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View Full Version : BUILD LOG: Gantry style CNC mill



giladv
24-07-2017, 03:40 AM
Hello everyone,

My name is Gilad, i'm 30 and i work as a software engineer.
for the past 6 months or so iv'e been working on this project mainly for educational purposes.
the machine was designed to mill hard and soft metals while being light and graceful enough to be run in my apartment:)

Technical stuff
- 20mm Hiwin linear rails on all axis
- 20mm/10mm pitch C7 grade ballscrews and bearings on all axis
- machined parts (incl the base) will be Al 7075 T6
- milling head: 8000rpm ATC BT30 90mm spindle, 1.8kw AC servo
- Y axis Al profiles are Item's 120X120mm heavy variant
- X axis Al profile is item's 160X80mm heavy variant
- gantry and side profiles will be filled with epoxy granite
- motion servo's X4 nema34 clearpath servo (CPM-SDSK-3421P-ELN)
- max travel 800X330X290mm

i'm gonna keep this thread updated with the latest images and videos of the build so stay tuned.

the machine:
222732227522274
22280

22276222772227822279222812228222283

Lee Roberts
24-07-2017, 09:39 AM
i'm gonna keep this thread updated with the latest images and videos of the build so stay tuned.

Deal :thumsup:

Clive S
24-07-2017, 10:19 AM
Hi Gilad and welcome to the the forum, It looks a nice project. How about a link to the spindle? I will be following with interest :thumsup:

giladv
24-07-2017, 10:23 AM
thanks!
it's skyfire's BT30
http://skyfirecnc.com/picshow2.asp?id=14

A_Camera
24-07-2017, 11:17 AM
the machine:

22280


Hi,

I am sure it's going to be a nice machine but based on my experience I'd suggest making some changes before it's too late.

My frame was originally similar to yours but I had to remove those wheels because of shaking caused by the G-forces. A fast machine with heavy gantry and Z movements will generate far too much shaking even if all the four wheels are locked. I changed my design, moved the wheels and the machine is now lowered to the floor on four wooden blocks, efficiently reducing vibrations and shaking. The wheels are still there but they don't touch the floor and gets lowered when the machine needs to be moved.

I assume your machine is going to be much faster than mine, considering you are using servos, so it would be a shame if you had to lower the speed and acceleration just to prevent the violent shake, so consider this before it is too late.

giladv
24-07-2017, 11:37 AM
@A_Camera, you are absolutely right, also i wouldn't be able to level the machine with the wheels.
i thought about a hybrid solution of using 2 wheels at the back and 2 anti-vibration legs at the front for stability.
there will also be corner brackets all around.

could you share an image of your solution?

thanks!

giladv
24-07-2017, 11:39 AM
hi Clive, thanks!
i used the BT30 spindle from skyfire
http://skyfirecnc.com/picshow2.asp?id=14

A_Camera
24-07-2017, 07:44 PM
@A_Camera, you are absolutely right, also i wouldn't be able to level the machine with the wheels.
i thought about a hybrid solution of using 2 wheels at the back and 2 anti-vibration legs at the front for stability.
there will also be corner brackets all around.

could you share an image of your solution?

thanks!

22288

There is really nothing to show. The machine is resting on four wooden blocks and the wheel is suspended by about a millimetre or two. If I need to move the machine I lift one end, remove two of the blocks, lower on the wheels and do the same for the other two feet. This gives me enough clearance to move it around. I think four steady feet is better than two with wheels.

routercnc
25-07-2017, 07:06 AM
Nice work so far. Can you show the detail behind the Z axis top covers. I'm guessing servo drive via belt to the top of the ATC spindle pulley?

Also, are the gantry ends just covers, or machined from solid (!)

I've looked at that skyfire spindle many times before and been very tempted. Let us know how you get on with it.

Chaz
25-07-2017, 12:00 PM
Nice work so far. Can you show the detail behind the Z axis top covers. I'm guessing servo drive via belt to the top of the ATC spindle pulley?

Also, are the gantry ends just covers, or machined from solid (!)

I've looked at that skyfire spindle many times before and been very tempted. Let us know how you get on with it.

Ive also considered the skyfire spindle. I may pull the trigger on one and report back.

Zeeflyboy
26-07-2017, 07:24 PM
looks brilliant!

giladv
28-07-2017, 10:47 AM
hello everyone!

the gantry ends (and all other parts) are machined from solid 7075 T651 but those are covers as well.
i'm including some images without the covers for clarification
223992240122400

Updates
this week iv'e FINALLY got my UDOO x86 single board PC which will be paired with Dynamotion's Kflop motion controller to create what i hope
is the best hobby solution today for machine control. (more updates on this soon)
22404

also, the work has begun on the machined parts(!!)
2240322402

Edward
28-07-2017, 03:26 PM
Hi giladv,
Very interested in your project as I am thinking of building something of similar compact size in the near future and your design looks great.

I also use Kflop with my CNC mill and I love it.

One question, the 1.8 spindle servo, can you tell us what servo you are planning to use? Is is a dedicated spindle servo for higher revs or just the usual 3000 revs?

Edward

giladv
28-07-2017, 09:01 PM
Hi giladv,
Very interested in your project as I am thinking of building something of similar compact size in the near future and your design looks great.

I also use Kflop with my CNC mill and I love it.

One question, the 1.8 spindle servo, can you tell us what servo you are planning to use? Is is a dedicated spindle servo for higher revs or just the usual 3000 revs?

Edward

thanks!
regarding the spindle: the ac servo should be 3500 rpm max (with the driver itself i was able to go only to 3000rpm).
but there is a 1:1.87 gear ratio between he spindle and the motor. so i'm planning on around 6000-6500 rpm at the spindle tip.

best,
Gilad

giladv
05-08-2017, 05:57 AM
hello everyone, just a small update:
2246222463

RobC
06-08-2017, 05:08 PM
Can't wait to see some more shots as you build it!

driftspin
18-01-2018, 09:40 PM
hello everyone, just a small update:
2246222463Giladv,


I am curious about your progress.

Any news?


Grtz Bert

Verstuurd vanaf mijn SM-A320FL met Tapatalk

giladv
21-03-2018, 05:51 AM
hey driftspin,

unfortunately i'm kinda stuck as my friends CNC shop is busy with some real work haha (crying inside).
i have all of the "off the shelf parts" waiting in my home for the machined parts for almost a year now i think.

i promise to update as soon as things start moving again:)

Gilad

Boyan Silyavski
21-03-2018, 07:52 AM
A question pops to my mind. Looking at the type of structure. WHY BT30 head?

I understand if you will tapp all day. But if not:

-you limit your speed more than half
-3kw spindle will cut through directly 1mm of mild steel with no problem and HSM with 6mm flute in that same mild steel any depth to 6mm!!! I know that from my machine
-forget about wood
-forget about engraving
- even aluminum needs 12k RPM at least with normal 6mm flute and 24k with 1/8 and similar

IMHO you limit severely your machine with this BT30 spindle. Its like driving a big black 4x4 near the seaside on a perfect road, while you must be driving a white cabrio sports car...


To me tapping could be solved differently and money spend towards better spindle, bigger spindle. At the end of the day it would be cheaper to make a dedicated servo+Z2+collet just for tapping.

Because from the looks that's not a machine for steel for me and i can not be easily convinced that it will be with that aluminum profiles.

Just some thoughts

PS. If you insist on this shape, size capability, then you need Epoxy Granite one, not a router, but mill. Ah, yeah. And extra spindle for small bits and engraving...

JAZZCNC
21-03-2018, 11:31 AM
A question pops to my mind. Looking at the type of structure. WHY BT30 head?

IMHO you limit severely your machine with this BT30 spindle. Its like driving a big black 4x4 near the seaside on a perfect road, while you must be driving a white cabrio sports car...

Don't talk stupid. I'd rather have BT 30 spindle with option of ATC than 3Kw ER spindle anyday of the week. However what it really needs are high rpm rated bearings which can be replaced if needed.



Because from the looks that's not a machine for steel for me and i can not be easily convinced that it will be with that aluminum profiles.

Why do you doubt Profile.? Your machine is made from mild steel tube which very similiar in density to Aluminium profile but it's it's hollow so much more resonant which is bad news if trying to cut hard materials like steel.

Can tell you know I'd much rather have Gantry made from HD profile than from thin/medium wall Mild steel box section. Unless that box section was minimum of 10mm thick wall which then opens up all lot of other issues regards Mass etc.

Just because it's made from steel doesn't always make it better or stronger.

Boyan Silyavski
21-03-2018, 11:38 AM
Don't talk stupid. I'd rather have BT 30 spindle with option of ATC than 3Kw ER spindle anyday of the week. However what it really needs are high rpm rated bearings which can be replaced if needed.

I'd rather not. I'd rather have a proper ATC spindle. A proper 7-15kw spindle. That BT30 spindle is limited to at most 10k RPM at the cost of rather expensive bearings.

If he needs a mill, a proper mill with BT spindle will be better, as DIY setup will not hold real tighter tolerance like a proper mill.

You know it, i know it. Thats why you have a router and a second hand proper mill. Ha, who are you trying to convince...

JAZZCNC
21-03-2018, 12:41 PM
You know it, i know it. Thats why you have a router and a second hand proper mill. Ha, who are you trying to convince...

That wasn't the question thou was it and I'm not trying to convince anyone of anything except that your talking bollocks when say 3Kw ER collet based spindle with minimum usable speed of 5000rpm is better than Servo driven BT30 Spindle.!! . . . . Lets see your 3kw spindle do bit of rigged tapping or fly cut with 150mm head..:stupid:

giladv
22-03-2018, 07:23 AM
@Boyan Silyavski - valid question/points:)

my machine is intended to be the best, most versatile R&D tool i could build because of space limitations.
but also, it should be a fun project which i will learn the most from. so with that in mind:

- this setup has more tinkering and planning in it than just buying a single piece plug and play off the shelf part.
- this setup costs MUCH less to a comparable BT/ISO30 integrated high speed spindle. because of the actual spindle and because of the expensive balanced tool holders required for a high rpm spindle. we are talking more than X2 the cost for a complete setup.
- torque > speed for versatility. i can always cut slower with small tools but i you cannot use a facemill/tap/fly cutter/sketchy-chuck-setup-for-one time-lathe-work on a high speed spindle.
- reliability - this is very important. lets say the motor or the pneumatic cylinder is malfunctioning, what do you do? i can just swap them out separately with any other semi-compatible components.
- attachments - i can attach anything with a BT30 taper in it to the spindle (lasers/extruders/drag knives/lathe tools). but also i have an active axis on that attachment because of the servo on the other end.
- inertia/momentum - big heavy spindle attached to a big heavy servo and a tool holder are way more ideal for hogging/roughing operations.
- saying a 7k rpm spindle cannot do Al work or engraving is plain wrong. just looks at one of the many Tormac videos doing both and doing it great.

regarding the machine itself, it might not look like that in the CAD but all those profiles are the thickest and biggest i could find (120mm and 160mm). but also, because of their shape and internal structure they are at least as rigid as plain square steel tubes.

in terms of precision reliability, assuming those tubes were stress relieved in the first place, the second you weld them you will need to take them again for stress relief (or they will distort over time) + facing/grinding.
Item's Al profiles comes extremely straight and flat and you use fasteners so you can build with it inside an apartrment.

i intend to deal with vibration by filling the profiles with EG. the gantry profile will be filled with EG mixed with carbon fiber trimmings (for extra rigidity and slightly less weight in the cost of less damping capabilities)

i hope i answered your question:)
thanks!