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Danielroyal25
28-01-2013, 11:12 PM
Hi all,

Im looking at building a 1250mm x 1250mm x 300mm (cutting capacity) cnc router / miller from scratch. Will be cutting the usual MDF, ply and occasionally aluminium.

ive read through millions of posts on the forum (very useful!) but I still have a few questions before I get started on the CAD model.

as the x axis will be fairly long I am undecided whether to have 2 ball screws or one and this leads on to the next question 1 stepper motor or two. I think the two ball screws will be beneficial but if I use two steppers is it easy to get them in sync (via a slave) or would it be better to power the ball screws via 1 motor all linked by belt drive or should I just go for the 1 balls crew in the centre and power off 1 motor?

next question is the controller. As times are moving on is it best to go with USB connection or parallel, again pros and cons for both with the parallel port being tried and tested and most popular or to go with USB as it will probably go down that route in the future and I will be able to connect my laptop to it.
i don't mind going parallel and mach3 but would be good to connect via laptop.

also generally what size aluminium extrusion do people typically use, would 80 x 40 be too lightweight for the size of the router?

Is there much difference in accuracy and life span between flat supported rails and round supported rails and are the ones sold on eBay from honk kong etc ok or is it best to go with UK suppliers?

finally, may need a few parts machined and more advice so any help would be appreciated.

Will get some images up of the concept model one these few queries have been answered so feel free to give your input.

cheers,

Dan

kingcreaky
31-01-2013, 11:29 AM
Greetings Dan.
Il answer what I can, however Im no pro...
*You want 2 ballscrews driving the X on a gantry that wide, to stop it crabbing
*in regards to one stepper or two, this is a bit of a sore subject on this forum. Both methods have their advantages comes down to personal choice. Im going for one stepper driving two screws.
*(controlelr/breakout board) This is talked about in lots of different threads by people far cleverer than I. So I wont comment.
*extrusion...get a design drawn up, its the design stage that will answer that question. Its all very well me saying yeah 80x40 but it depends on your design. Mine uses two peaces of 100x50 box 5mm thick in a L setup
*The HiWin type cartridge rails are the ones to get.. They are expensive but from what I read are about as good as it gets.
The supported round rails from china are what I went with, which I understand are good enough (so long as you pick the supported ones) but nowhere near as good as the HiWins

I would read ALL the build threads... If you had done this prior to the above post you would of been able to answer all those questions yourself, from the wealth of information you gather from reading them. Then get some designs uploaded and be prepared for them to be picked apart!!!

:-D wish you all the best with your build. make sure you keep this thread updated as there are some sad individuals (me) who regularly check for updates to build threads!!!

Danielroyal25
01-02-2013, 09:51 PM
Thanks for the reply / info.
just working on the CAD model now so will hopefully have a few images up here soon for everyone to give their input.
I have decided to go with two rails on the x driven by 1x motor via toothed belt. I have read a few more posts and learnt tons more and have seen quite a few heated debated over that issue but think the belt will eliminate any room for error as its mechanically sound.
I will have a read up on the controllers, I can see the ads / dis ads of both but I guess i just have to make a decision and stick with it.
Will keep you posted on the progress.

-------

Got quite a bit done on the model today but still a few bits to do before the pics go online.
Just want to confirm a few things before i progress any more. My shopping list for rails and ball screws are as follows (all lengths TBC):

Ball screws (machined with ball nuts)
X = RM1605 (400mm)
Y = RM1610 (1500mm)
Z = RM1610 (1500mm)

Linear round supported rails (with SBR20/25UU bearings)
X = SBR25 (1500mm)
Y = SBR20 (1500mm)
Z = SBR20 (400mm)

Looking at getting these from the famous ebay guy, does he machine the ball screws to accept pulleys to or just couplers? can the length machined for couplers be used for pulleys? has anyone used pulleys from cnc4you or does everyone generally use HTD pulleys?

On the X and Y's is it best to have BK15 bearings on both ends of the ball screws for extra support and BF and Bk on the Z or will BF and BK's all round be ok?

I was looking at using dia 20mm ball screws originally but after reading posts on here, will probably go with 16's.
As feed rates and resolution are always discussed regarding ball screw size is it just down to what the machine is used for, as to what to go with. Are the 16's a good all rounder for both?

kingcreaky
02-02-2013, 11:39 PM
Ok, il try and answer what I can...

First off, I think you are referring to Chai. http://http://stores.ebay.co.uk/linearmotionbearings

Next, have a look at this...
8122

When wording your email to chai, you need to specify your ballscrew dimensions carefully.

For example. I wanted 1500mm of actual travel, I wanted BK type bearings at BOTH ends. and then I wanted to put a pulley on. So I actually ordered
**1603mm Total length so 1500mm PLUS one end machined to type A (except dimension F to be 25mm instead of 15 (to accept pulley), and the other end machined again to type A, but without any F

I personally used HTD bearings from bearing station. However the guy at cnc4u is an extremely nice and helpful chap. In hindsight I should of ordered everything from him! that way I could of just kept ringing him with my questions rather than all the reading ive had to do.



remember; its all in design. dont rush into buying your linear gear until you've got it weighed up properly.... dont design around bearing sizes!. I wish I had spent longer designing as there is an amount of waste on my machine due to my inpatience in the design stages... Look at wilfy's build thread... that boy can design!

hope this helps look forward to seeing design.

martin54
03-02-2013, 12:58 AM
Bit of a novice myself but you might find that 1605 would be a better choice for the Z axis, no doubt one of the experts will give you some sound advice before you reach the stage of ordering anything.
As for the pulleys have a search on the forum as it's been talked about a lot. Just make sure when you do your design you are going to have somewhere to run the belts, the X axis one in particular because this is quite a wide machine so you are looking at a belt a bit over 2.5 mtrs in length.

Danielroyal25
04-02-2013, 02:31 PM
Yeah definitely want to get the CAD model 100% before ordering anything, as it will be a costly error! Thanks for the info and yes i was referring to Chai - he seems to be well recommended.

Correct with the Z axis it was a typo, X & Y should be RM1610 and Z should be RM1605.

Ive uploaded a screenshot so everyone can get an idea of the design when its being discussed. Its a long way off being finished tho. Please let me know your thoughts.

Also i have started to research controllers and wiring etc and am a little daunted by it all, does anyone know of any good links that talks through it step by step and any recommendations for controller (makes and model) - think i will go with a parallel controller and Mach 3 rather than USB / bespoke software. Is it best to go with separate drivers rather than built into the controller?

Cheers!

8143

martin54
04-02-2013, 03:21 PM
I looked at buying a board with plug in driver boards but couldn't find one that worked above about 36v. You might find that that is not enough for your choice of motors. The motors I used would have operated at 36v BUT I would never have got the best out of them so opted to go with 3 separate drivers that could handle a much larger voltage.

You will get lots of help with control box set up from members on the forum so don't let your lack of knowledge (at the moment|) put you off. Quite a few of the build logs have most of what is needed covered so reading them will give you a good start for your own system.

JAZZCNC
04-02-2013, 09:07 PM
Yeah definitely want to get the CAD model 100% before ordering anything, as it will be a costly error!

Yes and NO.?? . . . Draw the layout in cad to get the general machine design but don't order anything off the back of measurements taken from it other wise you will cock up somewhere.
Unless you have used models that have very accurate dimensions then your much better ordering important or components with critical dimensions has you go along taking measurements direct from the frame and machine has it's coming together.
Often you'll see people buy everything before starting only to find something is too long or too short or completely wrong and won't fit.!!

Components from Chai usually arrive in about 12days and within a day or so of starting the frame you'll have enough information to confidently measure from and order parts knowing they will fit exactly with no guessing or nasty surprises.
By the time you have finished welding or bolting the frame together they will have arrived and ready to fit.

The motors and drives I would buy from Zapp or cncdiy because you'll have backup and easy UK return if faulty. Again don't buy until your ready and need them.?
While it's seems nice to have them and spin them up on the bench etc in reality all your doing is wasting warranty and the Electronics are one of the last things you need. There's also the chance of new or better models being available for the same or less money by the time you actually do need them. The digital drive market is constantly evolving and getting cheaper each month.
DONT BUY the cheap 3 AXIS boards from Ebay you'll just be buying trouble and rubbish performance.
You want separate drives and if you can afford them I'd recommend digital drives. Also very important that you match the power supply(PSU) to the motors and drives.
Watch out for Kits that are sold because they have a nasty habit of bundling low voltage PSU's. Often it's cheaper and better to build your own if needing more than 50-60V
Getting the Voltage right is the key a to good running machine and often folks use to low PSU and don't take advantage of the machines full potential.

Also don't be afraid to over spec on the drives.? By this I mean if you can afford 80v drives over 50V then do so. You don't have to run them at 80V and having the overhead gives advantages. Firstly you have upgrade ability but more so they are not being constantly run close to there maximum capability's so are under less stress and will last longer.
Often folks will buy 50V drives and correctly run them at 45-46V but that means the internal electronics are constantly near there max ability with only a small margin of over head. Anything that easily handles the loads they carry will last longer, yes initially they cost more but it will be returned thru reliability and longevity in the long run.

Another often done thing.?? . . Don't go buying massive motors like 12NM nema 34's etc 3Nm nema 23 will be more than enough for this size type machine and cheap.

Regards the frame then it needs some diagonal bracing and if it's an adjustable bed which it looks then it needs much more support for the sides. Don't rely on the bed to for rigidity or strength, which it will do anyway, because when you come to adjust the bed the frame will move and flex knocking alignment and setup out every time.
This will be a real pain, also the frame will be flimsy and resonant which will affect cut quality.
Don't be skimpy on the frame Chunky is good, same with gantry don't be afraid of bit of weight it helps with cut quality and you'll be surprised how powerful the combination of ballscrews and steppers can be.!!

Hope this helps.

Danielroyal25
05-02-2013, 02:10 PM
Thanks for the info guys!
Just wanted to give some more info on the use of the machine and the design so far.

Im hoping to cut mainly large ply / MDF sheets on it so wanted it to accommodate the maximum capacity sheet (standard size: 8ft x 4ft).
i didnt want to build a router to this overall sheet size as i it will be a bit of a beast and also the cost comes into play. my thoughts were to make it accept the width of the sheet (4ft / 1220mm + a little) and then the length of the board could be machined in two halves by either feeding the material through of turning it through 180 degrees.

Does the length of the gantry pose a problem for general machining and would it be able to handle cutting aluminium? As long as the strength is there will it be ok and will the precision still be to a fairly high standard. If cutting aluminium or harder woods is
Will be looking at getting the water cooled spindle so im guessing the weight of the gantry and Z axis will be a fair bit so the gantry will have to be fairly substantial.

The bed is going to be in a fixed position so this can be bulked up with diagonals for strength and like suggested heavier gauge extrusion, just difficult to balance the desired design with the cost of parts.

The support in the Y direction behind the gantry was to mount the motor in the centre with pulleys to the X ballscrews, so didnt really want to add a support the other end as this was to allow material to be fed in / out but if i can position it in a way that the material can be slid under the support i may add this in.

JAZZCNC
05-02-2013, 07:28 PM
Does the length of the gantry pose a problem for general machining and would it be able to handle cutting aluminium? As long as the strength is there will it be ok and will the precision still be to a fairly high standard.

Yes Gantry length will greatly affect the machine but not so much for precision but more the quality of finish from machine. Precison or accurecy is down to combination of components and quality of build.
That doesn't mean you can't have long gantry but it does mean it will have to be very strong and substantial to resist resonance and flex which are the enemy of finish quality.
Take this strength to another level if you want to cut Aluminium and achieve good Finish quality. Really unless your only cutting Thin Alu sheet or Profiles etc that don't need good finish then forget cutting Aluminium on such a wide or long moving gantry machine. Yes it will do it but not very well.!!



The support in the Y direction behind the gantry was to mount the motor in the centre with pulleys to the X ballscrews, so didnt really want to add a support the other end as this was to allow material to be fed in / out but if i can position it in a way that the material can be slid under the support i may add this in.

No need One end support will be fine so long the frame is braced well, my machine has this one end setup and it works fine.

If your into wood can I suggest you have the rails slightly overhang the end of bed. Doing this simple thing will give you some nice options easily achieved.
Namely will allow end machining of boards etc for hinges, locks, Dovetails and oversize or oversize awkward parts by clamping to end of machine.
Also if you want a 4th axis makes it very easy to add one see pics for some idea of what I mean.
It's only a cad mock up so pay no attention to details like gantry has thats actually a design I use the other way round it just saved me some drawing time for showing the person it was intended for. It could be used that way round thou.!!

D.C.
05-02-2013, 09:05 PM
Jazz on those piccys you posted doesn't it make more sense to put the 4th axis level slightly lower than the table instead of several inches above the table?

That way you can fit the same diameter stock in there without needing several more inches of z-axis travel.

PS this design looks like it is meant to do almost exactly what I'm designing my machine for (the 4th axis and the ability to fix pieces vertically for doing dovetails etc) Have you actually built one like this and does it work ok?

JAZZCNC
05-02-2013, 09:35 PM
Jazz on those piccys you posted doesn't it make more sense to put the 4th axis level slightly lower than the table instead of several inches above the table?

That way you can fit the same diameter stock in there without needing several more inches of z-axis travel.

Not sure how you work that out because putting it lower will mean more Z axis extension required so longer Z travel required.? Also the longer Z extension will increase chance of chatter so keeping it to shortest requirement would be preferable.

But in any case like I said this was just a rough knock up model to give the person some visual idea of what I meant and in reality then it could go any height you like.

Regards actually building the machine then Yes and NO.?? . . . Yes I've built a few where they extend for end clamping option but not built 4th axis option on any yet.
My machine extends like this and have cut many tall or awkward parts using the end for clamping but I don't have the 4th axis bit but it wouldn't be very difficult to throw something together.
To be honest I'd probably use a converted rotary table to give higher resolution or high reduction gearbox.?

D.C.
05-02-2013, 11:24 PM
Assuming your z-axis can reach just below the top of the bed for surfacing it for doing flatsheets then that will be the lower limit of your z-axis travel. But for doing fourth axis work the lowest limit you need is the centre of the spindle, any material lower than that gets rotated upwards towards the cutting head.

So if you have the 4th-axis centred on the the z-axis limit of travel, you can cut 6 inch radius stock with 6 inches of z-axis travel. If you move the centre of the 4th axis up 2 inches this means you can only cut 4 inch radius stock with 6 inches of z-axis travel because the 2 inches you have below the centre will never be used for doing 4th axis work but your z-axis still needs to be travel that far to reach the bed when doing flat sheet work on the rest of the table.

Putting the centre at the same height as the bed results in the shortest required z-axis.

In reality you can position the 4th axis centre slightly lower than the top of the bed because your z axis will reach down that low for surfacing the bed and you never ever want to cut all the way through a piece of spinning wood that requires the support of two centres because it will fly off the machine at great speed doing a great deal of damage to any fleshy human type objects in it's path.

JAZZCNC
06-02-2013, 12:44 AM
Putting the centre at the same height as the bed results in the shortest required z-axis.

No it doesn't it puts it at the longest Z extension. It will only be shortest when cutting at the outer radius and ever millimetre towards the centre the extension gets longer weaker and therefore the chatter will get worse.
I know what your saying but really it's down to the size of radius you want to cut or the size your most likely to do often. Why would you want the centre 7" away when your mostly turning 2" stock.? You wouldn't set your rest 7" away from centre on a Manual lathe if you where turning 2" stock so why would you in this case.? . . .That would just be creating a weaker machine for the Odd occasion when you want to turn larger diameter.!

The ideal would be an adjustable position and that's what I'd probably do in reality.! . . BUT.!!. . . . Like I said it's only a mock up and if you wanted 6" from the floor then go for it. But this was drawn just to show the principle with simple Leg or spindle turning in mind so that's why it landed there.:rolleyes: . . Oh and it's 4.5" away there so thats 9" Diameter which is more than enough for most 4th axis work.!!

D.C.
06-02-2013, 01:12 AM
I suppose it depends on exactly what you want out of the machine. If you do more work on sheetstock using the bed than you do turning it would mean having an extra long z-axis for whenever you are doing all your sheetwork.

Unless you need far more clearance on the bed to insert really thick material than you do on the lathe which makes it a moot point.

alex wight
06-02-2013, 10:20 AM
These were the photo's Dean sent to myself, which will serve me very well. I,m looking at doing spindles, table legs ect with the odd 3d items thrown in at some point. I,m keeping it as high as possible, as opposed to as low as possible. The higher you go the less z travel there is which will keep it stronger. What the photo's dont show is that Dean has an adjustable table, which i will have as well. When i,m doing 200mm deep material (engraving fire mantles), the z is going to travel 30-40mm, and the table will be removed. When i come to do thinner materials, i,ll fix the removable table, which will allow the z to travel, again, 30-40mm, which will keep the machine as strong as possible. Once i get a start made to it, i,ll be running things by Dean just to make sure that i,m heading down the correct road, as i only want to build one machine once. I look forward to seeing your progress D.C.

JAZZCNC
06-02-2013, 11:11 AM
I suppose it depends on exactly what you want out of the machine. If you do more work on sheetstock using the bed than you do turning it would mean having an extra long z-axis for whenever you are doing all your sheetwork.

Unless you need far more clearance on the bed to insert really thick material than you do on the lathe which makes it a moot point.

Like I did say several times these drawings where just for showing the principle and general layout. Alex has specific needs, which I knew ence how it's roughly drawn and he will design the specific heights etc around his needs.
Obviously if he or anyone else was just cutting 1" panels then the Gantry and so therefore the Z axis and it's overall extension would be less so yes in this case you would want the 4th axis lower but it's horse for course's and really that's a different machine a "Panel router".

To be honest if I wanted to turn legs etc then I'd use a lathe because building a 4th Axis that can spin fast enough for turning and still give high resolution for good 4th axis detail is very expensive, not hard just expensive. 4th Axis come into there own when you want to engrave or decorate, flute or barly twist etc and it's for this I'd use one and not for the actual turning.!!

alex wight
06-02-2013, 11:35 AM
When I say spindles, it will be wrap around detailing I'd be doing, as opposed to just making normal spindles I knew what I meant lol

JAZZCNC
06-02-2013, 12:11 PM
When I say spindles, it will be wrap around detailing I'd be doing, as opposed to just making normal spindles I knew what I meant lol

Ah ah yes I knew what you meant or wanted has well Alex that comment was just for the benefit of others.!

alex wight
06-02-2013, 12:22 PM
Ah ah yes I knew what you meant or wanted has well Dean that comment was just for the benefit of others. :tennis: lol lol

Danielroyal25
06-02-2013, 02:30 PM
Thats a good idea by over hanging the X rails. I guess you could also have a removable section in the centre of the bed to do the same thing, but will obviously limit the size of the material that is being cut. May take the idea up and incorporate it into my design. What length overhang would you say? diagonal supports could be added for a bit more strength too.
Im debating over the Z axis travel now too. i originally stated 300mm, what is the norm? or will it be best to go with less around 200mm. I will be mainly profiling, but will occasionally mill in 3D (modelling foam), if pocketing im guessing the depth of Z travel will be restricted by the tool length?

Jonathan
06-02-2013, 02:35 PM
Im debating over the Z axis travel now too. i originally stated 300mm, what is the norm? or will it be best to go with less around 200mm. I will be mainly profiling, but will occasionally mill in 3D (modelling foam), if pocketing im guessing the depth of Z travel will be restricted by the tool length?

Make the Z-axis as small as you can afford to without compromising what you want to make. It is far easier to design a machine with a short Z-axis since the overhang is less, so the torque applied to the gantry, and hence in general the forces are lower.

JAZZCNC
06-02-2013, 03:24 PM
What length overhang would you say?
Depends on other factors like the gantry design, bearing separation and Z axis etc but you don't need much has unless you create an offset gantry then the tool naturely tends to overhang pass the bearings.


Im debating over the Z axis travel now too. i originally stated 300mm, what is the norm? or will it be best to go with less around 200mm.

I've never needed or built over 200m in any Z axis. Like Jonathan says just enough for your needs and no more. The adjustable bed takes the need for long Z axis away in most cases and Jonathan has quite a long Z axis but I bet he rarely has need for it.? . . Other than being too lazy to lift the Bed.!

Tooling length will be a limiting factor and while you can buy long tooling it often costs a fortune and requires large spindle collets. You'' be hard pressed to find longer than 200mm flute cutters with less than 12.5mm shank sizes that routers or common ER20 spindles take and even then you probably find the price prohibiting.!!

alex wight
06-02-2013, 03:40 PM
I,m building a machine as Jazz knows, that is able to take a half sheet ie 1220mm x 1220mm. My x is going to be 1700mm, y is going to be in the region of 1670mm/1700mm, and z will be finalised nearer the time, but will have travel of 100mm. The sides of my table will 250mm high, and the removable table will be sitting 100mm down from the top of the sides. When i have my 200mm material on the machine, my z travel is going to be in the region of 50mm (nothing is finalised at the moment apart from the table design). When i have thinner material on the machine, and the removable table is fitted, again, the travel will be 100mm. I,m hopeful that this will be in keeping with the strength of the machine, which i,m sure it will be. i,m looking at using 350mm of the over hang for the 4th axis. The way i,m doing as advised, is to keep it out the way of normal table operation, and this design is going to do just that. Just need to get the bloody workshop built, hopefully this weekend, now that the snow is away AGAIN.

Danielroyal25
07-02-2013, 10:33 PM
Should hopefully have a few more images up tomorrow as I will be working on the cad model.
Have changed the set up of the gantry rails so they are aligned vertically as advised, think I will mount the y ball screw at the rear of the gantry as I can get the spindle closer to the y axis and the ballscrew will be partially enclosed reducing exposure to cut material etc.
thanks for the info Alex, had a read through your log, do you have any images? Sounds like you will be busy setting up your workshop and machine.
I was thinking of whether to get a 4 axis controller so there is the possibility to expand in the future but heard the cam software is pretty pricey? Don't know whether to just get the 3 axis for now, depends on the difference in cost.
in terms of x rail position, is it best to align them with the supported rails (height wise)? Will hopefully have these mocked up in the cad model for comments.

alex wight
07-02-2013, 10:47 PM
I'm using the photos jazz has shown you, but with a few tweeks. I don't have any photos but will start soon. This weekend will see me build my workshop, and then it's all systems go. Although I want to get cracked on, I'm well aware for the need to be accurate throughout, so will be taking things easy, so that the errors are kept to a minimum. I will be seeking advice from jazz, no disrespect to anyone else, but by maintaining a one to one with one person, is going to save me some grey hairs due to getting mixed up with too much info. I'll keep you posted on my progress, and good luck with yours.

Danielroyal25
09-02-2013, 12:21 PM
Should have some pics up by next weekend, got some done on the model but still needs a bit more work pre comments. Probably a bit early to discuss but could someone give me a rough guide on machining costs for 20mm thick alu plate for the z axis and y sides. Will be able to to get some sizes up soon. When the parts are ready for machining I can provide cad models or detail drawings. Let me know if I have any volunteers (also would be nice to see a few bits being machined in person).
Also when fixing the plates together are they normally just drilled and tapped? The fixings will be going into the side of the plate, will this make it difficult to set up to drill accurately?

marbles
09-02-2013, 10:22 PM
Hi, I'm reading this part of the conversation about the long z axis with interest as i'm in the process of making a 1250 x 1250 with 500mm travel on the z axis. its designed specifically to cut deep styrene foam sheets where there is less resistance.

Where is a good source for long fluted cuttters like the ones your talking about and is it possible to buy a 1/8 to 1/2 shank adapter to take 1/2 cutters?

Danielroyal25
18-02-2013, 11:31 AM
Been a bit busy with work and jobs around the house so have not got much more done yet. I have been looking at the costs of materials and may be a bit pricey to use aluminium t slot extrusion on the machine.
i am looking at aluminium box section 60x60x4 for the frame and 120x60x4 (2x L shape config) for the gantry. Is there much difference in strength / deflection using box compared to the t slot ext and how does it deal with resonance? What materials are generally used to dampen if it is needed?

Danielroyal25
01-03-2013, 04:16 PM
Hi, here are a few more screen shots of the model. Done a lot of work on it, but still a few more hours to go... Please let me know your thoughts as i would much rather make the changes now than down the line. I have still got to add diagonals / gussets onto the frame to strengthen it up. What are peoples thoughts on the X pulley set up (i have left the cross bar unsupported so material can be slid through), ways to mount X ball screws and set up of motor / pulleys on Y axis?8308830983108311

kingcreaky
01-03-2013, 09:14 PM
nice work. i can see some time has been put in to these drawings.

Pretty confident the guys will tell you to mount the Z rails the other way round.. so the Y plate holds the bearings and the moving Z has the actual rails if you understand? see my machine

I suspect the pro's will suggest more strength under that bed.

To be honest, I took all the useful pointers from the guys on here regarding strength and rigidity and resonance with a pinch of salt..I use 6mm steel box section and 50x100x6 ali for the gantry.... every one of my mates told me its over-engineered.

Now, I sh*t you not. It is only now my machine is working I understand what they were talking about. Its literally got to be SOLID AS A ROCK otherwise you watch the thing flex when cutting hard wood let alone Ali. Your only down the road... Come and watch mine do it before you spend any money

JAZZCNC
01-03-2013, 10:25 PM
Pretty confident the guys will tell you to mount the Z rails the other way round.. so the Y plate holds the bearings and the moving Z has the actual rails if you understand? see my machine

If you look again Matt you'll see he's got it correct way round.!. . . BUT . . You have put the Ballscrew upside down with Fixed end at bottom. You want fixed end bearing near motor.




To be honest, I took all the useful pointers from the guys on here regarding strength and rigidity and resonance with a pinch of salt..I use 6mm steel box section and 50x100x6 ali for the gantry.... every one of my mates told me its over-engineered.

Now, I sh*t you not. It is only now my machine is working I understand what they were talking about. Its literally got to be SOLID AS A ROCK otherwise you watch the thing flex when cutting hard wood let alone Ali. Your only down the road... Come and watch mine do it before you spend any money

He really does shit you not.!! . . . Don't under estimate the forces they are high and if you want high Precision and accuracy then the average, and even well tooled up DIY-er can't over engineer.
Build it strong and don't be afraid of weight when it comes to gantry.? Better to have rigidity and sacrifice speed thru using larger motors than end up with flexy resonating gantry which gives crap finish.

Danielroyal25
03-03-2013, 10:52 AM
Yeah I am the same really, thinking that the framework can be fairly rigid (nothing too over the top) but not seeing many cnc routers in the flesh it's hard to judge how much force is actually created from them. The idea was to try and create some storage for sheets etc under the bed (as workshop space is limited already) but this can be sacrificed by adding some more support struts etc to beef up the frame.
i was worried about keeping the weight down too for some reason? But as its going to be in the same position in the workshop and weight is a key factor for reduction of resonance and improving quality of finish those worries are out of the window.
still unsure whether to go with alu or steel tho...
matt - my gantry design is based on 2x lengths of 50 x 100mm 6mm wall aluminium in a L shape config. And 60 x 60 x 4mm wall alu box for the frame. Based on your machine would you change the material of the gantry?

WandrinAndy
03-03-2013, 07:28 PM
The idea was to try and create some storage for sheets etc under the bed (as workshop space is limited already) but this can be sacrificed by adding some more support struts etc to beef up the frame.

To reduce the workshop space needed, it may be worthwhile considering going vertical..... JAZZCNC has a great design if you search the threads.

Danielroyal25
10-03-2013, 04:55 PM
Yeah I'd considered jazz's vertical design but going to go with the standard horizontal set up as it will better for setting up the jobs that I will be cutting.

I should have the "finalised" model up pretty soon so all comments will be welcomed as I will start ordering materials and components soon after.

Just a quick question on fixings, is there any reason why hex cap head bolts (with counterbores) are commonly used over hex head countersunk bolts? Is there much difference in strength or is it just personal preference?

Danielroyal25
15-04-2013, 10:24 PM
Hi guys. The design is now complete and into ordering parts!! Just arranging the machine parts so that they can be machined from one large plate. What is the minimum gap I can have between each part. I have made it 4mm so far will this be ok?

Jonathan
16-04-2013, 12:09 AM
6mm cutters tend to be convenient if the thickness of the material is roughly 10mm or greater, so I tend to space parts out by 7mm. You can get away with a little less, but the finishing pass tends to work better if there's a reasonable amount of clearance.

JAZZCNC
16-04-2013, 01:25 AM
6mm cutters tend to be convenient if the thickness of the material is roughly 10mm or greater, so I tend to space parts out by 7mm. You can get away with a little less, but the finishing pass tends to work better if there's a reasonable amount of clearance.

On top of this make sure there's room or spacing for a Lead-in and lead-out or ramping etc otherwise it means plunging into material and person doing cutting wont thank you for that.!

Really your better letting the person doing the cutting setup the layout to suit there clampings methods and machine.? If you try to cut it too fine on material it's easy to get into trouble so better having a little extra for safety sake.

Danielroyal25
16-04-2013, 09:31 AM
cool ok, Just laying it out roughly to get an idea of the overall sizes of the plates that i will need to order. I will go for 10mm gaps and then whoever cuts the parts should have enough room to reposition.

Danielroyal25
20-04-2014, 03:41 PM
Still yet to post the build images... But Was cutting some oak today and all was going well until the grub screw holidng the pulley to the stepper motor on the z axis come loose almost scrapping the material!
what do most people use 1 grub screw or more, any locking compond, keyways?
i checked the others before starting the machine again and they were all loose. They are stainless steel m4 screws but being so small the Allen key just rounds off if they are done up too tight.

JAZZCNC
20-04-2014, 04:40 PM
Minimum of 2 screws and I always use Lock thread on both shaft and screws. If you have trouble and can remove motors without needing to remove pulleys then get the Red compound that grips like shit to a blanket.! . . . . Just be warned you'll never remove the pulley again thou.!!

On ballscrews file a small Flat on shaft for one screw to land on.

Keys ways will stop pulley spinning but won't stop grub screw coming loose and pulley falling off.!

Really this isn't uncommon and for first few weeks/months it's good idea to keep going around machine checking screws etc until everything as settled down.

Now I'm answering no more questions until I've seen this bloody machine in one piece rather than load of aluminium parts and chips on my floor/bench which you've had now for best part of year. . Lol

GEOFFREY
20-04-2014, 05:55 PM
Surely small flats on the shaft in the grub screw area should stop that. I always thought "two screws were better than one"!!! G.

EddyCurrent
20-04-2014, 06:09 PM
I have two M4 hex grub screws 90 degrees apart on the pulley boss, one screw has a flat end that tightens onto a flat that was filed on the ball screw, the other has a point that digs into the shaft. One I've had the machine running a while and all is fine, some loctite will be put on the screw threads. Good quality screws and an allen key that is not worn means the hex socket does not round over.

Danielroyal25
26-04-2014, 11:20 PM
Here are a few images from the build. I wont go into too much detail with text, but if anyone has any questions just let me know and i will give more detail.
I am really pleased with how it has turned out, considering it is the first machine i have designed and built. Huge thanks to everyone for the help!!!

Things i would do differently next time:
Not use cheap Omron relays! i had around 3 faulty ones which caused a head ache fault finding.
Get the dust extractor set up before surfacing the bed!!!
oversize the control box, as the wiring become a little messy and cramped
make the bed heigh adjustable
add rail adjustment to aid levelling
use epoxy to level the rails

Things still to do:
fit limit and home switches on all axis
finish the dust extraction system including dust shoe
loctite the pulley and grub screws onto the motors
calibrate the spindle speed

Putting the hours into the design was worth it. The assembly went well with the machined parts, the frame went together well to with only a couple of holes needing opening out. Slotting parts and adding adjustment in the design was beneficial for setting up and assembly.

It has taken near enough a year from design to working machine (working weekends and the occasional week night).

Anyway, enjoy the pics...

1223212233122341223512236122371223812239

Lee Roberts
27-04-2014, 12:03 AM
Still yet to post the build images... But Was cutting some oak today and all was going well until the grub screw holidng the pulley to the stepper motor on the z axis come loose almost scrapping the material!
what do most people use 1 grub screw or more, any locking compond, keyways?
i checked the others before starting the machine again and they were all loose. They are stainless steel m4 screws but being so small the Allen key just rounds off if they are done up too tight.

Hi Daniel, try some blue lock-tite on the grub screws, also make sure your using the flat type screws not the pointed type, you could also use some thin brass sheet or shimming stock (steel, ebay?) to make some disks that live in between the screw and the shaft so as not to mark the shaft with the screw or if the pointed type, you could use a drill bit to make a matching divet on the shaft that the point of the screw will fit into.

Keyways are nice but for this you just need to support the grubscrew rather than the rotary motion, a little of the blue should sort it.

.Me

EDIT: Didn't notice there was a page 5 of this thread...it looks like you have enough ideas and the machine is coming along nicely!

GEOFFREY
27-04-2014, 12:44 AM
That machine is looking very nice. Well done. G.

longy
27-04-2014, 11:36 AM
Things i would do differently next time:
oversize the control box, as the wiring become a little messy and cramped


Looks good Dan, how big or small is the is the control box you've used ? like you say it does look a bit cramped in there.
Mike

Danielroyal25
27-04-2014, 04:38 PM
Thanks mike, it was 400 x 600 x 200. It weighs a ton!! I had to add an aluminium section on the bottom for cable entry etc which is around 40mm deep. This just about fitted all of the connectors an glands in. Would have a much larger box and add conduit / cable management in next time.
still new to mount it on the side of the machine and add vents on the top before it's completely finished.

longy
27-04-2014, 05:39 PM
Still looks very impressive to me Dan, looks as if I will have to keep my eye out for an 800 x 600 x 200 enclosure if it needs all that wiring and I will at some stage want to get 5 drivers in a case for my build. I noticed that on your Z axis which I have to looks fantastic very nice finish, that you've had both the parts machined to give clearance for the ball screw. Could you not have just packed out the plates where the rails and blocks are fitted and use a thinner plate ?
Mike

JAZZCNC
28-04-2014, 02:26 AM
Bloody hell Dan when I gave you parts and said use some decent sized bolts to bolt Z axis together I didn't mean "Raw Bolts" . .:hysterical:

Looking good mate but now you know we need the matching video. .:thumsup:

Danielroyal25
05-05-2014, 09:48 PM
Hi Mike, yes i could have used a thinner plate and packed the parts out but it just allowed all of the parts to be machined out of 1 sheet of material, saved ordering separate pieces.

Cheers Dean, will get some vids up soon. I was going for the industrial look with the bolts ha! i havent had much time to play around with it lately but as soon as i do i will get posting.

Danielroyal25
07-05-2014, 10:04 PM
Opinions please. The pulley on all of the axis were bored out manually on a pillar drill (I know, stupid idea - I had no acess to a lathe) so they are are slightly off centre. They have 1 m4 grub screw in also clamping onto the flat of the motor shaft / ballscrew shaft.
after the slipping episode I am wondering whether to
a- have them rebored to a larger diameter and have an insert made up and add another grub screw for fixing
b- order some new pulleys that are pre machined at around 70
how much would optio a cost (if anyone is up for the job) or would anyone want to buy my old pulleys to modify and use.

i was just going to loctite them in place as is but if they align at worst case the belts tighten and loosen which isn't the best.

next question.. My dust extractor is linked via a relay for Mach to control. When in e-stop mode the relay is inactive. When the machine is reset the relay is active and switches the extractor on. How do I get the relay to be controlled via the g code command instead. The vfd run start stop is controlled this way and works fine but I have wired the extractor in a similar way and it's not working as expected.

EddyCurrent
07-05-2014, 10:57 PM
My dust extractor is linked via a relay for Mach to control. When in e-stop mode the relay is inactive. When the machine is reset the relay is active and switches the extractor on. How do I get the relay to be controlled via the g code command instead. The vfd run start stop is controlled this way and works fine but I have wired the extractor in a similar way and it's not working as expected.

Some people use the relay built into the vfd to switch the extractor on and off, you will need to program it for this operation by consulting the manual.
You could use the Mist and Flood coolant outputs controlled by M7 and M8 in the G-code file. These are in the 'Ports & Pins / Spindle Setup' page of Mach3, you would then have to enable the corresponding output in 'Output Signals'.
This is just a similar arrangement to M3 and the relay you set up for the spindle.

JAZZCNC
07-05-2014, 10:58 PM
New pulleys required Dan don't waste time with bushes etc not worth the hassle and would take just has long to make as boring new pulleys.

My Lathe is down at the moment else I'd offer to bore some new pulleys for you but sure some other kind sole might offer there services.!!

Regards The Vaccum then you want it controlled by an output then use M7 or M8 to turn it on and M9 off. To do this is just the same as with the spindle.
Select an output # in Mach's Ports n pins and set to the Pin number your using for the relay, either one built into BOB or separate controlled thru an output pin (or both).
Then in Spindle setup in ports n pins uncheck the "disable flood mist relays" box then enter the output # number (not pin number but OUTPUT number used) for either M7 or M8 depending on which M code your going to use in the G-code for turning on the vacuum. You can set a delay for it to come on if you want in the box next to Output #.

Thats all there is too it.!!

PAULRO
30-06-2014, 01:21 PM
Ok, il try and answer what I can...

First off, I think you are referring to Chai. http://http://stores.ebay.co.uk/linearmotionbearings (http://http//stores.ebay.co.uk/linearmotionbearings)

Hi Lee, i have tried to contact the above address but have had no luck. is there some other way to contact Chai. has he a site i can order ballscrews, slides. etc? thasnks in advance Paulro.


p.s i'm just designing a cnc of similar size to this one and am at the drawing stage.

PAULRO
08-08-2014, 12:12 PM
Hi Daniel, great build. i have steel ordered for a similar build and am curious to know the inside dimensions of your m/c. the travel of your x and y axis. i have allowed 1440 mm inside dimensions allowed for 1220 mm standard width of sheet.

12995

i'm trying to minimize this dim so i can minimize the length of the gantry. i'm also curious about the distance from the spindle router collet face to the work table . as i say the steel is due in next Tuesday / Wednesday and i'll start cutting the frame members early next weekend so i have these last couple of days to refine and tweek the frame design. any input would be greatly appreciated. by the way ,it would be great to see videos of the m/c in action. !! cheers , Paulro.

Danielroyal25
08-08-2014, 08:35 PM
Thanks Paulro,
X & Y both have 1250mm travel so will cut a full 4x4 sheet allowing 15mm a side. Just make sure that you allow for the width of the z axis, so that when the z is at either extreme of its travel it passes the board to make full use of the sheet and allow a little extra so that the z axis doesnt max out on its travel.
i think i left 150mm between the collet and top of the bed, i should have made the bed height adjustable really, but maybe next time....
i will try and get some vids up soon, i have been tweaking it lately and trial cutting projects so once it is all ok i will post some videos. let me know if you need any more info, all the best!