Help. Difference in power feeds?
Close
Login to Your Account
Results 1 to 14 of 14
  1. #1
    Join Date
    Sep 2019
    Country
    AUSTRALIA
    Posts
    13
    Post Thanks / Like
    Likes (Given)
    2
    Likes (Received)
    1

    Default Help. Difference in power feeds?

    Hi all and thanks for reading. In a nutshell I’m looking on Feebay for a replacement X axis power feed. There seems to be a choice of two units, both made in China. The first is about $210 and the second is around $450. Both units list the same specifications and have the same control layout and while they are similar they’re not the same.
    So, Has anyone tried one or know if there is a difference in the quality or just the price of these Chinese units. Thanks Stu.

  2. #2
    Join Date
    Oct 2012
    Country
    UNITED STATES
    State/Province
    Iowa
    Posts
    420
    Post Thanks / Like
    Likes (Given)
    162
    Likes (Received)
    96

    Default

    I started with a USA brand, Servo, for my Wells-Index mill many years ago, sold by Enco. I think I paid $600 USD. They had the custom mount that fit my mill. I've had problems with it shortly after when it would go full speed during a cut. I've never figured out what was wrong with it, but suspect the rheostat potentiometer as the problem.
    I purchase very low cost Y and Z axis power feeds from Align brand, that were fundamentally copies of quality units. Internally they were all quality gears and mechanisms, and simple TRIAC or SCR speed control circuits.
    They have worked well with no issues.
    They all have the same problem with a very small speed range in their potentiometer travel.
    Cheapest USA eBay cost for one of these is $115;
    AS-250 X AXIS POWER FEED KNEE MILLS FOR BRIDGEPORT MILLING MACHINE 0-200 RPM 895800908645 | eBay
    It looks the same as the units I purchase 25 years ago.

  3. #3
    Join Date
    Sep 2019
    Country
    AUSTRALIA
    Posts
    13
    Post Thanks / Like
    Likes (Given)
    2
    Likes (Received)
    1

    Default

    Thanks for your reply it has helped me out. I think the unit on my Chinese Bridgeport which is 20 years old has a stuffed potentiometer as it makes very little difference to the speed and the red indicator light doesn’t work but I my pull it apart and have a look before buying a new one. Cheers Stu.

  4. #4
    Join Date
    Oct 2012
    Country
    UNITED STATES
    State/Province
    Iowa
    Posts
    420
    Post Thanks / Like
    Likes (Given)
    162
    Likes (Received)
    96

    Default

    Quote Originally Posted by Scrounga2 View Post
    Thanks for your reply it has helped me out. I think the unit on my Chinese Bridgeport which is 20 years old has a stuffed potentiometer as it makes very little difference to the speed and the red indicator light doesn’t work but I my pull it apart and have a look before buying a new one. Cheers Stu.

    I know your cost in Australia will be more with VAT and exchange rate. The phase control circuit of the SCR/TRIAC is just too simple, and I've tried to see about making the potentiometer have a larger range, it's just the nature of the circuit. And as I implied even my high end power feed has that same issue. But the runaway speed control is not one I've had with the cheap China copies.
    The bigger issue is the installation to get the bevel gear backlash correct so that brass gear is not worn out by too loose or too tight a fit.

  5. #5
    Join Date
    Dec 2013
    Location
    Fort Wayne, IN
    Posts
    851
    Post Thanks / Like
    Likes (Given)
    878
    Likes (Received)
    305

    Default

    Pots rarely go bad on these, I have probably only changed out 5 or so for the pot actually being bad. Sluggish or no response to feed pot movement is normally something with the motor, whether it needs cleaned or parts need replaced.

    @ignator, you are saying that your Servo just randomly speeds up to full speed? Is it a 140 by chance?

    Jon
    H&W Machine Repair

  6. #6
    Join Date
    Oct 2012
    Country
    UNITED STATES
    State/Province
    Iowa
    Posts
    420
    Post Thanks / Like
    Likes (Given)
    162
    Likes (Received)
    96

    Default

    Quote Originally Posted by HWElecRepair View Post
    Pots rarely go bad on these, I have probably only changed out 5 or so for the pot actually being bad. Sluggish or no response to feed pot movement is normally something with the motor, whether it needs cleaned or parts need replaced.

    @ignator, you are saying that your Servo just randomly speeds up to full speed? Is it a 140 by chance?

    Jon
    H&W Machine Repair

    No issues with motor, just this runaway problem from time to time.
    Servo 150;
    20210426_140630.jpg

  7. #7
    Join Date
    Dec 2013
    Location
    Fort Wayne, IN
    Posts
    851
    Post Thanks / Like
    Likes (Given)
    878
    Likes (Received)
    305

    Default

    Are either of your brush holders kinda loose?

    Jon

  8. #8
    Join Date
    Oct 2012
    Country
    UNITED STATES
    State/Province
    Iowa
    Posts
    420
    Post Thanks / Like
    Likes (Given)
    162
    Likes (Received)
    96

    Default

    I'll check that. Thanks Jon

  9. #9
    Join Date
    Dec 2013
    Location
    Fort Wayne, IN
    Posts
    851
    Post Thanks / Like
    Likes (Given)
    878
    Likes (Received)
    305

    Default

    Also, when you have the brushes out, check for continuity between the metal of the brush holder and ground. Sometimes they will come from the factory with the set screw overtorqued and it cracks the plastic and shorts to the holder. This can cause weird and intermittent issues with speed as well as circuit breakers popping.

    Jon

  10. #10
    Join Date
    Oct 2012
    Country
    UNITED STATES
    State/Province
    Iowa
    Posts
    420
    Post Thanks / Like
    Likes (Given)
    162
    Likes (Received)
    96

    Default

    Quote Originally Posted by HWElecRepair View Post
    Also, when you have the brushes out, check for continuity between the metal of the brush holder and ground. Sometimes they will come from the factory with the set screw overtorqued and it cracks the plastic and shorts to the holder. This can cause weird and intermittent issues with speed as well as circuit breakers popping.

    Jon

    Jon, do you have a schematic for this power feed? Can you share it?
    I installed this years ago, and the manual never had a schematic.

  11. #11
    Join Date
    Dec 2013
    Location
    Fort Wayne, IN
    Posts
    851
    Post Thanks / Like
    Likes (Given)
    878
    Likes (Received)
    305

    Default

    A schematic or a parts diagram? I dont have a schematic, but the parts breakdown has a rudimentary wiring diagram in it.

    What exactly are you looking for?

    Jon

  12. #12
    Join Date
    Oct 2012
    Country
    UNITED STATES
    State/Province
    Iowa
    Posts
    420
    Post Thanks / Like
    Likes (Given)
    162
    Likes (Received)
    96

    Default

    I was looking for the circuit card schematic, for the velocity control. I assume it's a half wave SCR circuit. And yes I could spend the time to remove the card, and reverse engineer it, but I understand, the factory would sell the complete assembly, and component level repair is probably not done.

  13. #13
    Join Date
    Dec 2013
    Location
    Fort Wayne, IN
    Posts
    851
    Post Thanks / Like
    Likes (Given)
    878
    Likes (Received)
    305

    Default

    Oh, no I dont have a schematic of that. The circuit boards have gone through a few rev's through the years, but I have done some base component R&R on them.

  14. #14
    Join Date
    Jul 2001
    Country
    UNITED STATES
    State/Province
    North Carolina
    Posts
    2,170
    Post Thanks / Like
    Likes (Given)
    243
    Likes (Received)
    511

    Default

    Servo and their import copies have a dog clutch.
    This will cause problems when trying to reverse
    the unit after traveling forward. You have to
    wait for the motor to coast down before reversing.
    else you get a gear crash.
    Servo designed an Import line of their product
    called the Servo Dynamo. This unit uses a magnetic
    clutch instead of a mechanical dog clutch. This is
    superior because you can not crash the unit when
    going from forward to reverse quickly. Instead of
    the lever control handle, these models have a thumb
    lever knob, not a stick and knob type handle.
    Like I said, these have the Servo Dynamo name on them
    but they are actually imported. I have one and so
    do some of my friends. Really nice. I would never
    buy the old design Servo unit after using this one.
    There are copies. Shars Tools seems to make a good one.
    I have seen others out there with the same thumb lever
    identifier, have not tried them. Just a heads up on
    my experience with BP power feeds. As I said, after
    using the Dynamo type unit and the better clutch that
    it has, I would never go back to the old design.

    --Doozer

  15. Likes neanderthal mach liked this post

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •