CNC PCB milling
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Quoting DavidSohlstrom from a thread on a different forum (https://discuss.inventables.com/t/runout-of-24v-dc-spindle/9984/11) in reference to vibration:
I've said it before and I'll say it again. This is a low cost DC motor that has a ER collet adapter attached to it. It is not a CNC spindle that incorporates the tool holder right into spindle with a minimum of stick out from the housing.
There is no bearing preload and the bearings are low cost bearings that have a lot of slop in them.
A bent motor shaft of just a couple of thou will cause a large run out at the tool.I notice that a lot of the available spindles are exactly that: a motor with an ER11 collet attached. So, the stickout is going to be greater. I haven't yet tried to find a proper CNC spindle like what he describes, where there's minimal stickout. In a perfect world, it sounds like that may be the way to go though.
@neverdie any half decent watercooled spindle should have the ER collet holder integrated. My 60k one has an ER8 and the default DC that came with the machine an ER11. Bought some ER high precision collets from ali, and some precision nuts and things got even better.
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This one would appear to fit @executivul 's criteria and also have a short stickout:
https://www.aliexpress.com/item/800W-electric-water-cooled-spindle-220V-ER11-with-65MM-diameter-158MM-length-for-cnc-router/32641099025.html?spm=2114.search0104.3.8.23ac8afeEe3r4S&ws_ab_test=searchweb0_0,searchweb201602_5_10152_10151_10065_10344_10068_10130_10324_10342_10547_10325_10343_10546_10340_10548_10341_10545_10084_10083_10618_10307_5711211_10313_10059_10534_100031_10103_10627_10626_10624_10623_10622_10621_10620_5722415_5711313,searchweb201603_2,ppcSwitch_5&algo_expid=da6db481-06cd-4131-b9a1-e7278ac9d3f2-1&algo_pvid=da6db481-06cd-4131-b9a1-e7278ac9d3f2&transAbTest=ae803_5&priceBeautifyAB=0It would seem to need some kind of controller to go with it though, plus a water pump, water tubing, and fittings and all of that. Definitely a major upgrade.
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This one would appear to fit @executivul 's criteria and also have a short stickout:
https://www.aliexpress.com/item/800W-electric-water-cooled-spindle-220V-ER11-with-65MM-diameter-158MM-length-for-cnc-router/32641099025.html?spm=2114.search0104.3.8.23ac8afeEe3r4S&ws_ab_test=searchweb0_0,searchweb201602_5_10152_10151_10065_10344_10068_10130_10324_10342_10547_10325_10343_10546_10340_10548_10341_10545_10084_10083_10618_10307_5711211_10313_10059_10534_100031_10103_10627_10626_10624_10623_10622_10621_10620_5722415_5711313,searchweb201603_2,ppcSwitch_5&algo_expid=da6db481-06cd-4131-b9a1-e7278ac9d3f2-1&algo_pvid=da6db481-06cd-4131-b9a1-e7278ac9d3f2&transAbTest=ae803_5&priceBeautifyAB=0It would seem to need some kind of controller to go with it though, plus a water pump, water tubing, and fittings and all of that. Definitely a major upgrade.
@neverdie that's ok. Beware you need a VFD for it (driving circuit) and it's bettery to buy as a kit so they match, my 2c
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@neverdie any half decent watercooled spindle should have the ER collet holder integrated. My 60k one has an ER8 and the default DC that came with the machine an ER11. Bought some ER high precision collets from ali, and some precision nuts and things got even better.
@executivul said in CNC PCB milling:
Bought some ER high precision collets from ali, and some precision nuts and things got even better.
How can tell you tell if the collet and nuts are "high precision" or not?
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You can tell by the listing title or after doing some tests either with a dial gauge or by running it and listening.
Beware 2: diameter, my 3040 came with 53mm spindle holder, single piece with z carriage, so the 48mm only needed a 3d printed sleeve, but to add a 63mm or 80mm diameter spindle some heavy mods were needed so that's one of the reasons I didn't go with them
Beware 3: weight, the frame must support it without complaining, z drop, backlash or whatever
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My 10^5*2c: get a 6040cnc with supported rails and a 0.8-2kw water cooled spindle, will serve you good for anything from pcb to alu or bronze milling, even some light steel work on the 2kw one and will save you a lot of hassle in the long run.
LE. 3020 and 3040 don't have supported rails and many don't even have ballscrews
And if you're really anal about it get the ballscrew frame only from rattm on ebay, a set of hybrid servos, a spindle+vfd+pump, a controller of your choice and you can say you have the best tool in the entry class of router cncs.
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My 10^5*2c: get a 6040cnc with supported rails and a 0.8-2kw water cooled spindle, will serve you good for anything from pcb to alu or bronze milling, even some light steel work on the 2kw one and will save you a lot of hassle in the long run.
LE. 3020 and 3040 don't have supported rails and many don't even have ballscrews
And if you're really anal about it get the ballscrew frame only from rattm on ebay, a set of hybrid servos, a spindle+vfd+pump, a controller of your choice and you can say you have the best tool in the entry class of router cncs.
@executivul Maybe I've missed it, but none of the Chinese 6040's I've seen have had supported rails. They all seem to require that as some kind of DIY "upgrade".
For that reason, I've been considering a c-beam type design. There exists a relatively cheap Chinese clone of that:
https://www.aliexpress.com/store/product/C-Beam-machine-large-Mechanical-Kit-DIY-C-Beam-machine-Large-bundle-C-Beam-Frame-kit/1752067_32846185306.html?spm=2114.12010608.0.0.55bc1dafCeSt8dor maybe the WorkBee, which seems to be an upgrade to the OX CNC (though I'd prefer something where the screw holes are already tapped):
https://www.aliexpress.com/store/product/OX-CNC-Upgrade-Version-WorkBee-CNC-Router-Machine-CNC-Mechanical-Kit-with-Nema-23-Stepper-Motors/1752067_32850266842.html?spm=2114.12010608.0.0.36611dafYZdcH4 -
@executivul Maybe I've missed it, but none of the Chinese 6040's I've seen have had supported rails. They all seem to require that as some kind of DIY "upgrade".
For that reason, I've been considering a c-beam type design. There exists a relatively cheap Chinese clone of that:
https://www.aliexpress.com/store/product/C-Beam-machine-large-Mechanical-Kit-DIY-C-Beam-machine-Large-bundle-C-Beam-Frame-kit/1752067_32846185306.html?spm=2114.12010608.0.0.55bc1dafCeSt8dor maybe the WorkBee, which seems to be an upgrade to the OX CNC (though I'd prefer something where the screw holes are already tapped):
https://www.aliexpress.com/store/product/OX-CNC-Upgrade-Version-WorkBee-CNC-Router-Machine-CNC-Mechanical-Kit-with-Nema-23-Stepper-Motors/1752067_32850266842.html?spm=2114.12010608.0.0.36611dafYZdcH4@neverdie please search for the 6040 frame only from "rattm motor", it's not stated I believe but you can clearly see in the photos with the bed beams removed that y rails are supported. X are not, but they are high diameter and pretty stiff for 40cm wide span.
Imho wheels on rails will never ever ever be as stiff and have less flex than the lousiest linear bearing. Wheels on rails are for printers and lasers.
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@neverdie please search for the 6040 frame only from "rattm motor", it's not stated I believe but you can clearly see in the photos with the bed beams removed that y rails are supported. X are not, but they are high diameter and pretty stiff for 40cm wide span.
Imho wheels on rails will never ever ever be as stiff and have less flex than the lousiest linear bearing. Wheels on rails are for printers and lasers.
@executivul You're right:
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@neverdie please search for the 6040 frame only from "rattm motor", it's not stated I believe but you can clearly see in the photos with the bed beams removed that y rails are supported. X are not, but they are high diameter and pretty stiff for 40cm wide span.
Imho wheels on rails will never ever ever be as stiff and have less flex than the lousiest linear bearing. Wheels on rails are for printers and lasers.
@executivul said in CNC PCB milling:
Imho wheels on rails will never ever ever be as stiff and have less flex than the lousiest linear bearing. Wheels on rails are for printers and lasers.
Even in the case of the Rattm Motors 6040, where the z-axis is hanging off an X-axis that is dangling by unsupported smooth rod? Is it still better even then?
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@executivul said in CNC PCB milling:
Imho wheels on rails will never ever ever be as stiff and have less flex than the lousiest linear bearing. Wheels on rails are for printers and lasers.
Even in the case of the Rattm Motors 6040, where the z-axis is hanging off an X-axis that is dangling by unsupported smooth rod? Is it still better even then?
@neverdie it might be better than a rigid x axis aluminium profile dangling on some wheels all together. Then comes the profile joining piece dance.
On the cnczone forums people go like: linear rails are the best, round bars are good, wheels on rails are for toys. That is for normal milling on a small machine. These things are routers by the way, real mills are taig style and are small size and meant for steel and heavy metal milling (no pun intended). For wood, plastic, soft stuff it might be acceptable though.
For pcbs you need high precision, flatness, high rpm etc.
For wood you need large size, think of table or door pieces. Tolerances are not so tight. You won't go like: look! Your door engraving is 0.1mm off in that corner!
For metal you need precision, high rigidity and power at lower spindle speed.The classic ebay cnc is a good all around tool but excels at nothing 😁
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@neverdie it might be better than a rigid x axis aluminium profile dangling on some wheels all together. Then comes the profile joining piece dance.
On the cnczone forums people go like: linear rails are the best, round bars are good, wheels on rails are for toys. That is for normal milling on a small machine. These things are routers by the way, real mills are taig style and are small size and meant for steel and heavy metal milling (no pun intended). For wood, plastic, soft stuff it might be acceptable though.
For pcbs you need high precision, flatness, high rpm etc.
For wood you need large size, think of table or door pieces. Tolerances are not so tight. You won't go like: look! Your door engraving is 0.1mm off in that corner!
For metal you need precision, high rigidity and power at lower spindle speed.The classic ebay cnc is a good all around tool but excels at nothing 😁
@executivul
How thick is the aluminum that such a 6040 machine could mill? -
@executivul
How thick is the aluminum that such a 6040 machine could mill?@neverdie you must use a chipload calculator according to your spindle power at requested rpm, tool diameter and tool profile. Stock can be as thick as you want, the machine has about 100mm of z travel, you mill in multiple passes anyway so milling depth per pass is based on the results from calculator, experience or many broken tools.
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Interesting way to make an inexpensive closed-loop stepper motor:
https://youtu.be/s2dpCpUqGnEI think a better way to do it would be to directly couple the encoder to a dual-shaft stepper motor, but that would, of course, mean purchasing a new stepper motor. Nonetheless, these small stepper's are pretty cheap.
The other way to do it with the existing single shaft stepper but without a belt might be to use a magnetic encoder, but I can't say that I've tried that, so I'm not sure how hard the retrofit would be.
Also, I guess the main point in doing this would be to hotrod your CNC, to make it move faster without skipping steps. i.e. you probably don't absolutely need to hotrod your CNC.
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Interesting way to make an inexpensive closed-loop stepper motor:
https://youtu.be/s2dpCpUqGnEI think a better way to do it would be to directly couple the encoder to a dual-shaft stepper motor, but that would, of course, mean purchasing a new stepper motor. Nonetheless, these small stepper's are pretty cheap.
The other way to do it with the existing single shaft stepper but without a belt might be to use a magnetic encoder, but I can't say that I've tried that, so I'm not sure how hard the retrofit would be.
Also, I guess the main point in doing this would be to hotrod your CNC, to make it move faster without skipping steps. i.e. you probably don't absolutely need to hotrod your CNC.
@neverdie said in CNC PCB milling:
I think a better way to do it would be to directly couple the encoder to a dual-shaft stepper motor, but that would, of course, mean purchasing a new stepper motor. Nonetheless, these small stepper's are pretty cheap.
I never looked, but do they make a dual notched pulley? Then you would only need to buy a pulley vs an entire stepper.
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@neverdie said in CNC PCB milling:
I think a better way to do it would be to directly couple the encoder to a dual-shaft stepper motor, but that would, of course, mean purchasing a new stepper motor. Nonetheless, these small stepper's are pretty cheap.
I never looked, but do they make a dual notched pulley? Then you would only need to buy a pulley vs an entire stepper.
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@neverdie it might be better than a rigid x axis aluminium profile dangling on some wheels all together. Then comes the profile joining piece dance.
On the cnczone forums people go like: linear rails are the best, round bars are good, wheels on rails are for toys. That is for normal milling on a small machine. These things are routers by the way, real mills are taig style and are small size and meant for steel and heavy metal milling (no pun intended). For wood, plastic, soft stuff it might be acceptable though.
For pcbs you need high precision, flatness, high rpm etc.
For wood you need large size, think of table or door pieces. Tolerances are not so tight. You won't go like: look! Your door engraving is 0.1mm off in that corner!
For metal you need precision, high rigidity and power at lower spindle speed.The classic ebay cnc is a good all around tool but excels at nothing 😁
@executivul
This guy bought a 6040 CNC with supported y-axis rails (just like the RATTM one), but starting at time index 4:52 he discusses the "well known problem" of flexing on the 6040's unsupported x-axis when milling aluminum:
https://youtu.be/6a57KtmIu-4He concludes that upgrades to the 6040 (e.g. possibly a supported x-axis rail) will be necessary.
It's just a pitty that an inexpensive, already "upgraded," 6040 isn't for sale. Instead, it becomes a DIY quest.
In fact, this guy did do the x-axis supported rail upgrade, but it solved only 50% of the problem:
https://youtu.be/ABLXVCkXmpg -
@executivul
Do you suppose that linear rails, rather than supported rods, would fix this twisting problem that people seem to be having?i.e. Notionally, something like:
https://www.ebay.com/itm/Portable-Steel-MGN12H-Linear-Sliding-Rail-Block-Tool-250-550mm-CNC-3D-Printer/382360155951?var=651145928342&hash=item590670f72f:m:mah05n6MWl2QkZTLIZW2vJQ
that's made out of steel.
