[CdRsKuLL]

Well hello all,

Wow.. I hope this is in the right place, don't think I've ever seen a forum with so many sections!

I'm currently designing my own cnc router. I'm on a tight'ish budget hence the diy route.

OK, after advice really and does' & don't on what I'm currently purposing...

Here is a list of my parts so far.
Y Bed (1200mm) - 2 x 30mm bright mild steel rods with linear bearings
Y Bed motor - 23 Stepper motor
Y Bed thread - M10 Stud 1.5 pitch

X Bed (830mm) - 2 x 20mm bright mild steel rods wit linear bearings
X Bed motor - 23 Stepper motor
X Bed thread - M10 Stud 1.5 pitch

Not got to the Z axis yet as I'm still designing it. My concerns are flex in the round bar's I've chosen 30mm round bar (mild steel) because of the price really and the diameter to try and reduce flex. For past experience would I be ok with this? And 20mm on the X axis (trying to reduce the weight on top)

The whole construction will be out of 30mm square extruded aluminium which works out about £6 a metre I think.

The router will be a stripped down Draper 1200w one for now as that's what I've got.

Design is being done in inventor which I started learning last week.. lol so that's a challenge in it's self.



Any help / advice would be most welcome :-)

thanks,

Steve

[ger21]

1) Yes, those shafts will flex a lot.
2) You MUST use hardened, precision ground shafts.

These would be infinitely better.
2 Set SBR20 1200mm 20 mm Fully Supported Linear Rail Shaft Rod with 4 SBR20UU | eBay

[CdRsKuLL]

Hi Gerry,

I simply can't afford them rails... The other option I have is putting some supports maybe under the rods at a few places and use open linear bearings maybe.

Something like these



At least this way it will stop any flex I think. My budget is only about £350 for the build.. maybe if I find I'm using it a lot then it would be worth the upgrade?

Thanks,

Steve

[robedney]

I -- on a similar shoestring budget -- used 1" black pipe for my X rails -- spanning five feet. I also have a somewhat heavy gantry. Flex, so far, has not been an issue. If it ever becomes an issue, I will add interim supports.

Please note that black pipe is anything other than machined or precision. However, if you use the bearing spider I came up with you can get away with it. The idea is to start with the bearings snug but not tight, run the machine a bit and then tighten a bit more. What happens is that the hardened steel skate bearings flatten/level the softer steel of the pipe -- creating their own tracks -- a sort of backwards method of machining.

I used a $99 wire feed welder from Harbor Freight and some scrap steel to make my bearing carriers. It was a fair amount of work, but well worth it. Learning to weld with one of these things is not all that hard, particular if you care about strength but not so much about looks. What you can't see in the pic below is the cutout in the bottom to allow placing supports under the pipe. By the way, those supports could be threaded rod, which would allow levelling the pipe along its length if needed.

Attachment 182237

[jckstrthmghty]

I -- on a similar shoestring budget -- used 1" black pipe for my X rails -- spanning five feet. I also have a somewhat heavy gantry. Flex, so far, has not been an issue. If it ever becomes an issue, I will add interim supports.Attachment 182237

How can you add support if your bearing surround the rail? I can assure you 1" pipe will deflect a considerable amount. I used 48" of 1" pipe partially supported and I could defect the gantry with one hand.

I think the build should be complimentry. If you are going to use expensive extruded for the frame then you should not cheap out on the rails or bearing. It would be better to use cheap framing and have expensive supported rails. Then the machine could do what it's designed to do, make accurate cuts, instead of looking pretty and making bad cuts. For £350 I have no idea how you are going to build a percise and ridgid cutting machine in extruded. Perhaps with MDF with gas pipe rail like a joes2006s you could build the frame with £350.

[robedney]

Look on the right side of the pic, where you can see the backside of the other bearing carrier -- there's a cutout like that on each one, you just can't see it on the front one because of the angle. You can therefore add as many supports as you want/neet. It could even be a continuous piece of steel.

I've heard the deflection argument before. Yes, if I put an appreciable amount of my body weight on the pipe with one hand I can deflect it. However, when is the machine under that kind of load in actual use??? I can cut a V down the length of the bed, and a pair of calipers will reveal that V to be the same width along its length -- indicating that the depth of cut is consistent, even without supports. Of course, part of the design of any machine is the tolerance you need to do what you want to do.

How can you add support if your bearing surround the rail? I can assure you 1" pipe will deflect a considerable amount. I used 48" of 1" pipe partially supported and I could defect the gantry with one hand.

I think the build should be complimentry. If you are going to use expensive extruded for the frame then you should not cheap out on the rails or bearing. It would be better to use cheap framing and have expensive supported rails. Then the machine could do what it's designed to do, make accurate cuts, instead of looking pretty and making bad cuts. For £350 I have no idea how you are going to build a percise and ridgid cutting machine in extruded. Perhaps with MDF with gas pipe rail like a joes2006s you could build the frame with £350.

[CdRsKuLL]

Hi guys,

Lots of good ideas here :-) , Rob love the home made bearings! lots of thought and effort have gone into them.

Yes, the open linear bearings have 50 degrees missing from the bottom so you can add a support to the rail. Which is most likely the way I'm going to go at the moment.

As for the aluminium extrusion it's really not that expensive and it's very easy and strong to work with. Here in the UK there's a place you can get it from and they will also precut all the bits for you which is a major bonus in my books :-) It works out at just over £6 a meter.. so if you're comparing it to MDF, yes it is slightly more but I would expect the whole Aluminium frame to cost about £75. Here's the site in case anyone else is after some.

6mm Slot ITM Profile

I used this place when I made my 3d printer :-). I've also ordered some Stepper motors / controllers etc for £200 from a guy in Germany. Ok... so I'm going to be slightly (cough) over my budget lol.. ?German&Free Ship?3Axis Nema23 stepper motor 425oz-in,3A & Driver CNC control | eBay Hopefully they will do the job. :-)

I'm still working on my design in inventor. I want to get everything working as it should before committing. I'm looking at M10 1.5 pitch threaded bar at the moment for each axis. so two revolutions should equal 3mm of travel.

Will keep updating as I go. :-)

again thanks for the input

Steve

[jckstrthmghty]

Look on the right side of the pic, where you can see the backside of the other bearing carrier -- there's a cutout like that on each one, you just can't see it on the front one because of the angle. You can therefore add as many supports as you want/neet. It could even be a continuous piece of steel.

Seems tight but cool.

However, when is the machine under that kind of load in actual use???

Anytime the machine changes direction for one. How about cutting at +100 IPM at 1/2" DOC. That is not unreasonable cutting parameters for a well built machine. There are many here cut 3/4" ply in a single pass over 300 IPM. What about plunging. This is where my pipe deflected the most.

Of course, part of the design of any machine is the tolerance you need to do what you want to do.

I think in the end everyone wants thier build to cut faster and more percise but in the end if your machine suits your purpose all is good.

[robedney]

It's all about context. The original poster isn't talking about speeds like 300 IPM -- I can guarantee that because the Long's motors and drivers he's using won't hit those speeds without stalling. It's a perfectly good motor kit -- I've got the same thing. It's all I could afford, so I made it work -- and work it does! It's certainly a challenge to build a machine on the cheap that actually works -- but it can be done. It's actually more labor intensive, and requires a much larger dollop of "clever", as well as scavenging. As I designed my machine I tried to take into consideration what might or might not work, and leave myself a modification if I had to change things -- like shaft supports, which I've allowed for. That's half the fun of it!

By the way cdrskull, if you need some help when you get to the point of wiring up your electronics, tuning and calibrating the motors, etc -- just holler. Having recently done it all with the same components I might be able to help.

Seems tight but cool.



Anytime the machine changes direction for one. How about cutting at +100 IPM at 1/2" DOC. That is not unreasonable cutting parameters for a well built machine. There are many here cut 3/4" ply in a single pass over 300 IPM. What about plunging. This is where my pipe deflected the most.



I think in the end everyone wants thier build to cut faster and more percise but in the end if your machine suits your purpose all is good.

[jckstrthmghty]

As for the aluminium extrusion it's really not that expensive and it's very easy and strong to work with. Here in the UK there's a place you can get it from and they will also precut all the bits for you which is a major bonus in my books :-) It works out at just over £6 a meter.. so if you're comparing it to MDF, yes it is slightly more but I would expect the whole Aluminium frame to cost about £75. Here's the site in case anyone else is after some.

30 x 30. I'm used seeing the 30x60 stuff or 45x90 so it will be interesting to see what kind of rigidity you achieve. Save some budget for quality multi start leadscrew. You won't regret it.

[CdRsKuLL]

Rob, just wondering what software you are using? Have you tried a few different ones?

Made a bit more progress on my cnc design :-) getting there now!



Steve

[robedney]

Someone gave me an older copy of Mach3 to try as the control software. It's Windows-based, and quite a good program. The same person gave me an older Vectric Aspire -- very pricey if you buy it, and I'm not sure I ever will. These are both licensed copies that were sitting unused. Aspire is an interesting program, a somewhat peculiar but ultimately functional interface, etc. It tries very hard -- and sometimes succeeds -- in making it easy to do complicated things. It seems to be targeted toward people who make signs, graphics, displays -- that sort of thing. The learning curve, however, is fairly steep -- the the price is astronomical.

I'm will probably try LinuxCNC before buying a new copy of Mach3. It appears to be very capable, well supported and is free. There's also a dirt simple installation that lets you install it on a Windows computer and boot into Linux separately. However, if $160 or so for Mach3 doesn't break the bank for you, it's a very good program that is well supported both by the company and in various web forums -- lots and lots of people use it. I will buy it -- if LinuxCNC doesn't work for me.

So far as CAD/CAM goes, there's a very promising avenue using the free version of Google SketchUp -- which is a powerful, free program -- and some sort of add-on to generate G-code. Currently, a updated version of Phlatscript -- renamed SketchUCam -- seems to work for this, and is free. I've given it a limited test and I'm impressed. A hint about Sketchup -- if you decide to use it, do some tutorials, read through the documentation, etc. Working in 3D is a different world, and SketchUp can be frustrating to learn if you just dive in. You need to get your brain into a different mode of thinking to use it, and once you've done that it's capabilities are awesome.

Here's a site to start studying now, so you can bring yourself up to speed on software while building your machine: cnc4free.org homepage It lists several alternatives that are free, and provides some good tutorials in how to use them.

All of this is assuming you're on the same sort of budget I am, and therefore interested in the open source software that's out there.

Rob, just wondering what software you are using? Have you tried a few different ones?

Made a bit more progress on my cnc design :-) getting there now!



Steve

[CdRsKuLL]

Hi fella,

thanks for all the info :-) I've had a look at mech3.. well read the config manual and it seems quite straight forward. I've downloaded the trial (limited version) so will give that a go. I've used sketchup before, I found it fine for doing simple things but if you needed to go back and change something it them becomes a right pain. I'm now using Autodesk Inventor which after a week of playing find it fantastic.. I only wish it had a following like sketchup with its warehouse of stuff. :-)

Just trying to get my design finished so I can get my final bits ordered.. looking forward to putting it all together.

Steve

[CdRsKuLL]

yep, another question....

Z axis.... just wondering what is an acceptable height adjustment? I realise the bigger the better, I've got about 90mm at the moment on my design.

thanks,

Steve

[harryn]

If you must use round pipe for the rail, consider to move to 2 inch / 50mm diameter. If possible, try to put it under tension when in use. At least then you have a chance at a useful machine. If you can't do this, then instead consider to use a 2 x 4 x 1/4 inch thick steel square tube rail ( 50 x 100 x 6 mm) and delrin or HDPE pads as the bearings.

The forces in these things, and small amount of deflection that messes things up will really amaze you.

For a much stiffer design, consider to use some of the ideas from this machine:

http://www.kronosrobotics.com/krmx02/index.shtml

[jckstrthmghty]

yep, another question....

Z axis.... just wondering what is an acceptable height adjustment? I realise the bigger the better, I've got about 90mm at the moment on my design.

thanks,

Steve

You mean z travel? If so the less the better. If you only need 90mm then build it that way. Clearance matters for changing bits but the shorter your rails the less deflection you will experience. I see many builds with 100-150mm of travel but some foam cutters I've seen have +250mm. Comes down to the materials you are cutting. I think you could easily add more travel without losing much rigidity by removing your front upper brace allowing your z carriage to go higher.

if not please disregard.

[CdRsKuLL]

Hi fella,

Yes the travel, sorry a bit new to all this terminology :-)

I've worked it to the router nearly touches the bed, but when on full height with a 50mm bit in it goes higher than the lowest point on the X axis. My design is nearly done now :-) just got to tidy it up and things like limit switch mounting holes etc. I'm using some 10mm thrust bearings which will be trapped by nyloc nuts so should be quite sturdy and take any force off the motor coupling.

here's an updated pic



more to come no doubt!

Steve

[robedney]

Looking good. One point: As you've got the X axis drawn you can add, if needed, supports along the pipe/rod. You might leave yourself the same option by using a piece of angle for the top and bottom of the Y axis on the gantry, and rotating your bearings so that the opening is pointing downward on the bottom. That way you could add bracing/stanchions along the lower pipe if needed, resting on the extending part of the angle. Replicate that on the top, and you have the option of pipe/rod supported by angle. If that made no sense, let me know!

Hi fella,

Yes the travel, sorry a bit new to all this terminology :-)

I've worked it to the router nearly touches the bed, but when on full height with a 50mm bit in it goes higher than the lowest point on the X axis. My design is nearly done now :-) just got to tidy it up and things like limit switch mounting holes etc. I'm using some 10mm thrust bearings which will be trapped by nyloc nuts so should be quite sturdy and take any force off the motor coupling.

here's an updated pic



more to come no doubt!

Steve

[CdRsKuLL]

Evening fella, I'm using 20mm x 2 for the X axis and I'm confident that there shouldnt be any movement on them at all.

I have however already obtained a router and electronics before I found this site. I'm looking at using some 425oz motors (I know, after reading) they might be under powders by my 36v PSU.. but anyway, my other concern is the actual router. It's a handheld converted draper 1200w with 6 variable speeds. I'm after cutting wood and plastic so I'm hoping I will be ok.

just need that extra nod.. lol

Steve

[CdRsKuLL]

All designed now :-) All parts ordered except for the threaded bar.. will do that next week :-)

I'm hoping I will have all the bits to get it built up next weekend. Total cost is about £500 I think.. 'opps'

will post some photos when done.

HOWEVER.. Software needed. I need some software to run on it. Everyone seems to recommending Mach3 but I really can't afford it since I've spent so much on my cnc. Any advice / help / links etc would be greatly appreciated.

thanks,

Steve