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ciscoeuk
28-01-2013, 04:51 PM
Hi all

i am not new to cnc, i have built a small version once before from mdf :distracted: but scrap it

i now need a requirement 8 x 4 cutting area actual size will 1500mm x 2500 :tears_of_joy: with 450mm z axis for carving vac form plugs, prominently used for wood, ply, etc and for cutting alloy sheet to 12mm, where possible, plastics, foam etc basically an all rounder!

i will be starting this build in march, most of the stuff is on order and awaiting delivery

build consist of

hiwin/equivalent rails all round
4 nema 34 motors kit with breakout and stepper drivers 1600 oz
rack and pinion, - near help hear please with mounting brackets and gear reduction ideas????
2.2kw water cooled spindle er20 with vfd, but looking into a 3kw

this is where i have dilemma, :indecisiveness::indecisiveness: i am not sure what to build the y and x base from as i need as much rigidity as possible to cut alloy/metal sheet

welded steel box for the base (x) ali on verticals

all from 8020 extrusion ( x and Y)

a hybrid of steel and 8020 and ali y/z verticals

and optimal height of gantry from table? as i need to be able to carve plugs up to 125mm in height from router tip

what grade/thickness of ali to use for the y/z gantry? and ali thickness

and help hear would not be rejected!

my main concern is frigidness of the gantry

i am also looking for volunteer/pay to help with cnc parts to be cut, i can help with any related IT issues as i am an IT engineer/Admin, no charge?

look forward to hearing from you all and all the suggestion and advice

would be great if i could meet up, or skype, i don't mind travelling, i live in Newark Notts :pride:

i will be posting design after i have got some advice :tennis:

ciscoeuk
28-01-2013, 04:52 PM
forgot if any member got any spare parts to sell or swap let me know, if the fit my needs, i will buy/swap

ciscoeuk
28-01-2013, 08:17 PM
806080598058

this is what i had in mind for the gantry y axis after do some basic calcs and using the spread sheet on here

the deflection for y and z had a tolerance of 0.054, this being 2 x 4 " ali u channel and 1 6 " channel with y axis = to 1500mm but this may get reduced to 1350mm this may be wrong

my calcs may be wrong as i may have use the ss in the wrong way:calm:

please put me right

ric

Jonathan
29-01-2013, 12:09 PM
Good to see someone using the spreadsheet. You'll find that if you change to similar size box section the deflection due to bending will be similar, but the bending due to torsion will be substantially lower. That's because the torsional stiffness of a channel cross section is very poor. Also put the rails for the Z-axis on the plate that moves up and down, so swap them round. It's much stronger this way since the distance between the supporting bearings and the tool is minimised. The best thing you could do to that design is loose the tall gantry sides, as they're invariably weak compared to the machine frame.

ciscoeuk
29-01-2013, 05:23 PM
Good to see someone using the spreadsheet. You'll find that if you change to similar size box section the deflection due to bending will be similar, but the bending due to torsion will be substantially lower. That's because the torsional stiffness of a channel cross section is very poor. Also put the rails for the Z-axis on the plate that moves up and down, so swap them round. It's much stronger this way since the distance between the supporting bearings and the tool is minimised. The best thing you could do to that design is loose the tall gantry sides, as they're invariably weak compared to the machine frame.

i take on board the board the issue of u channel and move over to box are recommending ali box on the y vertical as well :rapture::joyous:

the z axis is one i pick off the net to try the nema 34 motor to see where i could put the pinion drive? my version is similar but to take a nema 23 or 34

the z axis i am building is using hiwin rails and a lead screw set up :fat:

can you send me a photo the z axis u spoke about please or threads

on the height, i need to clear 6 " 150mm from tip of router to base and some of what we intend to d, is carve forming plugs, ie engine cowls what do you suggest? as this cnc is going to be used got mixed materials,

hope to speak soon


ric

ciscoeuk
30-01-2013, 12:59 PM
hi all this is an update of build i am in the design process stage here's what i been up to!

the cnc base (bed) is steel constructed from 75mm, 50, & 25mm steal box

i would like your thoughts please and weather this is up to the task?

if anyone wants anything welding in steel from Pm a line, not to bad at welding, new 200 amp Welder on its way :thumsup: :emmersed:

80818082808380848085

have a look

all welcome to comment

Jonathan
30-01-2013, 01:35 PM
Not a bad start, but a few changes will make it a lot easier to construct and stronger. The most important factor is how do you intend to fix the box section for the bed (25mm) to the rest of the frame? It looks like it's just welded on at the moment, which makes the bed nice and strong, but the issue is with such a large Z-axis (450mm) you want to be able to adjust the height of the bed. The general idea is for sheet material you put the bed high up, so where it is in your drawing, then for the occasions where you need more Z-travel you drop it down. This is easy enough to do if you drill a series of holes in the 6 vertical pieces, support the cross pieces for the bed on two 8' long prices of box section, then attach them to the frame with M12 bolts. If that's not clear then look at my build log (http://www.mycncuk.com/forums/router-build-logs/2288-1-7%2A0-74%2A0-4m-mill-router-building.html). You've got no chance of cutting 12mm aluminium and having 450mm Z-travel, without having an adjustable height bed.

It'll be a lot easier to make if you use 50mm box section, or something bigger than 25mm, for the bed and use less of it. Also add in some diagonal pieces to the main frame since without them it will skew relatively easily.

Since you want to use this for cutting aluminium, if only occasionally, I wouldn't use rack and pinion since the resolution and rigidity will be worse than with ballscres. You can easily use a ballscrew and 3Nm nema 24 motor on the 1500mm axis, however to use ballscrews on the 2500mm axis requires a large ballscrew and big motors, or rotating nuts.

ciscoeuk
30-01-2013, 02:25 PM
Not a bad start, but a few changes will make it a lot easier to construct and stronger. The most important factor is how do you intend to fix the box section for the bed (25mm) to the rest of the frame? It looks like it's just welded on at the moment, which makes the bed nice and strong, but the issue is with such a large Z-axis (450mm) you want to be able to adjust the height of the bed. The general idea is for sheet material you put the bed high up, so where it is in your drawing, then for the occasions where you need more Z-travel you drop it down. This is easy enough to do if you drill a series of holes in the 6 vertical pieces, support the cross pieces for the bed on two 8' long prices of box section, then attach them to the frame with M12 bolts. If that's not clear then look at my build log (http://www.mycncuk.com/forums/router-build-logs/2288-1-7%2A0-74%2A0-4m-mill-router-building.html). You've got no chance of cutting 12mm aluminium and having 450mm Z-travel, without having an adjustable height bed.

It'll be a lot easier to make if you use 50mm box section, or something bigger than 25mm, for the bed and use less of it. Also add in some diagonal pieces to the main frame since without them it will skew relatively easily.

Since you want to use this for cutting aluminium, if only occasionally, I wouldn't use rack and pinion since the resolution and rigidity will be worse than with ballscres. You can easily use a ballscrew and 3Nm nema 24 motor on the 1500mm axis, however to use ballscrews on the 2500mm axis requires a large ballscrew and big motors, or rotating nuts.

JONATHAN
thanks for the advice and taken on board,

i have decided to cut the z axis height down to 400mm ballscrew as the y gantry is 2x8 ali box

decided this after i found out the you can mill sections at a time and glue together to for a fibreglass/vac form plug i think mach 3 has that ability or was it artcam????:hopelessness:

at a later date build a cnc router for carving vac form plugs,the later cnc 800 x 800 from ali extrusion and plate this does not have to so stiff and rigid as it only carving foam/plastics and MDF and pine

since i posted i have modified the frame to be very rigid, see pics


808680878088

i know that using 50mm box would be better and save some pennis but i decied to stick to the 25mm as a way of spreading the weight and of course it looks nicer but this may change:tranquillity:

as for the x axis and using rack or ballscrews the jury is out on that at the mo , thanks for the spanner by the way:black_eyed: LOL

i will post my idea for using rack and pion and a lock plate,

i will have that idea up soon

speak later, buy the way i am on skype if u want to face to face pm me

ATB

ric

ciscoeuk
30-01-2013, 09:22 PM
PART TWO

Y GANTRY IDEAS

IDEA 1

80908091

hiwin rails, nema 34 x 2, rack and pinion, aluminium plate not to sure what thickness to use or use box section and mill a lap joint, bolted and ali welded


Idea 2
809280938094

hiwin rails x 2, nema 34 on spring drive plate, ali box section, rack and pin, use box section and mill a lap joint, bolted and ali welded

Ideal 4

8095 using ballscrew and thread 20mm or more use box section and mill a lap joint, bolted and ali welded

Idea 5
8096ball screw & tread moved to bottom 2 X NEMA 34 use box section and mill a lap joint, bolted and ali welded

this might be over engineered???????

let me know what you think

advice please

ric

ciscoeuk
31-01-2013, 12:43 AM
8098

oooooops i missed

idea 3

as idea 1 but using 2 or 3 stacked bearing and holder boc ali and direct drive nema34

ric

ciscoeuk
01-02-2013, 01:29 AM
811081118112

xyz
idea

Please comment on this idea i do like the design, but i not sure if this is going to had too much deflection so please advise?

i have reduced the hight y gantry from 400mm to 175mm from the bottom of the z axis

y gantry virtical and mount box section is welded steel, or welded ali

all comments welcome

ciscoeuk
01-02-2013, 07:20 PM
THE FINAL DESIGN

I THINK????? suggestions welcome please

for x y and z

the z axis is not final i need help hear please

using hiwin rails and ball screw, spindle using 2.2kw water cooled, clearance to table 165-175mm

8114

using nema 34 motors, but not sure i should use a high torque nema 23 on the z axis

rack and pinion x and y

the y axis can with take a reduction drive or should i go direct drive


help please!


ric

ciscoeuk
02-02-2013, 01:42 AM
final design

please post your thoughts


but i fo nee help on the z axis

8116
8117
8118
8119


has any one got drawings or photos of a z axis using hiwin type linear rails and blocks and ball scre set up

or point me to the thread please

ric

D.C.
02-02-2013, 03:49 AM
Hello cisco, I'm not one of the resident experts but as everyone seems to have sodded off I'll give it a shot.

Try this thread for photos and video of a z-axis

http://www.mycncuk.com/forums/items-sale/5527-z-axis-home-limit-switch-nema-23-3nm.html

You want the rails mounted to the plate that the spindle is attached to as it will add stiffness to the plate and if you are using hiwin type rails you really want to use ecocast aly for the plate as it is a lot dimensionally accurate than the cheaper stuff and hiwin rails need very accurate alignment to work properly.

Watch the round vs square rail video here to see what I mean:

http://www.thomsonlinear.com/website/com/eng/products/linear_bearings_and_guides.php

That big hunk of material that is your gantry, is that steel box section? If you intend to mount the rails directly to it you might want to consider finding a local machine shop with a surface grinder that can grind it reasonably flat for you.

ciscoeuk
02-02-2013, 08:32 AM
H

That big hunk of material that is your gantry, is that steel box section? If you intend to mount the rails directly to it you might want to consider finding a local machine shop with a surface grinder that can grind it reasonably flat for you.

thanks dc

base is steel and all the upper is 12mm ali plate and box section

cross member is 6 x 3 ali box, is this really necessary to get the box y gantry ground, if it is then my budget has been killed

but if you are taking about the box and plate that connects to rails, then i that's given! i will nee the plate cute to shape and the I bar making, the i bar is made from ali, but the was thinking of welding it in steal but this means get the cut on a water jet or laser?

been working on different ideals as you can see from by thread, but seam like almost no one is willing to giving advice or the own views, i welcome anyone who can talk from experience, good or bad,

i-beam is screwed together, but if i can find a ali wekder i will get his welded

8120

Jonathan
02-02-2013, 12:39 PM
been working on different ideals as you can see from by thread, but seam like almost no one is willing to giving advice or the own views, i welcome anyone who can talk from experience, good or bad,

I'm happy to comment on the new design, but I haven't posted as most of the things I have to say are the same as what I said in post #7. The main problem is still that the gantry is far too tall - it's best to have no gantry sides and lower the bed, that way the gantry is supported by the main frame not some flimsy bits of plate.

A 3Nm nema 24 motor is plenty for the Z-axis. Also, to get anything like good resolution on X and Y with rack and pinion, you'll need to have two belt reduction not one. Search on the forum for rack and pinion versus ballscrews and you'll find plenty of relevant information.

ciscoeuk
02-02-2013, 01:55 PM
I'm happy to comment on the new design, but I haven't posted as most of the things I have to say are the same as what I said in post #7. The main problem is still that the gantry is far too tall - it's best to have no gantry sides and lower the bed, that way the gantry is supported by the main frame not some flimsy bits of plate.

A 3Nm nema 24 motor is plenty for the Z-axis. Also, to get anything like good resolution on X and Y with rack and pinion, you'll need to have two belt reduction not one. Search on the forum for rack and pinion versus ballscrews and you'll find plenty of relevant information.

thanks for the advice

JAZZCNC
02-02-2013, 04:35 PM
Hi Richard,

This design is really only suitable for Wood/plastic cutting. While it will cut aluminium the finish won't be very good and the cutting conditions regards DOC and feeds speeds will be far less than ideal.
After our conversation and knowing your intentions to cut Ali to high finish standard then machine is all wrong. Even at half length it's all wrong.
Again knowing your needs better then a dedicated small fixed gantry machine using profiled rails matched and ballscrews along with either high flood coolant or blown air/mist system will be far better.

Regards this machine then I'd use supported round rail on X & Y for convenience and Budget, they will be more than good enough for just cutting wood/plastic.
Personally I don't like R&P and would use 2010 screws on a rotating ballnut if much over 1800mm. Below this then standard connection is fine.
That said I have used R&P in the past on large machines and it works OK but find it needs more maintenance and critical to keep free from debris. Needs much larger motors with matching drives with high ratio gearing to achieve decent resolution which together make it more costly than ballscrews with far less accuracy and efficiency.

For the Z axis even with R&P I'd still use profiled rails and ballscrew. The Z axis is the single most important part of the machine that takes all the cutting forces directly, it also directly affects cut quality finish and if it's weak or poorly designed or uses cheap components then it will show in finish or wear and perform badly.

The gantry design looks a little on the flimsy side regards it's sides and Box section for the gantry will be very resonant which is less than ideal and could directly affect cut quality and even motor performance if bad. If your using Aluminium box then it will need to be thick walled stuff 3 or 4mm won't be enough.
Don't be afraid of weight when it comes to the gantry, often folks believe and go out there way to make the gantry has light as possible thinking it improves the machine when in reality it compromises the machine where it matters which is when cutting.!
Mass helps significantly with cutting and damping resonance, light gantry only really helps regards allowing higher rapid speeds which come much lower down the pecking order of desirable requirements.

If you want an all round machine then really this design isn't the way to go. In my experience for a successful all round moving Gantry machine then the frame/gantry needs to be different with the gantry mounted directly on the X axis bearings with no gantry sides to speak of. The distance from bed to cutter or put another way Z extension needs to kept to a minimum for harder materials like Aluminium. This requirement is often restrictive to the requirement to cut softer often bulkier materials like wood.!
So away to accommodate both needs to be found.? You could just raise the material to the cutter for hard materials and keep the high gantry side design but this is less than ideal has the very high sides are weak area and allow flex and resonance that will show in the finish of harder materials like Aluminium. . . . Fine for wood plastics etc that need to hold less tolerance or finish.

To do this we get rid of the the gantry sides and mount direct to bearings by raising the frame sides.
Now we still need to accommodate the high clearance for bulky materials while still keeping the rigidity by not having the Z axis extend all the way down to the bed when cutting thinner Aluminium but at the same time we don't want to be messing around with Blocks to raise material.
To get round this we make the bed adjustable, doing this takes away all cutting restrictions meaning you can keep maximum rigidity for all materials with much higher clearance if required.
In real world use you will seldom move the bed and find a position that suits most of your requirements but for the times when MAX strength or large materials need to be worked on then you can and the whole machine is very configurable for ALL ROUND uses.
All you have to remember is that it will always be a Jack of all trades and master of none but will still do a bloody good job.!

hope this helps.

Look around the forum for Z axis examples I've posted several examples with pictures of them in pieces and complete.

ciscoeuk
02-02-2013, 05:07 PM
thanks jazz thanks has been helpful, thanks the chat after speaking to ken (friend)

we had decide to take your advice and build 18" x 24" unit dedicatted to metal only and encase it is a screen enclosure as this is more of a priority now all we nee now is a design

construction will be steel and ali 3 axis unit

as of now this thread is on hold and i will start a new one

ciscoeuk
03-02-2013, 01:01 AM
jazz and al


is this what you mean by adding structure to the y gantry shoe?

and i have lowered it 180mm (http://www.amazon.co.uk/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=180mm) to bottom of y gantry from table giving a cut of up to 125mm give or take

end plate for structure