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C-Beam™ Machine - Plate Maker

Discussion in 'CNC Mills/Routers' started by Mark Carew, Jul 16, 2015.

  1. RobertW

    RobertW New
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  2. jmdhuse

    jmdhuse New
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    Hi All,

    I've completed my C-beam machine build and just completed my first aluminum plate cut. The machine has a few changes to it from the original intention - I added side rails for the work surface so it would be more stable and could be widened to about 14 inches. I also used larger and more corner braces that I got from 8020.net... just a little paranoid about making it strong and square. I did the test pattern design with Sketchup and Sketchucam, and used the universal G-code sender to run the machine. The first cut did not finish because my laptop went to sleep (doh!) so I started it over with the laptop plugged into the wall and it went fine. I'm pretty happy with the quality of the cut. I set the router (Dewalt 611) to full speed (about 26000 rpm), set the feed rate to 3000mm/min and the plunge rate to 1500mm/min, turned on ramping and multipass with a depth of 0.25mm. The bit I used was a 3mm solid carbide two flute mill from MSC - Accupro ALTIN coated. I have to say that I'm pretty happy with the result and am very grateful for all the online resources I studied before determining a set of cutting parameters.

    Also, if anyone is interested, I've designed and printed micro-switch endstop mounts for X-min, Ymin, and Z-max. X and Z.jpg Y.jpg

    Pictures...

    machine.JPG First complete cut.JPG
     
  3. stargeezer

    stargeezer Journeyman
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    Very nice. I really appreciate that you made the extra effort to design and print your endstop mounts

    I'm hoping that some body can chime in about the speeds and feeds. I generally cut AL at around 12-13k RPM with a max feed rate of 70 inches per minute (sorry, I'm an old guy).
     
  4. jmdhuse

    jmdhuse New
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    I've had a 3D printer of one kind or another for 4 or 5 years now... I rarely pass up a chance to design and print a custom bracket or some such thing!
     
  5. RSW

    RSW New
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    Wow, those cut speeds are nice. I too am only cutting aluminum around 70 in/min like stargeezer.

    I have a very similar setup as yours, I increased my spoiler board size to 14 x 14 inches and added wheels on the outside of the C-Beam. I am interested in you design for the side rails under the spoiler your added.

    Could you provide a link to the end mill you are using, I think one of my biggest problems is using cheap end mills.

    1a.JPG
     
  6. jmdhuse

    jmdhuse New
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    The side rails are 500mm 40x20 Vslot rails mounted on their edges on either side of the screw drive C-beam - 110mm is the space between them. Each of the side rails has two Mini V Gantry plates that attach underneath the corners of the MDF build surface. The original build plate attached to the nut block was replaced with a C-beam gantry plate. That way the moving parts were all in the same plane and it made it easy to mount the MDF plate to them. A second MDF plate is screwed on to the first one to act as the spoiler board. I hope that is clear!

    Here is the link to the mill: 0.118" Diam, 0.354" Length of Cut, 2 Flute, 62773601 - MSC Less than $10 each and pretty quick delivery since they ship from Reno NV and I live near Phoenix AZ.

    When I did the cutting I did not use any lubrication or coolant, but I did hold the nozzle of a vacuum cleaner near the cutter to keep chips from building up.
     
  7. RSW

    RSW New
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    Thanks for the info. I have been thinking about adding some rails as I do get some side to side flex on the spoiler board, and your design looks like the solution, thanks.

    I'm going to order a couple of those mills and see if I can get my cut speeds up.

    Thanks again.
     
  8. David the swarfer

    David the swarfer OpenBuilds Team
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    The critical thing for cutting is 'surface feet per minute', that is how fast the cutting edge travels through the material.
    General numbers for aluminum are 1000 to 2000 SFM for carbide cutters this will vary depending on the alloy of course.

    So, working from 3mm diameter we get 33800 to 67700 RPM to get the above SFM
    As 2 thou per tooth we get 135 to 270 in/min feedrate for a 2 flute cutter.

    BUT we have to watch out for heat. by the time you are feeling the part is warming up, the chips are hot enough to microweld to the cutter. The TiAlNi coating can make this worse in aluminum, weird, no? At the above SFM you are probably going to get chip welding, and this is where some sort of lubricant/coolant comes in (or cut slower, but not too slow(note1) :) Kerosene is excellent on ali, but of course there are many brands of really good fluids for ali.
    NOT ORDINARY OIL, it is actually too good and prevents cutting, causing the tool to rub until the pressure is very high and suddenly cut too deep.

    So, you have 26000 rpm available.... so let's recalculate.
    That gives 104in/min at about 900SFM, this will work fine (-:
    (I am and advocate for calculating feeds and speeds, but the numbers are a bit flexible, except in Inconel and titanium!)

    How does all this relate to an OX or C-beam? These are good machines but are not the same as a 3000lb cast iron machine in terms of stiffness. What we do is use the calculated feedrate and reduce depth of cut so the machine can handle it.
    So your Haas VMC can do up to about 2x bitdiameter depth in a slot, but the C-beam is going to struggle with that, the 0.25 to 0.5mm range is about our size.
    and use ramping! and for holes, use a real drill bit, they are much better at making holes than an endmill.

    NOTE 1
    there is such a thing as cutting too slowly. Aluminum will chip weld to a hand file and that is hardly anywhere near the recommended 1000SFM. Too slow also causes rubbing which will blunt that expensive carbide tool quite fast. You want to be cutting a real chip, not little see-through slivers.

    So, do some test cuts on some scrap (but try to use a known alloy like 6061 or 7075) and figure out what your machine can do. This will save cut time but also material and toolbits. AND clear the chips, recutting chips makes for the worst surface finish, and blunts/breaks tools. Take a chip and put it on some ali plate. Take a craft knife and cut the chip in half. You will see dents next to the knife cut where the chip pressed into the plate before being cut.

    now, plastics.... plastics are a whole other ballgame (-:
     
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  9. David the swarfer

    David the swarfer OpenBuilds Team
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    That comes to about 5 thou per tooth and a bit more than 1000SFM. well within the numbers for aluminum.
     
  10. jmdhuse

    jmdhuse New
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    I arrived at my numbers using some on-line formulas I found... pleased it worked the first time - I've seen lots of horror stories of people dodging broken mills and bad finishes...
     
    David the swarfer likes this.
  11. Gary Bonard

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    can any one tell me what step res. they run on xy and z axis . I have set mine to 1/8 but seams slow so i change it to 1/4 seams much faster but moves are as fine ..? is there a torque lose through a finer Res. such as 1/8
     
  12. Bob R

    Bob R New
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    I've seen this article before, but most people don't fully understand what it means. You DO NOT lose torque or accuracy by increasing the number of steps...

    The article says "the INCREMENTAL torque per microstep drops off drastically".

    Well of course it does! But that doesn't mean the torque per degree has changed. In fact it doesn't. Let's try to understand this better...

    If you apply a steady current to each of the two motor windings and there is no load on the shaft, the motor will turn until it finds a resting position based on the magnitudes and polarity of the currents applied. At this position there is ZERO torque. If you try to turn the shaft by hand it will move slightly off of the resting position and fight you. It's now producing torque because it's not in it's happy position. So how much torque is it generating? Well that depends on how far you pushed it off its resting position. The greater the angle the more it's fighting to push it back. For small angles the torque is roughly proportional to the angle. If the angle becomes too great it will break free. At that point you've hit the holding torque limit.

    Table 1 tells you the amount of torque produced for various angles - the angles resulting from being 1 step off from the resting position. Well obviously if you use 256 microstepping and then apply 1 pulse, the new angle is tiny so the off angle torque is tiny.

    Let's say you are currently using 8-step microstepping, and lets say you apply 1 pulse. The incremental torque will be a certain amount.

    Now let's say you change to 256-step microstepping. But instead of applying 1 pulse you apply 32. Why 32? Because that will try to move the shaft to the same new position as a single step in the 8-step example. Take a guess how much torque will be produced. It's exactly the same as 1 pulse using the 8-step microstepping!!! No torque loss!

    If you had applied only 1 pulse with 256-step microstepping then you would expect the torque to be approximately 1/32 that of the 8-step example. Look in table 1 at the 8-step and it reads 19.51%, and for 256 it reads 0.61%. The ratio of the 2 numbers is 19.51/0.61= about 32 which agrees with what we expect.

    Also realise when you increase the stepping on your system (let's say from 8 to 256) the microcontroller that pulses the motor driver will increase the number of pulses it sends by the same factor - in this case by 32. Since it increases the number of pulses sent then in the end there isn't any torque lost. You simply have more resolution.

    There is a problem however with increasing the number of pulses that has nothing to do with torque. The stepper driver you are using has an upper limit on how quickly it can receive consecutive pulses. Additionally the microcontroller outputting the pulses has an upper limit as well. These upper limits will determine the maximum rotational speed of your motor.

    If you've increased the microstepping in your system and noticed a reduction in the maximum speed, it's got nothing to do with torque, but rather the upper frequency limit of your stepper system, which could be the driver itself, or the microcontroller that's pulsing it depending on your system.The software I use to control my stepper board is Grbl Panel and unfortunately it doesn't warn that you've exceeded the frequency limit on your system.

    He're another argument that the absolute (not incremental) torque doesn't change. If you think the torque drops with an increase in microstepping, then if there were a way to increase the stepping to be extremely high (like infinite) then there would be zero torque. There is a way to simulate infinite microstepping. Toss the motor driver and instead connect the two winding to two current regulated power supplies that you can adjust to any value you want. So you have infinite resolution. Does that mean the torque goes to zero? Of course not! For example if you connect a fixed current of 1 amp to each winding I can guarantee there will be torque if you try to rotate the shaft by hand. Yet this is equivalent to infinite microstepping since you have infinite resolution.

    There is no loss of torque by increasing the microstepping. Period. So crank up the microstepping and enjoy the smoother ride!

    If you find your maximum velocity is now lower than you require, then either reduce the microstepping or get a better stepper controller board which can handle the higher frequency requirement.
     
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  13. GrayUK

    GrayUK Openbuilds Team Elder
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    Bob R.
    Many thanks for that clear explanation with regard to Torque and Micro-stepping. :)
    I found it informative and quite easy to understand, which can be a challenge, when explaining something so potentially daunting. :thumbsup:
    I hope you don't mind but I've put a copy of this into the "Helpful Tools" section, as a reference. :rolleyes:
    Gray
     
  14. Bruce Fenstermacher

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    I've been trying to figure out how to do the exact same thing with out riggers on the cutting board. A few pictures are worth a thousand words. Can you post some more detail pictures to go with your description.

    Thanks a bunch

    Bruce
     
  15. daisosasen01

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    Finished my rebuild. For some reason I couldn't get the gantry to work correctly, so I swapped out to linear guide rails. As soon as I cut my plates, I'll add X linear guide rails and make the machine bigger.

    But for now, can I PLEASE get some help on getting started? I have tried the pen draw and it was half successful. The gcode for sample plate ran which is good. I'm a newbee and some help would be much appreciated. I can be found on facebook by: [email protected]
     
  16. p25o1

    p25o1 New
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    i like the micro-switch endstop mounts,

    can you share them with me , thx
     
  17. Jimmybuckets

    Jimmybuckets Well-Known
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    I like the idea of swaping out the current plate the table sits on for the x-large c-beam gantry plate. Would give a few extra inches of travel and seems like even though a little smaller would be a more sturdy base for the table. Anyone see any reason not too?
     
  18. rom

    rom New
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    Hello All.

    I purchased a C-BEAM machine a few weeks back and joining the community at this occasion.
    The build was quite easy to do and well explained, it was a breeze :)
    After a few "quick and dirty" tests, I am adjusting some elements on the machine, better endstops, enhancing the squareness of the machine, tramming the router bit, etc.

    I have pretty good success on all of that except the X/Z squareness. Let me explain:
    * I start by flattening the MDF base
    * I checked that my router was well aligned with the Z axis (putting a laser pointer instead of a milling bit and moving up/down)
    * I used then a homemade "tramming dial indicator" to check that the router was well square to the plane surface.
    * for Y/Z squareness, it was not very good, but I could adjust the whole gantry and all is fine now. With all the screws on the side of the gantry "pillars", I could adjust it progressively and secure it tight.
    * for X/Z squareness, I can see it is not right, but I don't know where I can "play with" the screws/bold/plates of the machine to fix it

    I short,; I have something like that (of course - very exaggerated on the image, I have just something like 1 or 2 degree off)
    [​IMG]

    As I understand it, I can only play with these elements:
    * Idea 1 : The way the wheels of the X axis are on the X-rail, moving the eccentric nuts or adding more eccentric on the other side.
    * Idea 2 : The way the Z axis 250mm C-BEAM is bolted to the X Plate, perhaps I can move it a few degrees if there is some margin on the Vslots.

    Note that for idea 1, the upper holes are 5mm and not 7.2mm - so I will certainly have to modify the gantry plate.

    Before starting my "adjustments", I wanted to have some advice from you. How did you correct this kind of misalignment on your machine ? Would you see other options ?

    Thanks a lot for you help
    see you soon !

    [​IMG]
     
  19. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    First, with the plate on the X beam, loosen all the non eccentrics in place and re-tighten them. This assures that they are all evenly pressed to the outside edge of the hole. Then check to see that you have the same amount of tightness on all the eccentrics. This is done both visually (looking at the alignment of the mark on the eccentric) and by using a finger to check the slip of wheels against the track. If they all slip with the same amount of pressure, the plate will inherently be square to the track. Move on to idea 2 or idea 3 (the mount not being square to the Z mounting plate). You'll find the problem is somewhere there. I would probably bet on it being the latter.
     
  20. rom

    rom New
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    Thanks for the quick reply.
    I'll do a general check of all the assembly. The "degree of freedom" of the wheels has been tested yesterday but not the eccentric nut alignement - I'll check all of that again, thanls

    Whey you say "the mount not being square to the Z mounting plate", you mean that my router milling direction is not perfectly parallel to the Z-axis motion ?
    I used the "laser point in chuck" hack to check that before all, but perhaps it is not the best method. How could I check that the mount (and the router) are accurately mounted ? just by visual inspection ?

    Thanks
     
  21. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    I'd just use a spirit level, checking to see that the router mount is level and parallel to the X beam. If not loosen all the mount and angle bracket screws and re-tighten in proper alignment.
     
  22. Jimmybuckets

    Jimmybuckets Well-Known
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    I found my C-Beams were not perfectly square at the ends so setting a level on top of the z caused me a bit of grief. The beauty of cnc and especially a small format machine...that generally is using a small diameter bit...small errors in square and true will not kill your final results unless you are trying to be accurate to the thousands. I would fun some cuts and see if your results are within your spec.
     
  23. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    For this issue, the level should be set across the top of the router mount not the end plates.
     
  24. Kevin Henning

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    I prefer to use a set or engineers square (but not a cheap combination square) rather than a level (or even the 3 - 4 - 5 measurements with a ruler) for the simple reason that I know that the surface that I have my machine on is flat, but not level in itself.
     
  25. David the swarfer

    David the swarfer OpenBuilds Team
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    maybe you can start with these videos?
    SketchUcam Howto - YouTube
     
  26. rom

    rom New
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    Thanks for all you suggestions.
    Having a close look revealed that everything is a little off on my machine :) I didn't saw that the parts could be moved and adjusted so much in the build process and I was tightening everything like crazy a little too soon and without checking the exact alignments of anything.
    Now I'm with my engineering squares looking for things to set square.

    I'll tell you how it goes.
    Thanks again

    [EDIT]
    This seems to solve my problem. Now I have around 0.2mm of difference on my "tramming dial indicator" of 160 mm diameter... that would be around 0.1% accuracy on the angle. 0.1 degrees. nice :) Thanks to all for your help
     
    #1436 rom, Jun 12, 2017
    Last edited: Jun 12, 2017
  27. daisosasen01

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    Thank you David. I found those moments after I posted. (stupid me didn't go back to edit my post). I am now back to ground zero with my c-beam from open builds. I finally got the frame setup and am working on the software end of it. I'm such a noob. I am using bCNC as the controller for the machine. Can't seem to get it setup :(
     
  28. daisosasen01

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    So in desperation to get my machine going I resorted to using the software from the assembly video "Grbl-Panel-1.0.9.14". Using the provided setting's image I attempted to change the settings BUT their isn't a "save" button for me to save changes. Additionally their isn't a $14 (auto start, bool) parameter for me to update. Every time I do anything what so ever in the software the old parameters repopulate. Any help?
     
  29. daisosasen01

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    UPDATE- resolved with uninstall - reinstall.
     
  30. Jimmybuckets

    Jimmybuckets Well-Known
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    To save you have to double click the parameter you want to change. You can only do one at a time.
     

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