CNC PCB milling

[NeverDie]

The sorbathane helped a little, maybe, but there's still a lot of vibration. Found this video on how to dampen a 3D printer. It has some Interesting ideas on how to dampen vibrations:
https://www.youtube.com/watch?v=OnfYA5QLA84

The video is aimed at Mk3 i2 owners, but I imagine similar tricks might work for a small CNC such as that discussed on this thread.

[NeverDie]

Based on a file test, it appears that the smooth rod is not hardened. Not sure how much improvement I might see if I upgraded to hardened.

Unfortunately, this thread seems to have fizzled out....

[NeverDie]

Looks as though upgrading to hardened and chromed rods is fairly inexpensive:

https://www.aliexpress.com/item/Optical-Axis-300-380-400-500-mm-Smooth-Rods-8mm-Linear-Shaft-Rail-3D-Printers/32838846750.html?spm=2114.search0204.3.2.7fc04405d43d4M&ws_ab_test=searchweb0_0%2Csearchweb201602_5_10152_10151_10065_10344_10068_10130_10324_10342_10547_10325_10343_10546_10340_10548_10341_10545_10084_10083_10618_10630_10307_5711220_5722320_10313_10059_10534_100031_10629_10103_10626_10625_10624_10623_10622_10621_10620_10142%2Csearchweb201603_2%2CppcSwitch_5_ppcChannel&algo_expid=04efdb04-9516-4d2e-a8d0-ec277a9f66b3-0&algo_pvid=04efdb04-9516-4d2e-a8d0-ec277a9f66b3&priceBeautifyAB=0

So, less sagging in the middle, and maybe less vibration also.

[dbemowsk]

@neverdie As part of my CNC build, I have gotten 8mm rods that I pulled out of old scanners and old ink jet printers, I guess I never checked to see if they were hardened or not. How much of a difference would it make?

[NeverDie]

@dbemowsk Well, let's put it this way: the set screws on my rods had come lose, so I noticed considerable sagging when the spindle got to the middle of the rods. When I tightened up the set screws, a lot of that sagging went away. So, I think that means the spindle is now, in part, being supported by tension.

Hardened rods should flex less. I'm sure there are formulas that could tell you by how much. Also, there are different degrees of hardness.

[NeverDie]

On the other hand, according to this thread:
http://forums.reprap.org/read.php?1,113177
deflection isn't affected by hardness. I had thought hardened would be stiffer.

[dbemowsk]

@neverdie So I have a few questions regarding your spindle assembly. First, do you know how many RPMs your motor is? Next, how many collets do you have and use for your setup. Third, is your collet and chuck assembly like this one?
https://www.amazon.com/Adealink-Spring-Collets-Extension-Holder/dp/B078JQQ5X7/ref=sr_1_2?s=hi&ie=UTF8&qid=1519193790&sr=1-2&keywords=5mm+shaft+collet

[NeverDie]

@dbemowsk said in CNC PCB milling:

@neverdie So I have a few questions regarding your spindle assembly. First, do you know how many RPMs your motor is?

I don't know. You could try asking the seller: https://www.aliexpress.com/store/product/Freeshipping-spindle-775-with-ER11-High-speed-Large-torque-DC-motor-Electric-tool-Electric-machinery-12/424291_32809235881.html?spm=2114.12010612.0.0.47291db35wj5jd

Next, how many collets do you have and use for your setup.

One.

Third, is your collet and chuck assembly like this one?
https://www.amazon.com/Adealink-Spring-Collets-Extension-Holder/dp/B078JQQ5X7/ref=sr_1_2?s=hi&ie=UTF8&qid=1519193790&sr=1-2&keywords=5mm+shaft+collet

Your link says its an ER11A, whereas I think mine may be just an ER11.

Though my spindle eventually gets the job done, I think a more powerful spindle could maybe cut faster

[dbemowsk]

@neverdie said in CNC PCB milling:

I don't know. You could try asking the seller

Thanks, I wasn't sure if you bought yours as a package deal where they had the specs on all the parts.

Your link says its an ER11A, whereas I think mine may be just an ER11.

I did find this link (http://www.cnczone.com/forums/cnc-tooling/319670-er11-type-vs-b-type.html) which states that the A should designate the style of the clamping nut. Looking at the different styles they have, it just looks like they just use different tools to tighten the nut. A looks like a standard wrench type.

This is the only information I have on the motor that I plan on using. I googled all the numbers and couldn't find anything.

It is a German made motor, so I am assuming it is a pretty good motor. It feels like it has pretty good torque. It is one that I had in my junk parts bin. it has a 5mm D type shaft. In the pic I just have one of my 5mm to 8mm couplers on it. I think I may order that collet assembly as it sounds like it should work. It says that it uses ER11 collets anyway.

[NeverDie]

@dbemowsk Maybe you'll want to try using TMC2130 drivers for your stepper motors?

[dbemowsk]

@neverdie I do already have the DRV8825's that came with the controller. I guess I'll try them and see how they work and if they don't seem to do well, I'll consider changing.

[NeverDie]

As it turns out, the smooth rods on my CNC are 10mm in diameter, not the more common 8mm found on 3D printers. Definitely not hardened: I can see grooves where the ball bearings have scratched into it.

Sanladerer strongly recommends using precision tolerance hardened chromed rods for 3D printers, so I can only assume the same would apply to CNC.

Since it's a relatively cheap upgrade, I may do it.

What tolerance should I get? h6? Also, what spec for surface roughness?

[scalz]

@neverdie said in CNC PCB milling:

Definitely not hardened: I can see grooves where the ball bearings have scratched into it.
Since it's a relatively cheap upgrade, I may do it.

What tolerance should I get? h6? Also, what spec for surface roughness?

not surprised it is not hardened for the price, cheap price->cheap quality
pity is sometimes even more expensive kits cheat on this too..

I would say as long as you use h6/h7 with roughness around 60 or more, so, precision hardened, chromed nice too, you should be very fine. day&night vs cheap rods which, in first place are not made for this job+precision..

[NeverDie]

I made some enhancements to the remote used with the CNC Monitor. Among other things, it's now more compact, and the top now has a ground plane (which may help the RF):

The bottom makes most of the connections and will hold the two AA batteries:

[dbemowsk]

@neverdie So I have an odd CNC related couple of questions. Next, when you put a bit in the chuck, do you always bury it in to the base of the bit? When you have your bit in for working on PCBs, what is the distance from the end of the chuck to the tip of the bit that you use?

[NeverDie]

@dbemowsk Is this for calculating deflection?

[NeverDie]

@dbemowsk I haven't been very consistent, but I'd say roughly 7/8 inch.

[dbemowsk]

@neverdie Actually, I am working on my Z axis and am trying to gauge how long I should have my rods. They are currently 8.25 in (209.55 mm). Wondering if there would be any benefit to leaving them that long or shortening them up some more.

This is the spindle frame as I have it designed so far. The blue piece on the motor shaft is just one of the couplers that I bought for the steppers to connect the threaded rods. It is just for looks until I get the chuck.

[NeverDie]

@dbemowsk said in CNC PCB milling:

@neverdie Actually, I am working on my Z axis and am trying to gauge how long I should have my rods. They are currently 8.25 in (209.55 mm). Wondering if there would be any benefit to leaving them that long or shortening them up some more.

In that case, what matters is whether you can raise the spindle high enough on the z-axis to remove the used bit and insert the next one. I wish my z-axis had a bit more height on it. Sometimes I have to move the spindle away from the workpiece in order to get enough clearance for a tool change. I suppose it doesn't help that I'm using a 3/4" waste board. ;)

[dbemowsk]

@neverdie said in CNC PCB milling:

I suppose it doesn't help that I'm using a 3/4" waste board.

Do you need 3/4"? Wouldn't 1/4" or 1/2" work? Do you drill in that far?