New Machine Design

[baranumut]

Hello i am new to cnc world yet i started to build a machine. Here is my design in attachment in fusion 360 format .f3d . It's my first time using a cad program so please forgive me. Any suggestions will be appreciated. At drawing i could not add ballscrews. I will use 1605 ballscrew in XY axes and 8mm acme in Z. Linear Shafts will be 20mm instead of 16mm in the drawing. 2nm Nema23 Steppers will be driven by TB6600. Right now i am tapping extrusions. Wish me luck on this build.

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[louieatienza]

Good luck, hope to see some progress pics...

[johncarpenter]

Use individual TB6600 drivers instead of the 4 axis board. When one blows you can replace the single driver. If you just gotta use the multiaxis TB6600 board then use low voltage. Maybe 24 volts. Mine burnt with 36 volts and I have heard people say it is the higher voltages that cause the problems. Never had a problem with the individual drives.

It looks like a really long distance from your gantry bearings to where the Z axis is connected to the gantry. This makes for a long moment arm for the cutting forces. And supported rail bearings are weakest for forces pulling the bearing away from the rail vertically. You might want to reduce the height under the table as much as possible and gusset the gantry uprights.

[baranumut]

Use individual TB6600 drivers instead of the 4 axis board. When one blows you can replace the single driver. If you just gotta use the multiaxis TB6600 board then use low voltage. Maybe 24 volts. Mine burnt with 36 volts and I have heard people say it is the higher voltages that cause the problems. Never had a problem with the individual drives.

It looks like a really long distance from your gantry bearings to where the Z axis is connected to the gantry. This makes for a long moment arm for the cutting forces. And supported rail bearings are weakest for forces pulling the bearing away from the rail vertically. You might want to reduce the height under the table as much as possible and gusset the gantry uprights.

I have 3 individual tb6600 and 27v 13a power supply. I just found out motors are not 2nm but 1.3nm. Hopefully it will be ok.

Should i shorten the blue parts in the image or whole gantry? I would like mill some musical instruments so i wish to z axis a bit deep. I will put gussets into red painted areas in the image.
Now i finished the tapping and im working on tool access holes. I can't drill them very precisely is it much important? Soon i will upload some pictures.

[johncarpenter]

With your 1.3 Nm stepper your 1605 ballscrew ought to give you around 350 lbs of force at stall. Which is way more force than the structure will be able to withstand without significant deflection. So if you already have your motors use them.

Gussets in the direction that you have shown will help prevent racking of the gantry structure. You also might think about added gussets in the direction 90 degrees (triangle visible from the side) to those also. But I think the main thing would be to keep the distance from the bottom bearing rails to the bottom of the gantry rails as short as possible. Figure out what is the least distance you need and design for that.

[baranumut]

How is like that? This is the picture of rails not yet assembled.

[johncarpenter]

Baranumut, please tell me you are using two bearing carriages for each rail and not the one carriage per rail shown.

[baranumut]

Baranumut, please tell me you are using two bearing carriages for each rail and not the one carriage per rail shown.

Yes 2 per rail i have total 12 of them.

[baranumut]

i have shortened the gantry and the feet of the table. Do you think any better like this?

[wizard]

It is probably a bit late to suggest this but you would maximize stiffness if the X axis rails where incorporated into the table top. This especially if you want a rather high X axis. Currently your design is adding several inches of leverage that will be applied the X axis bearing and the uprights holding the gantry beam.

With your current design you can address this to some degree by spreading out the X axis bearings so that they better resist the twisting forces but that does lead to a bigger machine or less capacity. How this will work out for you depends on what you are expecting out of the machine.

[baranumut]

I think i start to understand . Here is latest sketchs. It's so good that you guys giving me helping hand. Everyday i am learning more.

[baranumut]

Cad files if anyone interested
https://grabcad.com/library/cnc-design-on-progress-1

[johncarpenter]

I think your design is looking better. However bringing the two rails mounted on the gantry closer together is a move in the wrong direction. The more they are separated the better the resistance to tilt of the z axis. Instead of bringing them together, keep them separate as before but make the gantry upright shorter to get the Z axis down more to the table. I know you want Z axis clearance but this is not a particularly rigid design and you should keep the Z axis stroke as short as your work requirements will allow.

[baranumut]

I think your design is looking better. However bringing the two rails mounted on the gantry closer together is a move in the wrong direction. The more they are separated the better the resistance to tilt of the z axis. Instead of bringing them together, keep them separate as before but make the gantry upright shorter to get the Z axis down more to the table. I know you want Z axis clearance but this is not a particularly rigid design and you should keep the Z axis stroke as short as your work requirements will allow.

I tried a bit more

[johncarpenter]

I like this much better. The design is getting that short squat look that a rigid design has. Looking forward to seeing the completed design.

[baranumut]

Hello people
I am having some trouble about rail bearing screw holes and 2080 tslot aluminum. They are not aligned so i can use only half of the mount points. Any advice?

[wizard]

Hello people
I am having some trouble about rail bearing screw holes and 2080 tslot aluminum. They are not aligned so i can use only half of the mount points. Any advice?

The easy solution is to buy a drill and tap for the screws that you are using. Also I'd position the holes to space the blocks out as evenly as possible.

Another option would be to bolt a transition piece to the linear bearings and drill and tap that for the 20x80. This unfortunately adds height to the 20x80. Also it can be tricky to get the holes aligned such that there is no interference.

[baranumut]

The easy solution is to buy a drill and tap for the screws that you are using. Also I'd position the holes to space the blocks out as evenly as possible.

Another option would be to bolt a transition piece to the linear bearings and drill and tap that for the 20x80. This unfortunately adds height to the 20x80. Also it can be tricky to get the holes aligned such that there is no interference.

i have a drill press but i could't drill the extrusions where they have angle. Bit is just slipping. Maybe if i put endmill into it do i have chance? i came up with a solution like in the attached picture. İ will put gussets to the last screws. This solution gave me 15mm space between extrusions. Do you think it will be allright?

[wizard]

i have a drill press but i could't drill the extrusions where they have angle. Bit is just slipping. Maybe if i put endmill into it do i have chance? i came up with a solution like in the attached picture. İ will put gussets to the last screws. This solution gave me 15mm space between extrusions. Do you think it will be allright?

In this case i meant drill the bearing blocks. Generally it isn't a good idea to drill randomly positioned holes in aluminum T-slot extrusions for mechanical fastening.

Im on a bad connection so i didn't follow your link. Your general idea isn't bad you just need to drill some holes that more ideally align the bearings to the T-slot channels.