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Initial Design Check Please
Hello, im looking to build my first CNC, so i have been lurking around here for a while now looking and reading up. I recently met the builder of SweetDream at the engineering show, who gave me some great pointers and as a result i have altered my design more.
So im looking at building it 500mm x 400mm with 100mm Z axis. Im looking at using SRB20 supported rails and 1604 ballscrews throughout the design. I still need to do more drawing as you can tell ie the rest of the frame below the y axis rails, but if anyone can spot anything that would be great.
The gantry side plates and main spindle plate will be from 6082 20mm aluminium, and the box that wraps round the rails on the x axis will be from 6082 10mm aluminium. The gantry side plates will be joined to the y axis bearing blocks via 60x60mm x 4mm thick aluminium box and inside that i have mounted the ball nut into an aluminium block which is then joined to the aluminium box.
http://i120.photobucket.com/albums/o...k/CNC/cnc1.png
http://i120.photobucket.com/albums/o...k/CNC/cnc2.png
http://i120.photobucket.com/albums/o...k/CNC/cnc3.png
http://i120.photobucket.com/albums/o...k/CNC/cnc4.png
Trev
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Re: Initial Design Check Please
It will help with advice if you mention what materials you're intending to cut.
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Re: Initial Design Check Please
Sorry my mistake. I would like to mill plywood, carbon fibre and aluminium.
Im looking to make the frame it will sit on out of 50mm steel box. Just got to find a local welder.
Trev
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Re: Initial Design Check Please
Like Ian asks materials to cut will help but I've got a few why's.?
Why supportedround rails.?
Why 1604 ~(Do you mean 1605 ballscrews)
Why that size Profile.?
Why is there No bed.?
Got few a suggestions as well. Would make it so the Gantry sit directly on the bearings rather than between the bearing with brackets. This will make it easier to build and setup along with making accurecy easier to find. The way you have it will be much harder to setup without causing binding to bearings etc than sat directly on bearings.
Don't wrap a box around the gantry it doesn't add any strength really and makes setting up harder with bigger potential for causing binding bearings. The extra weight just means less potential acceleration.
Use thicker Rear Z axis plate as 10mm isn't enough and any resonance here will transfer to the finish quality.
Better if you can get the ballscrews down the side out the way as being stuck up high like that they are open to being lent on or caught with material when loading etc.
You don't show any lower frame so it's hard to tell what you thinking here but just bare in mind the base is the foundation for everything else so if this isn't accurate or strong it will impact the rest of the machine in a negative way.!!
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Re: Initial Design Check Please
Hi thanks for the reply
I went with the supported rails due to profile ones being out of my budget
yes they are 1605
i went with that profile as it lined up nicely with the holes in the supported rail, making it easy to join the two.
Sorry i know having no bed and lower frame makes it tricky to check, its just i wanted what i had drawn checking first in case my design is junk.
With regards to mounting the bearing blocks to the gantry sides, do you mean by bolting a plate to the bottom of the gantry side and then the bearings to that, forming like an upside down T shape?
Ok i will make the plate 20mm and remove the rear plate on the gantry. I saw the idea originally on the Sweetdream CNC which did seem like a good idea.
Is there any good reference design on this website i could look at at all?
Thanks again
Trev
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2 Attachment(s)
Re: Initial Design Check Please
Quote:
Originally Posted by
Gotty101
I went with the supported rails due to profile ones being out of my budget
Well if you haven't bought them already this is worth re-thinking. Profiled linear rails from china are now quite cheap and the difference isn't worth not using them.
Quote:
Originally Posted by
Gotty101
yes they are 1605
Well this again is worth reconsidering. 5mm pitch is fine for harder materials like aluminium but does restrict the speed for cutting woods and plastics correctly. 10mm is a better balance and while more biased towards softer materials it's still gives more than capable resolution for aluminium.
If you connect to the screws with timing belts, which I suggest you do for resonance reasons, then it's an easy ratio change to increase resolution if you ever find your mostly cutting harder materials which need torque and resolution.
Quote:
Originally Posted by
Gotty101
i went with that profile as it lined up nicely with the holes in the supported rail, making it easy to join the two.
Ok ye thought that may be case but layed flat like that weakens the material unless it's well supported from below which could be ok for the base if supported from below but the Gantry has is designed can't be so positioned like that so it will be weak in one direction. I'd think about using square rather than rectangle and beef it up a little, say 80x80 or 90x90, or go with "L" sahpe setup like I've posted on forum many times which is stiff in both directions.
Quote:
Originally Posted by
Gotty101
With regards to mounting the bearing blocks to the gantry sides, do you mean by bolting a plate to the bottom of the gantry side and then the bearings to that, forming like an upside down T shape?
Something like this I knocked up to show both screws and gantry but with a little more bracing etc. There's many ways but sat on the bearings is strongest and easier to do.
Attachment 13715Attachment 13716
Quote:
Originally Posted by
Gotty101
Ok i will make the plate 20mm and remove the rear plate on the gantry. I saw the idea originally on the Sweetdream CNC which did seem like a good idea.
Argh but he's only used to taking Pics of UFO's and knows nothing about CNC.! . . Lol . . (:joker: He's a mate not being rude.!!)
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Re: Initial Design Check Please
Thank you JazzCNC,
That really cleared things up, expecially with the pictures.
With regards to the profile rails i had a look on ebay and they seemed to get quite $$ when i was looking at the longer lengths, but ive found them on aliexpress and they seem alot better priced and with more options, is this where you get yours from?
i had a look for the Z axis for example and found these rails
http://www.aliexpress.com/item/EGR15...828633643.html
and these blocks
http://www.aliexpress.com/item/1PC-H...044267870.html
Are these the right kind of thing? Only reason im asking is there seems to be different versions ie HGR MGN.
Sorry about all the questions.
Thanks again
Trev
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Re: Initial Design Check Please
I would advise against the 15 size, the bearing blocks are an absolute pain to grease, go with 20's all round.
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Re: Initial Design Check Please
Quote:
Originally Posted by
Gotty101
Are these the right kind of thing? Only reason im asking is there seems to be different versions ie HGR MGN.
Sorry about all the questions.
Hi Trev,
No problem with questions that's why we are here to help each other and ask questions. Don't stop asking questions no mattter how daft they may feel, if your not sure ask.!!
Regards the rails and bearings then like eddy says 20mm tend to be a better size and not just for greasing, they make building the Z axis easier due to being taller and generally give better support with there larger bearings. The rails also sit on the profile better.
With the type then look on the Hi-win site and it will show the difference between the types, it's often very subtle differences like hole centres or bearing heights ratings etc.
Most use the HGH-CA for the slim type and the HGH-CW for the flanged wide type with standard pre-load Z0. If your wondering what pre-load means then it's the amount of pre-tensioning the bearings have when on the rails. Pre-loading removes any slop or play but at same time requires more force to make the bearings slide so we don't want it too high. Z0 is lower pre-load.
Those new to using profiled linear rails are often shocked to find that the bearings don't easily slide when on the rails but require a good shove and then stop quickly. This preload at work. Stand on the buggers and you'll end up on your arse as they work best under pressure and glide like on ice. .. Lol
If your buying from Ali express the look for Fred Lee. Personally I buy ballscrews and rails etc from from Chai at linear motion bearings but he doesn't sell Hi-win brand of rails, they are some other Taiwanese brand which can't think of at minute but they are very good quality do just the same job and a little cheaper.
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Re: Initial Design Check Please
Thanks guys for the help so far. ive scrapped and started from scratch. Ive based it heavily off the pics you posted Jazzcnc, they where a great help and have used 20 Hiwin rails as suggested. Ive done everything in 20mm ali and doubled up on the aluminium profile now. Ive still got a fair bit to draw like the lower frame and bed and stepper mounts with belt drives, and y axis ball screws. Unfortunately im off for a short break so im going to have to go cold turky from solidworks for the next few days.
im going to have to find a good source of 20mm plate next. I was talking to a close family friend about my project who is an ex tool maker so now i have access to his machine shop now which is a great help.
Thanks again all
Trev
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Re: Initial Design Check Please
Hi guys, ive done some work redoing the design as per the suggestions. The lower frame will be made from 50mm square steal box with 3mm wall. The total z axis travel is 120mm. Ive not drawn the bed yet but it will sit in the space at the bottom of the frame but also be adjustable upwards .
Ive still got some things to draw like the z axis screw and stepper ect and x axis stepper mounts.
http://i120.photobucket.com/albums/o.../CNC/cncb3.pnghttp://i120.photobucket.com/albums/o.../CNC/cncb1.pnghttp://i120.photobucket.com/albums/o.../CNC/cncb2.pnghttp://i120.photobucket.com/albums/o.../CNC/cncb4.png
Trev
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Re: Initial Design Check Please
You need some diagonal bracing on the base. How are you going to ensure the rails are on the same plane? There doesn't seem to be any adjustability in there.
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Re: Initial Design Check Please
Quote:
Originally Posted by
irving2008
How are you going to ensure the rails are on the same plane? There doesn't seem to be any adjustability in there.
He can shim the Profile between the box section. This will work well and be easy enough to get on same plane with careful setup.
Trev. Design looks ok but I'd build the frame differant regards how section is arranged.? Make the the legs extend down to the floor this will make the welding easier and give more support to the uprights. See pic knocked up to show what mean.
Attachment 13813
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Re: Initial Design Check Please
Thanks for the replies. My dads got the lower frame priced up built from a company who does work at his company. They gave the choice of carbon steal or aluminium in 50x50x3mm. I will see if i can have the design tweeked. I know they will do a first rate job as they do all sorts of precision work.
Ive just been working through the costs, to see if im in the right ball park. Do these seem right so far or does anyone know where i could get items for a better cost?
Hiwin 20 Rails 4x (off cut of two will build z axis) £155.15 http://www.aliexpress.com/item/750mm...832489900.html
Hiwin 20 Bearing blocks 12x £222.42 http://www.aliexpress.com/item/1PC-E...048643961.html
Gantry Profile £72.02 http://www.metallin.co.uk/
ball screws £250
spindle £183 http://www.ebay.co.uk/itm/2-2KW-WATE...item3f0a793189
steppers
drivers
controller
aluminium
Thanks again
Trev
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Re: Initial Design Check Please
Try these for profile they are cheap and quick delivery despite being in Germany. I buy my profile here and they are very good with accurate cutting.
http://www.motedis.co.uk/shop/Slot-p...91_999993.html
Tip with the gantry profile if you use Bosch rexroth BR type profile 90 x 45 then the BK/BF12 bearing holes match the slots. With Item 8 series type they don't and you'll need to make plates for mounting. I Make machines that use L shape arrangement with 90x45 and they are more than strong enough so don't worrie about using shorter widths.
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Re: Initial Design Check Please
Quote:
Originally Posted by
Gotty101
Thanks for the replies. My dads got the lower frame priced up built from a company who does work at his company. They gave the choice of carbon steal or aluminium in 50x50x3mm. I will see if i can have the design tweeked.
I think you will find mild steel is sufficient for the frame and will be much cheaper than aluminium, also the extra weight will be a benefit when the machine is working.
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Re: Initial Design Check Please
Quote:
Originally Posted by
EddyCurrent
I think you will find mild steel is sufficient for the frame and will be much cheaper than aluminium, also the extra weight will be a benefit when the machine is working.
Agree with Eddy and aluminium tends to crack around welds from vibration over time so wouldn't use it for the frame. I weld aluminium often and wouldn't build the frame from it unless weight was critical and even then I'd use much thicker aluminium than I would steel.
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Re: Initial Design Check Please
thanks for the replies guys.
With regards to the HGH20CA blocks ive found some at a great price but the spec is HGH20CAZOC Very light preload. Or should i go for Z1?
Ive had a look around and this thread said z0 (http://www.mycncuk.com/threads/3711-Hiwin-linear-blocks-HGW-20-CC-what-preload-to-spec)
Thanks again.
Trev
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Re: Initial Design Check Please
Stick with Z0 don't need higher preload than this. The HGH20CAZOC are normal grade bearings and will be fine.
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Re: Initial Design Check Please
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Re: Initial Design Check Please
I think i may need a few extra idlers in the middle between the two x ball screws at the back.
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Re: Initial Design Check Please
I got home yesterday to a card from parcelforce, so I think my hiwin bearing blocks are here. :)
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Re: Initial Design Check Please
I have removed this post and already placed to the right thread
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Re: Initial Design Check Please
Hi i just use printscreen and rezize it in photoshop.
With regards to the z axis i have cut a slot in the two plates for clearance. I suggest you open a design thread and ask the guys to give your design the once over before you go to far.
Trev
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Re: Initial Design Check Please
Thanks, Z axis principle is well documented here, this is just detail issue,
just I want to pick up all the evident or earlier discussed information
I will do my best with the design but have some definite ideas
As soon I have finished I will open the thread. You are right: design modification is much cheaper than re machining.
BR
István
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Re: Initial Design Check Please
Hi guys, well my Hiwin blocks have arrived. Ive ordered my ball screws now as i know the main dimensions are not going to change.
This is my idea for a bed, it will be a box as im going to be running suds. The bed can be raised and then bolted to the uprights to keep it in position.
Im going to order the hiwin rail next. I know ive got the FK bearings back to front, but can they be mounted this way? The only reason im looking to mount them this way is if i mount them the normal way im wondering if it will push the pully to far out to line up with the pully on the stepper motor.
http://i120.photobucket.com/albums/o...nc2/cncBed.png
Trev
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Re: Initial Design Check Please
JazzCnc are inductive proximity switches accurate enough to use as home and limit switches? Ive used magnetic hall probes in the past but never there.
Also would 3mm plate be strong enough for my cutting bed box with a 10mm drilled mounting plate installed in the bottom or shoul I make the box out of 5mm sheet?
Thanks Trev
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Re: Initial Design Check Please
Quote:
Originally Posted by
Gotty101
JazzCnc are inductive proximity switches accurate enough to use as home and limit switches? Ive used magnetic hall probes in the past but never there.
Yes they are very accurate see the vid I made.
http://www.youtube.com/watch?v=A11Zv...sgBQmxoJMvE40A
Quote:
Originally Posted by
Gotty101
Also would 3mm plate be strong enough for my cutting bed box with a 10mm drilled mounting plate installed in the bottom or shoul I make the box out of 5mm sheet?
Well if it's just box to contain coolant then yes will be fine but if your thinking to mount cutting bed in there and hang like the drawing suggests then NO WAY will it be strong enough.
To be honest when I first seen the drawing I wondered if you had in mind to put the cutting bed in the bottom of that box and dismissed it that you wouldn't be doing that but now I'm not so sure.! . . . . So which is it.?
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Re: Initial Design Check Please
Hi JAZCNC, Thanks for the vid, was a great help.
With regards to the bed, yes the actual cutting bed is mounted in the bottom of the box.
So i think i need to go back to the drawing board, i got the idea from the post by biketrialsdave of the red CNC.
http://www.mycncuk.com/threads/5549-...rials%29/page9
From the looks of it though maybe i should build the box frame in steal box section with a thick base and then mount the bed to that?
Im sure ive seen a blue machine with a similar design.
There is a nice idea by Jonathan on this post here http://www.mycncuk.com/threads/6484-...strong-machine 14th picture down on the left
Thanks again
Trev
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Re: Initial Design Check Please
Doesn't need anything too fancy Just make a strong frame which fastens to main frame and sit bed on it then surround bed with sealed sides and it won't be any issue but just hanging the bed inside the box will make it resonate and vibrate like crazy when cutting.
Would also use thicker than 10mm Ali for the bed 15/16mm minimum 20/25 better.
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Re: Initial Design Check Please
Thanks Jazz, ive just redrawn the lower frame and the bed but just need to finish a few bits before i post any more pics up. Ive ordered the prox sensors.
Thanks
Trev
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Re: Initial Design Check Please
Hi Jazz, ive redrawn the bed its now 20mm thick with a box thats 25x50 surrounding it.
http://i120.photobucket.com/albums/o...NCNEWFRAME.png
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Re: Initial Design Check Please
Better but will be difficult to achieve and be good enough. Far simpler to just make box section frame and sit the Bed on top then just use Thin sheet to make a surround for containing coolant.
Also how you going to drain and filter and remove coolant/chips because that box will soon fill up with chips/coolant.?
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Re: Initial Design Check Please
Hi Jazz, thanks for the reply. Ive altered it and hopefully im getting there. I am planning on using thin aluminium angle to build up a shallow surround. Im planning on using mist cooling and not flood.
http://i120.photobucket.com/albums/o...2/BedFrame.pnghttp://i120.photobucket.com/albums/o...ithGutters.pnghttp://i120.photobucket.com/albums/o...cnc2/Assem.png
With regards to electronics what kind of steppers do you think this cnc will eventually require would it need the 3.1nm or 4nm stepper, only reason im asking is to check the stepper space that ive got for the z axis stepper?
http://www.cnc4you.co.uk/CNC-Kits/Di...3.1Nm-x-3-Axis
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Re: Initial Design Check Please
Hi Jazz, does that look ok, the t slot plate will be bolted directly to the adjustable steel frame. Then gutters can be added to the steel frame if im going to be running coolant or not, these will be just aluminium angle.
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Re: Initial Design Check Please
Quote:
Originally Posted by
Gotty101
Hi Jazz, does that look ok, the t slot plate will be bolted directly to the adjustable steel frame. Then gutters can be added to the steel frame if im going to be running coolant or not, these will be just aluminium angle.
Yes but personally I'd have the rectangle cross pieces vertical so they provide more strength against deflection. Have a Flat base frame then sit Aluminium onto it then just make thin sheet surround which fastens into sides of ali plate.
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Re: Initial Design Check Please
Thanks again Jazz, ill update it. I cant wait to start the build, especially when you look at the build logs on here.
Trev
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Re: Initial Design Check Please
Well small update, ive started building the top part of the CNC with alot of help from a close family friend.
Here is a few pics of the progress.
http://i120.photobucket.com/albums/o...i_uk/CNC/a.png
Starting work on the spindle brackets
http://i120.photobucket.com/albums/o...i_uk/CNC/d.png
Main gantry uprights and bearing plates
http://i120.photobucket.com/albums/o...i_uk/CNC/b.png
Gantry bearing blocks
http://i120.photobucket.com/albums/o...i_uk/CNC/c.png
George and i on the Miller building the spindle plate.
With regards to the steppers for the machine, would the 4nm or 3.1nm steppers be best? Im im thinking 4nm ones from cnc4you and am882 for the drivers. I wont get the drivers yet as i dont require them just yet.
Trev
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Re: Initial Design Check Please
Quote:
Originally Posted by
Gotty101
With regards to the steppers for the machine, would the 4nm or 3.1nm steppers be best? Im im thinking 4nm ones from cnc4you and am882 for the drivers. I wont get the drivers yet as i dont require them just yet.
Trev
Looking nice so far, it's great when the action starts. I used those stepper motors and the AM882's, they work great but you might want to look at the updated drivers, the EM806; http://www.mycncuk.com/threads/8249-...5162#post65162
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Re: Initial Design Check Please
I was disappointed to see the discussion about steppers - from the earlier pictures, I had hoped that this would be the first steam-powered CNC machine!