512,954 active members
3,133 visitors online
Register for free
Login
Page 1 of 6 123
Results 1 to 20 of 105
  1. #1
    Registered
    Join Date
    Feb 2017
    Posts
    72

    DIY CNC machine on the cheap!

    Hello everyone,

    This is my first build and I've already gone against most people's advice of making a small first machine. At 600mm x 300mm x 75mm cutting volume, I think it will be a fairly large one, but I'm eager to see what lies ahead. I live in Africa and its really hard to ship things bought off the internet, so my biggest objective will be to source as many of the required parts as possible from local venders. Everything that will require tooling will be done by hand tools besides drilling (drill press), grinding, and perhaps cutting (angle grinder) the steel. The design I came up with doesn't require that much accuracy for drilling, so a drill press will suffice. All the bolts that will hold the machine together will be M8 bolts, besides those I'll use to attach the stepper motors, which will probably be M5. The plan, in short, will be to use a 9mm drill bit for the M8 bolt holes so i have a fair bit of play within the holes, which will help me make minor adjustments when assembling. This will especially come in handy when fixing up the linear slides nice and tight with as little play as possible. Most of the machine will be made up of standard 25mm x 25mmx 6000mm steel box tubing.
    I have bought some of the items I'll need on eBay, just waiting for them to arrive. I hope they reach me by post office *fingers crossed* (like I said, the physical address and mail delivery system in Africa still has a long way to go, so post office is probably my best bet at the moment). For now, a few snapshots of the frame are all I've got. I did the design in Sketch Up and I have attached the file so anyone can have a closer look and do with it what they may. Any ideas (from noobs to pros ) are welcome. I decided on a metal frame for the machine because I don't have the tools to machine MDF or other wood for that matter and hope I don't regret it!

    Isaac.
    Attached Files Attached Files

  2. #2
    Registered
    Join Date
    Feb 2017
    Posts
    72

    Re: DIY CNC machine on the cheap!

    Few more pictures!

  3. #3
    Registered
    Join Date
    Dec 2003
    Posts
    489

    Re: DIY CNC machine on the cheap!

    I would be concerned about the leverage exerted on the gantry by the Y axis.That 450mm height gives the forces quite a mechanical advantage and there is a desperate shortage of triangulation,which will be amplified by having bolts pass through holes that are 1mm oversize.I would suggest you increase the distance between the bearings on the Y axis and add some bracing and it would probably be a good thing to extend at least one of the box sections of the gantry so that an external brace can help hold the gantry rails square to the uprights.Good luck with the machine.

  4. #4
    Registered
    Join Date
    Dec 2014
    Posts
    640

    Re: DIY CNC machine on the cheap!

    Whew...I forsee lots of flex in that design. I agree with routalot that there's going to be lots of leverage on that gantry. You could still build your machine economically using other materials like MDF using torsion box design. That would be much more rigid than your current iteration.

  5. #5
    Registered
    Join Date
    Feb 2017
    Posts
    72

    Re: DIY CNC machine on the cheap!

    Hello routalot,

    Thanks for sharing your observation. I kind of realized that the gantry was hanging a little too high and I wasn't sure whether the eight bolts i had assigned the job of holding it up with all the associated weight and cutting forces would work, but i thought I'd build it and check for flex with the frame done. I'm glad you've mentioned that this early, so that's going to change for sure. Increasing the distance between the bearings on the Y axis would most definitely mean i would have to do the same for the X axis, which i really wouldn't mind if it reduced the flex on both axes. Increasing the distance between the bearings on the X axis to facilitate triangulation would increase the overall length of the machine along that axis, which i also wouldn't mind, however, i would have to start thinking about revising that linear mechanism to be fully supported. I haven't had any experience what-so-ever with CNC machines, never actually seen one doing its thing! Only videos on the web, so i haven't a clue what specific design considerations to keep in mind to make the frame rigid. You can't imagine how helpful I find your advice. Thanks again.

    Isaac.

  6. #6
    Registered
    Join Date
    Feb 2017
    Posts
    72

    Re: DIY CNC machine on the cheap!

    Quote Originally Posted by fretman_2 View Post
    Whew...I forsee lots of flex in that design. I agree with routalot that there's going to be lots of leverage on that gantry. You could still build your machine economically using other materials like MDF using torsion box design. That would be much more rigid than your current iteration.
    Thanks for the recommendation to switch to MDF, fretman_2. Unfortunately, I don't access to power saws, or sanding machines to guide me with cuts. Most DIY machines I've seen other hobbyists do using MDF are usually cut by either another (sometimes bigger) CNC router, or a couple of wood working power tools, which I don't have either. If I can cut MDF straight and true using hand tools, I'd gladly consider using MDF. It's interesting that I thought the first concern most CNC'ers would have would be the linear slide design for the Z-axis with the ball bearings running a long the rim edge (because of the small contact area and lateral load on the bearing), but that doesn't seem to bother you guys that much.

    Cheers
    Isaac.

  7. #7
    Registered
    Join Date
    Feb 2017
    Posts
    72

    Re: DIY CNC machine on the cheap!

    Quote Originally Posted by routalot View Post
    I would be concerned about the leverage exerted on the gantry by the Y axis.That 450mm height gives the forces quite a mechanical advantage and there is a desperate shortage of triangulation,which will be amplified by having bolts pass through holes that are 1mm oversize.I would suggest you increase the distance between the bearings on the Y axis and add some bracing and it would probably be a good thing to extend at least one of the box sections of the gantry so that an external brace can help hold the gantry rails square to the uprights.Good luck with the machine.
    I'll make modifications to the design tomorrow (it's getting a little late now) and post them, starting with triangulating the gantry. I'll also try to figure out a way i could support the X axis because lengthening it would most definitely require it.

  8. #8
    Registered
    Join Date
    Dec 2014
    Posts
    640

    Re: DIY CNC machine on the cheap!

    Well...the linear slide could be a concern, but likely less than the flex. A long moment arm is the same as using a long stick to move a big rock...takes less pressure on the other end to do the work. You might ask yourself if you really need all that clearance under the gantry. You didn't really go into what you intend to cut with your machine. I designed mine to cut out guitar necks and bodies. So I limited the Z cutting travel to about 3 or so inches to keep the forces down when I cut. I lacked the engineering skill to project those forces, but I did have an understanding that they could be higher with an excessive amount of Z travel.

    Nothing particularly wrong with using skate bearings the way you have them I suppose. It looks as if you have a cross member under the machine that keeps the two bearing assemblies from spreading. You might have some issues later with using steel on aluminum...depends on how often you use it.






    Quote Originally Posted by imbaine13 View Post
    Thanks for the recommendation to switch to MDF, fretman_2. Unfortunately, I don't access to power saws, or sanding machines to guide me with cuts. Most DIY machines I've seen other hobbyists do using MDF are usually cut by either another (sometimes bigger) CNC router, or a couple of wood working power tools, which I don't have either. If I can cut MDF straight and true using hand tools, I'd gladly consider using MDF. It's interesting that I thought the first concern most CNC'ers would have would be the linear slide design for the Z-axis with the ball bearings running a long the rim edge (because of the small contact area and lateral load on the bearing), but that doesn't seem to bother you guys that much.

    Cheers
    Isaac.

  9. #9
    Gold Member
    Join Date
    May 2005
    Posts
    3903

    Re: DIY CNC machine on the cheap!

    I’m not sure what suppliers can do for you in your country, but many around here they can rip sheet goods to size. If you know the width of the boards you need you can have the MDF or plywood pre cut.

    Not having tools can be a huge problem which is where kits come in so handy. The problem with kits. Ring the big jump in parts costs over raw materials and shipping charges. It might not be effective to ship a kit that distance but you might want to look for shops near you with the ability to cut materials to size. Even a wood working shop with a table saw can help with wood or aluminum products.

    It is completely possible to get straight cuts with hand power tools simply by using guides for a saw or router. It is a bit harder to get them parallel. For a guide the edge of factory fresh plywood may do the trick. Parallel cuts require a lot more work on the builders part to align the straight edge.

    I have to agree with others here the gantry will likely be a problem. Gantry are in fact a weak link in many DIY builds. What you want to do here is define the capabilities you need and then design and build to suit.

    Running short on time - hope this helps.

  10. #10
    Registered
    Join Date
    Feb 2017
    Posts
    72

    Re: DIY CNC machine on the cheap!

    Quote Originally Posted by fretman_2 View Post
    Well...the linear slide could be a concern, but likely less than the flex. A long moment arm is the same as using a long stick to move a big rock...takes less pressure on the other end to do the work. You might ask yourself if you really need all that clearance under the gantry. You didn't really go into what you intend to cut with your machine. I designed mine to cut out guitar necks and bodies. So I limited the Z cutting travel to about 3 or so inches to keep the forces down when I cut. I lacked the engineering skill to project those forces, but I did have an understanding that they could be higher with an excessive amount of Z travel.

    Nothing particularly wrong with using skate bearings the way you have them I suppose. It looks as if you have a cross member under the machine that keeps the two bearing assemblies from spreading. You might have some issues later with using steel on aluminum...depends on how often you use it.
    Right,... thanks to you guys, I realised many things of vital importance my gantry lacked that I had completely missed!!! Only after I imagining the machine cut along each axis at a time did I notice how much flex is actually inherent in this particular design, so i came up with a major revision! I intend to use it primarily for engraving lettering in wood and plastic (mostly acrylic for signs although i do sometimes need custom cut parts for small speaker enclosures out of MDF. As i mentioned earlier, I live in Africa and the nearest CNC in 350kms away, and only good for about 150mm x 200mm x 20mm cutting volume, so that's useless! I know for sure I'll get clients for the machine, but I don't want to get ahead of myself just yet. So, in rev 2, solved most of the flexing problems with the gantry as you can see.

  11. #11
    Registered
    Join Date
    Dec 2003
    Posts
    489

    Re: DIY CNC machine on the cheap!

    Well actually I can't see.Its good that you have been visualising the loads on the machine and the additional information suggests to me that a 90mm Z axis travel would do what you need.Which would allow you to reduce the gantry height significantly and by doing so you would reduce the leverage exerted by pushing the tool through the work.The other thing that you might want to consider is that the forces applied to the gantry will tend to twist it and the two lengths of box section in your initial design are sub-optimal.I don't have an easy answer,but you description of how limited the facilities are should be seen as a challenge and not a limitation;a determined man will get the job done.

  12. #12
    Registered
    Join Date
    Feb 2017
    Posts
    72

    Re: DIY CNC machine on the cheap!

    Rev 2 modifications:

    1) Added triangulating bars on both sides of the gantry. that should take care of flexing when cutting along the X-axis alone.

    2) Also added a piece of timber snugly between the each pair of the gantry uprights. That should prevent flexing when cutting along the Y axis alone and finally;

    3) Added another piece of timber whose face runs parallel to that of the cutting table, underneath the table. This should resolve racking (or at least minimize it) of the gantry from side to side probably by keeping the X-axis bearings nice and parallel.

    I can't think of anything else I could possibly add to the gantry to make it any more rigid that it already appears. As an extra precaution, to prevent the X axis rails from sagging under that weight of the gantry, I think I'll add some 2mm L-section steel running along the edges of the table (Not yet added in the pictures). This will serve the purpose of both stiffening the X-axis rails and keeping saw dust from jamming the X-axis linear bearings during operation.

  13. #13
    Registered
    Join Date
    Feb 2017
    Posts
    72

    Re: DIY CNC machine on the cheap!

    Quote Originally Posted by wizard View Post
    I’m not sure what suppliers can do for you in your country, but many around here they can rip sheet goods to size. If you know the width of the boards you need you can have the MDF or plywood pre cut.

    Not having tools can be a huge problem which is where kits come in so handy. The problem with kits. Ring the big jump in parts costs over raw materials and shipping charges. It might not be effective to ship a kit that distance but you might want to look for shops near you with the ability to cut materials to size. Even a wood working shop with a table saw can help with wood or aluminum products.

    It is completely possible to get straight cuts with hand power tools simply by using guides for a saw or router. It is a bit harder to get them parallel. For a guide the edge of factory fresh plywood may do the trick. Parallel cuts require a lot more work on the builders part to align the straight edge.

    I have to agree with others here the gantry will likely be a problem. Gantry are in fact a weak link in many DIY builds. What you want to do here is define the capabilities you need and then design and build to suit.

    Running short on time - hope this helps.
    Hello Wizard,

    Getting factory cut parts around here is a rarity and if you insist, it's waaaayy to expensive. I guess the only people that order them are those really meaning to do business with them. It also doesn't help if you only order a few parts. This is why I'm insisting on a build that can easily be replicated by anyone else interested in building a cheap CNC machine with easy-to-find parts. I know it won't be easy, but I'm aiming to design something which anyone with basic machining skills and a few tools can build. I have visited most of the local hardware stores and to my shock, couldn't find majority of the most common parts most DIY builders use to build their machines!! This has kind of reinforced my insistence on using locally sourced standardized parts. If the prototype turns out great, I believe I'll probably experiment with cutting aluminum (after all, the machine's made of steel), see how well it performs. Should anything break, easy.... just walk up to ANY hardware store and buy what I need. I might have to cut a little and drill a few holes out, but it sure beats the hell out of ordering ridiculously expensive custom parts or ordering a new component off the internet and having to wait! That's my strategy.

    Thanks for your suggestion though, unfortunately, not possible.

  14. #14
    Registered
    Join Date
    Feb 2017
    Posts
    72

    Re: DIY CNC machine on the cheap!

    Quote Originally Posted by routalot View Post
    Well actually I can't see.Its good that you have been visualising the loads on the machine and the additional information suggests to me that a 90mm Z axis travel would do what you need.Which would allow you to reduce the gantry height significantly and by doing so you would reduce the leverage exerted by pushing the tool through the work.The other thing that you might want to consider is that the forces applied to the gantry will tend to twist it and the two lengths of box section in your initial design are sub-optimal.I don't have an easy answer,but you description of how limited the facilities are should be seen as a challenge and not a limitation;a determined man will get the job done.
    You are right about the height of the gantry, I will make it lower. Anything to cut down on costs. I might have to add that to the model later as I have run out of time for now. I have to say, it will definitely be a challenge and I'm looking forward to it. Wouldn't it be nice if all that was needed to build a CNC machine was just a drill press and a table saw (aside from the obvious wrenches, screw drivers and the like)?

    Thank you all and Goodnight! Your ideas were all very helpful!

  15. #15
    Gold Member
    Join Date
    May 2005
    Posts
    3903

    Re: DIY CNC machine on the cheap!

    Quote Originally Posted by imbaine13 View Post
    You are right about the height of the gantry, I will make it lower. Anything to cut down on costs. I might have to add that to the model later as I have run out of time for now.
    .
    That gantry is very high.
    I have to say, it will definitely be a challenge and I'm looking forward to it.
    Building things can be a lot of fun. It can be a struggle to balance low cost against the performance you need. Wood products can actually help with cost control.
    Wouldn't it be nice if all that was needed to build a CNC machine was just a drill press and a table saw (aside from the obvious wrenches, screw drivers and the like)?
    I still break down plywood sheets with a handheld circular saw.
    Thank you all and Goodnight! Your ideas were all very helpful!
    Due to the lack of local machinery you might want to build this machine with the intent to make parts for a better machine. There are all sorts of ways to go about this. One consideration is cast aluminum parts. A man named Gingery published a series of books outlining how to build a machine shop out of scrap metal (mostly aluminum) that might be of interest. This might sound extreme but the methods are perfectly valid though not focused on router sized machines. Even if you only use the methods for small parts it might be of benefit for an improved router.

  16. #16
    Registered
    Join Date
    Dec 2003
    Posts
    489

    Re: DIY CNC machine on the cheap!

    Having now seen the gantry in it's revised state it appears to me that you could leave out the wooden brace and drop the rails significantly.Then if you left one of the rails a bit longer you could add a triangulating brace on the outside of the gantry.It would get the forces applied to a shorter lever and retain the stiffness.Looking further ahead,what type of motor will you use and what software to run the machine?

  17. #17
    Registered
    Join Date
    Feb 2017
    Posts
    72

    Re: DIY CNC machine on the cheap!

    Hello guys!

    Just done with another major revision! You think you're done and only after putting the model back together do you realise more areas that might require close attention! Anyway, here are some pictures of Rev 2!

  18. #18
    Registered
    Join Date
    Feb 2017
    Posts
    72

    Re: DIY CNC machine on the cheap!

    Quote Originally Posted by wizard View Post
    .
    That gantry is very high.

    Building things can be a lot of fun. It can be a struggle to balance low cost against the performance you need. Wood products can actually help with cost control.

    I still break down plywood sheets with a handheld circular saw.


    Due to the lack of local machinery you might want to build this machine with the intent to make parts for a better machine. There are all sorts of ways to go about this. One consideration is cast aluminum parts. A man named Gingery published a series of books outlining how to build a machine shop out of scrap metal (mostly aluminum) that might be of interest. This might sound extreme but the methods are perfectly valid though not focused on router sized machines. Even if you only use the methods for small parts it might be of benefit for an improved router.
    I agree with you about how much cheaper machines get if wood is involved, but it's a little more challenging for me to use compared to steel box section. Transporting the steel is far easier from the store to my "workshop", i wouldn't have to worry about timber warping or bending when I have to pause working on the machine for significant periods. None of that stress with steel. That's my excuse and I'm sticking to it!

    I did have the intention of using this first build to modify itself if the need arises. I wouldn't mind a steel/wood mix for the structure, but I kind of find it counter-intuitive to use a machine made of steel to make a machine made of wood! I don't see myself cutting any metal with this machine, so I'm assuming that's what you meant. I would only consider building a second machine if the first got too busy. We'll see how things turn out.

    I'd love to take a look at Gingery's book, but only just to see what principles he applies. I don't have to resources to cast any metal parts just yet. Perhaps in the near future, still not sure. Thanks for the reference.

  19. #19
    Registered
    Join Date
    Feb 2017
    Posts
    72

    Re: DIY CNC machine on the cheap!

    So, what modifications did I make?

    1) First and most importantly, I caved and lowered the gantry from the original 450mm. It now stands at 350mm from the same references.
    2) Because of the now limited space underneath the Y-axis rails, I shifted the wooden brace to between the Y-axis rails. This has replaced the vertical supports I had between the rails to keep them parallel under the compression of the bearing running up and down them. The brace also helps prevent flex when cutting along the Y-axis.

  20. #20
    Registered
    Join Date
    Feb 2017
    Posts
    72

    Re: DIY CNC machine on the cheap!

    Quote Originally Posted by routalot View Post
    if you left one of the rails a bit longer you could add a triangulating brace on the outside of the gantry.It would get the forces applied to a shorter lever and retain the stiffness.
    GREAT IDEA!!! Hadn't thought of that! That's actually a lot easier than looking for a 1" thick piece of wood to cut to size and jam in there. The clearances between the bolts holding that brace and those attaching the Y-axis motor are painfully tight! My original intention was to build a machine that didn't require precision drilling, but I was starting to worry that that might get thrown out the window from this point on. Fortunately, with this idea, we can still proceed with my original objectives! I'll try that into the model tomorrow and see how best I can implement it. That would probably be that best this design could get. Thanks again.

    Quote Originally Posted by routalot View Post
    Looking further ahead,what type of motor will you use and what software to run the machine?
    I really hadn't thought that far ahead yet. I was taking it one step at a time, but being a beginner, I'll probably start with freeware just to wrap my head around the mechanics of computer aided manufacturing. It's a steep learning curve, so 'll do my best to worry about one thing at a time. I'd be glad to hear your recommendation. If you're referring to the stepper motors, I'll probably go with NEMA 23. I need relatively high cutting speeds. I'm aware there are many factors that determine this, but I don't want the stepper motors to be the weakest link in that chain! As far as the spindle goes, I have a small Chinese made (brand name: DCA) die grinder in storage that I bought a few years back but have never used. 3mm collet (probably 1/8" for the imperial guys). 16,000 - 30,000 RPM at 220VAC I suppose. I'll start with what I've got on hand and work my way up.

    Boy!...... To think back how confident I was with the first design, if I had only known! Just glad I hadn't even started to build all those weakness into the machine!

    I appreciate everyone's advice! It was very helpful. Still waiting for the parts to arrive. I'll get started as soon as i get the first items!

    Goodnight for today!

Page 1 of 6 123

Similar Threads

  1. cheap cnc machine
    By s3rius385 in forum Open Source CNC Machine Designs
    Replies: 3
    Last Post: 12-28-2010, 04:11 AM
  2. looking for a cheap machine
    By randomguy737 in forum Want To Buy...Need help!
    Replies: 1
    Last Post: 08-02-2010, 08:34 PM
  3. new cheap mdf machine
    By Hobbiest in forum DIY CNC Router Table Machines
    Replies: 36
    Last Post: 02-25-2004, 05:54 AM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •