I'm new to the site, and I'm looking for some advice. I'm planning on retrofitting a topwell 5BVK knee mill, similar to a yamazen or kent. It was originally equipped with anilam control, but the actuators and control are gone. The ballscrews luckily remain. I've been doing some research, but I'm coming up blank on a few subjects regarding my build. I want to do things gradually as I'm on a budget, but I want to source the right components. I've asked a fellow owner of a yamazen mill what size servos were used on his machine, and they spec'd out as follows: 40 in/lb constant stall torque, 143V 6.5A DC brushed motor (ServoDynamics MT30U4-42). I'm very green regarding CNC control construction, but I'm eager to learn. I realize some of these questions may be quite vague/general, please excuse my ignorance.
-What specifically should I be looking for in a servo motor? Is a NEMA 42 a typically used framesize for this application? I do realize oversizing is not necessarily desireable. The mill is roughly 3500lbs with a 50 x 10 table. If I recall the ball screws are 1" x 5 TPI. I'd like to see accuracy under .002" Speed is not reallt a concern, this a home garage, not intended for full production, mostly jobbers.Who would be a good source for low priced servos?
-I intend to use gecko drives to run the servos, I assume I need one for each axis. My goal is 3 axis, (cross feed, table, and quill). I presume that the basic power path begins with the PC signals, sent via a breakout board, to the drives which act as amplifiers to supply power to the servos. I'm not really clear on the operation or routing of the feedback coming from the encoders/tach. For that matter I'm not certain of the desired resolution or difference between a tach and an encoder. I do understand the benefit of having the encoder or tach being packaged with the servo, and would like to source my motors accordingly. Do I want a 2000 line? Optical?
-How does one instruct software to compensate for a 3:1 timing pulley reduction? I'm guessing this would reduce my servo requirements. Is there a standard sheave that the industry uses? I'd like my machine to be as conventional (excuse the pun) as possible. I don't want to build a frankenstien. Do builders typically incorporate tensioning adjustment when mounting servos, or are dimensions static and based on center distance and belt length? I've been trying to decipher long range photos and haven't been able to tell for sure. Also, How are limits and home position expressed to the controller?
-What software is typically used in a PC based servo actuated machine? I get the notionthat Mach's step by step configuration is more suited to steppers? I don't know for sure, please educate me.
-Based on my dwindled budget, are servos a poor choice? I'm not sure what the difference in bottom line is from a financial standpoint. I would like to get through this for around 2 to 3 thousand dollars. I intend to machine as many components as possible, but the controls/actuators/power supply I will obviously buy.
-How is the quill feed servo usually oriented? From what I can observe they aren't directly driving the pinion. Is there a pulley/sheave reduction?
-My power source is single phase 230V. I intend to use a 5HP AB 1336 plus vector drive VFD, and a 3 phase 3HP motor. I forget the frame size, but it is a flange mount TD face, was originally a 5HP but I'm already pushing my luck with a 3 HP due to the derating factor of the drive producing 3 PH from 1 PH. The shaft is extra long. The motor is also among the missing, so if anyone has a serial number or similar motor, please provide the specs.
-Am I going to have trouble supplying a power supply for the servos with my current input power of 240V single phase? I'm not really sure on the sizing or voltage of the power supply, just know that it has to be roughly 100VDC. Is there a standard supply/voltage that is typically used? I'm competent electrically, but not clear on spec'ing components of this nature. I'm also a millright/industrial mechanic, so don't fear for my well being.
I thank you all in advance for reading and providing any helpful knowledge, I am grateful to benefit from such a broad knowledge base. Any comments or advice will be greatly appreciated. I do hope I've posted in an appropriate forum.If you require further information to answer my questions please don't hesitate to ask. I realize I'm asking for a lot of hand-holding, please humor me.
Thank you
Dale
Topwell Knee mill Retrofit 5-BVK
Posting Permissions
Reply with Quote