[ckinney]

Hello CNC Zone community!

Over the years, I have been longingly perusing these forums, yearning to build a CNC machine of my own. Now that I actually have money, I am ready to make my first foray into the exciting world of CNC machining! I have a reasonably sound mechanical engineering background (currently studying), but there is quiet a bit of CNC machine-specific knowledge that I lack. And, hopefully, that's where you guys come in. I just need some guidance and suggestions on what path to take in designing my CNC router, and then possibly some feedback along the way as I refine my design.

Here are the constraints that I am considering for my project (in order of importance):

• Budget: $1000-1250
• Target Materials: wood and aluminum
• Work Envelope: 18" x 36" x 6" or 24" x 48" x 6" if budget allows
• Accuracy/Tolerance: not sure what's reasonable for the budget and target materials

Some of my questions regarding my proposed constraints:

1. Are my expectations reasonable for this budget range, target materials, and size? If not, please let me know so that I have a better idea of what I can expect to build.
2. What kinds of accuracies/tolerances could I get with these constraints?

I've decided to build a moving gantry CNC router, but I still have a lot of questions about which parts would be best for my price range and constraints:

1. Frame Material: not sure whether to use extruded aluminum, metal pipes, metal stock, etc.
2. Linear Motion System: don't know what form of rails, extruded aluminum, etc.
3. Drive System: not sure what type of screw to use
4. Motors: not sure which size to get and how many for each axis
5. Spindle: I have absolutely no idea here
6. Electronics: again, no idea here

I can't wait to build a CNC router, but I want it to be very well thought out before I even buy a single part. I know I've asked a lot of questions, but if you can help with any of them, it would be greatly appreciated. Thank you!

[awerby]

Hello CNC Zone community!

Over the years, I have been longingly perusing these forums, yearning to build a CNC machine of my own. Now that I actually have money, I am ready to make my first foray into the exciting world of CNC machining! I have a reasonably sound mechanical engineering background (currently studying), but there is quiet a bit of CNC machine-specific knowledge that I lack. And, hopefully, that's where you guys come in. I just need some guidance and suggestions on what path to take in designing my CNC router, and then possibly some feedback along the way as I refine my design.

Here are the constraints that I am considering for my project (in order of importance):

• Budget: $1000-1250
• Target Materials: wood and aluminum
• Work Envelope: 18" x 36" x 6" or 24" x 48" x 6" if budget allows
• Accuracy/Tolerance: not sure what's reasonable for the budget and target materials

Some of my questions regarding my proposed constraints:

1. Are my expectations reasonable for this budget range, target materials, and size? If not, please let me know so that I have a better idea of what I can expect to build.
   
   [Your budget's pretty tight for building a machine that can cut aluminum with any hope of success. A decent spindle costs about what you want to spend for the whole machine, and that's without a VFD. Are you good at scrounging, with access to promising dumpsters to dive in? Have you got a well-equipped shop to work in, perhaps at your school? ]
   
   
2. What kinds of accuracies/tolerances could I get with these constraints?

[You can hope for a lot, but you might have to settle for what you can get.]

I've decided to build a moving gantry CNC router, but I still have a lot of questions about which parts would be best for my price range and constraints:

1. Frame Material: not sure whether to use extruded aluminum, metal pipes, metal stock, etc.
2. Linear Motion System: don't know what form of rails, extruded aluminum, etc.
3. Drive System: not sure what type of screw to use
4. Motors: not sure which size to get and how many for each axis
5. Spindle: I have absolutely no idea here
6. Electronics: again, no idea here

I can't wait to build a CNC router, but I want it to be very well thought out before I even buy a single part. I know I've asked a lot of questions, but if you can help with any of them, it would be greatly appreciated. Thank you!

[If you can deal with it, steel is a good material for CNC router frames. Box-section hot-rolled steel tubes with a 1/4" wall thickness work well, and it's a lot cheaper than the equivalent in aluminum T-slot extrusions, which would take up your whole budget.

Profile rails with ball trucks are best, followed by V-wheels and rails, followed by supported round rails and bearings, followed by all sorts of junk.

Precision-ground ballscrews are best, followed by high-precision rolled ballscrews, followed by acme screws, followed by rack and pinion drives.

Build your frame before investing in motors and electronics; things change over the course of a design process, and it gives you more time to research.

For the materials you've got in mind, a VFD powered spindle is best, but a hand router will work (for a while).

[ger21]

Are my expectations reasonable for this budget range, target materials, and size? If not, please let me know so that I have a better idea of what I can expect to build.

$1000-$1250 buys you almost nothing when it comes to a CNC router.

1) Frame Material: not sure whether to use extruded aluminum, metal pipes, metal stock, etc.

What kind of tools, and fabrication skills do you have?
Aluminum extrusions will likely be out of your budget range.
Welded steel is the best, and can be fairly inexpensive, if you have the tools and skills to build it.
Most people with your budget build machines with MDF or plywood frames.

2) Linear Motion System: don't know what form of rails, extruded aluminum, etc.

Your budget will most likely limit you to skate bearings on cold rolled steel or pipe, or possibly round linear shaft and bearings from China.

3) Drive System: not sure what type of screw to use

Cheapest is probably a direct belt drive, but I wouldn't recommend it. I'd recommend 1/2-10 multi start acme screws.

4) Motors: not sure which size to get and how many for each axis

Design the machine first, as the design will dictate the motors required. Don't worry about the electonics yet either.

5) Spindle: I have absolutely no idea here

Anything from a $100 handheld router to a 2.2Kw spindle and VFD.

Whatever you end up building, it's very likely that you'll want to improve it as soon as it's finished. While it is possible to build a working machine for $1000, it's almost impossible to build a good one for that price.

[ckinney]

$1000-$1250 buys you almost nothing when it comes to a CNC router.

While it is possible to build a working machine for $1000, it's almost impossible to build a good one for that price.

Well, the most important thing to me is that I build a solid design and don't cheap out on the components and regret it later. With that being said, I can increase the budget to allow for a better design. How much do you think I should increase the budget in order to get a solid CNC router for the other constraints I specified?

What kind of tools, and fabrication skills do you have?

I have easy access to a drill press, hand tools, and basic power tools, and then I can gain access to the university lab for anything that requires more advanced machinery.

Welded steel is the best, and can be fairly inexpensive, if you have the tools and skills to build it.

Welded square steel tube sounds like a good choice for the frame, but I've never welded anything in my life. I would be willing to learn or might be able ask someone at the university lab to help me out. Would it be sufficient to use brackets and bolt the square tube together instead? Or could I even ask a welding shop to weld the tubes together for a reasonable price if I give them the plans?

[FandZ]

For your 1st machine there is nothing wrong with going with MDF. There is so much to learn. As long as cutting aluminum won't be a daily ordeal you can get by with it. 1/2 5start acme screws is a must to me. When you start looking at affordable electronics and motors you will see that you want to be able to cut around 180ipm or more. That will be sweet spot for the stepper motors and driver combo and to get that you will need a 5 start screw. Less design issues if you go with 2 motors, 1 on each side, to drive your gantry. As far as bearings go, make sure they are running on steel. Don't waste your time with plastic bearings on aluminum. Whatever rail you use make sure it is supported. For my first machine I would probably use angle steel with v bearings. If you search up mechmate rails, you will see how people have made angled rails for their V bearings using a grinder and a jig. Even if you don't angle your rails it will still work. You will just need to tighten your bearings ever so often until they wear a track into the angle. I would add a couple more hundred on your build and buy a machine made Z axis.My 2c.

[ckinney]

For your 1st machine there is nothing wrong with going with MDF. There is so much to learn. As long as cutting aluminum won't be a daily ordeal you can get by with it.

The ability to cut aluminum regularly is quite important to my design, and to my understanding, I should use metal framing to prevent flex if I want reasonably accurate tolerances.

Less design issues if you go with 2 motors, 1 on each side, to drive your gantry.

That makes a lot of sense, I've seen this numerous other places and I intend to incorporate it into my design.

[ger21]

The ability to cut aluminum regularly is quite important to my design, and to my understanding, I should use metal framing to prevent flex if I want reasonably accurate tolerances.

Can you provide some detail on what type of aluminum things you'll be cutting, and define "reasonably accurate"?

You can cut aluminum on a $500 chinese machine, but even a $50,000 router isn't an ideal machine for cutting aluminum.

[wizard]

Your questions are similar to others asked recently. The sorts of answers you will get will vary significantly. It is yor exoectations that matter and this is something that only you know and understand fully. So for another perspective I will try to answer your questions.

Hello CNC Zone community!

Over the years, I have been longingly perusing these forums, yearning to build a CNC machine of my own. Now that I actually have money, I am ready to make my first foray into the exciting world of CNC machining! I have a reasonably sound mechanical engineering background (currently studying), but there is quiet a bit of CNC machine-specific knowledge that I lack. And, hopefully, that's where you guys come in. I just need some guidance and suggestions on what path to take in designing my CNC router, and then possibly some feedback along the way as I refine my design.

One path to take is to NOT design your own machine. If you aren't familiar with CNC systems and machine tool design it might make sense to use a proven machine design or at least borrow from one.

Here are the constraints that I am considering for my project (in order of importance):

• Budget: $1000-1250
• Target Materials: wood and aluminum
• Work Envelope: 18" x 36" x 6" or 24" x 48" x 6" if budget allows
• Accuracy/Tolerance: not sure what's reasonable for the budget and target materials

1. That is a tight price range. It is realistic only if you are extremely good at scrounging and can wait for good deals to crop up.
2. Once you start to consider machining metals the demands on the structure increase significantly. If you really want to support Aluminum machining to any extent you need to consider a metal frame.
3. The bigger the machine the more expensive it becomes. If the budget is tight you will need to consider a smaller machine.
4. This is really tough because it depends heavily on what you have access tooling wise. You could easily blow a good portion of your budget on tools just to inspect and align the machine. Here I'm talking hand tools, inspection gages, reference squares and the like. That is expenses just to assemble the machine.
   
   This doesn't even include the expense of machining things to a high tolerance. If you have access to a machine shop the difference in the accuracy you can achieve can be significant. There are ways around becoming bound to a machine shop but they aren't cheap either. Basically precision costs big bucks.

Some of my questions regarding my proposed constraints:

1. Are my expectations reasonable for this budget range, target materials, and size? If not, please let me know so that I have a better idea of what I can expect to build.
2. What kinds of accuracies/tolerances could I get with these constraints?

What expectations? As far as I can see you haven't layed out any. As for target materials extensive machining of aluminum pretty much requires some sort of lube/coolant so that rules out a cheap machine built out of wood.

As to your second question that is very difficult to say because so much depends upon what you are capable of doing. The simple answer is that in your price range I wouldn't expect much.

I've decided to build a moving gantry CNC router, but I still have a lot of questions about which parts would be best for my price range and constraints:

Moving gantries are desirable for large machines but not so much for smaller machines, especially where you expect to maintain high precision. In the context of machining aluminum you really need to define what your expectations are.

1. Frame Material: not sure whether to use extruded aluminum, metal pipes, metal stock, etc.
2. Linear Motion System: don't know what form of rails, extruded aluminum, etc.
3. Drive System: not sure what type of screw to use
4. Motors: not sure which size to get and how many for each axis
5. Spindle: I have absolutely no idea here
6. Electronics: again, no idea here

1. I generally recommend steel for the frame material. It is cheap, easy to work with and has very desirable mechanical properties. However if you don't have the time, abilities nor tooling to work with steel then aluminum extrusion kits might make sense.
2. Profile rails are in order for a machine destined to machine aluminum. However such rails need to be installed with precision. The next step down is supported round rails.
3. Ball screws or acme screws are you only real choices. Neither is perfect.
4. This depends upon many factors but you need not worry about it until you have your mechanical desires firmed up.
5. If you want to machine aluminum or possibly other metals you need a spindle capable of supplying power at lower RPMs. At least relative to wood working speeds. Many operations in aluminum can be done with very high spindle speeds but not all thus the need for power at lower speeds. In the end what you do with the machine will tell you what sort of spindle to get.
6. There are literally hundreds of ways to go with electronics. As such you either copy some bodies else's approach or engineer your own solution. Like the steppers you can put this issue off for a bit and finalize the approach after the mechanical design gels.

I can't wait to build a CNC router, but I want it to be very well thought out before I even buy a single part. I know I've asked a lot of questions, but if you can help with any of them, it would be greatly appreciated. Thank you!

We can help but you need to reflect a bit on exactly what you want out of the machine. You talk about precision and accuracy but provide no real numbers. Accuracy isn't free, so you need to be realistic considering your budget.

Also realize that a CNC can't do much on its own. You need to learn G-Code at the very least and a little bit about modern CAD/CAM software.

[ckinney]

Can you provide some detail on what type of aluminum things you'll be cutting, and define "reasonably accurate"?

You can cut aluminum on a $500 chinese machine, but even a $50,000 router isn't an ideal machine for cutting aluminum.

I would like to be able cut aluminum enclosures for electronics projects, cut shapes out of aluminum sheet metal, and then cut some small 3D aluminum parts for prototyping projects. As for tolerances, I just want parts for my prototypes to have proper clearances, so I would guess maybe 0.01" (If that isn't too difficult) sounds right.

[ckinney]

One path to take is to NOT design your own machine. If you aren't familiar with CNC systems and machine tool design it might make sense to use a proven machine design or at least borrow from one.

I think I have a good idea of how CNC machines work, just not the cost of the different options for parts and which options are superior to others. That being said, since I'm a mechanical engineering student I want to design my own machine simply for the challenge of doing so, but I do need some guidance on which parts I can afford and how should I size the budget for the type of machine I want. Of course I will be looking at other machines people are building for inspiration and ideas.

Also realize that a CNC can't do much on its own. You need to learn G-Code at the very least and a little bit about modern CAD/CAM software.

I have a good amount of experience using CAD and CAM software, and basic G-Code knowledge.

Alright, so obviously I need to be more clear about exactly what I would like my machine to be capable of, otherwise it's difficult for you guys to help me out. So, here are my revised specifications:

• Work Envelope: 18" x 36" x 6"
• Target Materials: Wood and Aluminum
• Target Tolerances: 0.01" (or less)

Conservatively, how large should my budget be in order to build a machine that meets the above specifications? (Including the cost of all parts and excluding the cost of software and tools)

Assuming steel as a framing material, what types of rails, threaded rods, spindle, etc. would be the best that I could afford in the budget set in the answer to the question above?
And, how much could I expect to spend on each of the above categories of parts?

Thanks for all of the replies and information guys!

[louieatienza]

I think I have a good idea of how CNC machines work, just not the cost of the different options for parts and which options are superior to others. That being said, since I'm a mechanical engineering student I want to design my own machine simply for the challenge of doing so, but I do need some guidance on which parts I can afford and how should I size the budget for the type of machine I want. Of course I will be looking at other machines people are building for inspiration and ideas.


I have a good amount of experience using CAD and CAM software, and basic G-Code knowledge.

Alright, so obviously I need to be more clear about exactly what I would like my machine to be capable of, otherwise it's difficult for you guys to help me out. So, here are my revised specifications:

• Work Envelope: 18" x 36" x 6"
• Target Materials: Wood and Aluminum
• Target Tolerances: 0.01" (or less)

Conservatively, how large should my budget be in order to build a machine that meets the above specifications? (Including the cost of all parts and excluding the cost of software and tools)

Assuming steel as a framing material, what types of rails, threaded rods, spindle, etc. would be the best that I could afford in the budget set in the answer to the question above?
And, how much could I expect to spend on each of the above categories of parts?

Thanks for all of the replies and information guys!

I'd suggest at least a 3HP (2.2kW) spindle that has max 20k+ speed, minimum 20mm C7 rolled ballscrews with anti-backlash ballnuts, 20mm SBR fully supported rails minimum, 20mm profile rails preferred, NEMA23 steppers or 60mm frame AC servos.

You'll need a VFD for the spindle, couplers for the ballscrews, fixed and free end ballscrew supports, motor mounts, a lot of socket head screws... I'd try eBay first for part costs.

[ckinney]

I'd suggest at least a 3HP (2.2kW) spindle that has max 20k+ speed, minimum 20mm C7 rolled ballscrews with anti-backlash ballnuts, 20mm SBR fully supported rails minimum, 20mm profile rails preferred, NEMA23 steppers or 60mm frame AC servos.

You'll need a VFD for the spindle, couplers for the ballscrews, fixed and free end ballscrew supports, motor mounts, a lot of socket head screws... I'd try eBay first for part costs.

Just as an estimate before I get set on anything, what kind of budget would I need to cover all of these parts?

[louieatienza]

Just as an estimate before I get set on anything, what kind of budget would I need to cover all of these parts?

Again, check eBay...