beginning steps to building my cnc

[scnc]

Hi all,

I have attached the beginning steps to building my cnc machine. I hope to make it approximately 4x3 or 5x3 foot

Attached is the image of the metal fabricated framework, with brackets on each corner which will house the plyboard bed. There will be no top and bottom framework but only on the sides, in order to allow full sheets of boards to be cut continuously hopefully if this can be achieved). If there was framework on all four sides I am limited to that bed space. Is that right?

Also Can anybody give any clues about what stepper motors, ball screws, router, belts if i need any? bearings, tracks, brackets and drivers I would need?

How long would it take to make? and how difficult will it be?

I do think the best way would be to get someone to build it for me.

[njhussey]

Hi all,

I have attached the beginning steps to building my cnc machine. I hope to make it approximately 4x3 or 5x3 foot

Attached is the image of the metal fabricated framework, with brackets on each corner which will house the plyboard bed. There will be no top and bottom framework but only on the sides, in order to allow full sheets of boards to be cut continuously hopefully if this can be achieved). If there was framework on all four sides I am limited to that bed space. Is that right?

If you're going with a frame that big you'll need supporting beams under the bed otherwise you'll get deflection and vibration, cross bracing etc. I'm presuming that you're making it out of steel? Box section would be best in terms of strength, something around 50 x 50 x 4. I'd suggest having a look at Jonathan's build thread to give you some ideas http://www.mycncuk.com/forums/router...-building.html or Bruce's (motoxy) http://www.mycncuk.com/forums/router...challenge.html or one that's just starting is wobblycogs http://www.mycncuk.com/forums/router...s-cnc-mk1.html plenty to chose from ;)

Also Can anybody give any clues about what stepper motors, ball screws, router, belts if i need any? bearings, tracks, brackets and drivers I would need?

As a rough guide without knowing too much else (especially your budget) the norm seems to be 3Nm NEMA 23 steppers and something like the M752 drivers (from Zapp), ideally Profiled rail and linear bearings (expensive) or alternatively 25mm supported rail (cheaper) and bearings. Ballscrews 1610 with anti-backlash ball nuts as you're going up to about 1500mm, anything over this and you'll need to . Ball screws (2 on the X axis because of the length you want) driven by belts and reduced 2:1 to the stepper.

How long would it take to make? and how difficult will it be?

How long depends on how deep your pockets are, how much time you have to put into the project, how skilled you are, what tools you have available to use...etc. etc. i.e. how long is a piece of string lol How difficult is it....again depends on your skill level with tools, ability to learn new things, willingness to learn etc.

I do think the best way would be to get someone to build it for me.

Could always buy an off the shelf CNC router?

[scnc]

Thanx For your help Neil,

That would be very useful and helpful,

I think the best way would be to design the cnc with help, and learn from the forum with help from people like you. Thanx again much appreciated.

My budget is about a £1000 and i would like it to be a stable machine dont really want too many problems in the long run as i would be using it for work. Would be nice if I can cut aluminium, mdf, ply, composits and acrylic sheets.

Thats about all of it really,

I will re attempt some design work today based on the information you gave me and see how I can implement it in to the design. I hope by doing this I have a perfectly designed and well understood cnc machine :-)

Thanx again

[njhussey]

Thanx For your help Neil,

That would be very useful and helpful,

I think the best way would be to design the cnc with help, and learn from the forum with help from people like you. Thanx again much appreciated.

I think that's by far the best way as not only will you be able to service it, repair it and upgrade it yourself easily but you'll get a far better understanding of how it works.

My budget is about a £1000 and i would like it to be a stable machine dont really want too many problems in the long run as i would be using it for work. Would be nice if I can cut aluminium, mdf, ply, composits and acrylic sheets.

Thats about all of it really,

For that you should be able to get a CNC machine that will be able to do what you want it to...will be tight but doable from what I've seen

I will re attempt some design work today based on the information you gave me and see how I can implement it in to the design. I hope by doing this I have a perfectly designed and well understood cnc machine :-)

Thanx again

That's it...before you know it you'll be hooked and forever tweaking it or planning your next build ;)

[kingcreaky]

You need to read... ALL OF THE BUILD LOGS. from start to finish. You'll need some strong coffee.

Dont take anything I say as gospel, as im just learning. but you'll see for yourself designing it is key. You want to draw a proper 3d model. for this download google sketchip 'aka Trimble' its free and there are plenty of tutorials all over the internet.

When your reading the build logs you'll see the amount of thought that goes into designing against 'flex' or 'deflection' and 'vibration' all of these factors need a lot of thinking about right from the start of your design. after you have seen a few designs evolve from the original concept ideas the following versions to the final versions you can see how the strength of the design improves.

Worry last about the electronics, as its only after you have made a design to suit your requirements that a guage on the size of electronics is possible.

for cheaper gear, with less support, chai is reliable http://stores.ebay.co.uk/linearmotionbearings
for better service, with good support, you want zapp Zapp Automation Ltd

good luck with your build. Youtube is a good source of videos :D

[martin54]

Some good advise to start you off although I would start saving the pennies, very much doubt you will be able to produce a machine of that size on your current budget, cost of supported rails, 1610 ballscrews + blocks & bearings will cost half of that if not more. Electronics won't be to far away from the other half. Doesn't leave anything for the frame itself & other bits you will need like pulleys & belts or couplings depending which road you go down. On top of that you will need some sort of software to run it all & although you can get some reasonable free software it will depend on how much time you have to spare to learn how to use it. If this is going to be a production machine you can't really afford to scrimp on anything so I would look to double your current budget & if you have money left at the end then it's a bonus & you can treat yourself.

[Jonathan]

My budget is about a £1000 and i would like it to be a stable machine dont really want too many problems in the long run as i would be using it for work.

With only £1000 it will be tight - you certainly will have to make it yourself to achieve that.

The electrical parts, i.e. 4*3Nm stepper motors, DQ860MA drivers, PSU, breakout-board will be about £300
2.2kW spindle + VFD, which is the only one worth getting for this size machine since you want it to last and cuts lots of different things, about £240
Water pump for spindle, £15
Steel for frame, about £50
You'll need something like this for the ballscrews and rails:
RM1610-1500mm, *2
RM1610-1200mm, *2
RM1605-250mm, *1
Bearing blocks for ballscrews, *4
SBR25-1500mm rails
SBR20-1200mm rails
SBR20-300mm rails
That's about £520 (bit of a guess but should be within 10%).
Pulleys and belts, maybe £35
Total: 300+240+15+50+520+35=£1160

So actually it looks like £1000 isn't realistic for this size machine. There will be other small parts I've not included in that list which all add up, like fasteners, material for bed. Plus I've not included the metal to make the Z-axis and maybe Y, so easily another £100 there - more if you can't cut it yourself. So a realistic budget for this size machine, capable of cutting the materials you suggest, is nearer £1500.

Just to be clear, the above is not intended to be a shopping list - get the design done first before buying anything otherwise you'll have no chance of making it cheaply.

Would be nice if I can cut aluminium, mdf, ply, composits and acrylic sheets.

So basically everything!

[scnc]

Thank you for all your replies, I have looked at all the feedback and redesigned the cnc. Please let me know what you think. If it goes over my budget then its not too much of an issue. just a few issues which I dont understand :

(As mentioned and illustrated on the design attached)

1) where does the driver go and how do we connect it to the steppers?

2) what would be the best rails to use and how would I attach and make these?

3) linear bearings which are the best to use? for the size of this table?

4) where would the belt go?? the belt in question is it a timing belt?

5) Also Im thinking of making the frame stand out of mild steel and the cnc bed frame out of aluminium box section. Would this be okay?

Thank you all!

[martin54]

1) where does the driver go and how do we connect it to the steppers?

A lot of people use an old computer case for the electronics so the Power supply, drivers, bob & any control relays would all go in the box. Connected to the motors usually with shielded cable.

2) what would be the best rails to use and how would I attach and make these?

Profile rails would be the best but because they tend to be expensive a lot of people use supported rail, the rail is fitted to the machine frame with cap screws or something similar.

3) linear bearings which are the best to use? for the size of this table?

I'm new to all this myself but from what I have read 25mm on the longest axis & 20mm supported rail on the other two.

4) where would the belt go?? the belt in question is it a timing belt?

Yes they are timing belts, pulley fitted to each of the motors & ballscrews< the belt fits between the motor & ballscrew to turn the ballscrew.

5) Also Im thinking of making the frame stand out of mild steel and the cnc bed frame out of aluminium box section. Would this be okay?

Yes that would be OK but if you are making the stand from steel why not just make the whole frame from steel. Would be more ridged & probably cheaper to construct.

Oh & yes that picture is of a ballscrew & nut

[scnc]

Thanx for your reply Martin,

How hard would it be to do the electronics, is it a difficult job for someone who has no knowledge in electronics?? I should be able to get help but can this be learnt?

also ive seen a pic of the rail so im assuming the stepper motor is attached to the ballscrew via a coupling and this resides in a box with the profile rails either side. Is that right?? something like below.