I'm thinking of getting a gas spring to counterweight the head. Is it nessecary to "keep it symetrical"? Or can i use just one gas spring on the right side of the head? Will it wear out the dovetails faster? :P
I think it doesn't have to be symmetrical.
A cheap alternative, that may be easier to optain and maintain is a simple pneumatic cilinder (ebay) and an air tank. If you pick a smaller cilinder and a larger tank you'll have very little pressure increase in the stroke.
You can also use a counter weight.
I intent to use no such thing. The weight of the head takes out any play.
Erik Jan
What goes down, should come up.
I don't think the stepper will move the head without help(or some serious gearing). I have only 2,2 Nm :P
http://www.danahermotion.com/design_..._selection.php
You can download a little piece of software here for free (the highest in the list) in which you can virtually build a motion mechanism (like a leadscrew mechanism with dovetails) and calculate what motor you need. How many rpm and torque you'll need for given speeds. You can see what the effect of a different transmission will be, different pitch, etc, etc.
Has a built in database for DC Servo, AC Servo and steppers.
I found it very easy to work with and best of all....
.
.
It's free for personal use!!!
Erik Jan
What goes down, should come up.
Does anyone have any info on Dunkermotoren Type GR 63x55 SNR 88442 01278 1500rpm.so l don`t know how much torque they have ..
l cannot find anything about these motors and l can buy these really cheap maybe there is a good reason for the low price !!!
Have you looked here:
"http://www.dunkermotoren.de/default.asp?id=9&mid=12&gid=0&cid=0&bid=0&sid=0&la ng=2"
lots of info but appears to be 3,000rpm
Phil
Originally Posted by GOR
Last edited by phil burman; 03-04-2006 at 11:46 AM.
They are standard 3000 (~3500rpm) motors but can be customized to specific needs. They are very good motors! I have 4 of them and would like to have more. http://www.dunkermotoren.de/data/tec...x55.pdf#page=1
They are 100 Watt motors with 0,27Nm contiuous torque and a peak (starting torque of 2,1Nm at 3500rpm). At 1500 rpm the torque doubles making it about 0,6Nm.
There is a but however.
Since they are DC motors they cannot be controlled with a normal controller.
I'm building UHU servo controllers for them (see my thread in the open source controllers "diy servo controller")
The 1500Rpm is great for BF20 control (x and y axis) since you only need a small reduction. I'd say buy them if you can use them, if not give me the adress ;-)
Succes ermee,
Erik Jan
What goes down, should come up.
l purchased 2 today and l`m going to buy 1 more next week and l`ll ask if he can get anymore so l`ll let you know ..
Glen
Z-axis may need something stronger for good speed. I have an 80x80 (240W) for that. If you can get more than you need, email me, I might be interested.
Where do you live in the Netherlands and what are your plans with the motors.
Erik Jan
What goes down, should come up.
l live in gelderland near Lochem ...l have just purchased a BF 20 Vario mill and l want to make it into a cnc but this cnc thing is all new to me L do a lot of 2D/3D drawing at work and at home and l do a lot of my projects and working with steel, alu etc is no problem but my electronic knowledge is limited ...so l could use all the help l can get l was thinking of buying a kit from damenCNC or stappenmotor.nl but l saw these motors just sitting thereand l`m a real sucker for a challenge...
glen
The mechanical part is easy.
http://www.dirt-page.de/metall/cnc/umbau1.htm
This is a conversion that you can follow.
Reduction can be less (say 1:2 or 2:3) depending on the spindles you'll use.
Allthough expensive everybody does recommend a conversion to ball screws.
I'll use HTD timing belts since they have no backlash and are easy to obtain.
If you are quick I'll order some for you at Maedler.de. They are cheap (50% less than what I'd pay for them here in the Netherlands) with stuff like this. A guy in Germany is willing to order some for me and ordering 4 is just as easy a ordering 8.
I got my Z-axis spindle cheap and convert that right away. I'm stil in doubt if I'll convert the other 2 axis right away. I may start out using the original spindles.
Ball screws have a much higher efficiency (~90%) than acme or trapezoid (~50%), and their backlash and wear are minimal and constant whereas trapezoid will wear out the nut much faster.
Electronics can be either very easy or a bit more chaanging.
Easy with those Dunkers is buying Geckos (320 or something like that)
More challenging (but more rewarding imho) is building those UHU controllers.
Check the UHU controller subforum @ www.cncecke.de for more info.
Power supply is easy.
Buy yourself a big torriod (sec voltage around your motors nen voltage).
Most torriods have 2 secundary windings. Find out what the start is of each winding and hook them in parallel. Hook up both secundaries to an equalizer bridge (gelijkrichter) and hook the gelijkrichter to a bank of capacitors.
My setup is 2 500VA torriods 39V secundary (with 40Volt dunkers). I've switched the secundaries of each torroid together and fed each torriod into it's own equalizing bridge. After the equalizer bridges I've switched them in parallel and hooked the up to a capacitor bank (54000uF at 63V).
To prevent my fuse blowing I've added an NTC into the circuit for the primary winding of each torriod. At normal temperatures they have a certain resitance value. As current flows trought them they heat up (and get very hot). As they heat up their resistance drops to virtually zero ohms. Torriod transformers draw a very high current when switched on. This prevents that peak. After a few seconds I bypass the NTC's allowing them to cool and readying them for the next start.
This setup give me a DC power supply that generates 52V without load. With maximum load (~26A) the DC voltage will be around 42V DC.
This is enough to allow for some hefty peak current for the DC motors.
Erik Jan
What goes down, should come up.
Sorry this is a bit offtopic, but where can you get one of these mills in the US? They look very nice.
Hello EveryOne
Finally, the X Y cnc works (Z need still developpement ...), using USB connection
Looks nice, USB? what controller are you using(computer program)?
Jon
Hello
I made the software, the USB device is IOWarrior 24 input-output(http://www.codemercs.com), output info are the same as using parallel port
1 byte for impuls, 1 byte for drive way
Just finished Z!!I made a oldham coupler of MDF (had no other material home hehe) Works fine until i can make something more serious! Made a simple test...
haha very inventive!
hi guys
i can see yall been havin some fun on your bf20's
now i'ld like too ask you if anyone took his millinghead(spindle etc.)
a part yet for what i'ld like to know is :
if a gear/drivebelt modifiation would be able too crank that rpm up a lil like the sieg
were they replace the plastic gears for better quality drivebelts and achieve as well a more silent run as some extra rpm's
and offcourse i'ld like too know if anyone has any ideas how the spindle will react too more speed
thx in advance guys(i'm still hopin i'll be able too convert mine soooon)
Rob van Zyl
Hi Guys , just joined this forum
I have converted a BF20 Vario to 3 axis cnc and seem to have been through most of what you guys are discussing. I have played around with upping the spindle speed as high as 12000rpm. I removed the gears inside and the quill feed mech. I made an additional bearing plate on top and coupled the motor with a poly-v belt. I started with a 1:1 ratio but quickly wanted to get little cutters spinning properly and changed to 3:1. At 8000rpm plus the grease starts to burn and the motor wine. I stripped and cleaned the spindle bearings and added just a light rub of Klueber high speed grease and took the seals off the top bearing. After running in for a few hours the bearings run warm but stable at 12000rpm now. The correct preload is tricky!. The bearings are taper rollers which are not ideal for high speed and should be replaced with a matched pair of angular contact bearings $$$$. The next problem is I have the high speed for engraving and fine work but nothing for normal milling, the electronic speed control eventual blew up trying to hold low rpm. I am in the process of fitting a 3phase 750W motor with inverter control. Time to stop messing around!!
I should have tried the other option of attaching a small belt drive to a MT2 taper and drive a small engraving spindle off the side of the main spindle on an adapter plate.
I have many tips on adapting this machine and advise for anyone willing to try. mostly what not to do! its a great little machine!!
Rob
some pics of my machine, operating but still undergoing developement. I would like to enclose the whole thing to contain the spray and mist. I am drawing plans for a integral stand and enclosure with a removable swarf drawer.
Rob
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