PDA

View Full Version : BUILD LOG: Small scratch build 3 axiz CNC



bofred
07-03-2015, 10:10 PM
Hi all,

I will document my first CNC build here. I started this to learn about CAD, CAM and CNC carving. I am not in a hurry and it can take a while between the updates.
The parts used is mainly from the scrap yard and cheap Chinese electronics.

Machine goal: A small machine that is able to cut small aluminum parts.

bofred
07-03-2015, 10:22 PM
Frame:
Mostly build of 80x80 heavy extruded aluminum rods. The linear bearings are mounted so that they are able to be adjusted in order to make things straight.
http://www.mycncuk.com/attachment.php?attachmentid=14826&stc=1 http://www.mycncuk.com/attachment.php?attachmentid=14827&stc=1

Electronics:
Motors: Used BoR NEMA 34 steppers, Flange size 86mm
Stepper controller: Wantai 80V 7A
Breakoutboard: Cheap serial port card
Computer: Old DELL with printer port
Powersupply: 80V scrapyard trafo (10-12A) with a small 24V built in. (edited)
http://www.mycncuk.com/attachment.php?attachmentid=14828&stc=1

Spindle:
None yet

Ball screws:
None Yet

routercnc
08-03-2015, 11:52 AM
Looking good so far. You could use the machine to make reinforcement plates to brace the gantry (assume you don't have milling machine etc) as that profile is not as stiff as steel and it looks like you are using simple fasteners to hold it all together.

Once you get the weight of the y and z axis fitted and the spindle give the gantry a thump with a soft hammer and you will feel it vibrate. just something to think about as you progress.

bofred
08-03-2015, 03:47 PM
Thank you,

I plan to make 10mm aluminum plates on the sides to fasten the Xmotor and make it more rigid. I have some friends that are building another kind of machine and I can use the same side plates they are ordering from the vendor. A plate behind the X is also under consideration.

Then I plan to reinforce the Y rods with a pair of brackets. Hopefully it will be firm enough.
The bolts are ordinary M8 and M5 for the linear bearings. But there is allot of them.

Next up is to choose what kind of ball screw Im going to use. Ill try the hammer:positive:




Looking good so far. You could use the machine to make reinforcement plates to brace the gantry (assume you don't have milling machine etc) as that profile is not as stiff as steel and it looks like you are using simple fasteners to hold it all together.

Once you get the weight of the y and z axis fitted and the spindle give the gantry a thump with a soft hammer and you will feel it vibrate. just something to think about as you progress.

bofred
10-03-2015, 08:48 PM
I have started to plan how to measure and adjust the axis and I think I am able to get it fairly straight after a lot of adjustments. The frame is about 0.05 to 0.1 mm off before any adjusting. It might be different when I have all parts on the frame and tighten every thing up.

The linear bearing had a little banana shape so I straightened the first one up by clamping it to a straight surface and tightened it so it is real straight. The other side I plan to fasten after the wagon is mounted so that it will follow the one I straightened. That was a strange sentence, I'm sorry for my English..

I have also ordered three ebay 16mm diameter ball screws with bearings. Now the fun part begins:rugby:http://www.mycncuk.com/attachment.php?attachmentid=14847&stc=1 http://www.mycncuk.com/attachment.php?attachmentid=14848&stc=1

GEOFFREY
11-03-2015, 07:21 PM
That looks nice and tidy. Don't worry about your English, it is pretty good and I am sure that is a thousand times better than most forum members Swedish. G.

bofred
13-03-2015, 09:02 AM
Thank you Geoffrey. Its good practice and as long as I'm being understood I'm happy:) Min svenska är lite bättre dock ;)

T0rnado69
14-03-2015, 01:31 AM
Min svenska är lite bättre dock ;)


what he said........ :shame:

what ever that means :hopelessness:

looking good and keep the updates coming :)

routercnc
14-03-2015, 04:42 PM
Min svenska är lite bättre dock - ‎My Swedish is a bit better though
(thank you google translator!)

Now I can see the side view of the gantry the lower gantry beam is actually supported underneath as well as at the rear - should be better than I originally thought from the first photo.

Once you get the side plates added it will be a nice machine. But before you do I would add kiln dried sand to the gantry beams to add weight and provide damping. As this is a fixed gantry machine there is absolutely nothing to loose and it will help with the finish of the cut. Add one end plate, turn the machine on its side and fill to the top with sand, then add the second plate.

On the electrical side - and I'm not an electronics expert so I might be worrying over nothing - is it good practise to put the stepper driver right over the top of the transformer coil (trafo in swedish)? Is there a risk of electrical interference?

bofred
16-03-2015, 12:13 PM
Yes, google translate is spot on:)

And thank you for all feedback. I really need feedback since this is my first CNC.
The sand filled beams sounds nice. Problem is that I have so many holes to plug. The lower Xbeam has a total of 26 holes in it. 8 on each side to fasten it to the Zbeam and 10 for the linear bearing screws. I once had loudspeaker with sand filled stands and that worked really good.
I'm a bit worried that the Z moving part becomes weak but that is a later problem.

The electric cabinet could be as you say a bit noisy. Thank you. When I made it I figured the drivers had grounded houses and the "ring trafo" should not radiate that much magnetic fields. But I have the break out board unprotected and I don't know how sensible it is. I am able to fit a plate between the trafo and the drivers if I need. I planning on having shielded cables for the motors but the "on to the break out board cable" from the PC is unknown (cheap cable).

Here is a short video clip of when I test ran the motors. The wantai driver seems to have plenty of power. Cheers!

https://www.youtube.com/watch?v=foV1_A2lzSA

http://www.mycncuk.com/attachment.php?attachmentid=14928&stc=1
http://www.br-automation.com/downloads_br_productcatalogue/BRP44400000000000000144858/MASMOT-ENG.pdf
http://www.mycncuk.com/attachment.php?attachmentid=14930&stc=1

bofred
25-03-2015, 08:35 PM
Ive got the side plates. They are water cut in 10mm thick aluminum. Ive tighten the upper part of the gantry and it feels really stiffer than I thought. I tried hitting it with a peace of wood and I could feel really small vibrations when hitting from the side so I might need the back plate as well. Otherwise it feels like hitting a rock:love-struck:

http://www.mycncuk.com/attachment.php?attachmentid=14961&stc=1http://www.mycncuk.com/attachment.php?attachmentid=14962&stc=1

bofred
07-04-2015, 09:11 PM
The Y-plate is on its place and all screws in the frame work is tightened firmly (a lot of screws). It took me almost two hours just to saw the plate out of 20mm aluminum and machine the edges. And one hour more to make the holes for the screws. It seems to slide nicely on the bearings and it feels solid already. No ball-screw installed yet.
http://www.mycncuk.com/attachment.php?attachmentid=15106&stc=1

GEOFFREY
07-04-2015, 09:23 PM
Starting to look very useful. Parts mainly form the scrapyard? We could do with a few scrapyards over here that keep all that lovely ally profile in stock!!! Great stuff. G.

bofred
08-04-2015, 08:40 AM
Thank you. Yes. The item rods are from scrapped out prototype machines. As well as the stepper motors. I have been working with machine tests for 18 years on different kinds of machines mosty in the pick and place buisseness. So I know where to find the goodies ;)

JAZZCNC
08-04-2015, 10:21 AM
Looking good Bofred but I see a potential trouble spot that could be made much stronger for not a lot work.? . . .

The gantry rails mounted directly to the profile with no reference edges for alignment and support could slip under use just hanging from the rail bolts. I would mount rails to a piece of plate with machined reference edges that is same width and height as gantry then mount that to profile. It will massively stiffen the gantry and allow much easier setup.
I would also put a slot in front of plate for ballscrew bracket to come thru which will offer protection to the ballscrew/nut.

bofred
08-04-2015, 06:14 PM
Looking good Bofred but I see a potential trouble spot that could be made much stronger for not a lot work.? . . .

The gantry rails mounted directly to the profile with no reference edges for alignment and support could slip under use just hanging from the rail bolts. I would mount rails to a piece of plate with machined reference edges that is same width and height as gantry then mount that to profile. It will massively stiffen the gantry and allow much easier setup.
I would also put a slot in front of plate for ballscrew bracket to come thru which will offer protection to the ballscrew/nut.

Thank you Jazzcnc for good feedback,
I might have underestimated the forces on the X linear rails but my milling skills is very limited. Its only M5 screws on the linear rail.

Maybe I can make a support plate screwed in the item rod slot above the rail and after the X-rail is aligned against the Y-plate slide and tighten the support plate against the rail so it will not slip out of position. That would be an easier solution for me.

I also might combine the support plate with the ballscrew protection plate you suggested with a slot for the X-linear movement. That was a good idea. I dont know how the connection between the ballscrew and X-plate looks like yet. But it might work :)

njhussey
08-04-2015, 06:29 PM
Thank you Jazzcnc for good feedback,
I might have underestimated the forces on the X linear rails but my milling skills is very limited. Its only M5 screws on the linear rail.

Maybe I can make a support plate screwed in the item rod slot above the rail and after the X-rail is aligned against the Y-plate slide and tighten the support plate against the rail so it will not slip out of position. That would be an easier solution for me.

I also might combine the support plate with the ballscrew protection plate you suggested with a slot for the X-linear movement. That was a good idea. I dont know how the connection between the ballscrew and X-plate looks like yet. But it might work :)
I've got a slotted Y axis (you call it X I think?) It looks like this from the back...

http://images.tapatalk-cdn.com/15/04/08/96d10bbc71d2415023f9bc3fcd70b0fd.jpg

bofred
08-04-2015, 07:58 PM
I've got a slotted Y axis (you call it X I think?) It looks like this from the back...


Nice picture Neil. That looks robust enough with nice machined parts. I might able to do a similar solution. Thank you.
Yes my X seems to be your Y. I'm stuck in the split axis world. But I don't really understand why gauntries call that axis Y :)