I need advice on what specs I need

Mostly Printed CNC - MPCNC Advice
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Hello, community,

I plan to buy the MPCNC Primo Kit, and 3D print the parts to construct it.

I would like to use this CNC to cut ABS / Polycarbonate plastic, of 1/8 inch thickness. I currently use a mac, and would like to use free CNC programs to take CAD exports from onshape and send them to the CNC. I only need one square foot of workable space, so this will be a small CNC. Hopefully being so small will also make it more stable.

I have never used a CNC before, but I have used a laser cutter many times.

Based on this information

Which program should I set up on my computer? I would like the basic abilitity to do V carving, assuming this CNC is capable of that

Where do I find the files to print the 3D printed parts for the Primo Kit, and if there are multiple different types of 3D parts, which should I use.

What stepper wiring kit and control board do I need, and why? I think I should go with the series rather than dual endstop kit, because I have no idea what the benefits are and the website says the dual endstop kit isn’t beginner friendly.

I assume 3 meters of belt will be plenty.

Where do I get the rails, and what rails do I get if there are options.

Finally, perhaps the most important question, what Spindle and Bits do I get. My understanding is that for plastic, I need a lower RPM higher torque spindle. However, in the scheme of things I don’t know what specs are considered optimal for what I want to do. I would like to, if reasonably possible, use a 2mm or 1/16 inch drill bit, assuming they would be strong enough to cut plastic. Additionally I would like the ability to V carve with a V carving drill bit

Please help me in determining what I need to build a fully functioning CNC kit.

Is the V carving requirement going to make this much more expensive? I was hoping to complete this close to $400

Thank you

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Unless you have a 3d printer and some of the electronics, you’re going to blow that budget.


Put your email in there so you’ll get a notification when the mini rambo is back in stock, they’re back ordered at the moment.
1" version at the recommended size, which gets you a little over your size requirement.

router
https://www.amazon.com/Makita-RT0701C-1-1-Compact-Router/dp/B00E7D3V4S

Router collet adapter so you can use smaller endmills.

You didn’t say where you live, but you’ll need to find a place that sells 1" TUBE. Can be stainless or regular steel. Not 1" conduit from the big box store, that’s a different size.

Rural King or Tractor supply sometimes carry it in the welding section if you have one close. Metals supermarket for online.

I think that’s everything? One of the other guys can check my list if I forgot anything.

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What software do you use for laser cutting if you bbn can output DFX that is half the work done Estlcam is what most people are using here still for CAM

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Hopefully being so small will also make it more stable.

Small makes the machine more accurate, but you are unlikely to be stressing the machine with 1/8" plastic. The height of the machine has more impact than the XY footprint.

onshape and send them to the CNC.

I’m not an OnShape user, but I’ve read on this forum that Kiri:Moto provides CAM directly inside of OnShape. There is some work getting it setup so that the GCode works with the MPCNC.

I would like the basic abilitity to do V carving, assuming this CNC is capable of that

The machine is capable. The question is what ability does your CAM solution provide for V carving. I use Fusion 360, and engraving/VCarving is not a problem. Of course Fusion 360 has a steeper learning curve than many other hobbyist software solutions, and recently Autodesk has moved to provide additional limits on the hobbyist license.

Where do I find the files to print the 3D printed parts for the Primo Kit, and if there are multiple different types of 3D parts, which should I use.

Thingiverse has all the files. There are three versions. A 23.5mm version that uses electrical conduit from a big box store. A 25.4mm version that used 1" tubing (not pipe), and a 25mm version primarily used in metric-centric countries. The 23.5mm conduit version is the cheapest, though given your small footprint, a tubing version would not be all that much more expensive.

What stepper wiring kit and control board do I need, and why? I think I should go with the series rather than dual endstop kit, because I have no idea what the benefits are and the website says the dual endstop kit isn’t beginner friendly.

Given that your board supports them, you can upgrade to dual end stops fairly easily if you find you want them later. Primarily they provide a way to square the machine, but this is less important given your small size and the adjustability of the Primo (vs the earlier version). The MiniRambo board does not allow you to add dual endstops. The Rambo does. Ryan is having trouble keeping both of these boards in stock.

Finally, perhaps the most important question, what Spindle and Bits do I get.

Being able to adjust the speed of the router will be important. The Makita router that Berry references is a common choice. I purchased a nearly identical router from Carbide that comes with precision collets for both 1/8" and 1/4" bits. Carbide has published some speeds and feeds for acrylic that will give you a starting point for your settings.

I assume 3 meters of belt will be plenty.

The size calculator will give you your belt lengths, but the kit comes with enough belt for a 2’ x 2’ machine.

I was hoping to complete this close to $400

Realistically, with a router and a few bits, you are looking at closer to $500. If $400 is really important, there is some corner cutting you might do.

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I have access to a 3D printer that I can use for free, to print as much as I really want, so that will not be a cost factor. Do you recommend the 23.5, 25.4, or 23.5 conduit? I am in America so im not a metric-centric country, but I am more than familiar with the metric system and will probably end up using it anyway.

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What does dual endstops actually do? You said squaring the machine, though I dont know what that means.

Do you think I will be able to find a 1/16" or 2mm drill bit that will work with the Makita and cut through ABS / Polycarbonate (It is a blend of ABS/PC, for reference)?

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Where do I leave my email?

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2x2 or smaller, conduit is fine (3/4 conduit is 23.5 OD) But steel tube isn’t terribly expensive, 24.5mm for 1 inch OD.
The dual endstops help square your machine to compensate for a tendency of one side to move without the other side (x1 and x2 for example). You could also just use hard stops and power up, then you’ll be fine.

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Mine will be just 1’x1’, so the 23.5mm electric conduit should be fine then I think

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I think so. Couple guys were cutting aluminum on 2x2 conduit burleys. Carefully, but cutting aluminum. The primo is a step up from there, so there’s that, too.

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New question for ya. Does the makita have a laser guide? In other words can I have it trace the cut with a laser to show me where exactly it will go before I actually press go?

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What does dual endstops actually do? You said squaring the machine, though I dont know what that means.

There is a stepper motor on each end of the X and Y axis. When you turn the machine on, it assumes the location of the stepper motors are the 0,0 position. But there is no guarantee that both steppers are the same distance from the ends of the machine. If the steppers are not the same distance, trying to cut a square will result in a parallelogram. This distortion is subtle in most cases. Dual end stops allow you ‘home’ your machine to assure that the stepper are exactly the same distance from the beginning/end of the machine. Note many long-time users don’t use dual end stops. Some knowledgeable people on this forum will argue you can accomplish the same thing by adding some physical stops to the machine and just dragging the machine against the physical stops before powering on.

There is one other thing that both dual end stops and physical stops give you…a repeatable home position that can be used as a reference to repeatedly find a specific coordinate on the spoil board. This is very helpful if you are repeatedly milling some item in a fixture.

Do you think I will be able to find a 1/16" or 2mm drill bit that will work with the Makita and cut through ABS / Polycarbonate (It is a blend of ABS/PC, for reference)?

I’m sure it can be done, but it may take some significant testing to get the recipe right. Heat is the big issue with plastic. Cuts can weld themselves closed during cutting or the bit can become encased in plastic if the feed and speeds are not right. You may get away with some normal bits, but be aware there are specialty plastic cutting bits. The bits can be pricy. I’ve only cut plastic a few times…very simple contour cuts. I used a burr bit. It got the job done, but I can’t say it was the right choice. I suggest posting this one issue as its own question so that someone with plastics experience can give you some insight.

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No laser on the Makita. You can author a contour cut above your stock and watch the bit trace above your stock. I think you are going to find there is a lot more ‘hand’ work with an MPCNC compared to your laser experiences.

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Electrical conduit can be rough. I would recommending sanding the conduit to get a smooth exterior. Even with sanding, you may not get the butter smooth movement you would with stainless steel. But the difference won’t be noticed in your cutting.

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You’re not going to see a difference with either. It’s not that rough, and the galvanizing will flake off after a couple hours of use.

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Bite the bullet and buy SS tubing in the end it will pay off in spades!!! Long term you’ll see. That’s why it’s Ryan’s recommendation.

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If stainless is a little too rich for you, regular dom steel tube will work as well. Just need to wax the tubes so they don’t rust.

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And I’m going to say this because I’m the nit-picky pedantic nerd around here… Don’t use a drill bit! What we use are actually end mills, which have specially designed geometry for the way that they are used. Drill bits are made to go straight into material, and pull the waste out. End mills are designed to cut from the sides, not just the tips. Trying to use a drill bit will lead to… unpleasant things happening.

Robert talked about using a burr to cut plastic. That’s basically just grinding the plastic away. Functional, but probably not a good long-term solution. Because it melts so easily, plastic can be very finicky. Not too fast on the RPMs, or too many flutes on your bit, as you don’t want to touch the plastic too often, but by the same token, you want to keep the toolhead moving at a decent speed. All this means you should be taking decently large bites with each pass of the blade, so your bit needs to be sharp. You can help keep things cool and clean by adding an air assist (air compressor blowing at the bit to help remove chips and heat).

Also, it should be noted that you should take a moment to stop and think about what your real goal is. What are you really after. What are your real requirements. Because you can do it all with a 3/4" EMT rig using a Dremel with hard endstops, and a handful of cheap endmills from ebay. Or you could build a 1" SS rig with a water-cooled spindle, dual endstops, and a full set of high-end cutting tools and collets. There will be a difference between the two. Will it be worth the cost? That’s a debate you have to have with yourself. We shouldn’t make that choice for you.

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Is there stainless steel tube at 23.5mm? Or should I just go with the 24.5 stainless steel tubes. Also, where do I get these?

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Do you have any recommendations for a water cooled spindle that would work for the Primo?