Results 1 to 5 of 5
  1. #1
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    23,068

    Default Mechanised DP table height control.

    A few years ago I picked up a box of linear actuator sfrom a hospital demolition site. The beefiest one was this beaut used "cherman" actuator, powered by 240V and switch control is via two pressure switches. Activating one of the pressure switches drives it in and the other drives it out. It has a 200mm stroke, rated to lift 65 kg and it has fuses in the control box to protect against accidental overload. I think it came out of a hospital bed or chair.

    I played around with a few ideas about how I would use it but recently after struggling with adjusting the height of my DP table after adding the extra heavy 5" cross slider vice to it, I thought I would have a crack at using the actuator for this purpose.

    I should add I already have a home made "easy riser" on the DP and some 20kg of lead counter weights but fine adjustment of the table height is still tricky. Typically I find the table just a tad too high or a whisker too low. To make that last adjustment I typically loosen the column clamp enough so the tables doesn't just slide down the column and swing the table slightly from slide to while applying a small up/down force - like I said its tricky.

    In the last week I have slowly built enough of the support mechanism so I could at least try it out to see if would work.

    Here is a short vid showing how far I have got that shows how it works.


    To generate the the pressure needed for the pressure switches I temporarily forced the tips of two long plastic pipettes into the pressure switch inlets. Squeezing one pipette makes the actuator go up the other makes it go down.

    IMG_3709.jpg

    I had no trouble getting the table to go up but the table arm would intermittently jam on the column when the table was going down - then it dawned on me the "easier riser" was tilting the column clamp and causing it to jam. It's not completely jam free going down but perhaps some extra lube will sort that out

    When it gets to the top of its stroke, if the "up" pressure switch is held under pressure the actuator motor keep running but as it's run out out of thread the piston/rod doesn't go any further. and just sits there with the thread rotating inside it.
    At the bottom of its stroke the actuator piston/rod rotates, so to prevent wear between the underside of the table and the top of the actuator arm I have added a large roller ball like this.
    I will replace the pipettes with something more suitable once I get all the mechanisms sorted
    IMG_3707.jpg

    The bottom of the actuator is bolted to a circular platform that can be jacked up and down using a small hydraulic car jack. This will be employed to generate the lift required to preposition the table and actuator when the 5" cross slide vice is not in use.

    The 6mm thick steel platform rides on 20 mm steel rods that slide up and down in holes machined into the brackets bolted to the DP base. Ance the actuator is fully lowered the actuator and platform can be completely lifted out of the way if required.
    IMG_3708.jpg

    There's quite a bit more to do before I feel safe in using it.
    It will need an interlock on the column clamp - if that is tight I would like the up pressure switches to be disabled otherwise I will be replacing a lot of fuses.
    Then I do still want to be able to swing the table to either side so a curved plate bolted to the underside of the table bracket will be needed.
    An of course better switches than a couple of pipettes

    The expected use is just lowering and raising the table but once a hole is started it might be possible to use it to drill holes longer than the DP stroke. The 65kg force the actuator can generate should be more than enough for this sort of thing especially in wood.

  2. # ADS
    Google Adsense Advertisement
    Join Date
    Always
    Location
    Advertising world
    Posts
    Many





     
  3. #2
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    23,068

    Default

    I've done a bit more on the DP auto riser/actuator.

    Clamp to hold the actuator vertical to the DP column.

    Clamp5.JPG

    Gizmo to still enable the table to rotate 45 either side of centre position.
    RotationPlatform2.JPG

    Interlock so the power is cut to the actuator when the table is locked to the column.
    Interlock1.JPG

    When the red LED is lit this mean the table is no longer locked to the column and there is power at the actuator so it can be used.
    Interlock3.JPG

    More details in the MWFR thread if you are interested.
    Mechanised DP table height adjustment

  4. #3
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    23,068

    Default

    Lick of paint and it's ready to do some work - not going t worry about the other interlock - let's see if I blow some fuses.

    AllDone.JPG

    Still deciding about whether I will do something in place of the pressure switches, kinda like the quirky way they work now.
    Meanwhile it needs to get back to work.

  5. #4
    Join Date
    Dec 2003
    Location
    lower eyre peninsular
    Age
    70
    Posts
    2,044

    Default

    you got any farming history, Bob, Ive seen farm workshops where anything is possible and if its not possible then lets fluff around and get one made.

    Love your inventiveness
    Life expectancy would grow by leaps and bounds if green vegetables smelled as good as bacon.

  6. #5
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    23,068

    Default

    Quote Originally Posted by Tonto View Post
    you got any farming history, Bob, Ive seen farm workshops where anything is possible and if its not possible then lets fluff around and get one made.

    Love your inventiveness
    Cheers TT.
    No farming history but most of my relatives are pretty inventive/innovative.
    My bro is into customising cafe racer motor bikes.
    Two cousins run a CNC operation that uses timber stock up to 13m long and 600 x 600 mm in cross section. Timber in, and all the bits needed to make a house come out. It's pretty mind-blowing.
    Other cousins developed a printing anything on plastic technology, its a production line process - two blokes can print many thousands of products a day, anything from logos on sports shoes, ski boots and Motorcycle boots to clothing labels, sporting goods there's no end to it.
    One of my cousins runs a specialised/custom electric motor factory. Nearly all the motors run on single phase but internally are 3 phase and come standard with built in VFDs.
    One relative was a very creative custom jeweller another is into fabric painting and has invented many innovative processes, she is also a pretty fair abstract picture painter as well..
    And one uncle is pretty good at brewing many flavours and strengths of grappa!

Similar Threads

  1. Scroll saw table height
    By Lyle in forum SCROLLERS FORUM
    Replies: 14
    Last Post: 28th Oct 2015, 12:53 PM
  2. Bandsaw table height
    By Big Shed in forum BANDSAWS
    Replies: 9
    Last Post: 22nd Jun 2007, 12:36 PM
  3. Bandsaw table height
    By derekcohen in forum BANDSAWS
    Replies: 6
    Last Post: 20th Jun 2007, 11:04 PM
  4. Bandsaw Table Height
    By watson in forum BANDSAWS
    Replies: 6
    Last Post: 28th Oct 2006, 05:25 PM
  5. Table Height
    By Corunetes in forum WOODWORK - GENERAL
    Replies: 10
    Last Post: 10th Nov 2005, 08:54 AM

Posting Permissions

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