Tons of question before printing/building

New Home Forum Mostly Printed CNC – MPCNC Advice – MPCNC Tons of question before printing/building

This topic contains 10 replies, has 5 voices, and was last updated by  DerEchteLanger 2 days, 6 hours ago.

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  • #43737

    DerEchteLanger
    Participant

    Hi! Im consindering building a MPCNC, mostly for Plexiglas (PMMA) and Aluminium. But i have tons of questions before i can properly plan this out. I have a 3D Printer so i know a bit about such machines, but a router seems to be operating very differently.

     

    A few questions about the workflow:
    -How does the router know where de workpiece is? If i understand this correctly you simply bolt it somewhere on the worktable. So you have to place the toolhead in exactly the right location relative to it, right? How do you do this?
    -Apparently this machines use similar gcode to a 3D printer, thats why it can also operate with the same hardware. So the gcode is created in an equivalent of a slicer for 3D printing, but for CNC, isnt it? Ive read of “Estlcam” as such a software, but i dont understand why its considered to be compatible with an Arduino Uno but not Mega. It shouldnt care what executes the code it outputs (on a SD card?)
    -How does one prevent the machine from cutting into the groundplate when cutting something?

    About materials:
    -Do i need a controllable spindle for aluminium? Or is a fixed speed of 35000 1/min ok? Are 530W enough?
    -Plexiglas has a realy low melting temperature, so i guess it needs to be cooled. Does anybody have advice how to do that the easiest way?

    About the build itself:
    -How do you mount the MPCNC? Big wooden plates with decent thickness seem to be extremly expensive.
    -A Ramps 1.4 has 5 outputs for steppers, why are only 3 used but 2 of those in parallel/serial?
    -There seems to be two options to drive a Ramps 1.4: An Uno and a Mega. Is there a noticeable difference?
    -Whats the purpose of the “pineapple coupler”?

    #43744

    Jeffeb3
    Participant
    So the gcode is created in an equivalent of a slicer for 3D printing, but for CNC,

    That’s called CAM and it’s not as Automatic as slicing. EstlCAM had two components ) kind of like repetier). The CAM software is highly recommended and can be easily used to creat gcode for MPCNCs using Marlin firmware. The EstlCAM firmware and controller reprograms the Arduino and it’s been used, but isn’t as well tested as Marlin around here. I don’t know where you saw it doesn’t support mega though, I thought people were using that successfully here.

    How does the router know where de workpiece is?

    You set the origin in your CAM. I usually do the lower left corner, at the top surface of the work. Then I move my machine so the bit is touching the surface in a spot where the lower left should be. If you need something very precise or very repeatable, you can use the machine to cut some guides, like holes for dowels.

    How does one prevent the machine from cutting into the groundplate when cutting something

    You attach a “spoil board” that is replaceable. You’ll cut into it all the time.

    Do i need a controllable spindle for aluminium?

    I haven’t done aluminum, but I bet you’ll want a speed control for plastic. If you are using the dw660, you can buy a router speed control. The cheap Triac ones work.

    How do you mount the MPCNC? Big wooden plates with decent thickness seem to be extremly expensive.

    Shouldn’t be extremely expensive. What materials are you talking about? IIRC, 3/4″ pine plywood is $20 for a 4×8 foot sheet. Dimensional lumber works too.

    A Ramps 1.4 has 5 outputs for steppers, why are only 3 used but 2 of those in parallel/serial?

    Dual x and dual y are possible in the firmware, there’s just one trick to remap the pins of E0. I would start with just the three drivers, until you have something working, then you can narrow down the problem.

    An Uno and a Mega. Is there a noticeable difference?

    Uno operates at a higher speed, but the mega is high enough.

    Whats the purpose of the “pineapple coupler”?

    It couples the motor to the shaft, and it gives you a place to manually move the axis.

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    #43751

    DerEchteLanger
    Participant

    Thanks a lot for the answers. If a Uno is faster but also cheaper, why would someone choose the Mega at all?

    #43770

    Jeffeb3
    Participant

    Well, if you’re looking for help here, it’s very common.

    In general though, is it cheaper? Even for the cheap clones? A cloned Mega is what? $10?

    #43771

    Jeffeb3
    Participant

    Oh, I’m sorry. I was confused. I was thinking Due, not Uno. The Due is like the Mega but faster. The uno doesn’t have enough I/O.

    #43910

    SQLException
    Participant

    Moin,

    I came from 3D printing to (mp)cnc too. Usually it shouldn’t matter where exactly you start to mill, so where ever you screw down the workpiece, set zero point (Nullpunkt setzen) then go. Well that’s how I do it, but I’m a newbie.

    After finding estlcam I used to mess with marlin-firmwares. There’s no need for this, just use estlcam (with the built-in firmware load function) and be done with the ramps firmware. I don’t now about Uno tho. Just any cheap 25 EUR ramps 1.4 will do.

    If you use estlcams firmware, there is no LCD support. I don’t see why one would need it tbh. Everything can be done from a USB connected laptop. If you really need SD card support I don’t know.

    @cutting into groundplate: I screwed about 60-80 threaded sleeves (http://www.ebay.de/itm/172587109291) into my workbench. Now I screw down a spoil board (Opferplatte) onto it, then the workpiece on this spoil board. Sounds like overkill and annoying to do everytime, but I think that’s how it’s done (as I said, I’m new to this as well).

    So its: surface of workbench with threads -> spoil board on top -> workpiece on top. Can post pictures tomorrow if you want.

    I got the Katsu router (makita clone), with controllable speed (manual, not through software, but doesn’t matter imho). Costs about 50 EUR from ebay.co.uk. Also got a 6mm into 3.175mm Adapter, because the standard collet with the Katsu is 6mm, and having only 6mm bits sucks.

    For acrylics (plexiglas is a trademark, you know?) I use a co2 lasercutter. Not sure if it’s worth it to mill acrylics, will probably be a mess.

    @mounting the mpcnc: I specifically built a workbench with the right size for the mpcnc. Guess thats not uncommon here. Its a 10mm (or 12mm) Siebdruckplatte (not sure the word for it in englisch; some multiplex, medium-high quality, flat woodpanel) for the top, with a 28mm OSB-Platte (same :)) underneath. So its about 40mm wood for the table. Imho the legs are more important for the riggidy of the mpcnc. My legs are 70x70mm Kantholz/square wood. Luckily one side of the table is screwed to the wall, otherwise this workbench would probably not be stable enough, for my taste. Work in progress picture:

    https://imgur.com/a/fZtIe

    The estlcam firmware uses all 5 drivers of the ramps board btw.

    I couldn’t figure out the use of the pineapple coupler. Yes, I do use leadscrews and not threaded rods, but even with a threaded rod I don’t see how this thing works.

    #43991

    Bill
    Participant

    Uh, one big reason to use the Mega over the other models is the RAMPS board. It plugs directly into the Mega and (IIRC) doesn’t on a Uno or Due.

    #43998

    DerEchteLanger
    Participant

    Thanks again, i ordered a Ramps&Mega.

    SQLException, could you provide me with a link for that Katsu machine? I have a Bosch POF 500 here, but since it can only run at 29000rpm i may need an alternative.

    #44008

    Brumby
    Participant

    I found mine at ebay. Search for: “katsu trimmer“.

    #44009

    SQLException
    Participant

    Theres only one Katsu machine out there. One model. Its also in my thread in the “Your Builds” section.

    https://www.google.de/search?q=katsu+router

    • This reply was modified 2 days, 8 hours ago by  SQLException.
    #44019

    DerEchteLanger
    Participant

    Thanks, wasnt sure since there isnt much written about this katsu machine.

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