MPCNC Size vs Lowrider for Mold Creation

New Home Forum Mostly Printed CNC – MPCNC Advice – MPCNC MPCNC Size vs Lowrider for Mold Creation

This topic contains 18 replies, has 7 voices, and was last updated by  Bill 7 months ago.

Viewing 19 posts - 1 through 19 (of 19 total)
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  • #96542

    Eric Dant
    Participant

    Hey all!

    Long time lurker here, first time poster! Figure I’d go ahead and ask my questions!

    I’m fixing my 3d printer (upgrading to MKS Gen L tomorrow!) so I will have alot more confidence in my prints, so I figure its time to build a MPCNC!

    Use: Building long boards and molds for electric skateboards.

    I’ve designed a few of my own long boards and built a 20 ton hydraulic press in my garage, but the thing that is holding me back is getting the actual molds cut out. I had a friend that had access to a huge 8 foot CNC but he just lost it! So I want to be able to do it myself!

    Here is a photo of a long board mold like I will be making.

    park1

     

    They are all made out of hard wood that is laminated together (mine are mainly oak). My main board is going to be 44 inches long, first I need to carve out the mold block, then once I press the decks, I would like to be able to use the CNC to cut out the final shape and possibly route out a rectangle on the bottom for a battery recess.

     

    I’m thinking just building a long but narrow MPCNC (maybe 1.5-2 ft wide, an 48 inches long) would help maintain rigidity along the X axis but I figure I ask everyone on here for your advice!!

     

    I’ve only bought the 3/4” EMT conduit so far in 5 ft sections, so I can change up my build right away!

     

     

    Also, I read somewhere someone used the Makita RT0701C trim router instead of the Dewalt DW660 since it is a bit more powerful….good choice or stick with the DW660? My home depot has the makita in stock right now so I can go grab it right away!

    I also will want to CNC alu and make motor mounts and such!

    Thanks everyone for your time and help!

    #96581

    Barry
    Participant

    You’d probably be alright with the wood, but not sure about the aluminum.  Might need a second smaller cnc for that.  Definately need midspan supports.

    1 user thanked author for this post.
    #96589

    Eric Dant
    Participant

    Might need a second smaller cnc for that. Definately need midspan supports.

    I’m wondering if there is a way to make it “modular”

    What I mean is have the one with the large foot print, then have a different belt and x/y axis that I could quickly swap out to make it a smaller one.

    Or would the set up required to get everything squared and dialed in be too much of a hassle to switch back and forth.

     

    OR! Have a set of X axis support bars that I could insert to stiffen up the entire frame and just used the first 1-2 feet of the bigger foot print.

     

    Just don’t have unlimited funds to be able to build 2 CNCs right away!

    #96595

    Ryan
    Keymaster

    I’m with Barry, A second machine for aluminum because you will be wanting really thick aluminum. You have a printer, so the printed parts are dirt cheap you can make it “modular” by swapping the most expansive part, the control board between your builds.

    1 user thanked author for this post.
    #96597

    Josh
    Participant

    I have never had a horsepower issue with the DW660 but I rarely use any bits over 1/8″.  I suppose if you were worried about job time a bigger spindle might help but I think you would start having frame issues.   I think swapping parts would be a hassle.

    #96614

    Eric Dant
    Participant

    swapping the most expansive part, the control board between your builds.

    So I have a sort of a harness made up than I could quick disconnect from the board/machine and just swap it over to the smaller machine. Hmmmm sounds like a fun project.

    I’ll keep the big one for wood and a smaller one (maybe 2 ft by 2 ft?) for aluminum so it stays rigid. For the smaller one, will I see any benefit by usiing steel pipes vs conduit?

    Also, I found some 3/4in steel pips but its listing the OD as 1.05 inches….will that fit within the tolerances of the 25.4 mm printed parts? (a difference of 2.2mm)

     

    One last question, has anyone upgraded their stepper motors to a nema 23 or a 34? just seems like the strength of the 17 (76 oz) is a bit light compared to other CNC’s out there.

    #96621

    Jamie
    Participant

    Nema 23 motors come up frequently.  There is no benefit because they are not the weak link in the system.

    Fortunately or unfortunately, there is no one weak link.  The deflection of the conduit and the stretch of the belts and the torsion on the center assembly (for short z-axes) are not way off, so I would say that to get significantly better stiffness requires basically starting over with a new design.

    Now having said that, I have at times fantasized about the possibility of a pantograph, basically using leverage to get shorter travel with higher forces and stiffness, provided the pantograph itself is stiff.  But it is just a fantasy — I haven’t put any real thought into how such a thing would be constructed.

    #96627

    Ryan
    Keymaster

    maybe 2 ft by 2 ft

    Nope, smaller. You are at a common place, this all comes up all the time. Build the machine for your main use, not the What if or maybe, all the rest will be more clear once you start using it. No need to change anything from the suggested build list. If there were good upgrades that only cost a little more money I would suggest them.

    1 user thanked author for this post.
    #96640

    Kelly D
    Participant

    And I would definitely vote for a well made harness for swapping the control unit. Until you find you wish you could run them both at the same time ; )

    1 user thanked author for this post.
    #96672

    Eric Dant
    Participant

    And I would definitely vote for a well made harness for swapping the control unit. Until you find you wish you could run them both at the same time ; )

    Has anyone done this yet (made a harness for hot swaps?)

     

    and yea….I’ll probably end up wanting to run both!

    #96686

    Kelly D
    Participant

    I’m not sure if I’ve ever seen it here on the forum but then again I’ve never looked. To my knowledge, no matter what plug assembly you use you should be fine. The stepper motor wires are something like 22AWG which should give you all kinds of options in terms of what plug assembly you could use. The only downside is having to make all those tiny pin connectors to insert into the plugs but with the right crimper and a little practice it’s a manageable task. One of those, put a good album on, grab a hot coffee and sit down with the wire strippers and crimper kinda jobs.

    How many pins in the plug is the big question. You may want to plan ahead for things like dual endstops, Z touch plates, laser control (you’ll need this given your plan) etc. Just a bare minimum, miniRambo setup would require 12 pins? Add four more for the laser. That sounds totally doable. I made more Dupont connections just extending my stepper wiring…..you DEFINITELY need the crimper though.

    #96690

    Ryan
    Keymaster

    (made a harness for hot swaps?)

    Never hot swap, power down. No need for a harness it is 3-5 motor wires and a power block, take you 30 seconds to move it.

    #96691

    Kelly D
    Participant

    (made a harness for hot swaps?)

    Never hot swap, power down. No need for a harness it is 3-5 motor wires and a power block, take you 30 seconds to move it.

    Why do you always have to swoop in and make things all simple Ryan? Every single time. “Use belts…it’s so much easier”, “Use a vacuum, it’s so much easier”, “Use a hammer….”

    Hahahaha

    Although on the topic of hot swapping….I’ve recently discovered that I can remove and insert my SD cards without power cycling my machines……that was a big discovery on my part. Is this actually a no-no?

    #96692

    Ryan
    Keymaster

    Memory card is fine, for some reason a few do require a power cycle to read. Never figured out why.

    #96698

    Eric Dant
    Participant

    Never hot swap, power down

    Oh gah, I can’t believe I wrote hot swap….I’m at work and I work in a data center so hot swap was just stuck in my brain.

     

    Yea I would def want to power everything down and get a full reboot on the board!

    you DEFINITELY need the crimper though.

    I got the crimpers! I’ve been building electric skateboards….its all jst connectors of various sizes so I made sure to get a decent set of crimpers for this stuff.

    I also ordered a huge pack of dupont connectors from aliexpress a while back so I’m covered!

     

    You guys have been so helpful…..too many ideas rolling around in my head now, time to go to tractor supply and see what they have locally and make my decision.

     

    I have a spare MKS Gen L board, but I think I like the options on the RAMBo boards for CNC.

    #96711

    Kelly D
    Participant

    Let’s really overcomplicate it for Ryan and build Bluetooth communication fobs so you don’t even need to plug or unplug anything!

    1 user thanked author for this post.
    #96713

    Ryan
    Keymaster

    Double dog dare you.

    #96715

    Eric Dant
    Participant

    Double dog dare you.

    Oh no…..you got my brain spinning.

     

    Technically its possible but I’m not sure about congestion over bluetooth….do you guys know what sort of bandwidth/data pulls these boards go through when they are running through their g-code?

    #97528

    Bill
    Participant

    Technically its possible but I’m not sure about congestion over bluetooth….do you guys know what sort of bandwidth/data pulls these boards go through when they are running through their g-code?

    Well, when you’re running something really, really detailed and small the 250000 serial port tends to add pauses into the workflow, typically fixed by running off the SD card instead. So figure on 250kbps as a maximum. Much slower if you’re cutting long straight lines of course…

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