5x5 Tool plate and Extrusion build

[dabears]

Hello. I have a design drawn and could use some feedback please. What motors should I pair with it? I currently have it drawn with a NEMA 34 motor mount from Automation4less. Anyone have any luck with their mounts/supports? Also looking at either going the Avid electronics/Mach4 route or going from scratch with Acorn with the best bang for the buck motors I can find.
I'll be machining primarily hardwoods and plywood.

5x5 XY 7.625" Z work area
3/4" tool plate and Misumi 9090, 45180, 80160 Rigid extrusion
Hiwin HG25 rails and medium preload blocks
RM2010 Ballscrews
Avid Pro 8" Z


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[NIC 77]

I think that's a fairly decent design you've drawn.

I looked through your posts, I see you designed one with rack and pinion years ago....did you ever build anything?

You're going to be cutting wood, so you'll want some decent speed. I'd consider 20mm (or even 25mm) lead on the X and Y and 10mm on the Z. The 10mm on the Z is so the Z can keep up with the X and Y if you end up doing alot of 3d carving, but depending on how heavy your spindle is, you may need to counterbalance the Z with a pneumatic strut, or simply live with the fact that the Z may creep down and rest on the table when you power off the machine.

Is your gantry a single piece of 80x160 T-slot? You could bolt a 6" x 3" rectangular steel or aluminum tube on the back of it to add a bit more stiffness. You could even fill that tube with some form of epoxy if you wanted to.

The first machine I made had a cutting area 5' wide. I never once used a sheet of anything 5' wide. I'm assuming that you have something in mind that you want to do on this machine to make it 5' wide? If not, consider a cutting width of just over 4' and length of 6'.

The extra foot of length is to park your gantry at the end, making it easier to load and position your stock with the gantry out of the way. Also it can allow for a spot off the end of the main table if you want to add a rotary axis, or cut something long on it's end.

I've never used an Acorn board, but it looks pretty well thought out on their website, and has some good reviews. You'll want a board that allows you to autosquare your gantry during homing. The acorn board can do this, so can the plug and play electronics from AVID. From what I saw of the Acorn board on the centroid website (perhaps there is an expansion that I an unaware of?) it can only support 4 motors. Meaning that you would never be able to add a 4th axis to this design if that is something you wanted to do in the future.

I've never tried the Automation 4 Less mounts, but the Nema 34 SYK mounts I have are really nice.

When pricing out your motors and drivers, also have a look at the Teknic Clearpath SD servos (which do not require drivers).

For drivers, I'd stick with Leadshine or Gecko, some of the newer Trinamic offerings are quite tempting but I'm not sure if those would be appropriate for Nema 34's.

For motors, the Nema 34 Avid (cncrouterparts.com) sells @48V should do fine, but there are others you can find that may be a little less expensive and can offer a bit better performance. If you're going to do this, just make sure they are low inductance, around 2mH or less, and get a copy of the torque vs speed chart to compare it to the ones from Avid (it's on their website) at the max RPM you wish to use.

I wouldn't bother with "closed loop" steppers, for the extra money, the Clearpath SD are a better choice IMO. But regular steppers will also get the job done.

[dabears]

Thanks for the advice. Never did get that together but the idea persisted. Do you happen to know where I can find higher lead screws? The ones I have found are affordable Chinese screws. I’ll be doing alot of 3d carving and pocketing for guitar parts in hardwood. I haven’t had the chance to dive into the effects of lead on precision versus speed. Is it in the thousandths area of precision lost with increase in lead or is it bigger?

The gantry is a single piece of 80160 but has a 3/4” piece of tool plate attached to the front. I’ll look at adding more material.

I went with this cutting area to fit 5’ wide plywood. It also makes it easier to hold 4’ pieces and not approach/crash into the high sides with the Z. I compared the costs of the 4’ screws and extra table material and it was a small difference. I’d add length but I’ve found most of this design process was highly determined by what screws I could find online that fit within my budget.

Thanks for the info about motors...exactly what I was hoping for. Working through it now.

[dabears]

Looking at hole clearance. Anyone have advice about fit? For example, the Hiwin linear rails have the mounting holes at 7mm or a loose fit for the 6mm socket head bolts. On the tool plate table top where the rails attach, there are through holes for 6mm bolts that will screw into tslot nuts in the 9090 which is underneath. I plan on using a jig like the one Avid uses to adjust the parallelism of the linear rails. I'll attach the jig to the vertical side of the table top and clamp the rail to the jig. Should I just keep the same 7mm diameter clearance hole that the linear rails have or go for a tighter fit? On other plates where I am relying on the positional accuracy of the clearance holes to keep parallelism, I have the holes drawn as 6.6mm. I'd want to avoid anything binding but don't want any of the linear motion to go out of parallel and bind. Without prototyping its hard to know how things will fit together even with a CAD drawing. Short of building two machines, i.e. one to learn from and one to perfect the design, how do you guys go about designing a new machine?

[NIC 77]

Thanks for the advice. Never did get that together but the idea persisted. Do you happen to know where I can find higher lead screws? The ones I have found are affordable Chinese screws.

Where are you looking? The affordable Chinese screws come in all different varieties. Wait, are you saying that you do or you don't want to use the Chinese screws?

https://www.aliexpress.com/item/4001...563b3ee5TgkmHd

You write to the seller and tell him the lengths and end machining that you want for your free and fixed end supports and ask for a quote. Best to send him a drawing with dimensions. You're not limited by what lengths you can find on EBay, and even most of those sellers will do the custom end machining. It's usually the same price.

I’ll be doing alot of 3d carving and pocketing for guitar parts in hardwood. I haven’t had the chance to dive into the effects of lead on precision versus speed. Is it in the thousandths area of precision lost with increase in lead or is it bigger?

For precision there are a few factors

Backlash

Could be in the ball screw and the bearing supports and the coupler.

I'm not aware of the higher lead single nut inexpensive Chinese variety having any more backlash than it's lower lead counterparts. Perhaps others can offer their opinions on this subject. It's a bit like rolling the dice sometimes.

Do you need to worry about this? Possibly, yes.

Is going with a larger lead going to effect this? I doubt it.

Stepper Motor Resolution

If you look at a 1.8 degree per step bipolar stepper, it's about 0.002" of movement per step with a 10mm lead, and about 0.004" of movement per 20mm lead.

But with at least 10X microstepping with a good quality driver, I'm guessing your actual stepper accuracy will come out to around 0.001" even with a high lead screw.

There is lots of debate on this subject online and I don't claim to understand it....I wonder what the resolution of the Clearpath SD servos is? I'll have to look that up or someone can tell us.

If you look at rack and pinion routers, The Avid Nema 34 Pro rack and pinion set up gives you about 0.98" linear travel per revolution of the motor or about 0.005" of linear movement per full step and I haven't heard anyone complain about this not being accurate enough after microstepping is applied.

Do you need to worry about this? IMO, No, you don't.

Spindle Runout

This creates a wobble effect on the rotating bit, and the loss in accuracy increases according to the length of the bit. If you get a spindle with alot of runout, this inaccuracy can dwarf all other aspects of the machine.

Do you need to worry about this? Yep.

But I'm not the guy to ask what kind of spindle you should get.

[NIC 77]

On the tool plate table top where the rails attach, there are through holes for 6mm bolts that will screw into tslot nuts in the 9090 which is underneath.

Why? Why not just bolt the rail onto the tool plate and bolt the T-slot extrusion to the tool plate separately? It would make it easier IMO.

I plan on using a jig like the one Avid uses to adjust the parallelism of the linear rails. I'll attach the jig to the vertical side of the table top and clamp the rail to the jig.

How much is that approx 5' x 5' sheet of tooling plate going to cost you? How thick is it?

In practice I see you putting a sheet a MDF on top of it and surfacing that with your machine as a spoil board.

If that tool plate table top is expensive, you could redesign to get rid of it. But as drawn, I don't see that jig working as you describe.

The Avid machines have that jig for mounting the rails on the sides of the machines, yours are on top.

You assemble the gantry first, you put that on the bed tool plate with the blocks and rails on there, get it all aligned and sliding back and forth nicely using the assembled gantry and side plates with blocks as your guide. Use a couple of clamps to hold the rail ends. Then you centerpunch the first and last hole on each of your two rails. Drill and tap those, then, again using the gantry as the alignment tool, you run it back and forth to make sure it's good and smooth, tighten those 4 M6 screws, and centerpunch the rest of your holes as you slide the gantry just past each of them. Disassemble, drill, tap, and reassemble.

I know that manufacturers will suggest things like alignment pins and machined edges to align the rails but without some really precise machining, you will make things worse and perhaps introduce some binding into the system by trying to do this on your own.

For any 6mm clearance holes you need in the design, just use a 1/4" or 6.35 mm drill bit. Easy to open those up to the next size if you need to later on.

Short of building two machines, i.e. one to learn from and one to perfect the design, how do you guys go about designing a new machine?

Yeah, my first machine fell short of my expectations. We don't really seem to share plans, do we? Find something that works (with extensive video proof) and copy it, that's a good way. You can't trust opinions, you need to see the videos. If you just believe the hype you will end up with a crappy Shapeoko.

I seem to do alot better at starting machines than I do finishing them.

If you order T-Slot aluminum from 8020 (one of the big brand names in T-Slot), they will cut it for you and machine the ends so that they are square and to the exact sizes that you want. Other places may do this too, I don't know, I've only bought from 8020, and they had very good quality control on this.

I very much doubt that Avid cuts the extrusions in their kits. My guess is that the T-slot comes cut from 8020 already packaged up. Then they add the rest of the items to the kit. I'm not dissing them, that's a smart way to do it if that's what they're doing.

[NIC 77]

Find something that works (with extensive video proof) and copy it, that's a good way.

Check out these videos, not my stuff, I just happened by it on Youtube:

I'd recommend watching the one below on Youtube so that you can read the questions and replies.





If you're going with Nema 34's then I think the 20mm lead is still good.

But this gentleman is getting surprisingly good results from inexpensive 180W servos with integrated drivers turning 1605 ballscrews, although I think he was talking about changing them to better quality 1610 ones, I could be wrong. In the comments I think he recommends using 2010 with belt driven 2:1 gear reduction from the servo.

https://www.ebay.ca/itm/180W-3000rpm.../333469553872?

I think that's what he's got.

I'd ditch the really long Z travel and the moveable bed for cost and simplicity. I didn't catch how much travel his machine has. Just remember that the deflection of a beam is proportional it it's length cubed when considering your gantry dimensions and extra stiffening.

Your design is already quite similar to his.

I'm actually kind of interested in these JMC servos myself now, so it was worth it for me to write this reply. Has anyone here used them?

[dabears]

I submitted quotes for the 5x5 plate to some online machining websites...will see. Might be a no go. I was able to find one place for some of the smaller pieces that will supply material and machine them out of 6061 for around $90 each. I might hand drill the 5x5 out but I'd hate to waste about 1k in material if I screwed it up. This place has the best pricing for tool plate I have been able to find https://www.midweststeelsupply.com/s...BoC_0QQAvD_BwE

I wasn't aware that 8020 would machine the ends. I contacted one of their distributors to see if 8020 would mill some extrusion flat like Misumi and they said no. I've gotten a few quotes from distributors and there is always a large cost added to the order in comparison to the 8020 website. I planning on getting the extrusion from Misumi. Its easy to order the machining on their website. My other plan is to build up high Y sides with their flat milled extrusion. Seems like a stable/rigid way to do but it might be harder to get it squared and leveled in comparison to this newer design.

[NIC 77]

I wasn't aware that 8020 would machine the ends.

You don't have to ask for it, it just comes nice and square and on size. You do have to ask if you want the ends threaded, but that is easy to do yourself. It's been a while since I ordered it, but I'm guessing they'll machine the counter sinks, etc as well if you order those fasteners. It makes building a machine easier if you don't already have a machine.

Thanks for the link on the supplier, I'll check them out for my own build if I can't find what I need locally.

I came across another build thread here that is using the JMC servos, but 400W. Looks like they make 180W, 400W, and a couple sizes below 180W.

https://www.cnczone.com/forums/diy-c...75998-cnc.html

So the 400W is about $240 USD per including shipping, while the 180W was $121 USD per including shipping. And you don't need a driver, it's built in.

https://www.ebay.ca/itm/400w-3000rpm.../264564413603?

If you look at the Avid website, a Nema 34 is $119 and a Gecko G201X is $117, and that's plus shipping (and tax obviously). You could find those things a bit cheaper but it works out to close to the same at the end as the 400W servo. You'll need to buy a couple pulleys and belt for the servo, but you may save out on the motor mount...I don't see a huge difference in cost there. To me, it seems like a no brainer to go with the servos, based in no small part on some good reviews. Too bad, I don't think I can use them on my build.

Clearpath SD servo would be the next to look at.

Regardless, you should decide on the motors before you choose the screw lead. For a machine of your travels, I would not go below 10mm lead, for example 2010 at 2:1 belt driven gear reduction, say 3000 RPM of the servo max, 1500 RPM of the screw max, or 15 000 mm/min (590 IPM) max speed for a JMC 400W servo, that's decent.

I've talked myself out. I think I will take a break for a few days from this and let someone else talk. Good Luck, and take your time, no need to rush!

[Teknic_Servo]

Hi NIC 77,

I'm an engineer with Teknic and I recently came across this post. I thought it might be helpful to answer your question about the ‘resolution’ of the ClearPath servos. The answer is that your positional accuracy and resolution will depend on the motor you choose and how you configure and set up that motor. I realize that this may be a longer response than you were expecting, but please bear with me because I want to be complete.

Repeatability:

Regardless of your specific ClearPath part number or how you configure it, the motor will repeatably position to 1/12,800th of a revolution (for the NEMA 23/34 servos), and 1/64,000^th of a revolution (for NEMA 56/143/145 and IEC D100).

Motor selection and positioning resolution:

The positioning (or commandable) resolution of a ClearPath motor is the smallest increment that a user could command the motor to move with an individual step. How far you actually move is based on your “user selectable input resolution”, but more on that later.

Most ClearPath servo models are available in one of two positioning resolution configurations. You will see Teknic refer to these as the “Regular” (R) resolution and the “Enhanced” (E) resolution. If you select a motor with the Enhanced Option, you will have eight times the available positioning resolution.

NEMA 23 and 34 servos have a positioning resolution of either 800 (R) or 6,400 (E) encoder counts per revolution.

NEMA 56, 143, 145, and IEC D100 servos have a positioning resolution of either 4,000 (R) or 32,000 (E) encoder counts per revolution.

User-selectable input resolution:

When you first acquire a ClearPath motor, users will set-up and configure it with an “input resolution” setting. The input resolution tells the servo how many steps it needs to receive in order to move one revolution. If there are no controller output frequency limitations, then customers generally select the largest input resolution (i.e. most number of steps per revolution) that matches their motor’s positioning resolution. When this happens, one step is equivalent to one encoder count.

If the controller is not capable of outputting steps at a fast enough frequency to meet your speed requirements, then you might set the input resolution to a lower value. If you set the input resolution to a lower value (e.g. 200 steps per revolution), then regardless of the motor’s positional resolution the motor will only ever move to one of 200 unique locations per motor revolution . In all situations, the motor’s repeatability or precision will still be 1/12,800^th of a revolution for the NEMA 23/34 servos and 1/64,000^th of a revolution for NEMA 56/143/145 and IEC D100.

If you already have a ClearPath motor and want to understand what your motor is capable of, you can visit our website and view your specific part number, or use the general part number key listed here: https://www.teknic.com/clearpath-part-number-key/

I hope this was helpful. If you have any questions about sizing or using ClearPath, please feel free to give us a call at 585-784-7454, or use our "Contact Us" form online. (https://www.teknic.com/contact/).

Best,

Aaron B. - Teknic Servo Systems Engineer