Fixed Gantry Mill

For a while, I have been looking at building a new milling machine.

This is the design I came up with. The machine will be primarily for aluminum and maybe some mild steel. The base will be cast out of concrete within the frame.
I will be running flood cooling, so there are also 3 x 100mm drains in the base which will run into a catch tank under the table. This will also be for chip collection.
The cutting area will be 750 Y, 900 X, 250 Z

50 x 50 x 5mm square tubing filled with concrete for the frame.
50 x 5mm angle for all the rail mounts with nuts welded under for more thread strength.
HGR20 Linear rails and bearings
1500mm Y, 1000mm X, 500mm Z
Sika Shrink compensated cement for the concrete mix for the base with 4 layers of 10 x 50mm grid reinforcing mesh
(this is for weight and volume to reduce vibrations and increase rigidity)
Nema 23 3nm motors with 24tooth 15mm HTD belt pulley on all the axis
1605 Ballscrews with 60tooth 15mm HTD belt pulley on all the axis

Today I got the frame weld up. Hoping to have all the plugs and hardpoints done in the next 2 weeks.
Then will be on to the casting. It will be left to cure for about 40 - 60 days. In that time I will be building the mold for the gantry.

The gantry looks super solid and the table seems to be substantial.which makes it puzzling that the Z axis features a comparatively skinny backplate attached to the spindle by a solitary mounting bracket at one end.It looks like a much weaker link in an otherwise solid machine.It may help you to create a model of the spindle with a tool in place and to see what kind of limitations the geometry will lead to regarding machining in corners and by the side of vertical walls.

All the Z axis Plates are 200mm x 20mm thick Aluminum.

1> Do you think adding a second bracket to the spindle will help?
2> Will boxing the spindle will 5mm steel plate give a significant improvement?

Quote:

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Originally Posted by Saintgp

All the Z axis Plates are 200mm x 20mm thick Aluminum.

1> Do you think adding a second bracket to the spindle will help?
2> Will boxing the spindle will 5mm steel plate give a significant improvement?

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2 Mounts are always a good idea

I wouldn't worry too much about the z axis, the way you designed it is cheap so you can always make it better once the frame is cast.

The additional bracing in post #3 would definitely stiffen things but it would also add protrusions that limit how close you will be able to get to projecting parts of the workpiece.The second spindle mount will go a long way to eliminating the potential problem

I have been busy at work, so the progress on the machine is slow. I did manage to get the Y-axis rails and ball screws on. I also made some room for NEMA 34 motors just in case I am not happy with the NEMA 23.

I fitted a NEMA 34 closed-loop motor with and made a small test jig, using an Arduino Mega with GRBL and UGS.

I plan on using a 32" touch screen, mounted in portrait, and will be running Mach3.

I was looking into the Pokeys57CNC for a controller. Good or Not?

Also is there any Mach3 Screen Set in 1080 x 1920 resolution?

update

After seeing the machine move I decided to go with the NEMA 34 closed-loop motors as I believe the NEMA 23 will run out of torque at high speeds.

I managed to get the table frame welded up and the Y-Axis ball screw and motor fitted.

I changed the ball screw from 1605 to 2010. I found that 1605 had a lot of wip at high speeds.

I also changed the ball screw gear to a 24 tooth giving me a 1:1 ratio from the motor to the screw.

I'm waiting on the brass rod to arrive so that I can make the fixturing points and braze them in place before casting the table.

here is a video of the table moving with just the basic settings.

the first move is from Y0 to Y800 which will be the Y limit and back and then to 100 and back and 200 and back and so on

https://youtu.be/BZomUIe74Ak

I am extremely happy with the repeatability of this axis 0.01

Nice job, hopefully it wont deviate much from this with a full weight of table+workpiece.

I have found that Nema 34 motors tend to be very lacking in power, because of the high inductance. To use them properly IMO they need to be driven with several hundred volts. Otherwise a typical Nema 23 with a belt reduction will outperform them in both speed and torque.

Directly AC powered drivers are available and affordable and can push nearly 300V and on paper that gives excellent performance. The motors are *typically* rated for over 500 volts isolation, often much more, but ground them properly if using these voltages.

Quote:

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Originally Posted by strostkovy

I have found that Nema 34 motors tend to be very lacking in power, because of the high inductance. To use them properly IMO they need to be driven with several hundred volts. Otherwise a typical Nema 23 with a belt reduction will outperform them in both speed and torque.

Directly AC powered drivers are available and affordable and can push nearly 300V and on paper that gives excellent performance. The motors are *typically* rated for over 500 volts isolation, often much more, but ground them properly if using these voltages.

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Do you have a link for a suitable AC Driver?

How much you paying for those nema34's? you might end up paying the same for a smaller servomotor instead.

Lichuan : https://www.aliexpress.com/store/1907567
Wenling Yuhai : https://wlyuhai.en.alibaba.com/

Quote:

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Originally Posted by Saintgp

Do you have a link for a suitable AC Driver?

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It's been a while since I was in the market for it but pretty much any AC input driver that can be set to the proper current will be fine