like this good RPM helps a lot with surface finish. I used the system out of a old thrown away treadmill and got the controller and motor for free for my small mill. Most of these controllers are ajustable and a breakout board will control them.


You say hobby, but when spending you might as well get the best for your money. The better the machine is the more you will be able to do. I wish I had a lathe this size to do small work with. I have a RF-45 and a X1 mill and I will soon pick up a fair size lathe. But like with the mills I have I found a smaller one comes in very handy all the time. Its really amazing what a small machine can do if you use your head and think about things. I havnt had one of these lathes like your in my hands but I see a lot of people using them. It should make for a nice little setup when you get it going.



Keep us posted with what you do here. ANd when you go look at those steppers I linked to they have atleast 20 different once that will work so look through them.


Jess

[alpinasjofallet]

Thank you Jess. That was a good link. I'll keep you updated.

[gavinkong13]

I am sure many more can be found. They have many cheap Nema 23 steppers also if you did go the other mounting

[gavinkong13]

That was a good link. I'll keep you updated.