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  1. #21
    Quote Originally Posted by GTJim View Post

    What are your thoughts on these Chinese screws as I dont want to work to microns?
    I dont know about other chinese ballscrews but I have bought and fitted dozens from Chai at linearmotionbearings and they are very good considering the money. . . More than good enough for Diy.
    I have some of chai's screws on my big machine and they are just starting to show signs of wear after 3 years of very very hard use cutting mostly Ali plate and in the worst possible conditions due to the fact they are uncovered and partly in the firing line.!! . . It's one of them " I'll do it later" jobs that after 3yrs still aint got done.!!! . . . .

    BIG TIP . .DONT Start the bloody thing up untill you've done every thing you planned else they'll never get done.!! . . . So much fun you'll never want the down time.

  2. #22
    Quote Originally Posted by JAZZCNC View Post
    BIG TIP . .DONT Start the bloody thing up untill you've done every thing you planned else they'll never get done.!! . . . So much fun you'll never want the down time.
    :heehee: Yep I agree entirely. That's why I don't have any switches on it, or covers and only crude dust extraction ...

    My ballscrews are also from Chai. Only just got round to putting better computer on it that I've had for a while. What a difference...RM1610 screw on Y-axis is now going at 36m/min which is the critical speed and it seems fine. I wonder what their limit is :naughty:

  3. #23
    Quote Originally Posted by Jonathan View Post
    :heehee: Yep I agree entirely. That's why I don't have any switches on it, or covers and only crude dust extraction ...
    No Switch's.! . . Not even Home switch's.?

    Next to touch probe the Home switch's are the best and most time saving thing you could put on your machine. Can't count the number of times they'e got me out of trouble. . . must be in the hundreds.
    They must have saved me hundreds of pounds in material that would have been lost or wrecked due to loss of position when an error or tool breaks. . . . . Nothing worse than a tool braking after several hours cutting one job. . . No problem and Simplizz's with home switch's.
    Send machine home to reset it's position, rewind the code to just before the tool broke and away you go again. . . Brilliant.

    No limit switch's on the large machine, IMO you can live with out them on larger machines, soft limits are more than good enough and in the 3yrs using the big machine I've never hit the hard stops or the soft limits other than me trying to drive the thing into them.

  4. #24
    Quote Originally Posted by JAZZCNC View Post
    No Switch's.! . . Not even Home switch's.?
    Nope...I did get round to wiring one switch but it's not attached yet. I generally either make a mark at the home position with the tool to reference from if it stalls, or note the position of the ballnuts or screws. Granted that's not as quick as homing assuming it'll home at a reasonable percentage of the rapid feedrate. One day I'll do it...

  5. #25
    Quote Originally Posted by Jonathan View Post
    Nope...I did get round to wiring one switch but it's not attached yet. I generally either make a mark at the home position with the tool to reference from if it stalls, or note the position of the ballnuts or screws. Granted that's not as quick as homing assuming it'll home at a reasonable percentage of the rapid feedrate. One day I'll do it...
    Jonathan Honestly do it ASAP you wont regret it I must use it 1 in 3 times I use the machine. Infact only to day I was cutting some a parts which had small bearing pockets and followed by an outer profile pass.
    The code rough'd the pockets first then was to finish them with 0.2mm pass, now I'd forgot to the set code to continue with out stopping between rough n finish pass's so when it went to x0,Y0 and stopped I thought it wanted a tool change so changed for the outer pass tool.! .
    When I hit cycle start it went on it's way at full rapid 10mtr/min. . . But to the wrong place. . . . . Luckly I was watching and hit the Oh-shite button before it did damage. Now as you know at full 10mtr rapid to dead stop it obviously lost position probaly not too much but it did.
    This I probably could have got away with doing it your way for the non critical outer profile pass but my pockets where 0.2 under size and this I couldn't live with so part would have been lost.

    With home's it was a 2 minute affair.! Send it home, change tool back and reset tool height, rewind code with "run from here" to finish pass and away I go back on track and in precise position. . . . . Thats why there so good.:tup:

    Edit: Actually the part wouldn't have been lost and I could have made use of the next best thing to you can add to a machine "The PROBE" . . Could have Probed to find the centre of the pockets and tracked my way back from there, works good but still not ideal and more time consuming.
    Last edited by JAZZCNC; 02-09-2011 at 08:41 PM.

  6. #26
    Hmm, I guess I'll do it when I attach the profile rails as that'll require a few changes anyway. I can get it plenty accurate enough generally by eye or zeroing from a hole but obviously it can take a while.

    Just got my Y-axis going at 51m/min! Seems reliable at that...I don't think limit switches would be much help at that speed!

  7. #27
    Quote Originally Posted by Jonathan View Post
    Just got my Y-axis going at 51m/min! Seems reliable at that...I don't think limit switches would be much help at that speed!
    !!!! . .51M/Min .. !! . . . . What you using for motors.? Servo's.? Thats 5000rpm with 10mm pitch. . . . What stepper you got to do that speed and still give torque enough to drive gantry etc.?
    Also what you using for drives and computer because if Mach you must have a good computer and parallel port that will let you set the Kernel high enough to give them speeds.?
    Think even my smooth stepper would struggle to get usable steppers to that speed and that blows the PP away.!!

    Please Dont take my asking has me not believing you, I honestly do and I'm genuinely interested how you've done it.! . . . . Does the rotating nut make that big a differance on a small machine.?
    Post a video bet it looks amazing. .

  8. #28
    I'm not doing anything special really but yes it's a bit hasty. It's not for long though as the acceleration is only 2m/s^2.

    I just got 1m/s! Will post a video soon...

  9. #29
    GTJim's Avatar
    Lives in Coventry, United Kingdom. Last Activity: 2 Weeks Ago Has been a member for 8-9 years. Has a total post count of 110. Received thanks 3 times, giving thanks to others 20 times.
    I've just started looking into the possibilities for pulleys for the ball screws and stepper motors.

    I understand HTD belts have been recommended, but my problem concerns the spindle on the motor I'm considering, it's Dia 8mm x 21mm long approx. I don’t really want to use a belt less than 15mm wide but can't find a pulley to fit the length of the motor shaft.

    What has been used before, any ideas?

  10. #30
    The pulleys I use on steepers are HTD 20T 15mm they measure 25mm wide with 5mm boss. You can either use 4mm set screws thru the boss which leaves the shaft 3-4mm short of being flush.
    Or do like I do and drill in the middle of the pulley between the teeth with a larger 5 or 6mm set screws which allows better purchase, just make sure the head of the screw sits below the bottom of the teeth.
    This hisn't a problem because of the wider OD of the teeth theres more metal to work with. Then I either machine the boss down less so the pulley sits flush or some times dont bother and just turn the boss to the outside.

    Unfortunatly I haven't got any machined to show you but I do have some unmachined pulleys which I've just taken pics of to give an idea of what I mean, also give you some idea of scale against a nema 23 stepper.
    The set screws are M5's note the blue tak holding them took me 15 mins before I gave up trying to balance them in those groves.:whistling:

    I've never had any problems with slipping doing it this way even with just one set screw, thou I always use at least 2, some times 3 120deg apart.!

    Other option if going thru paltes etc is to have some extension shafts machined, thou not too long. Either Jonathan or I could do that for you if no access to lathe.
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