30"+ work space low cost diy CNC router parts kits?

[routalot]

I have been reading this thread with a mixture of amusement and concern.I hope the outcome is a success,but I am a long way from convinced that it will be.I am rather surprised that the carbon is being utilised as a very heavy flat sheet.Why not a cored sheet of better yet,a cored sheet with flanges perhaps a couple of inches deep to form a channel section?Much less material and a lot more stiffness if you do it that way.The emphasis on producing what will literally be a carbon copy of the machine elements as they would be made in metal plate seems to prevent making good use of the properties of the material,one of which is its ability to conform to the shape of a mould.

Such a mould does not have to be the end result of the process of making a highly finished plug and then making a mould and ultimately a component.You can simply use a flat surface-which seems to be available-and fix a temporary upright flange to it with hot glue or similar while you make the item required.The upright flange can be something as simple as melamine faced chipboard.The fact that the reverse surface may not be optically flat is hardly a concern as far as bedding a few washers on it is concerned.

Looking further ahead,when or if the machine is completed,what software is envisaged?Not only for machine control,but for 3D modelling and determining toolpaths.Just constructing the machine is no more than the first of a series of mountains to climb in my view.

[Goemon]

I have been reading this thread with a mixture of amusement and concern.I hope the outcome is a success,but I am a long way from convinced that it will be.I am rather surprised that the carbon is being utilised as a very heavy flat sheet.Why not a cored sheet of better yet,a cored sheet with flanges perhaps a couple of inches deep to form a channel section?Much less material and a lot more stiffness if you do it that way.The emphasis on producing what will literally be a carbon copy of the machine elements as they would be made in metal plate seems to prevent making good use of the properties of the material,one of which is its ability to conform to the shape of a mould.

Such a mould does not have to be the end result of the process of making a highly finished plug and then making a mould and ultimately a component.You can simply use a flat surface-which seems to be available-and fix a temporary upright flange to it with hot glue or similar while you make the item required.The upright flange can be something as simple as melamine faced chipboard.The fact that the reverse surface may not be optically flat is hardly a concern as far as bedding a few washers on it is concerned.

Looking further ahead,when or if the machine is completed,what software is envisaged?Not only for machine control,but for 3D modelling and determining toolpaths.Just constructing the machine is no more than the first of a series of mountains to climb in my view.

I read this post with a mix of amusement and concern (see how douchey it sounds when you start a post like that?). Actually I just wanted the time the back.

I haven't stated what gantry design I plan to use yet so there is nothing to comment on. Nothing. Notice how nobody else is offering a critique of my gantry? That's common sense as they have never seen it....

My use of cf plates and a desire to make them as flat as possible is for the surface layer - the one that will hold the rails. Any mold will only be a mirror of the plug used to make it.

I am well aware how to design a cf part for maximum strength. If you are going to talk down to someone, you should check to make sure you actually know more than they do on the subject. I have designed and built many carbon fiber parts. It's my main business. You don't seem like someone who is qualified to be giving advice on making carbon fiber parts to anyone. You shouldn't try.


When I have designed and built my gantry... and posted pics, feel free to give me your valuable critique then but know this, I don't post pics in forums where other people come for advice and tips unless I have tested a product and know it to be functional.

I suggest showing a little more respect in your future posts if you want or expect any in return. Do you honestly expect people to react well when you start a post like that???

[routalot]

Carry on then son.I've only been working with carbon for forty years and CNC machines for twenty.You are the one asking for help.I will lurk here when I feel curious.Good luck-you will need it.

[Goemon]

Goemon - When you get around to making your gantry please post pics. In my opinion, Carbon Fiber is the holy grail of materials for a CNC gantry. I'm in the process of building a steel CNC router right now. I would have used CF for the gantry but I'm aware of my talents and limitations and, making CF parts is not in my skill set. Good luck with your machine.

I will - when I have it up and running. When I am happy that it is all working as intended I'll be happy to post a short tutorial if there is any interest. It would be good to be able to give something back as people have spent so much of their time helping me.

I also think that cf has the potential to be that "holy grail" for this purpose. It has obvious potential advantages if done right. It's strong, rigid, light, less sensative to heat distortion and doesn't rust. It's not without it's issues though.

It doesn't hold screws well at all so I need to figure out how to connect the gantry to the linear bearings in a way that doesn't become a point of weakness. On a rifle stock I would just cook in some aluminum pillars but that won't work for this....

[1Jumper10]

Possibly embed a steel rail on the inside so the rails bolt into steel threads and sandwich the CF?

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[Goemon]

Possibly embed a steel rail on the inside so the rails bolt into steel threads and sandwich the CF?

Sent from my Pixel XL using Tapatalk

I was thinking something similar except I want the metal on the inside and cooked in so it doesn't become a point of weakness. That's what I do with aluminum pillars on carbon fiber rifle stocks and it works well enough.

Another possibility is using bar clamps that provide a strong mechanical grip between metal clamps and cf bars. I have been testing this to connect the two sets of bearing blocks from each side of the X axis. This cross bar will run under the table and provide a little extra rigidity.

I have a little more time to focus on it properly this week so I can get this part done.

[Goemon]

Is anyone here using one of these mini milling heads instead of a CNC spindle?

Mini Mill Head Assembly, R8 Spindle 1663 - LittleMachineShop.com


They allow the use of larger end mills than an equivalently priced CNC spindle and they look a little more robust (in the pics). Are these better than the higher speed CNC spindles for working on aluminum? Or are they mainly for harder metals like steel?

[louieatienza]

Is anyone here using one of these mini milling heads instead of a CNC spindle?

They allow the use of larger end mills than an equivalently priced CNC spindle and they look a little more robust (in the pics). Are these better than the higher speed CNC spindles for working on aluminum? Or are they mainly for harder metals like steel?

Well, the lower RPM will limit you maximum feed in aluminum. You may be able to take a larger, deeper cut at a lower speed, but that would require a lot more spindle HP. Which would run contrary to the philosophy of making a lightweight gantry to increase speed.

[Goemon]

Well, the lower RPM will limit you maximum feed in aluminum. You may be able to take a larger, deeper cut at a lower speed, but that would require a lot more spindle HP. Which would run contrary to the philosophy of making a lightweight gantry to increase speed.

This is the part I don't understand with spindle HP. A of the milling heads (even ones from larger vertical mills) seem to have less hp than some of the smallest CNC router spindles. I keep reading that you can't do a direct comparison because the motors on milling heads achieve higher hp at lower rpm without gears. I.e. 1hp from a milling head produces considerably more power than 1hp or 2hp from your average CNC spindle.

While you can cut aluminum on a cnc router, I have never heard anyone say it's actually a better tool for the job than a CNC mill.

You can see how a man could get confused.... there is one spindle with 1/2 hp being sold to cut steel and aluminum while another spindle is being sold with 3hp with instructions to stick to smaller end mills for aluminum and shallow passes only...

I don't think they could have made the process of choosing spindles and collets for routers, mills and lathes any more confusing if they put their best people on it...

[ger21]

I keep reading that you can't do a direct comparison because the motors on milling heads achieve higher hp at lower rpm without gears. I.e. 1hp from a milling head produces considerably more power than 1hp or 2hp from your average CNC spindle.

1HP is HP, regardless of the type of spindle.
The difference is that a Mill might have 1HP at 3000 rpm, while a router would have 1HP at 20,000 rpm, with HP decreasing as RPM decreases.

While you can cut aluminum on a cnc router, I have never heard anyone say it's actually a better tool for the job than a CNC mill.

That's more to do with machine rigidity, then the spindle. All else being equal, a faster spindle can cut faster. There are mills with 40,000 rpm spindles that move and cut faster than routers.
In the end, they're all just CNC cutting machines, regardless of if you call them a mill or router. Router is the term typically used for a wood cutting machine, and mill is the term for a metal cutting machine.

That minimill spindle with 2500RPM max is going to limit your feedrate considerably.
While cutting, you want each flute of the tool to remove a given amount of material, known as the chip load. Whether the spindle is spinning 2500 or 15,000 rpm, it takes the same amount of power to cut the same size chip. But at 15,000 rpm, you have to move 6x faster to get the same size chip.
What more horsepower does, is allow you to make deeper cuts.

[louieatienza]

This is the part I don't understand with spindle HP. A of the milling heads (even ones from larger vertical mills) seem to have less hp than some of the smallest CNC router spindles. I keep reading that you can't do a direct comparison because the motors on milling heads achieve higher hp at lower rpm without gears. I.e. 1hp from a milling head produces considerably more power than 1hp or 2hp from your average CNC spindle.

While you can cut aluminum on a cnc router, I have never heard anyone say it's actually a better tool for the job than a CNC mill.

You can see how a man could get confused.... there is one spindle with 1/2 hp being sold to cut steel and aluminum while another spindle is being sold with 3hp with instructions to stick to smaller end mills for aluminum and shallow passes only...

I don't think they could have made the process of choosing spindles and collets for routers, mills and lathes any more confusing if they put their best people on it...

A CNC router in my view denotes larger format, higher travel speed, and non-ferrous metal, composite, wood, plastics cutting. Typically mills have lower travel speeds, lower speeds from heavier construction, and capable of cutting ferrous metals. There are machining centers capable of over 1000ipm, but they also have 15k-24k spindles that can produce in excess of 30HP or more. Power is just the amount of work you do over time. Think of a loading dock at a warehouse. You have a pallet to lift onto the loading dock. Or you can push it up a ramp. You're doing the same amount of work, but one is faster but more difficult over a short distance and one is slower and easier but over a longer distance

I have a CNC mini mill, but I have installed a 2.2kW (3HP) 24krpm spindle. But I cut mostly aluminum with it, some plastics and composites, some wood, and rarely steel.

[louieatienza]

How much horsepower do you need? Figure out what endmils you need first. Then you can determine how fast you need to cut depending on the RPM of your spindle. Feedrate = spindle speed X # teeth # chipload (for a 1/4" endmill, it's about .002"-.003" per flute in aluminum). Should note here that there is an upper limit on theoretical max feedrate, because the SFM rating of the tool has to be considered.

Now you need to calculate the material removal rate (MMR), which is the federate x radial DoC (or stepover) x axial DoC (or your depth of cut in Z per pass).

Finally, the spindle HP needed is calculated by multiplying the MRR by a quantity called the unit power which is different for different materials. It's about .4 for aluminum.

From here you can draw some conclusions. Since the mill can absorb greater cutting forces and the spindle has more torque at a lower speed you can take deeper, slower cuts. Or, with a router, which is less rigid, but has a spindle with more power at the higher RPM range, you can take shallower passes, but at a higher feedrate. So it's more or less analogous to the ramp example.

[Goemon]

How much horsepower do you need? Figure out what endmils you need first. Then you can determine how fast you need to cut depending on the RPM of your spindle. Feedrate = spindle speed X # teeth # chipload (for a 1/4" endmill, it's about .002"-.003" per flute in aluminum). Should note here that there is an upper limit on theoretical max feedrate, because the SFM rating of the tool has to be considered.

Now you need to calculate the material removal rate (MMR), which is the federate x radial DoC (or stepover) x axial DoC (or your depth of cut in Z per pass).

Finally, the spindle HP needed is calculated by multiplying the MRR by a quantity called the unit power which is different for different materials. It's about .4 for aluminum.

From here you can draw some conclusions. Since the mill can absorb greater cutting forces and the spindle has more torque at a lower speed you can take deeper, slower cuts. Or, with a router, which is less rigid, but has a spindle with more power at the higher RPM range, you can take shallower passes, but at a higher feedrate. So it's more or less analogous to the ramp example.

I'm not really sure how much HP I need and I am going to want to use a range of end mills.

My needs have changed slightly since I first started working on this in that making aluminum molds is now more of a focus than plastic ones. I am tired of breaking my plastic and resin molds under pressure. For the molds I make manually, I have started making them out of carbon fiber to get the strength I need. That won't be an option for the CNC machine.

It sounds like I am better off with a high speed spindle for aluminum than a low speed milling head.

[louieatienza]

I'm not really sure how much HP I need and I am going to want to use a range of end mills.

My needs have changed slightly since I first started working on this in that making aluminum molds is now more of a focus than plastic ones. I am tired of breaking my plastic and resin molds under pressure. For the molds I make manually, I have started making them out of carbon fiber to get the strength I need. That won't be an option for the CNC machine.

It sounds like I am better off with a high speed spindle for aluminum than a low speed milling head.

Yes, especially with finish passes with ball endmill, you want a high spindle speed...

[Goemon]

Yes, especially with finish passes with ball endmill, you want a high spindle speed...

I found an interesting piece of practical research on this topic and the findings are consistent with what you said. The piece I read was about people installing lower power but higher speed spindles on their vertical mills to cut aluminum.

There is no concencus on the optimal speed for cutting aluminum but that makes sense as some alloys are harder than others and there are too many other variables (like how much hp you get at each speed with the specific spindle).

The part I am fairly confident of is that the right choice for me is the most powerful higher speed CNC spindle I can afford and not a lower rpm milling head.

[louieatienza]

I found an interesting piece of practical research on this topic and the findings are consistent with what you said. The piece I read was about people installing lower power but higher speed spindles on their vertical mills to cut aluminum.

There is no concencus on the optimal speed for cutting aluminum but that makes sense as some alloys are harder than others and there are too many other variables (like how much hp you get at each speed with the specific spindle).

The part I am fairly confident of is that the right choice for me is the most powerful higher speed CNC spindle I can afford and not a lower rpm milling head.

The only technical "speed limit" on a tool is determined by the SFM rating of the tool. Even then, modern toolpaths enable SFM double to triple the mfr.ratings.

With a VFD, the torque is usually constant so power is directly proportional to speed. That said, I'm around 32ipm per flute with a 1/4" endmill for roughing, and drop 50% for finish pass. A ball endmill is less efficient because the center basically runs at 0rpm. I'd like to make a fixture with an auxiliary spindle tilted 10° to get a better cut with finish milling, and some CAM actually have that in their 5 axis modules.

[Goemon]

The only technical "speed limit" on a tool is determined by the SFM rating of the tool. Even then, modern toolpaths enable SFM double to triple the mfr.ratings.

With a VFD, the torque is usually constant so power is directly proportional to speed. That said, I'm around 32ipm per flute with a 1/4" endmill for roughing, and drop 50% for finish pass. A ball endmill is less efficient because the center basically runs at 0rpm. I'd like to make a fixture with an auxiliary spindle tilted 10° to get a better cut with finish milling, and some CAM actually have that in their 5 axis modules.

How come people talk about the optimal speed for specific materials? I get it for materials like wood and plastic which can burn or melt if too much heat is generated with the cut, but how does it apply to aluminum or steel?

Are you saying that with a CNC router, you can go as fast as the SFM rating states and that there is no point in trying to find the "optimal" speed as some people suggest?

I assumed that the practical limit was dictated by the material. E.g. people mill steel at lower speeds because that produces the best results and they avoid using a high speed spindle because it is not possible to achieve comparable results with one.

[louieatienza]

How come people talk about the optimal speed for specific materials? I get it for materials like wood and plastic which can burn or melt if too much heat is generated with the cut, but how does it apply to aluminum or steel?

Are you saying that with a CNC router, you can go as fast as the SFM rating states and that there is no point in trying to find the "optimal" speed as some people suggest?

I assumed that the practical limit was dictated by the material. E.g. people mill steel at lower speeds because that produces the best results and they avoid using a high speed spindle because it is not possible to achieve comparable results with one.

Which people? It doesn't matter what the material is - there's a specific chipload and SFM for pretty much any material. They're all guidelines, optimal as dictated by the manufacturer, and you'll likely tweak the numbers based on how your machine performs and experience. You can go on YouTube and see guys side milling steel in excess of 500ipm. There's a video of a CR Onsrud machine cutting 3/4" plywood in one pass at 2200ipm. The practical limit is dictated by the machine. The more rigid the machine and more powerful the spindle, the faster and deeper you can cut.

About 6 or 7 years ago I started trying to cut aluminum. There was not a lot of info on this at all in the DIY world. But after many tests, research, and broken endmills, I was able to figure out speeds and feeds that worked well for me. I was actually almost exactly at the feeds and speeds recommended by a couple online calculators. And it's all more or less proportional to the tool size. Might have taken the easy way out but I'm glad I went this route because it taught me a lot about cutting aluminum, which further helped me with other materials. I discovered for myself then, that with the way routers work, that running a single edge tool at higher speed performed best. Once I got a larger router and SuperPID, I was able to use 2 and 3 flute tools at a lower RPM.

The late, great Benny Hill famously said in a skit, "Never assume... you make an A$$ of U and ME!" I was a little kid then but it stuck with me. The mantra given to me when I asked about aluminum cutting was "very low feedrate, tiny DoC, tiny stepover, the fastest spindle speed you have, 4-flute cutters..." I found for the most part that the truth was almost all the opposite of what was said. Today, everyone and their mother seems to know what a single-edge spiral-"O"-flute cutter is. Or, "I'm getting a crappy edge on my part and my tools are dulling fast; I need to increase the spindle speed..." That's opposite - more than likely, the federate has to increase of the spindle speed has to decrease. It's almost counterintuitive for newbies to hear that. But for the most part (except for the finish pass) it's true.

[Goemon]

Which people? It doesn't matter what the material is - there's a specific chipload and SFM for pretty much any material. They're all guidelines, optimal as dictated by the manufacturer, and you'll likely tweak the numbers based on how your machine performs and experience. You can go on YouTube and see guys side milling steel in excess of 500ipm. There's a video of a CR Onsrud machine cutting 3/4" plywood in one pass at 2200ipm. The practical limit is dictated by the machine. The more rigid the machine and more powerful the spindle, the faster and deeper you can cut.

About 6 or 7 years ago I started trying to cut aluminum. There was not a lot of info on this at all in the DIY world. But after many tests, research, and broken endmills, I was able to figure out speeds and feeds that worked well for me. I was actually almost exactly at the feeds and speeds recommended by a couple online calculators. And it's all more or less proportional to the tool size. Might have taken the easy way out but I'm glad I went this route because it taught me a lot about cutting aluminum, which further helped me with other materials. I discovered for myself then, that with the way routers work, that running a single edge tool at higher speed performed best. Once I got a larger router and SuperPID, I was able to use 2 and 3 flute tools at a lower RPM.

The late, great Benny Hill famously said in a skit, "Never assume... you make an A$$ of U and ME!" I was a little kid then but it stuck with me. The mantra given to me when I asked about aluminum cutting was "very low feedrate, tiny DoC, tiny stepover, the fastest spindle speed you have, 4-flute cutters..." I found for the most part that the truth was almost all the opposite of what was said. Today, everyone and their mother seems to know what a single-edge spiral-"O"-flute cutter is. Or, "I'm getting a crappy edge on my part and my tools are dulling fast; I need to increase the spindle speed..." That's opposite - more than likely, the federate has to increase of the spindle speed has to decrease. It's almost counterintuitive for newbies to hear that. But for the most part (except for the finish pass) it's true.

My experience of cutting aluminum with routers is limited so I am more than happy to take advice from people that have done it before. It sounds like you have quite a lot of experience with aluminum.

Do you have a preferred alloy for CNC machining? I.e. One that machines easiest and produces the best looking finish.

[louieatienza]

My experience of cutting aluminum with routers is limited so I am more than happy to take advice from people that have done it before. It sounds like you have quite a lot of experience with aluminum.

Do you have a preferred alloy for CNC machining? I.e. One that machines easiest and produces the best looking finish.

Most alloys that are harder and not stringy will produce a goid finish. The harder alloys will produce smaller chips that are easier to evacuate. I prefer cast tooling plate (Mic-6) as it's Blanchard ground on both sides, eliminating need for surfacing, and being cast it forms nuce chips that break off easily. As a bonus, drop offs can be bought on eBay for a fraction of their original cost. Other than that, I like using 7050, 7075, 2024, 6061...