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Unread 06-15-2017, 10:47 PM
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Custom CNC Router (Looking for feedback)

So I've been wanting to design and build a CNC Router for a couple of months now since our team is losing our base of operations, and only getting a limited amount of tools for next year. After reading through the CNC thread for some knowledge, I designed this router that is a mix of a 6040 and a VeloxCNC style.

I am looking for some feedback on how I can make it more rigid or any other tips that would help it be as accurate as possible for cutting aluminum, thanks!



Here is the Solidworks CAD Model (I can provide a STEP File if anyone wants):

https://grabcad.com/library/custom-cnc-router-1
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Unread 06-15-2017, 11:34 PM
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Re: Custom CNC Router (Looking for feedback)

I guess my general input just glancing at it would be that it certainly looks pretty rigid (though maybe a little weak torsionally between the X-axes members, so need to mount to a strong base.

I looked at build vs. buy about 3-4 years ago, and the other piece of feedback is just to make sure the reason why you want to build is at least mostly educational. It is very likely to not be significantly cheaper (unless you already have a lot of linear motion and control equipment), and you may or may not get the desired result depending on your level of skill. I opted to buy just because I wanted to make things with CNC machines, not make CNC machines.
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Unread 06-16-2017, 12:21 AM
Travis Schuh Travis Schuh is offline
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Re: Custom CNC Router (Looking for feedback)

I second the recommendation to make sure you are clear about why you are doing this. We put about a build season of work into designing and making a custom router, and looking back we could have bought a pretty capable router for the same budget and would likely do that if we were to do it all over again.

That said, below are some questions/comments based on our design and build experience (because you did post a design...):

About the design, is there a reason you are not using the square rail linear bearings (I can't remember the exact name, but the Chinese version of https://www.mcmaster.com/#ball-beari...ges/=1837pom)? They have better stiffness than the open round bearing architecture.

Is there any way to create a box structure out of your Y axis? That will be torsionally stiffer than the two uncoupled linear rails.

How are you going to sync the two motors on the X axis? The machine will likely run fine with them "out of sync", but it will cause a perpendicularity error between your X and Y axis. We were surprised when building our router how much you could get the two out of alignment before we installed the drive belts. In the same line, how are you going to make sure that the two axes are perpendicular during assembly?

Have you looked at lead screw twirl? That will likely limit how fast you can go. We didn't run the numbers ahead of time and got surprised on our X axis top speed (being noticeably lower than we wanted). Also, are those lead screws or ball screws?

Have you looked at how much deflection will occur in the X axis screw/motor mount plates under peak acceleration? That looks like a weak point in the stiffness, and could probably be improved with some simple bracketing.

What spindle do you have in there? That looks like it may be a standard wood router spindle... I think having the right spindle in there is important for having good cutting performance, as the spindle is the heart of the machine. Also, how are you going to tram the head?

How are you going to control the what looks like steppers/what is your electrical architecture? Mechanically, how are you going to manage your cables and how are you going to home your axes?

Are you going to put in a mist system (needed for aluminum) or vacuum system (a good idea for wood)? If so, it would be good to include mounts for it.
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Unread 06-16-2017, 12:52 AM
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Re: Custom CNC Router (Looking for feedback)

I've been building my CNC between work and school for the last year and I'll be finished this summer. Originally I thought I would have it finished in one summer - but there is so much to learn and read online before actually doing it.

CNCzone is the best website for any information related to homemade CNC. mycncuk is another one, but imo cnczone has more experienced users who are more than happy to help with specific design/engineering questions. If you have done any research then you have probably come across the site. Post a pic of your design there and have it critiqued.

I would use square rails and ballscrews are a must. I am in Canada as well and I have ordered from aliexpress seller BSTAutomation. Message them for custom orders (Fred should message you) and free custom machining. They sell legitimate hiwin products and their prices and shipping are top notch. Don't use leadscrews.

Your Y axis motor mounts and end supports are very unsupported. Also, none of your holes look slotted for adjustment. You must have play in the proper directions for fine tuning adjustment to make everything square. Small variations over long distances (0.005" over 3 ft can cause binding and unnecessary friction in linear guides and ballscrews).

The way you have the bearing trapped in the motor mount looks cool but it's not practical for adjustment. Keep everything as simply designed as possible with wiggle room. All parts should be adjustable without having to remove another piece.

Also I would strongly consider steel. It's far stronger and much heavier which is important in a CNC machine. The heavier the better.

There's always more leaning to be had when building these things. I've still got a long way to go and I've spent countless hours reading forums. Good luck and have fun!

Last edited by Matthew.Mc : 06-16-2017 at 12:54 AM.
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Unread 06-16-2017, 01:58 AM
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Re: Custom CNC Router (Looking for feedback)

Quote:
Originally Posted by Travis Schuh View Post
How are you going to sync the two motors on the X axis? The machine will likely run fine with them "out of sync", but it will cause a perpendicularity error between your X and Y axis. We were surprised when building our router how much you could get the two out of alignment before we installed the drive belts. In the same line, how are you going to make sure that the two axes are perpendicular during assembly?
I've seen several architectures that wire both stepper motors to the same controller so each motor gets the same signal at the same time (though you have to account for additional current draw). Granted there may still be some error if the starting point of each motor varies, but it should at least keep everything consistent.

That said, I would be curious to know how practical it would be to drive it with both sides mechanically driven together (through belts, chains, gears, etc.), on the one hand it would insure uniformity, but I would be concerned about potential backlash.

Another thing I've seen a few CNC routers use is a rack and pinion arrangement for driving the Y axis, which seems like another viable option though might be more expencive.


Quote:
Originally Posted by Travis Schuh View Post
Have you looked at lead screw twirl? That will likely limit how fast you can go. We didn't run the numbers ahead of time and got surprised on our X axis top speed (being noticeably lower than we wanted). Also, are those lead screws or ball screws?.
The screws in the model appear to be normal lead screws. One concern I have with this arrangement is the potential for the screws to deflect when the carriage is at one end of the track or the other, though I'm not sure if this would affect performance or just longevity. As Travis mentioned above, it's also important to keep in mind that lead screws act like a huge gear reduction, so if you're using the same kind of lead screws commonly used in X axis drives, the router will likely run incredibly slow, lead screws are typically used only on the Z axis because that axis moves the least frequently so the speed is not as important (it also reduces issues with back-driving caused by the weight of the Z axis).


Beyond that, speaking from experience, if you're going to build your own CNC router, consider building it with closed-loop controls. Many issues with consistency on these types of machines are due to them being open-loop, and any error caused by an external force (changes in friction, table vibration, etc.) throws off the rest of the build until the machine is re-zeroed.
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Unread 06-16-2017, 06:18 AM
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Re: Custom CNC Router (Looking for feedback)

Cheap leadscrews will likely need to be straightened. You really need high feedrates on a router. Rack and pinion (CNCRouterParts for example) is a good method for achieving this. You should at least consider ballscrews in your design as they are very inexpensive directly from China.

You will want to use profiled linear guides such as Hiwin HGR15 series if you can afford it. Check eBay.

You didn't mention how you are going to fabricate the parts. Will you be able to machine parts?

Do you already have the router for your spindle? You can look into one of the generic Chinese spindles and VFD if not. Pay attention to the input power - many require 240V single phase.

What control system are you using MASSO? LinuxCNC? Mach3/4? Smoothieboard?

Can you make a larger machine?
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Unread 06-16-2017, 08:55 AM
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Re: Custom CNC Router (Looking for feedback)

Something you might want to consider is using off the shelf hiwin rail and ball screw linear actuators to make construction simpler and way stronger.
https://item.taobao.com/item.htm?id=...cket=15#detail
https://item.taobao.com/item.htm?id=43142051562
Also add as much mass to the base as possible to dampen vibrations, for a while I considered building my own CNC router on top of a granite surface plate as it's great at absorbing vibration.
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Unread 06-16-2017, 09:34 AM
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Re: Custom CNC Router (Looking for feedback)

Quote:
Originally Posted by Travis Schuh View Post
I second the recommendation to make sure you are clear about why you are doing this. We put about a build season of work into designing and making a custom router, and looking back we could have bought a pretty capable router for the same budget and would likely do that if we were to do it all over again.

That said, below are some questions/comments based on our design and build experience (because you did post a design...):

About the design, is there a reason you are not using the square rail linear bearings (I can't remember the exact name, but the Chinese version of https://www.mcmaster.com/#ball-beari...ges/=1837pom)? They have better stiffness than the open round bearing architecture.

Is there any way to create a box structure out of your Y axis? That will be torsionally stiffer than the two uncoupled linear rails.

How are you going to sync the two motors on the X axis? The machine will likely run fine with them "out of sync", but it will cause a perpendicularity error between your X and Y axis. We were surprised when building our router how much you could get the two out of alignment before we installed the drive belts. In the same line, how are you going to make sure that the two axes are perpendicular during assembly?

Have you looked at lead screw twirl? That will likely limit how fast you can go. We didn't run the numbers ahead of time and got surprised on our X axis top speed (being noticeably lower than we wanted). Also, are those lead screws or ball screws?

Have you looked at how much deflection will occur in the X axis screw/motor mount plates under peak acceleration? That looks like a weak point in the stiffness, and could probably be improved with some simple bracketing.

What spindle do you have in there? That looks like it may be a standard wood router spindle... I think having the right spindle in there is important for having good cutting performance, as the spindle is the heart of the machine. Also, how are you going to tram the head?

How are you going to control the what looks like steppers/what is your electrical architecture? Mechanically, how are you going to manage your cables and how are you going to home your axes?

Are you going to put in a mist system (needed for aluminum) or vacuum system (a good idea for wood)? If so, it would be good to include mounts for it.
I do really want to learn, I'm a student in summer right now so I have alot of time. All of the 6040 style CNC's that are within my budget (Max $1500) dont really seem to cut aluminum without upgrades so I thought making my own larger one while learning would be my best bet.

From what I have seen the SBR16 rails have less play in them than the Hiwin ones, routers like VeloxCNC's use them and same as many others, and they are cheaper from what I've seen, so I went with them, I might have to look in further.

My idea with the Y Axis is to have one 8020 extrusion vertical and one horizontal so that in both flexing directions it would have more strength than just one orientation, I might add a few connecting extrusions on the back.

Its not in the CAD yet but I was just going to add limit switches to home the axis. I wasnt sure how useful slots would be since you want to be a rigid as possible, I was scared or slots for bolts would just ruin the machine.

I have 4 start T8 Leadscrews in the CAD because they were cheaper, but have been used by other CNC's that work so I went with them, I might switch to faster more reliable ballscrews if the price is right.

Good point, I can put more L bracketing into those plates.

I chose the Dewalt 611 for the CAD but might switch to the Makita router, is not a VFD but I think it will do to get me started, I've seen lots of posts on success cutting aluminum. I believe tramming is when you square the endmill correct? If it is then hopefully the machine should be made square enough (Not sure what tramming is even after googling )

I was going to choose my controller after the machine is made since it shouldnt really effect design, I was thinking maybe an arduino with shield, but am considering a Gecko g540 since its apparently amazing.

I have not seen that mist system is required for cutting aluminum, I was thinking just standing by my machine while it runs (Which is generally good practice anyways) and spraying some coolant manually should suffice.

Thanks for the great feedback!


Quote:
Originally Posted by Matthew.Mc View Post
I've been building my CNC between work and school for the last year and I'll be finished this summer. Originally I thought I would have it finished in one summer - but there is so much to learn and read online before actually doing it.

CNCzone is the best website for any information related to homemade CNC. mycncuk is another one, but imo cnczone has more experienced users who are more than happy to help with specific design/engineering questions. If you have done any research then you have probably come across the site. Post a pic of your design there and have it critiqued.

I would use square rails and ballscrews are a must. I am in Canada as well and I have ordered from aliexpress seller BSTAutomation. Message them for custom orders (Fred should message you) and free custom machining. They sell legitimate hiwin products and their prices and shipping are top notch. Don't use leadscrews.

Your Y axis motor mounts and end supports are very unsupported. Also, none of your holes look slotted for adjustment. You must have play in the proper directions for fine tuning adjustment to make everything square. Small variations over long distances (0.005" over 3 ft can cause binding and unnecessary friction in linear guides and ballscrews).

The way you have the bearing trapped in the motor mount looks cool but it's not practical for adjustment. Keep everything as simply designed as possible with wiggle room. All parts should be adjustable without having to remove another piece.

Also I would strongly consider steel. It's far stronger and much heavier which is important in a CNC machine. The heavier the better.

There's always more leaning to be had when building these things. I've still got a long way to go and I've spent countless hours reading forums. Good luck and have fun!
Yes I've been around both those sites, they are really good. Again, I've seen very few CNC's online that use those square rails, so I was hesitant to use them, and have seen successful builds with these SBR16 rails. I have heard I need ballscrews and I will most likely switch to those instead of these "3D Printer" leadscrews, I was hoping they would scrape by for the intial build, maybe not

I was scared to use slots because obviously you dont want any wiggling in your machine, and wasnt sure if slots would come loose after a while and completely ruin the machine.

Well since I will be machining all the plates (Most likely) I was pretty confident in them being accurate enough without need for adjustment.

I have not been able to find 8020 steel variant, and haven't seen a single machine that uses steel as the main extrusion, its also harder to machine.

If you don't mind me asking, how large is your machine and how much has it cost you?

Quote:
Originally Posted by cbale2000 View Post
I've seen several architectures that wire both stepper motors to the same controller so each motor gets the same signal at the same time (though you have to account for additional current draw). Granted there may still be some error if the starting point of each motor varies, but it should at least keep everything consistent.

That said, I would be curious to know how practical it would be to drive it with both sides mechanically driven together (through belts, chains, gears, etc.), on the one hand it would insure uniformity, but I would be concerned about potential backlash.

Another thing I've seen a few CNC routers use is a rack and pinion arrangement for driving the Y axis, which seems like another viable option though might be more expencive.




The screws in the model appear to be normal lead screws. One concern I have with this arrangement is the potential for the screws to deflect when the carriage is at one end of the track or the other, though I'm not sure if this would affect performance or just longevity. As Travis mentioned above, it's also important to keep in mind that lead screws act like a huge gear reduction, so if you're using the same kind of lead screws commonly used in X axis drives, the router will likely run incredibly slow, lead screws are typically used only on the Z axis because that axis moves the least frequently so the speed is not as important (it also reduces issues with back-driving caused by the weight of the Z axis).


Beyond that, speaking from experience, if you're going to build your own CNC router, consider building it with closed-loop controls. Many issues with consistency on these types of machines are due to them being open-loop, and any error caused by an external force (changes in friction, table vibration, etc.) throws off the rest of the build until the machine is re-zeroed.
I am most likely going to switch to ballscrews.

Thanks for the closed loop suggestion, ill look into that!

Quote:
Originally Posted by protoserge View Post
Cheap leadscrews will likely need to be straightened. You really need high feedrates on a router. Rack and pinion (CNCRouterParts for example) is a good method for achieving this. You should at least consider ballscrews in your design as they are very inexpensive directly from China.

You will want to use profiled linear guides such as Hiwin HGR15 series if you can afford it. Check eBay.

You didn't mention how you are going to fabricate the parts. Will you be able to machine parts?

Do you already have the router for your spindle? You can look into one of the generic Chinese spindles and VFD if not. Pay attention to the input power - many require 240V single phase.

What control system are you using MASSO? LinuxCNC? Mach3/4? Smoothieboard?

Can you make a larger machine?
I will most likely be able to machine parts, but my backup backup plan is to near 100% infill print them, which will be definitely rigid enough, then CNC proper plates and replace.

Honestly after seeing these Hiwin rail suggestions ill have to take a more time on the choice, but I really have seen little machines use them, including commercial ones.

I was going to go with the Dewalt 611 or Makita router, they will get me started, and have seen good reviews on them.

I have not figured out the control system yet, I was going to pick one when I was beginning the build process / waiting for parts to arrive.

I made this machine the size I am able to store in my house / garage.




Thanks for all the feedback, I'll research the things everyone suggested and see if they are right for me, much appreciated!
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Unread 06-16-2017, 09:35 AM
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Re: Custom CNC Router (Looking for feedback)

Quote:
Originally Posted by mman1506 View Post
Something you might want to consider is using off the shelf hiwin rail and ball screw linear actuators to make construction simpler and way stronger.
https://item.taobao.com/item.htm?id=...cket=15#detail
https://item.taobao.com/item.htm?id=43142051562
Also add as much mass to the base as possible to dampen vibrations, for a while I considered building my own CNC router on top of a granite surface plate as it's great at absorbing vibration.
I didn't want to use the premade stuff because there isn't CAD for it so I wont know how to mount it, and they don't come in large enough sizes.
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Unread 06-16-2017, 09:40 AM
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Re: Custom CNC Router (Looking for feedback)

Quote:
Originally Posted by DopeCADSwag View Post
I didn't want to use the premade stuff because there isn't CAD for it so I wont know how to mount it, and they don't come in large enough sizes.
The 12mm linear guideway will be far more rigid than the supported rail you have right now and they can be ordered in custom lengths.
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Unread 06-16-2017, 10:16 AM
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Re: Custom CNC Router (Looking for feedback)

Linear guides are prolific in CNC machinery. They are a cost-effective way to build serviceable precision machinery. My 3D printer and CNC mill have them. When you use them with aluminum profile extrusion (80/20), make sure to get a compatible screw size for the linear guide and the nut that goes into the profile extrusion slot.

You should investigate the control system, as this may be a hidden cost to you at the moment. You really don't want sticker shock after building the machine.
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Unread 06-16-2017, 03:45 PM
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Re: Custom CNC Router (Looking for feedback)

Quote:
Originally Posted by DopeCADSwag View Post
Yes I've been around both those sites, they are really good. Again, I've seen very few CNC's online that use those square rails, so I was hesitant to use them, and have seen successful builds with these SBR16 rails. I have heard I need ballscrews and I will most likely switch to those instead of these "3D Printer" leadscrews, I was hoping they would scrape by for the intial build, maybe not

I was scared to use slots because obviously you dont want any wiggling in your machine, and wasnt sure if slots would come loose after a while and completely ruin the machine.

Well since I will be machining all the plates (Most likely) I was pretty confident in them being accurate enough without need for adjustment.

I have not been able to find 8020 steel variant, and haven't seen a single machine that uses steel as the main extrusion, its also harder to machine.

If you don't mind me asking, how large is your machine and how much has it cost you?
My machine is a little over 5' x 5' x 8" and cost approximately $8,000. This may seem high, but the final machine will be very capable of seriously cutting aluminum and will comfortably cut steel while easily cutting wood which will be it's main use. I've already got side jobs lined up for it when it's finished in a couple months so the machine will pay for itself. The high cost comes from the quality and size of parts I'm using. Plus all parts I've bought have been in USD and most components are heavy so shipping costs are very high.

The machine uses:

closed loop servos
huge 35mm THK rails (these were given to me by a friend) for x&y
25mm hiwin rails for the z axis
25mm diameter 10mm lead dual ballscrews for y axis
single 25mm diameter 10mm lead for y
20mm diameter 5mm lead ballscrew for z
4kw 18000rpm spindle with vfd
3/8" structural steel tubing for gantry and machine bed
3/4" 6061 alumiunum plate for all motor mounts and connection plates
1/4" structural steel for table

Honestly it all depends on what quality of parts you want to use on the machine. A dude on my University's robotics team built a dirt cheap router (12" x 12") that cuts aluminum very well for ~$1000. He used super small steppers, with small PSU's and these cheap as hell stepper drivers (around $1). The most expensive things were the ballscrews, the round linear rails and bearings, as well as the spindle (which was a mini makita handheld router but he said it burnt out from constant aluminum machining). The bearings inside regular wood routers are not meant to run for long periods of time and are suited to take loads from cutting wood not metal.

I was impressed by how cheap he made it. He well engineered it and I just went with overbuilding which has cost me more than I planned in the beginning. Not to mention cost of buying my own tools. I'm not a believer in cheap tools lol.

For FRC you don't need super precise parts and a 0.005" tolerance is acceptable imo, which is more than possible using cheap electronics and the round rails you've used. I would just change to use ballscrews and strengthen up your design. Square rails are nice, but not a must.

Check out this guys videos on his router. This has been one of my favorite designs I've seen:

https://www.youtube.com/watch?v=gg2UvbRsLP0

This CNCzone post is what I based my design on:

http://www.cnczone.com/forums/diy-cn...-software.html


Here's another I bookmarked which uses the round rails:

https://www.youtube.com/watch?v=FbwB___wGtQ
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Unread 06-17-2017, 08:58 PM
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Re: Custom CNC Router (Looking for feedback)

After all the great suggestions yesterday, I did some more research and noticed a particular design on CNCZone.com that seemed to fit all my criteria. I found reasonable prices on Ballscrews and MGN15 Linear Guideways. The main extrusion is 6060 (mm), hopefully making it much stronger than the 2040, at around the same price. The X gantry plates are 0.5" with the large side plates being 0.75", and all the plates are tapped and bolted together well. The only part I feel I havnt found a good price for
is the spindle. After reading up on routers, they are way too loud, and I pretty much realised I need a VFD Spindle if I want to cut aluminum consinstantly. My delima is on Ebay.ca (Im in Canada), aliexpress, amazon.ca, and a few other sites, the cheapest I can find a 110V Watercooled Spindle with the VFD and pump is $450 CAD. Has anyone sourced cheaper?

Also to add, Ill probably be going with an Arduino + CNC shield, since its cheap and looks like it works just fine as a starter for me (Its 8 bucks for the shield, I have arduinos)

Here is a render of the updated CNC:

https://www.chiefdelphi.com/media/photos/45344?

And here is the CAD (Solidworks):

https://grabcad.com/library/custom-cnc-router-v2-1
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Unread 06-17-2017, 11:53 PM
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Good ideas and advice! I've been meaning to CAD up a DIY CNC lathe so I'm definitely referring back here when I do!
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Unread 06-18-2017, 02:27 AM
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Re: Custom CNC Router (Looking for feedback)

Quote:
Originally Posted by frcguy View Post
Good ideas and advice! I've been meaning to CAD up a DIY CNC lathe so I'm definitely referring back here when I do!
Wait same actually. Pretty neat!
I've been following this thread and might rework my lathe to use 6060 extrusion or something similar, although steel extrusions might be better for my purposes.
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