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Thread: CNC Vacuum bed query...level issue

  1. #13
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    Default Re: CNC Vacuum bed query...level issue

    Quote Originally Posted by dragon_sa View Post
    I should be able to shim it reasonably easily unless its glued down, as you can see in the cross struts under the machine, so I will give that a go...the bed does appear to be a very hard rubber, its all 1 piece and been routed out on the machine, but I dont think it was done with the machine.

    The vacuum bed runs with 2 x 2.2kw vacuum pumps, vacuum ports are routed into the lower part of the bed as you can see in the pics also, the bed is broken into 4 vacuum sections which I can turn any of on and off, they also supplied rubbers to go into the grooves of the bed for isolating sections.

    I wondered how the vacuum bed worked with a spoil board, what is the recommended thickness mdf sheet for that?
    Do i use the rubbers in the grooves with the spoil board?

    Does mach3 have a surfacing function or do I need to setup a job in my cad/cam software?

    I dont have a surfacing tool, what would be a good one to get without spending hundreds of dollars?

    The cuts I have done so far are not too bad as I work out feed rates etc..

    The machine has delta servos and drivers and runs of an ethernet controller and uses a 3kw spindle.

    Really appreciate everyones help and feedback its been great thank you.
    You should post who the manufacture is of this machine, what I see under this machine is alarming for this size machine a single Ballscrew for this size machine is a bad idea

    From lack of table supports is why the table is not flat, when you machine plastic like this it is going to move all over the place, they machined this top after they assembled the machine

    Adding a spoil board is your best solution, and yes you will need rubber seal / gasket around the outside edge of the spoil board or how ever it works out with the slots to your sheet size

    I don't know how the spoil board is going to work out though, because once you turn the vacuum off the spoil board could move, you will want to mount it some way so it can't move after it has been surfaced and would have to use the vacuum every time you use the machine, not a great idea having to use the vacuum every time you want to cut something

    You may be better off to take this table off and attach a 2 layer MDF table top

    Mactec54


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    Default Re: CNC Vacuum bed query...level issue

    I would just screw the spoilboard in place with enough brass screws to prevent the MDF sliding around.Brass because when-not if-you make a mistake it will do the tool less harm.For cutting sheet material,I wouldn't bother with a rubber gasket as the sheer area allows the sheet to remain in place by virtue of it's surface area needing relatively little vacuum to generate a large clamping force.



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    Default Re: CNC Vacuum bed query...level issue

    Hi All

    Thank you for valuable information...Im a complete newy to these machines..my main products will be mdf and acrylics....template and cabinet based....maybe some signage..I have cut a few things and it seems to be ok apart from me working out feed rates and depth of cuts...correct cutting tools....actually lots of things

    The company is printed on the front...Acctek...the machine is completely hand made and you can see...there are lots of little...hopefully small issues to deal with...

    I should have room for some counter sunk screws in the mdf on the sides as the bed is wider and longer than the cutting area.

    You have brought to light the fact that the machine bed is only suspended from end to end...which is something I never considered/thought of...before making the purchase.
    I think if it is unable to handle the materials I want to cut ( mdf, laminated boards, acrylic) I may look at reinforcing the beams with an extra steal c section welded to each side to increase the span weight capacity...depending on cost and current performance aswell....I may be able to add an extra servo and ball screw to control the y axis..spread apart to the sides..possibly allowing the cutting of the sliding beam.

    Based on your feed back I am going to shim the bed on the rails...surface the rubber and add a 12mm mdf spoil board also surfaced and fixed down on edges beyond cutting capability.

    cheers all still open to any more feedback.



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    Default Re: CNC Vacuum bed query...level issue

    Quote Originally Posted by dragon_sa View Post
    Hi All

    Thank you for valuable information...Im a complete newy to these machines..my main products will be mdf and acrylics....template and cabinet based....maybe some signage..I have cut a few things and it seems to be ok apart from me working out feed rates and depth of cuts...correct cutting tools....actually lots of things

    The company is printed on the front...Acctek...the machine is completely hand made and you can see...there are lots of little...hopefully small issues to deal with...

    I should have room for some counter sunk screws in the mdf on the sides as the bed is wider and longer than the cutting area.

    You have brought to light the fact that the machine bed is only suspended from end to end...which is something I never considered/thought of...before making the purchase.
    I think if it is unable to handle the materials I want to cut ( mdf, laminated boards, acrylic) I may look at reinforcing the beams with an extra steal c section welded to each side to increase the span weight capacity...depending on cost and current performance aswell....I may be able to add an extra servo and ball screw to control the y axis..spread apart to the sides..possibly allowing the cutting of the sliding beam.

    Based on your feed back I am going to shim the bed on the rails...surface the rubber and add a 12mm mdf spoil board also surfaced and fixed down on edges beyond cutting capability.

    cheers all still open to any more feedback.
    You would want screws in the middle as well or where ever there are supports then you won't have to run the Vacuum each time you want to cut something, 12mm would be too thin 19mm would be more ideal, this would give you more resurfacing options just remember you have to take probably more than the 1.5mm off to start with and counter sink the holes there would not be much for your screws to hold it down if you use 12mm

    Mactec54


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    Default Re: CNC Vacuum bed query...level issue

    The reasons I advocate 12mm MDF are that it is thin enough for the vacuum pump to draw air through easily and that in my climate a change in atmospheric humidity won't give too much of a change in thickness.As it is I currently have 95% humidity,in a couple of days it might be 65%.These changes cause MDF to move a bit and the thicker the material,the greater the amount of movement.

    For several years I have held 12mm MDF on a router using 1"X6 brass screws it was never a problem as there were just enough to prevent the spoilboard sliding and we didn't have any other hold down arrangements than a vacuum.If a smaller job needed to be held I used a carrier sheet of 9mm ply screwed to the workpiece with brass screws or several pieces of good quality double sided tape.For the machine we are discussing here I would be seeking to minimise the weight I added to the table to keep any sagging to a minimum.



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    Default Re: CNC Vacuum bed query...level issue

    Quote Originally Posted by dragon_sa View Post
    Based on your feed back I am going to shim the bed on the rails...surface the rubber and add a 12mm mdf spoil board also surfaced and fixed down on edges beyond cutting capability.

    cheers all still open to any more feedback.
    Here is a video on how to make a duel purpose table and you will get the best of both world vacuum and a T track top, you can make this any size you want to suit your machine



    Mactec54


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    *Registered User* dragon_sa's Avatar
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    Default Re: CNC Vacuum bed query...level issue

    Thanks everyone....I have shimmed the bed now..wasnt that hard in the end..I am going to go with a 16mm spoil board, I will run the surface planer over my rubber bed first, that will act like the first layer in that video, then take a skim off both sides of the spoil board then laminate the edges, I will then fix it down to the bed with counter sunk brass screws and hopefully good to go



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    Default Re: CNC Vacuum bed query...level issue

    Its good to know that the shimming went well.You appear to be well on the way to success and your plan looks very promising.I do believe that you would be able to just skim one side of your spoilboard, rather than both as the objective is to ensure that the working surface is parallel to the Z plane of the machine.



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    Default Re: CNC Vacuum bed query...level issue

    I'm new to cnc as well but I'd surface both sides of the spoil board, while you do want to ensure that the spoil board is flat the reason you've been told to surface both sides is to remove the hard surface on the MDF to allow better draw from the vacuum motors.

    Good luck
    Gary



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    Default Re: CNC Vacuum bed query...level issue

    Quote Originally Posted by Gary-Wiant View Post
    I'm new to cnc as well but I'd surface both sides of the spoil board, while you do want to ensure that the spoil board is flat the reason you've been told to surface both sides is to remove the hard surface on the MDF to allow better draw from the vacuum motors.

    Good luck
    Gary
    Cheers...taking the hard finish off is spot on why both sides...I am also going to route a 1mm groove in the back of the spoilboard where the rubbers are so they dont get crushed



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    Default Re: CNC Vacuum bed query...level issue

    I don't understand what kind of 1mm groove you are proposing or it's purpose as the total force acting on the board is a function of the area and the level of vacuum.Could I suggest testing the vacuum force generated before surfacing anything,then again after surfacing one side and finally after skimming both sides?The answer would be of interest.



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    Default Re: CNC Vacuum bed query...level issue

    Yeah that information would be interesting. Also check with your lumber supplier & see if you can get an LDF or ULDF



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CNC Vacuum bed query...level issue

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