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Discussion in 'General Talk' started by Dean Suominen, May 29, 2017.

  1. Dean Suominen

    Dean Suominen Well-Known
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    New to CNC and 3D software but I'm jumping in head first and building myself a 4'x8' machine on a tight budget. As I get more experienced the plan is to upgrade and modify the build with stronger components for the drive. I chose using belt and idler pulleys for the X and Y and ACME screw for the Z. Eventually going for rack n pinion for the X and Y or possibly a screw for the Y, dunno yet.

    From what I've read, a 4x8 table is a big build and has lots of obstacles in terms of accuracy. The largest material I'm currently planning on cutting is 4'x8'x1" MDF and 4'x8'x3/8" polycarbonate. Once I get the hang of things (on the software side) I would like to do more intricate pieces.

    Being so new to CNC, my biggest hurdle is the CAD software in a 3D space. Any suggestions for something relatively easy to use and make basic pieces would be very welcomed. I have downloaded trials of MACH3 and 4, QCAD CAM, Design Spark, FreeCAD, HeeksCNC and SprutCAM. I have yet to really get used to them and have seen "drag n drop" style software which I would appreciate anyone that has had an easy time with certain ones.

    Cant wait till my parts get here!
     
  2. Grantman

    Grantman Veteran
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    Your biggest obstacle in accuracy will be the 8' rubber bands moving the gantry.

    Planning my build, so "tight budget" gave me a chuckle. Seems to me building a large mill is akin to hot-rodding cars/trucks/bikes. Price your build, penny to the ridiculous, then double it.
     
    #2 Grantman, May 29, 2017
    Last edited: May 29, 2017
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  3. Dean Suominen

    Dean Suominen Well-Known
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    True that! The hotrod section of the garage is on the other side hahah! The C Beams here are awesome! The concept alone saved hundreds and their versatility is phenomenal... and I havnt even held one yet. If I can initially get an accuracy of .0625 or even as high as .125 my projects would be more than acceptable. In my head, running a single pass belt on each side of the gantry along the X and having 2 stepping motors roll along the belt using idler pulleys for tension around the pinion, seemed to be the most affordable and flexible solution. With the same concept, I could easily lower the motors and swap pulleys for gears and run gear racks later on and reverse the motors. I quickly opted out of trying to use a 102" long ball screws for obvious reasons... cost, stability, heat/cold variances, cost... did I say cost? (the list goes on).

    For a gear drive on the X and Y, have people found using direct drive better/worse than a reduction assembly in terms of lash? Again this build is basically a cool way of removing all the legwork in chopping parts out of a 4x8 sheet and trying to use a jigsaw to cut circles.

    I think I got everything built in my head using these parts (the tables table excluded):
    1/4" x 8mm Flexible Coupling 155 1
    3GT (GT2-3M) Timing Belt - By the Foot 626 / By the Foot 30
    3GT (GT2-3M) Timing Pulley - 20 Tooth - 9mm Belt - 8mm Clamp Bore 2130 2
    8mm Metric Acme Lead Screw
    (Length: 250mm) 25 - LP 1
    8mm Shim 835 4
    Aluminum Spacers
    (Size: 40mm) 95 9
    Anti-Backlash Nut Block for 8mm Metric Acme Lead Screw 1055 1
    Ball Bearing 688Z 8x16x5 780 2
    C-Beam® Linear Rail
    (Length: 1500mm) 50 - LP 6
    C-Beam™ End Mount 965 1
    C-Beam™ Gantry Plate - Double Wide 2026 4
    Delrin V Wheel™ Kit 500 32
    Eccentric Spacer
    (Length: 1/4") 70 16
    Idler Pulley Plate 570 4
    Lock Collar
    (I.D.: 8mm) 840 2
    Low Profile Screws M5
    (Length: 8mm) 946 - pack 8
    M5 Drill Tap 116 2
    Motor Mount Plate - NEMA 23 Stepper Motor 910 2
    Smooth Idler Pulley Wheel Kit 550 4
    Threaded Rod Plate - NEMA 23 Stepper Motor 920 1
    Timing Belt Tension Torsion Spring 75 10
    3GT (GT2-3M) 9mm Timing Belt - Closed Loop 2120 1
    3GT (GT2-3M) Timing Pulley - 20 Tooth - 9mm Belt - 8mm Clamp Bore 2130 1
    Aluminum Spacers
    (Size: 40mm) 95 20
    Aluminum Spacers
    (Size: 3mm) 175 10
    Cast Corner Bracket 490 12
    Idler Pulley Plate 570 1
    Smooth Idler Pulley Wheel Kit 550 1

    Like building anything in your head, there is bound to be "OH CRAP" moments when everything is laid out and ready to assemble, AAAAAANNNND I forgot some parts....but then again that's half the challenge. Weight reduction makes it go faster right??? LOL
     
  4. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Solid V-wheels are stiffer and will generally provide better results.
     
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  5. Dean Suominen

    Dean Suominen Well-Known
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    How does the aluminum handle the hardened wheels?? I contemplated them but after seeing the wear and tear on aluminum over the years i figured the steel wheels would dig into the c beams.


    *edit* OH yeah those, i went with the V incase i wanted to try and use the rails on here rather than buying bunches of different wheels.
     
  6. David the swarfer

    David the swarfer OpenBuilds Team
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    Since most of the stuff you will cut on a big flat router is big flat things ... we call this 2.5D in that you have 3 axes that move but most cuts are just the X and Y moving and Z is constant depth. as when cutting a flat sheet into parts.

    And the easiest to use CAD -> CAM solution is Sketchup + SketchUcam. You don't even need to do any 3D drawing at all since SketchUcam cannot use it anyway, it uses simple flat 2D drawings.

    Once you run out of things you can cut with that you will want to do real 3D cutting, and for that I recommend Fusion360 (free for personal use). I have used it for a few hours and it really is impressive. More useful though is the large body of howto videos on Youtube.

    Keep in mind that anything you choose will have a learning curve, some steeper than others. Sketchup + SketchUcam will allow you to cut parts TODAY. This way you can be cutting parts while you are learning the more complicated software.

    Just like mathematics which is a method of thinking , CAD/CAM is also a method of thinking, which takes time to learn.

     
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  7. Giarc

    Giarc Master
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    If you do an ox style, you can do a 1500 mm x 1500 mm and feed the sheet through using pin-hole registration. You would have a much better machine because you could use 6 foot 1/2 - 10 5-start acme threaded rod from Mcmaster-Carr. They are cheaper and more accurate than all the belting. At least they were when I bought mine. You would also not have to worry about joining c-beam pieces end to end.
     
  8. Dean Suominen

    Dean Suominen Well-Known
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    WOW great responses David and Giarc! Thank you.

    I have been using Designspark for a few days now (the drag and drop extrusion feature is amazing) to take in my head measurements to drawing then being able to fit the pieces together and see discrepancies. I was looking at SolidWorks but the $6K price tag is a little out of my reach. The 2.5D routing is what I intend to start with till I get the hang of the G Code and thinking in terms of coordinates and the programming, then all 2.5D work will probably be just written instead of drawn then converted. I just downloaded Sketchup and SketchUCAM and will see what I can do with those... Looking into Fusion360 now....

    Giarc, the ball screw was an initial option but the cost was a LOT more than belting. Rack and pinion is a next step upgrade. as for the conjoining C-Beams, I can design my work/material layout to "skip" over the seam so the gantry doesn't have to roll over it to complete the piece. Basically 2 5x5 routing tables sharing a single router.

    Much appreciated on the responses!!! Thank you!
     
  9. Dean Suominen

    Dean Suominen Well-Known
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    Note to self: dont order parts dead tired. The pulleys are 9mm and the belt is half that (read complete listing first 20/20 vision)... Just received my order today... now I see how the belt is going to be a problem.
     
  10. Grantman

    Grantman Veteran
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    Been there, done that. Luckily the last time stuff hadn't shipped so I managed to cancel. Looked at my order the next morning,"90-90° angle brackets???? Was I high??? Cancel!! Cancel!!"
     
    #10 Grantman, Jun 2, 2017
    Last edited: Jun 3, 2017
  11. Dean Suominen

    Dean Suominen Well-Known
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    LOL and now I have 200 8mm screws that need a place to go that don't really fit anywhere... decorative studding coming up....
     
  12. Grantman

    Grantman Veteran
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    Eh, could be worse. Could be 40 mini-v wheels that you didn't need. Luckily after fondling them a bit I'm finding them rather versatile and using them up.
     
    #12 Grantman, Jun 3, 2017
    Last edited: Jun 3, 2017
  13. Dean Suominen

    Dean Suominen Well-Known
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  14. Grantman

    Grantman Veteran
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    Been thinking about your build and butting C-beams. A 20x40 makes a nice joiner if you're not using the channel and a gap wouldn't matter if you have enough wheels bridging it.
    Really liking the look of Estlcam, pretty intuitive.
    20170603_142648[1].jpg 20170603_142707[1].jpg
     

    Attached Files:

  15. Dean Suominen

    Dean Suominen Well-Known
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    That's basically what my intention was to use itself as a connector. After going through all the parts I ordered, I have realized in a grumbled face palm moment that these parts aren't a completely interchangeable "build whatever you want" system. The plates are specific to a size of wheel, the gaps are specific to a design and hardware/spacer, and the pieces aren't going to work for my build as intended. I've spent the day in the garage laying the pieces out in multiple positions and combinations to come up with "its not gonna work". Back to the drawing board and parts store.
     
  16. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    If you could give us a better idea of specifically what you're attempting and what's not working we might be able to save you a few trips to the parts store. A Sketchup model or any hand sketches would be great if you've got them.
     
  17. Daniel Harbin

    Daniel Harbin Well-Known
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    I was looking at this type machine the Maslow CNC. Maslow CNC - a $500 open source 4 by 8 foot CNC Machine I dont invest in Kickstarter programs as I want to buy a proven concept. But you said low budget and this fits your requirements, otherwise a decent 4x8 cnc would cost at least 2K depending on your materials. Dunno about the accuracy claims as the router is kinda freewheeling and it might only be good for cutting out parts and not any sculpting or 3D.

    I was looking at it because of the compact size and portability, at least it looks portable.
     
  18. Dean Suominen

    Dean Suominen Well-Known
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    Daniel, I seen that video... neat concept and very economical, and yes specific for cutting out large scale shapes from 4x8 stock. Not exactly what I am looking for in a build but it was a consideration!

    Rick, I had several ideas flowing through my head when I bought everything, and the ideas collided and mixed themselves up. In retrospect, something similar to this: Stainless OX but big enough to cut a 4x8 sheet and possibly some finer more detailed work once I get the hang of the software and code. Now that I am going back and looking at more of the specific examples, I purchased everything under the guise that there was a lot more flexibility in mounting options for linear motion. On one hand I initially found this website and this community by searching for linear rail pieces after finding double V wheels, then seeing how the C-Beams are designed to accommodate the V wheels directly into the slots, I lost sight of the OpenRail (but kept the larger wheels).

    The table I have planned in my head is to be a routing table, large scale plotter/printer, maybe laser/plasma cutter and possibly a 3D printer in one small section. Construction as planned 4 C-Beams for Y (2 on each side end to end), approximately 15" of clearance between a finished waste board (planed) to the bottom of the X axis C-Beam (60" wide) and a Z axis with 7" of travel with adjustable height depending on the work being done. If all things considered, it is my understanding that once a waste board has been set, if it is moved and put back in to place, it will loose its accuracy/orientation with the router head and will need to be re-done. In the event that it is removed and a steel sub structure is installed for cutting with plasma, I am fine with that, MDF is cheap. The support table I am building to put this all on is being made out of T slot aluminum I won a bid on from 8020inc. This t slot is awesome!!

    Looking back at the parts store, instead of 4 of the double wide gantry plates, I should have purchased the XLarge gantry plate. My intention was to use a double wide plate for the top wheels and one for the bottom wheels and have a vertical C-Beam connect them between the Y rails while rolling on the top/bottom of the Y axis and have the Y C-Beams supported on the outside of the table. It was very late when I ordered and for some reason I thought 4 wheels could be mounted along the edge of the double wide plates (they can but not full sized double V wheels, only the mini's) The original plan with the OpenRail system is still an option and being considered with the metal V wheels as a future upgrade, and then SBR20 supported linear shafts and bearings if I get any good with this.

    I have a 2'x3' piece of 3/8" T6 aluminum left over from a project for one of my vehicles that I have decided to cut custom gantry plates out of for the double v wheels using the double wide gantry plates as a guide. I might be a little on the ambitious side with this build and its expectations, but after seeing how each of these plates I have are used on the website, I will probably wind up making a much smaller machine with them for fine detailed routing/engraving.

    My initial challenge was based on the preconfigured kits all over the internet and the thought that I could build something bigger and just as good if not better for the same price while learning along the way. That idea was quickly put to shame when I started pricing the lengths of SBR16 and SBR20 shaft rails, the lead screws and ball nuts and found they are geared more for industrial quality machines with industrial sized budgets. I was attempting to build a machine for under $1500 which I am well past after buying odds and ends tooling (saw blades etc), wiring, limit switches, connectors, fasteners, frame structures and on and on.

    Once I get the hang of Sketchup, I will post a "this is what it should look like". I have only recently started exploring 3D cad software (coughs, a couple weeks) but I am familiar with AutoCAD since release 12 back in the early 90's enough to draw 2D concepts then cut them out using hand tools. It is a lot of information to cram and as stated in so many posts, a steep learning curve going from CAD to CAM to building and understanding the machine its all being used on all at the same time.

    All part of the challenge.

    The stuff I will be cutting at first will be components for advanced design speaker enclosures, furniture parts, engraving tabletops, geometric shape artwork, polycarbonate fabrications, computer cases, miniatures (doll house parts for my wife) and other stuff she thinks is neat.
     
    #18 Dean Suominen, Jun 4, 2017
    Last edited: Jun 4, 2017
  19. Dean Suominen

    Dean Suominen Well-Known
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    router1.jpg router2.jpg router3.jpg OK... I bashed my skull against the keyboard a few hundred times... still cant find the apostrophe... and came up with these drawings. Sketchup is an AWESOME program!!! Thank you and congratulations to those that took the time to draw up each component for the OPENBUILDS library! Now if I could only afford DesignSpark.

    Anyway, the pics are the basic concept of my design as best as I could master Sketchup in 4-5 hours. Rather than having just the router move along the Z axis, I want the whole Z axis to move. Was thinking about having the whole X gantry move up and down doubling the design of the Z axis but figured the weight would be too much and would take 5 motors instead of 4.
     
  20. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Thanks, nice explanation and drawings. I have a much better idea where you're headed.

    Overall the concept is sound but you're trying to stretch it a bit too far. While the 4'x8' layout is possible the 15" high gantry is going to haunt you. In the three years I've been a mod on this forum I've seen a lot of attempts at a tall gantry and not a single success. Tall gantries induce too much flexibility into the system and flexibility is the enemy of a CNC system. It allows the bit to wander and cuts come out sloppy and rarely on track.

    I suggest you refocus on the primary mission and you'll wind up with a much better machine, one that makes clean, repeatable cuts. And the best way to do that is to keep the machine low and lean. I'm away from my main computer for the day but when I get home tonight I'll throw together a quick sketch of what I'm referring to.

    One question I do still have is what type of router you'll be using. Hanging too big of a load off the side of a 1500mm long gantry results in torsional flexure of the beam. Again, something that causes the bit to wander.
     
  21. Dean Suominen

    Dean Suominen Well-Known
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    I was thinking about the deflection on having that much movement and you bring up a valid point. Shorter is stronger. Would have to make very VERY small thin cuts which means a very long drawn out process. The router im initially going with is a DC kit i found on amazon just to get started with and noise levels. Again, once I get the hang of everything or the motor burns out, either a makita or dewalt router with 12K-30K rpm, the DC one I have is 0-12K.

    The images are a basic representation for concept. From my understanding of weight distribution, an angled forward facing plate towards the head of the router to offset balance under load so the center of gravity is at the bit instead of the support of Z axis. The X and Z axis shouldnt want to tip forward or backwards if free wheeling (including pull and tug from wires, hoses etc).
     

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