DIY hobby cnc design thoughts?

[Keonfrey]

Hello all, this is my first post on here however I've been browsing on here every now and then if I need answers. About a week ago I decided to try designing and making my own cnc router and have spent the week designing and thinking about parts materials etc. Its my first build and I'm a woodworker so I decided on doing an MDF build here. The bed dimensions are 40" in x and 30" in y. I'm hoping for about 2-2.5" in z travel. For linear motion I'm using v-bearings on steel DIN Rails. For drive I'm thinking of using 1/2-10 ACME lead screws with delrin AB nuts on 170+ oz/in nema 23 steppers. (recommendations welcome!) I've heard good about the gecko 540 4 axis control board in regards to bang/buck too. I'm thinking probably a 24v PSU. Any help or ideas would be appreciated! What kind of tolerances do you think I can get? Are those motors powerful enough? Will I have problems with lead screws with my travel range? Will I be able to get decent tolerances with my linear bearing and mdf design?

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[Keonfrey]

https://3dwarehouse.sketchup.com/use...d-1f0b2a7fbaa6 Here is my google sketchup 3d warehouse profile. The design is downloadable here if you wish to!

[fretman_2]

I like it! I've got some steel v wheels just waiting on a project! Got to see if I can get some of that DIN rail locally.

Hello all, this is my first post on here however I've been browsing on here every now and then if I need answers. About a week ago I decided to try designing and making my own cnc router and have spent the week designing and thinking about parts materials etc. Its my first build and I'm a woodworker so I decided on doing an MDF build here. The bed dimensions are 40" in x and 30" in y. I'm hoping for about 2-2.5" in z travel. For linear motion I'm using v-bearings on steel DIN Rails. For drive I'm thinking of using 1/2-10 ACME lead screws with delrin AB nuts on 170+ oz/in nema 23 steppers. (recommendations welcome!) I've heard good about the gecko 540 4 axis control board in regards to bang/buck too. I'm thinking probably a 24v PSU. Any help or ideas would be appreciated! What kind of tolerances do you think I can get? Are those motors powerful enough? Will I have problems with lead screws with my travel range? Will I be able to get decent tolerances with my linear bearing and mdf design?

[ger21]

Go with a multi start acme, and bigger motors and power supply if you plan on using a G540. You'll get at least 3-4 times more speed, for just a little more money.
G540 4-Axis kit Stepper Motor | Stepper Motor Driver | CNC Router | Laser Machine | 3D Printers For Sale

Also. drive both sides of the gantry. You'll get racking with a single screw in the center.

[Keonfrey]

Alright, thanks for your input! I was wondering if a single centre drive would be OK for the gantry. If one X drive misses steps will it get out of square eventually? I mean that's not a big issue because one can always recalibrate. Dual screw would be OK still for x drive or do I have to go rack and pinion? I don't have to go to nema 34 though for size do I?

[awerby]

I never heard of using DIN rail like that; did someone tell you it would work? It doesn't have the right shape to mate with V wheels; you'd be better off using V rail instead, even if it did cost more. Here's a source (not that I'm recommending this particular seller): v groove rail You want hardened steel V-rail to go with your steel wheels. That place also has hard-coated aluminum rail that goes with delrin wheels; it's not going to work as well as the hardened steel, but it's better than steel wheels and DIN rail.

[Keonfrey]

Someone had given me the idea but hadn't proved it. I'll be the test dummy. It's kind of a rounded shape and I'm sure it will wear some, but I'm not very concerned about that as long as the wear is fairly even because my bearings will be adjustable. I don't plan that this build will be finished much before a higher quality machine will be built and I would like to test the DIN rail out of curiosity. I bought the steel rail not aluminum like a majority out there. I think I will save the hardened steel v for a later version maybe! I think I will change the x drive to a dual screw as well and go with a bigger motor driver kit so I can upgrade my machine to the motors.

[ger21]

Alright, thanks for your input! I was wondering if a single centre drive would be OK for the gantry. If one X drive misses steps will it get out of square eventually? I mean that's not a big issue because one can always recalibrate. Dual screw would be OK still for x drive or do I have to go rack and pinion? I don't have to go to nema 34 though for size do I?

Properly setup machines don't miss steps. So no, it's not an issue.
Dual screws are fine. I've been using them for 7-8 years now.
Nema 23 are fine.

[Keonfrey]

Properly setup machines don't miss steps. So no, it's not an issue.
Dual screws are fine. I've been using them for 7-8 years now.
Nema 23 are fine.

Great I'll do that I think!

[MConner]

I just finished a 800 x 900mm laser build using linear v-guides from open builds, and was pleasantly surprised with there product. They might be a cost effective alternative to designing your own V-groove/DIN rail system... which by the way is a clever use of materials, I will keep that idea in my tool box for something in the future. BTW also built a center drive router (1500 x 800) the key to preventing the "racking" was expensive LM guides, a strong motor, and a very precise/sturdy build.

[wizard]

Hello all, this is my first post on here however I've been browsing on here every now and then if I need answers.

A key consideration is understanding what you expect to get out of the machine! Without that you might not be having pay with the build.

About a week ago I decided to try designing and making my own cnc router and have spent the week designing and thinking about parts materials etc. Its my first build and I'm a woodworker so I decided on doing an MDF build here.

I don't personally like MDF, really hate working with it, however if your only goal is wood working a serviceable machine can be built with MDF. If you have any intentions, dreams or other desires to work stuff outside of wood, I'd suggest leaving MDF behind.

The bed dimensions are 40" in x and 30" in y. I'm hoping for about 2-2.5" in z travel.

Normally I get concerned about people, building gantries that are too high and weak. Here I have a different concern. The problem is you need enough Z travel to clear any tools you might use. Even if the gantry isn't that high I'd strongly suggest more Z travel, especially if you can see yourself chucking a dill bit or other longish tools.

For linear motion I'm using v-bearings on steel DIN Rails.

Honestly you would be wasting your money with DIN rail. I've used a huge variety over the years in controls work and can't imagine how this would very work well.

For drive I'm thinking of using 1/2-10 ACME lead screws with delrin AB nuts on 170+ oz/in nema 23 steppers. (recommendations welcome!) I've heard good about the gecko 540 4 axis control board in regards to bang/buck too. I'm thinking probably a 24v PSU. Any help or ideas would be appreciated! What kind of tolerances do you think I can get?

DIN rail linears? I can't imagine this stuff holding up well under load and thus tolerances would likely be crap requiring light loading and constant maintenance.

Are those motors powerful enough?

Again it is a question of expectations. Your machine isn't that big but you are better off designing for higher speeds.

Will I have problems with lead screws with my travel range?

nope

Will I be able to get decent tolerances with my linear bearing and mdf design?

I hate to be blunt but I'm going to say no. V rollers are less than ideal for routers in general. Running them on DIN rail, that is too thin, just compounds the problem. Again it comes down to your expectations but you would be better off with round rail on an MDF build.

[Keonfrey]

Thanks wizard! I'm not looking for terribly good tolerances in this one. I'll be cutting foam and maybe wood with it max, just to get the general basics of building a Cnc since its my first I'll stick to cheap parts and get the concept of Cnc building then I'm looking to go with a steel frame and expensive rails once I have already built one. Your thoughts will definitely be taken into consideration for a more extensive precision build. I want to learn how to make a working Cnc and then learn to make a good Cnc later as I learn more and make less mistakes that way!

[Keonfrey]

I just finished a 800 x 900mm laser build using linear v-guides from open builds, and was pleasantly surprised with there product. They might be a cost effective alternative to designing your own V-groove/DIN rail system... which by the way is a clever use of materials, I will keep that idea in my tool box for something in the future. BTW also built a center drive router (1500 x 800) the key to preventing the "racking" was expensive LM guides, a strong motor, and a very precise/sturdy build.

Thanks! Yes I'm testing the DIN rail in case I want to use it for a project that doesn't require loads or tight tolerances!

[Biggs427]

My hobby CNC has the same kind of design as yours and I've tried DIN rail and it doesn't work. Unless you machine it to make the rail flat where the V-Groove bearing sits and to have the same width, it is gonna be worse than a drawer slide setup.

I tried to replace the drawer slide on my Y axis with DIN rails; that's why I can compare.

Since I was too lazy to redesign my gantry, I ended up putting 12mm profile rail and for wood working it does a good job.

[Keonfrey]

My hobby CNC has the same kind of design as yours and I've tried DIN rail and it doesn't work. Unless you machine it to make the rail flat where the V-Groove bearing sits and to have the same width, it is gonna be worse than a drawer slide setup.

I tried to replace the drawer slide on my Y axis with DIN rails; that's why I can compare.

Since I was too lazy to redesign my gantry, I ended up putting 12mm profile rail and for wood working it does a good job.

OK so you're saying it doesn't work at all? Not even poorly? I'm trying to save money for my first build so I can afford better setup for the second one. If it absolutely no way will work I would consider better rails...

[Biggs427]

It worked but it was worse than a drawer slide.

Measure the width of the rail and you'll see lot of variation.

I made a prototype truck to work with a DIN rail and some time it binds so the truck is very hard to move and sometimes it loose making the truck moving all around the place.

To me it wasn't usable. My standards aren't not that high given the fact that I started with a drawer slide axis and I was ok with that.

[wizard]

Thanks wizard! I'm not looking for terribly good tolerances in this one. I'll be cutting foam and maybe wood with it max, just to get the general basics of building a Cnc since its my first I'll stick to cheap parts and get the concept of Cnc building then I'm looking to go with a steel frame and expensive rails once I have already built one.

I guess my point here is that DIN rail is extremely flexible and frankly not that cheap. You could instead go with angle iron an remain in the same ball park cost wise. This isn't angle iron to frame the machine with but rather something for the wheels to run against.

Your thoughts will definitely be taken into consideration for a more extensive precision build. I want to learn how to make a working Cnc and then learn to make a good Cnc later as I learn more and make less mistakes that way!

That is perfectly fine but with just a bit of effort your first machine could be good enough to build parts for the "good" CNC.

The thing I worry about, with DIN rail, is that the stuff is just thin sheet metal and would likely have issues even trying to machine wood. You will likely need to screw the rail down every inch or so to keep flexure under control. I base this on spending years snapping relays and other control panel parts off and on DIN rails.

If you do go the DIN rail route you may find that you have clearance issues behind the rollers. This depends upon the exact type of roller you buy and the mounting method of course.

One other suggestion, down size this machine. If you just want to learn the basics of CNC systems building a big machine, that won't perform well, just doesn't make sense. It is a lot of money down the drain that can be used to build the second machine. In fact I'm not even sure leadscrews make sense on such a machine. With DIN rail linears you might as well do belt drive of the axises. It would result in a cheaper machine that can support you desire to learn CNC systems.

[wizard]

OK so you're saying it doesn't work at all? Not even poorly? I'm trying to save money for my first build so I can afford better setup for the second one. If it absolutely no way will work I would consider better rails...

Believe me I understand the money side of the equation, but once you realize that you are working with a thin sheet metal part you will see that there is a real problem. Flimsiy and subject to rapid wear doesn't inspire a lot of confidence in the material.

Now given that you have a couple of options.

1. Would be to build your first machine as a robust and fully capable machine. Skip the use of low end linear motion stuff and build a machine tha fully meets your expected needs. Some are highly resistant to doing such a build for their first machine. This is sorta like the guy that buys a $99 table saw one year and realizes the second year that he needs a more capable unit.

2. If you want to go the cheap machine to learn on then keep that machine small to make it affordable. V-roller bearings are perfectly suitable here, you just need to run them on more substantial runners. There are a number of examples in these forums of guys that have used angle iron or even aluminum angle extrusions to build machines using V-rollers. Your design would have to change a bit but cost wise it isn't going to be hugely different than going the DIN rail route. Either approach is subject to wear and tedious alignment to get the saddles to move smoothly but people have gotten good results for their needs. You can't confuse this sort of construction with metal framed machines running fancy linear bearings but that isn't the point. The point rather is to build something that solves your needs at the right price point.


In any event I'm not too sure the idea of building a small cheap machine (that can't do much) to learn on, makes sense. A good portion of what you need to learn to run a machine effectively requires learning software and design concepts that don't really need a machine but rather a computer and software. Building out a fully capable machine at the start isn't all that difficult. If you can imagine building a low end machine you can just as easily imagine building a more capable machine.

[Keonfrey]

Believe me I understand the money side of the equation, but once you realize that you are working with a thin sheet metal part you will see that there is a real problem. Flimsiy and subject to rapid wear doesn't inspire a lot of confidence in the material.

Now given that you have a couple of options.

1. Would be to build your first machine as a robust and fully capable machine. Skip the use of low end linear motion stuff and build a machine tha fully meets your expected needs. Some are highly resistant to doing such a build for their first machine. This is sorta like the guy that buys a $99 table saw one year and realizes the second year that he needs a more capable unit.

Good point! I guess if there is this much help on the forums any minor or major problem can be brought here! So If I do start off with building my "good" Cnc, aluminum don't tickle my funny bone at all I'd rather weld something steel.

2. If you want to go the cheap machine to learn on then keep that machine small to make it affordable. V-roller bearings are perfectly suitable here, you just need to run them on more substantial runners. There are a number of examples in these forums of guys that have used angle iron or even aluminum angle extrusions to build machines using V-rollers. Your design would have to change a bit but cost wise it isn't going to be hugely different than going the DIN rail route. Either approach is subject to wear and tedious alignment to get the saddles to move smoothly but people have gotten good results for their needs. You can't confuse this sort of construction with metal framed machines running fancy linear bearings but that isn't the point. The point rather is to build something that solves your needs at the right price point.

If I want to machine aluminum and have a steel Cnc framework any recommendations on linear motion parts?

In any event I'm not too sure the idea of building a small cheap machine (that can't do much) to learn on, makes sense. A good portion of what you need to learn to run a machine effectively requires learning software and design concepts that don't really need a machine but rather a computer and software. Building out a fully capable machine at the start isn't all that difficult. If you can imagine building a low end machine you can just as easily imagine building a more capable machine.

Should I have everything designed to every detail and parts orderd before I start the build or should I order parts as needed? Which do people generally prefer? I guess with building a production Cnc if you buy the right equipment no it wouldn't be that difficult to build.

[awerby]

Build the frame first, and then think about the motors and electronics. You don't want to be stuck with inappropriate hardware when your design morphs a bit (as it seems to be doing already). If you want to build a steel machine and cut aluminum, get profile rails with bearing trucks, not round ones or V-rails, and certainly not experimental linear motion components cobbled together out of junk.