newbie just built a very low budget CNC router looking for a bit of advice

[alanesq]

Hi,

I have just joined the forum, I am based in the UK and recently decided to have a look if I thought 3D printers were developed enough yet to be of any use to myself, I decided yes but a decent one is way out of my budget, I then drifted on to looking at the cheap cnc engravers on Banggood..................next thing I knew I had set about building myself a cnc router - lol

My plan was just cobble together something very cheaply to get a bit of experience, have a play with, see what this CNC is all about. Whilst individual parts can be found cheaply they all do mount up and I ended up spending £200 on it (more than I had planned).
As I tend to do, I just jumped in without doing much in the way of research so there is plenty of classic mistakes in my build I am sure but I have done a few cuts now and it does surprisingly seem to be working :-)

What I would like to get some advice on is what router bits to buy to use with it. I seem to be overheating the bits I have tried so far despite keeping the feed rate and cut depth low (just bits I have from my hand-held router), I suspect the spindle may be too fast really (unloaded speed of 35,000rpm)?
I have Googled it but just getting totally confused as to what would be best to get me started?
BTW - cheap as possible of course, ideally from ebay in UK.





more pics here: Directory listing of http://files.alanesq.com/CNC

btw - I copied the idea for the linear bearings from - https://www.rcgroups.com/forums/show...ch#post7469041

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[ger21]

What I would like to get some advice on is what router bits to buy to use with it.

Depends what you want to do. There are many different types of bits, for many different applications.

The reason you are burning your bits is due to the combination of high rpm, and low feedrate. At 35,000 rpm, you'll really never be able to go fast enough to prevent burning on that machine. 15,000 rpm and 3000mm/min would be a good place to be at.

For general cutting, cheap carbide tipped router bits work fine. Carbide spiral bits are better, but can cost 2-3x more.

[alanesq]

Thanks for the reply

That would explain a lot, I had been slowing the feed down thinking this would reduce the heat build up - Doh!

I will do some experimenting tomorrow.....

[ger21]

Nope, it's just the opposite.

[alanesq]

Thanks again for your advice.

This morning I fitted a speed control to the router (crude motor speed controller which is basically a dimmer switch for power tools), this allows me to vary the power to the router. I have also upped the cutting speed to the max my setup can do (not a lot as I am using threaded bar for most of the lead screws).
This has helped a lot, I have now managed to do some cutting without it turning the wood dark brown (before it looked like it had been cut with a CO2 laser - lol).

I think I need to get myself some better router bits now (and do some work to reduce some of the play in my setup), then I think I should be able to do something useful with it :-)

[coherent]

If you use ebay or amazon, they have some low priced bits that will work. A single flute bit (vs a 2 or 4) will generate less heat and can be ran at faster rpm than a multi fluted bit. Welcome to the world of CNC and congratulations on building your first machine! I personally get just as much enjoyment building them as using them and you definitely learn more. Even after years, it's still fun watching them cut something and seeing the results. Good luck!

[alanesq]

Thanks - I have ordered some and hopefully they will arrive today
By the time I found out what the problem was I had already destroyed all the router bits I have - lol

BTW - I wasn't at all impressed with the DIY linear bearings I had made, but this morning I finally cracked how to set them up and have now changed to very impressed with them. They are now rock solid (by comparison anyway).
Next thing is to sort out an anti-backlash nut of some kind for my threaded rod as I have just used a standard nut at the moment.

[fretman_2]

You'll probably get some wear if you have metal bearings on aluminum angle. May not be an issue if it's not a production machine, Nice job!

[alanesq]

You'll probably get some wear if you have metal bearings on aluminum angle. May not be an issue if it's not a production machine, Nice job!

Thanks :-)

I suspect you are right but the two main sets of bearings cost me £40 total where as if I bought bearings it was looking like costing several hundred pounds so decided to go for the cheap option. I don't really know how much I will use it, was more interested in building one than having any idea why - lol

Here is a pic of my progress so far:

[alanesq]

I have now ordered myself some proper lead screw as I think it worth spending a bit more money now I know it is actually going to work ;-)

Thought it might be of interest to show what this build has cost me:

Plywood around £10
metal for linear bearings (angled aluminium) £30
stepper motor controllers £7 each (3 of)
skate bearings £10 (16 of)
stepper motors £45 (first I bought new for £30, then picked up 3 used on ebay for £15)
24v power supply £11
threaded bar and misc nuts&bolts £20 - replace threaded bar with lead screw cost me £20
mini router £30
z axis bearing kit £25
stepper motor couplings £6
Misc electronics, wiires, arduino, screws etc. I already had in stock. I probably wasted around an extra £30 buying wrong parts etc.

BTW - I fitted all the electronics inside the wooden box which forms the main gantry. I am sure there are reasons this is a bad idea (electronic interference, vibration??) but I was pleased with this idea as it makes it a nice self contained unit and simplifies much of the wire routing. The only problem I have had so far is that when the router turns on (240v) this triggers the limit sensors but I found replacing the mechanical relay with a solid state one resolved this.

[wizard]

I have now ordered myself some proper lead screw as I think it worth spending a bit more money now I know it is actually going to work ;-)

Did you have any doubts?

Thought it might be of interest to show what this build has cost me:

Plywood around £10
metal for linear bearings (angled aluminium) £30
stepper motor controllers £7 each (3 of)
skate bearings £10 (16 of)
stepper motors £45 (first I bought new for £30, then picked up 3 used on ebay for £15)
24v power supply £11
threaded bar and misc nuts&bolts £20 - replace threaded bar with lead screw cost me £20
mini router £30
z axis bearing kit £25
stepper motor couplings £6
Misc electronics, wiires, arduino, screws etc. I already had in stock. I probably wasted around an extra £30 buying wrong parts etc.

Wondering what that cost is in real money ha ha.

Seriously though your list highlights that it is possible to do very low end machines.

BTW - I fitted all the electronics inside the wooden box which forms the main gantry. I am sure there are reasons this is a bad idea (electronic interference, vibration??) but I was pleased with this idea as it makes it a nice self contained unit and simplifies much of the wire routing. The only problem I have had so far is that when the router turns on (240v) this triggers the limit sensors but I found replacing the mechanical relay with a solid state one resolved this.

Sadly it is probably a bad idea if you use the machine a lot. On some slightly different machinery I repair at work, the gantry mounted controls do suffer from the vibration. It isn't so much the printed circuit boards that suffer but the mounting hardware for PCB. The builders even isolated the control panel on these machines with rubber standoffs and in the end things still degraded, fell apart or sheared off. That is a 24/7 operation. On the other hand in some jurisdictions it is not permitted to mount controls in side machine frames.

I really don't see you having a huge issue with the electrics as you will not be able to run this machine hard anyways. I've actually considered a controls in the frame design for a 3D printer I'd like to build one day. Just design your electrics with a minimal of connections and then use high quality connectors and you should be all right. Most long term problems seem to reside in the connections.

[alanesq]

Did you have any doubts?

I was still having serious doubts as late as this morning - lol
Discovered that most of my recent problems has been down to blunt router bits..............

I have upped the feed rate a lot and whilst not perfect I am now getting results which I am more than happy with.

Latest demo video:

[kyokahn]

Seeing all the expensive, large, commercially sourced and complex builds around here... It's refreshing to be reminded that some people are at the same point I am. I did spend a bit more mostly cause I calculated I'd need supported rails and 2 steppers on the Y, but just like you, I built the frame entirely (ply torsion box), as an experiment but also wanting to get decent functionality out of it to justify it into my limited budget. Most painful to me was actually paying for customs fees for some of the items since those are a bit high around here.

4x nema 17 87oz/in - cheapish at around $16 each with bracket and coupler and around $25 for a 24v PSU
4x 1000mm thinnest supported rails available - chopped 2 into 700mm and 300mm pieces to cover the 3 axis - $120 total lucky find including 8 bearings, bought 4 more for $15
4x threaded rod (1000mm/1000mm/700mm/300mm) - T8?, 8mm thick, 8mm per rotation (agree on the anti-backlash nut... i definitely need those) - don't quite remember but around $65
500w chinesium spindle w/supply $120
Random 1/8 bits around $50 total (straight single and 2 flute, ball nose, tapered, engraving pointy bits, etc) and 1/4 bits from my old router will have to do for now. I'll get some decent ones once i figure out what I'll use the most.

Anyway... this past weekend i got it to move. Not sure how fast I should push it but it moved uncompromised for 30 minutes without overheating (steppers cold) at around 4000mm/m and trying to stop it manually with quite a bit of pressure didn't cause deflection or skipping. I would REALLY appreciate any ideas on speed and acceleration settings/tests for my setup, but otherwise I'll keep pushing it slowly. It hasn't touched wood but I'm quite optimistic it will be up to the task coming this weekend.

[alanesq]

I think you made the right decision using 2 steppers for the Y axis. I think mine would have a lot less play in it if I had done this.
I spent a lot of time worrying about trying to get any play out of it but I have found that it is nowhere near as important as I had imagined (not with the light cuts I am doing anyway). I had suspected the first time I tried to cut some wood it would go in to some kind of resonance and throw its self off the table, but despite the fact if I hold the router I can get a couple of mm movement in any direction I am still able to get some decent accuracy out of it. I was struggling with it jumping about when crossing other cuts etc. but after spending ages trying to make it more solid I discovered this was mostly down to blunt router bits.

btw - feel free to post some pics here - good luck wit your first cuts :-)

[kyokahn]

I really didn't trust a single nema17 to carry all that load. I have no detectable play except for backlash on the lead screws, I'll credit the linear bearings and the rigidity of the torsion box at the bed, sides and gantry for that. I can only hope that translates into better feed rates and/or cleaner cuts. I'll add some pics of the build process.



I added the "dividers" forming the core's grid later on to ensure they were pressure-fit.






Too many dog supervisors...



Yeah, no dedicated space means assembling on top of your table saw as the only flat surface around.



Glamour shot of el cheapo lead screws



Finally - mostly assembled




And a couple videos cause I know people like to see it shake





I definitely have to increase the acceleration (and maybe the speed too) and dampen the motors. There are some ugly harmonics making the leadscrews bounce up and down at low speeds, fortunately, that moves the spindle less than I could measure with a dial indicator. I think the whole thing is rigid enough to upgrade to a 2.2kw chinesium spindle later on. Now THAT would be fun!

[alanesq]

Thats a very nice, solid looking unit you have built there.

I would like to replace my y axis bearings with something like yours but I am determined not to spend any more money on it until I discover if I am actually getting much use from it. Although I have this idea that as all the electronics is in my gantry esulting in a pretty self contained unit, I wonder if some kind of train tracks on my workbench could be made so that when I want to use the cnc I just lift this unit on to the tracks and have the whole workbench surface to use????

[kyokahn]

Thanks! Not sure what you mean with the train tracks thing. The best way I've come across to be able to use a surface or a different tool in the same footprint was to make a flip-top table. Some woodworkers use it to keep their lunchbox planer and drum sander or a similar pair of tools of similar weight within a single area, but I'm not sure that'd work for something the size of a CNC machine, even a small one.

[alanesq]

Hi,
The Y axis on mine has a set of 4 bearings holding it down to the table and a set of 4 holding it left to right.
Looking at it, it just occurs to me that if there is plenty of weight in the carriage then the bearings holding it down to the table could be removed, just relying on gravity to hold the unit down. if you then removed the lead screw and instead had the stepper motor operating some drive wheels it would result in a completely self contained unit running on tracks.......these tracks could be as long as you wish and the cnc unit lifted off when not in use or the tracks on a frame which can be placed on top of a sheet of plywood etc.

For light cuts, engraving at least, I can't see why it wouldn't work if slippage on the tracks could be avoided?

[kyokahn]

Oh! I get it now. Yeah, you could theoretically remove it from the base and mount it directly on the material you want to cut. Whatever you use for rails would be screwed down on the material. I'd recommend you make layout spacers so you know the rails are perfectly aligned. If you're creative you can even make them so that they allow you to continue a cut after moving the rails around the workpiece. It should be easy enough for you to move from the workbench onto the material if your electronics are self-contained . Sort of like we do with the router, using a router table or handheld, take the material to the tool if it's small, and take the tool to the material if it's big.

[wizard]

realistically you cant rely upon friction to drive a CNC axis so that idea wont work as suggested. However if your goal is plotting or maybe even light engraving then consider a timing belt drive. Timing belts, if well matched to the application, can do plotting duty very well.

As for your railroad track idea, dont rely upon weight to keep it in place, retain it via idlers at the very least. If for nothing ekse it will be much safer if something goes wrong. Eventually domething will go wrong. It would be pretty simple to make the bearings removable and frankly they would be of help even for light machining/engraving.

All that being said, i do have to agree with the above comments about fliptop machines stands. Assuming you have in mind a reasonably small machine a flip top stand allows for two or three tools in the foot print of one.

Being very space constrained myself i understand the feeling of being cramped. As such at least one flip top stand is planned as a future project. Simply reducing the foot print for small tools can go a long way towards making room for bigger tools.

The other side of the equation is that these CNC's are expensive and as such if you go to build one i would focus on minimizing compromizes while keeping the budget in check. In otherwords if you are about to spend lots of money on a tool id focus on trying to get max performance for my dollar. Making a machine that is easy to break down in my mind would lead to a good chunk of money going to a compromised design.

Lastly every time you reassemble such a machine you would need to realign it. So in a nut shell id look for an alternative to a demountable gantry.

Hi,
The Y axis on mine has a set of 4 bearings holding it down to the table and a set of 4 holding it left to right.
Looking at it, it just occurs to me that if there is plenty of weight in the carriage then the bearings holding it down to the table could be removed, just relying on gravity to hold the unit down. if you then removed the lead screw and instead had the stepper motor operating some drive wheels it would result in a completely self contained unit running on tracks.......these tracks could be as long as you wish and the cnc unit lifted off when not in use or the tracks on a frame which can be placed on top of a sheet of plywood etc.

For light cuts, engraving at least, I can't see why it wouldn't work if slippage on the tracks could be avoided?