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Thread: GME's New 80/20 CNC Build - My Design

  1. #49
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    Default Re: GME's New 80/20 CNC Build - My Design

    Quote Originally Posted by davida1234 View Post
    Yes, HDPE is slippery and I do not advocate that you use it as a spoil board. But the
    material checks most of the other boxes so it is a compromise you would have make.

    It also depends a bit on your style of holding material on a spoil board. I personally
    rarely use clamps as I don't like always making sure I don't hit any of those. Too easy
    to break a bit for my taste. I almost always drill some holes in the material and screw it
    down. If you are into serial production, those screw holes get bad pretty quickly in MDF.

    HDPE does hold screws very well and doesn't go bad with screw holes but it is not as
    easy to drive a screw first time into it as with MDF. A pilot hole works well but is not as
    convenient as with MDF or BB.

    I have both a BB plywood and HDPE as spoil boards for the Brygga, If you follow my
    thread, you can see how it will fare. I will make some videos with clamping and screwing
    down on the HDPE.

    Thanks, David. I'm thinking about BB for a base layer into which I cut dados for the t-track. I can then put MDF on top and cut slots to open up the t-track. The slots in the MDF will be the same width of the t-track slots, which means the MDF will overlap the top edges of the t-track. With this arrangement, you don't have to bother with screwing the t-track down. An elegant solution, but not one I came up with. It is explained by Peter Passuello at CNCnutz. He has some practical suggestions on his Youtube channel, CNCnutz. https://www.youtube.com/channel/UCQ3...lKOcjcaxkOfr6w, Episode 51, Don't Spoil Your Spoilboard, covers the basic idea.

    I've been following your very interesting and informative thread. Is it your plan to extend your design to something as large as a 4 x 4? I like the rotating ball nut concept, and have enjoyed watching the progress you've made. You are a talented guy.

    Gary




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    Default Re: GME's New 80/20 CNC Build - My Design

    I know Peter Pasuello and his site from Joe's Forum.
    He is a great guy and very resourceful.

    Yes, I do plan to offer Brygga models for purchase.
    Sizes will be from a 2x2 to a 4x4.

    I am not sure yet if it should be offered as DIY kits,
    semi-assembled or fully assembled and tested.



  3. #51
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    Default Re: GME's New 80/20 CNC Build - My Design

    I wound up spacing my t-track at 3" on center. What I just recently did is clamp down a piece of MDF that is a true spoil board that I can screw parts to as well as mill holes in for indexing pins for two sided machining. So far it's working out well and my table top is still pristine. I wound up doing it this way for a job I'm running that is a bunch of nested parts that needed to be held down in the middle of the material. I found the setup is much faster when you just screw the material down and mill the indexing holes straight through the material into the spoil board. It's also cheap to replace once it's chewed up and only takes like 30 seconds to clamp down to the machine bed with the t-track.

    Dan



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    Default Re: GME's New 80/20 CNC Build - My Design

    Quote Originally Posted by Ntl View Post
    What I just recently did is clamp down a piece of MDF that is a true spoil board. I found the setup is much faster when you just screw the material down and mill the indexing holes straight through the material into the spoil board.
    I do mostly the same except that I screw down the spoilboard-spoilboard to the actual spoil board.



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    Default Re: GME's New 80/20 CNC Build - My Design

    Quote Originally Posted by Ntl View Post
    I wound up spacing my t-track at 3" on center. What I just recently did is clamp down a piece of MDF that is a true spoil board that I can screw parts to as well as mill holes in for indexing pins for two sided machining. So far it's working out well and my table top is still pristine. I wound up doing it this way for a job I'm running that is a bunch of nested parts that needed to be held down in the middle of the material. I found the setup is much faster when you just screw the material down and mill the indexing holes straight through the material into the spoil board. It's also cheap to replace once it's chewed up and only takes like 30 seconds to clamp down to the machine bed with the t-track.

    Dan

    Thanks, Dan. I've toyed with 3" t-track spacing. 3" or 4" sounds about right. I've also considered using a "removable" spoilboard for those "special projects," like 2-sided machining. I like using the blue tape and super glue method of work holding, but it takes more setup time than using t-tracks and hold downs. Tape/super glue does work nicely when you need support at more than just the edges. It's also good when you don't want to use tabs (for whatever reason).

    Gary




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    Default Re: GME's New 80/20 CNC Build - My Design

    I went with 3" just because it makes the math simpler for setting up work pieces and setting the WCS so far I'm liking the spacing. I started at the center of the table and worked outward. Originally I wanted to do a grid with the t-track but it was going to be a bunch of work to get it right. I still need to add two more rows since I ran out of t-track since I changed my spacing. So far I'm liking the setup though, eventually the plan is to install aluminum t-slot plate when I have the extra dough.

    Dan



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    Default Re: GME's New 80/20 CNC Build - My Design

    It's Y axis linear rail installation time. Here's how I did it:


    I started out by borrowing an idea from CNCRP. They have a custom fixture they call a "rail alignment jig." IMO, it is a good idea for setting general alignment, but not to get the rail anywhere close to precise. CNCRP instructions tell the builder to fix one jig at each end of the axis, clamp the rail up against the jigs, and tighten all of the rail screws. That gets you a rail in a generally straight line, but if the rail isn't perfectly straight "out of the box", to a greater or lesser degree, you are going to get something shaped like a snake, or have a bow in one direction or the other. Even if the rail is perfectly straight out the box, just tightening screws can change things. Probably adequate for the user who just wants to get the machine assembled and running, and doesn't have the tools or skills to do it better. Good enough to work, but not anything like "precise".

    My first step was to fabricate two alignment jigs. The pics of the CNCRP depicts a pretty think chunk of metal (probably aluminum). Since I decided that clamping to the jig was unnecessary, I used thinner metal. I used a piece of 1/4" thick aluminum angle. Since the 90 degree junction is too large to allow the angle to site flat on the extrusion, and aluminum angle is notorious for not being square on the legs, I fixed everything on my mill. Here's a picture of the finished product:

    GME's New 80/20 CNC Build - My Design-img_0569-jpg

    I have to admit to a mistake. You will see 2 mounting holes drilled. I got my dimensions (I built it on the fly with the plan in my head) wrong, and 2 screws wouldn't fix next to one another. Turned out to not be an issue. One well tightened screw worked fine.

    The next step was to locate the jigs on the extrusion. I placed them about 34" apart, starting at the front end. With all of the screws in the linear rail, but loose enough to allow me to flex it, I pushed the linear rails up tight against the two jigs. Here's a photo:

    GME's New 80/20 CNC Build - My Design-img_0570-jpg

    Then, I placed my 36" Woodpecker straight edge up tight against the linear rail. (Note: the straight edge was one of Woodpeckers One Time Tools, which means orders were taken over less then a 30-day period, and once sales closed, the product is retired. This straight edge was ground to a tolerance of .0002"/12" - about as accurate as one could hope for. It is 2-1/2" wide and 7/32" thick. As between the linear rail and straight edge, the linear rail will flex first). Here's a photo:

    GME's New 80/20 CNC Build - My Design-img_0571-jpg

    With the straight edge still pushed tight against the linear rail at the jig points, I use 2 C-clamps to hold the straight edge into position. I then used a piece of .001" shim stock to check for gaps between the linear rail and straight edge. I then started 3 rounds of tightening the bolts within the length of the straight edge. I started from the front and worked toward the back. The first round was to get the screws barely snug. Then checked for gaps with shim. None. Second round was to snug the bolts down about half way between barely snug and and fully tight. Third round was final tightening. All went very smoothly and easily.

    The next step didn't exactly give me fits, but it made me do a bit of troubleshooting.

    I removed the C-clamps and moved the straight edge toward the rear 18". That left half on the part that was known to be perfectly straight, and the other half on the unsecured part. I replaced the C-clamp at the forward end, and the 2nd at the rear. The front half was tight all the way along, but the rear part had a gap of around .002". I was able to flex the rail, but it wasn't regular along the back half the straight edge. So I tried again. Same result. Tried a third time. Same result. Obviously, I was doing something wrong, but that "something" wasn't obvious to me at the time.

    When I regrouped, I put one C-clamp at the forward end, and a second at the midpoint. No gaps to the midpoint. Then, I added a third C-claim at the rear end of the straight edge. Success!!! I grasped the linear rail and held it tight against the straight edge as I when through the three rounds of tightening. Checked with .001" shim. Couldn't get it in over the 36" length of the straight edge.

    Using the same successful technique, I moved the straight edge to the far rear and clamped it in place (with 3 clamps).

    Here is a photo depicting the 3 clamps.

    GME's New 80/20 CNC Build - My Design-img_0573-jpg


    Install of the Y-axis master rail complete.

    Next up: Installing master rail on X-axis (gantry).

    Gary







    Attached Thumbnails Attached Thumbnails GME's New 80/20 CNC Build - My Design-img_0569-jpg   GME's New 80/20 CNC Build - My Design-img_0570-jpg   GME's New 80/20 CNC Build - My Design-img_0571-jpg   GME's New 80/20 CNC Build - My Design-img_0573-jpg  



  8. #56
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    Default Re: GME's New 80/20 CNC Build - My Design

    Looking good.



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    Default Re: GME's New 80/20 CNC Build - My Design

    Grabbed a bag of popcorn and i will be following closely this post!
    I was to build a machine a bit like cncrp pro 4x8 but i might start from scratch like you did !



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    Default Re: GME's New 80/20 CNC Build - My Design

    Gary it appears your machine is going to be pretty much like the Saturn2, even to the placement of the linear rail on the top. That leaves you no up/down adjustment (other than shims) and subject to the straightness of the aluminum extrusion. The CNCRP places their rail on the side to allow adjustments, they seem to have a proven design with no issues with accuracy.

    Last edited by wmgeorge; 05-08-2019 at 09:23 AM.
    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router Mach4 Kimber 1911 45ACP


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    Default Re: GME's New 80/20 CNC Build - My Design

    The CNCRP places their rail on the side to allow adjustments, they seem to have a proven design with no issues with accuracy.
    I don't think they mount them to the sides to provide adjustment. That's an adjustment that few of their customers would be able to do. They mount them with a jig, parallel to the rails.

    Extrusions are likely to be much straighter than steel, and short of mounting to machined surfaces, Gary's method is about as good as you can get. You certainly don't want to be shimming the rails.

    Personally, I prefer side mount, as it potentially gives you a flat edge to edge table, with no interference from anything,

    Gerry

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    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Default Re: GME's New 80/20 CNC Build - My Design

    They use a Jig to aline with the top of the rail, side mounting gives them a way to adjust the up/down if needed. Same method CAMaster uses. On top your counting on the top of the rail being perfect otherwise you need to shim. There is a reason why CNCRP does what it does. Steel rails can also be ground flat, if needed. Why would aluminum be more true than steel?

    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router Mach4 Kimber 1911 45ACP


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