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  1. #11
    Which do you call the X axis.? one with twin screws or single.?

    If it's the twin screw then this could be resonance from the long extension of the Z axis or tool deflection.? I get this on my machine when I'm pushing it too hard and too deep with large Z extension, thou I'm talking 3mm+ Doc in ALI.!

    There are ways round this.

    Lift the work closer to the spindle and keep the Z extension small as pos.
    Keep the tool extension out of collet short as pos.

    Take deeper slower cuts.!! . . Yep sounds crazy I know but there's more of the tool engaged so supported more. Try 1.5mm @ 800-1000mm/min 17,000rpm
    Use a slower full depth finish pass with a small 0.1-0.2 stepover.
    Try and clear the chips as much as possible, lube stops sticking but also clogs the slot and makes the chips stick which then get recut. This at best the gives a poor finish and if extreme can cause tool deflection and overheat then breakage. You can tell if recuts a problem because there'll be little random dents on the surface, not like what you have which is a nice wave rib thats why I think it's resonance from deflection, tool or Z axis.?

    I've found the best solution is constant low pressure air clearing the chips with the odd shot of coolant to help with stickage. Just keeping the slot clear with the odd blast of air works ok and better than just coolant but for best affect the air needs to be constant so all chips are gone. ( Gets bloody messy, you'll have chips darn ye kegs in crack your arse every where.!! Get the Sudocream ready.:rofl:)

    Personaly I'd just back off the feed, up the Doc and try again and clear the chips as much possible. If you need good finish then use a full depth finish pass.

    Edit: Looking at the pics again, it looks like you have cut the chamfer on the outer profile line.? Try using an offset so the centre of the V is not on the line. This will get rid of that little step you have.
    Some times the software will have chamfer tool path and in it there'll be an option to set the offset and it will calculate the rest to give you the correct depth for the chamfer length you need.
    If not then when you offset you'll lose a bit of chamfer length so just cut a little deeper to regain the lost length.
    Last edited by JAZZCNC; 23-02-2012 at 11:34 AM.

  2. #12
    X is the twin ballscrew axis here.

    Quote Originally Posted by JAZZCNC View Post
    Edit: Looking at the pics again, it looks like you have cut the chamfer on the outer profile line.? Try using an offset so the centre of the V is not on the line. This will get rid of that little step you have.
    I think that's the most likely cause. Was going to mention it yesterday...Since the centre of the tool is moving at a much lower speed than the outside it will not cut as well, as is the case with a ballnose cutter. If you move further out the speed is greater, and more consistent so it will cut efficiently with a sensible spindle speed and lower force, therefore lower deflection.
    If you're using a 90 tool then it's easy to work out. If the depth is equal to the offset then the tool is at zero. For instance if you add an offset of 3mm (using the allowance box in V-carve, or just select a 6mm cutter) and start at Z=-3 then the tool is at zero, so cutting down to Z=-5 will get a 2mm chamfer. In reality it's easiest to use this as a starting point and just lower the Z-axis until the chamfer looks nice as that generally matter more than the absolute value!
    Be wary of what the other side of the V-cutter is doing as clearly with too great an offset and nested parts you may end up cutting adjacent parts too much.

    What cutter did you use for the chamfer? I just use a standard 90 1/2" router bit.

  3. #13
    Eh Jonathan don't know if you saw hint in earlier post but I've gone and done it.!! . . . .She's now up against the wall. . It's . .:dance::dance:

    Should have done it months ago, it's still in test mode and one piece in case it didn't work or didn't like it.!!. . . .BUT BLOODY LOVE IT. . .so she'll be getting the chop and a face lift very shortly while I've got the Mig out on another job (Yes I've started Neil..lol)

    It works absolutly fantastic makes absolutly no difference to the performance, not had to change a thing. No retuning nothing.

    I've postioned it different to how said I was going to and the X Axis(twin screws) are vertical so gantry goes up and down, Y goes horizontal. Better this way for access and chips etc not falling on screws and just easier in general. . . . Down side being heavy gantry fighting gravity not lighter Y axis, which was a fear and why it didn't get chopped.
    Basicly it just got up-ended and lent/bolted against the wall for testing. . . . If didn't work then would have put it on it's side to try. If still didn't work nothing lost but several hours setting backup. . . . BUT MAN did it work, far better than expected. (Gob smacked me even!!)

    To test I cut several piece's of Ali at different depths and feeds like I would normaly with the max being 3mm DOC, using 6mm and 12mm cutter and it handled them no probs.
    Then as a test I did a 10MM single pass thru that resin impregnated MDF which is hard and abrasive full length of the machine 1200mm on the vertical up stroke where it's working the hardest against gravity at 7mtr/min which is basicly flat out on my machine(thou it's tuned down and capable of 11mtr/min) with a Knackerd 6mm single flute cutter in case it snapped and it didn't bat an eye lid. !!

    All the chips just fell away while cutting making perfectly clean cut, no chip recutting, no air needed (thou I will still use a little) with lovely nice neat pile of chips on the floor and when I make a tray/tank it will have full flood cooling with chip collector in the bottom . . . BUT BY FAR THE BEST BIT . . . I've got my work shop back because now it takes no more space than a double wardrobe. . :dance:. (Infact it's going to look just like a fat wardrobe when I put wardrobe doors on the front..:rofl:)

    It's still very rough at minute but when finished and properly in place and setup I'll post a thread.

    Edit: Sorry James I won't nick anymore of your thread, I'm just stocked with how well it's gone and Jonathan's one of the few who knew the plan.!
    Last edited by JAZZCNC; 23-02-2012 at 03:57 PM.

  4. #14
    Quote Originally Posted by JAZZCNC View Post
    Eh Jonathan don't know if you saw hint in earlier post but I've gone and done it.!!
    I did notice, but there's been a day since I read that post and I've been watching too much star trek so I forgot to respond!
    You've nicely proven the point that a bit more force, and therefore more mass, on the gantry doesn't make that much difference to the feedrate you can get which is why rotating ballnuts are so good even thought they add a bit of weight to the gantry. I wont bore you with the calculations but I'm not surprised it didn't make much difference to the feedrate.

    Does it still work as well when cutting on the axis which is still horizontal? I should think it would as the cutter will tend to throw the chips out...

    Originally I was going to go one step further (pun not intended) and mount mine on the ceiling ... but now it's too heavy for that. Perhaps I should reconsider.

    Quote Originally Posted by JAZZCNC View Post
    with a Knackerd 6mm single flute cutter in case it snapped and it didn't bat an eye lid.
    Do you regrind the single flute cutters when they get chipped or worn? I do and can get equal if not better finish after grinding the cutter by hand...

    Quote Originally Posted by JAZZCNC View Post
    when finished and properly in place and setup I'll post a thread.
    I look forward to it and not post any more on the subject in this thread.

  5. #15
    Quote Originally Posted by Jonathan View Post
    Does it still work as well when cutting on the axis which is still horizontal? I should think it would as the cutter will tend to throw the chips out...

    Originally I was going to go one step further (pun not intended) and mount mine on the ceiling ... but now it's too heavy for that. Perhaps I should reconsider.
    Last I'm going to say on james thread and I will start a thread later tonight when I get time so you and others can ask Q's. . . .But I'll answer this here.

    Yes it works almost as good thou obviously not got full gravity and clearence like on up stroke, but still far far better than when flat and like you say chips throw and fall away better.

    There is only one negative over conventional and that is clamping, well not clamping but holding the material while clamping. This is an easy get round and I'll just have an sliding rest that holds material while I clamp then slideout the way for cutting. This I think would be the biggest flaw to your Idea of ceiling mounting.!!

    Yes I regrind some times but usually when stuck for a cutter not as a matter of course. Thou I have got a nice little collection growing to give a friend to take to work for regrinding on a proper tool grinder.

  6. #16
    WOW Jazz I can't believe you've reinvented the wheel :rofl::rofl::rofl:

    what a great idea :idea: I think you suggested it to me some time ago and even suggested it in some one build post ??

    the only draw back I can see is length of material you could use(ceiling to floor distance) :naughty::naughty:and the fact you wouldn't use the front of the machine that much as it is near to the floor ??

    James:dance::dance:

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