Ballscrew Accuracy

[JermNZ]

I am having some trouble with my ballscrews on my router and thought someone on here might be able to offer some advice.

I purchased the RM1605 screws from linearmotionbearings several years ago. A couple of the ball nuts seemed to have significant backlash in them so I sent them back for replacements, these were marginally better but I continued with my build.

During assembly I never quite understood how you were supposed to securely fix the ballscrew into the fixed side bearing block using the retaining nut. It seems impossible to stop the screw from turning while tightening the nut?? Does anyone have any tips for doing this?

I ended up tightening them as much as I could (not that much) and securing the locking grub screw.

The machine has been cutting wood very well for a couple of years, although I've always been aware of some "backlash" or movement in the spindle when external force is applied by hand.

I had some time off work this week and decided to try and get to the bottom of this issue.

I started with the X axis (across the gantry), I positioned two dial indicators, one on the side of the z carriage which is directly coupled to the ballnut holder/balllnut. And the other on the end of the ballscrew. By doing this I was attempting to determine how much of the movement was due to the ballnut/screw interface or the movement of the whole screw in the fixed side bearing block. Obviously the force applied was self regulated and in no way 100% consistent, but it would at least allow me to see where the majority of the movement was coming from.



My results were as follows:

I found that the movement had two distinct regions. With an external force applied back and forth along the axis of the screw there was a degree of "slop". For example I'd push to the left, the Z carriage would move 0.07 mm and the screw would move 0.02 mm. I'd release the pressure and there was no further movement. When force was applied to the right, everything would move back to the initial position. It was a consistent "looseness" in the x axis direction. I think I am correct to refer to this as "backlash".

Once the applied force reached the end of the backlash region, I was still able to apply more force and achieve further movement, about another 0.06 mm for the screw and 0.15 mm for the z carriage. Although this movement was different in that it was "springy", when the force was released, the indicators would return to their initial position.

Backlash: Screw 0.02 mm, Nut 0.07 mm
Flex (with further applied pressure): Screw 0.06 mm, Nut 0.15 mm

In conclusion, I think I am seeing some movement/lack of rigidity of the mounting of my ballscrew, probably something to do with the fixed side bearing mount? And also some general slop in the ballnut. At the force (by hand) I was applying, I was seeing a total movement of the spindle of about 0.195 mm in each direction, this seems (feels) like a significant amount.

I'm hoping that you guys can help me make light of these findings??

Also, I'm interested in knowing if anyone else has tried taking similar measurements with their screws? Are these numbers actually normal for this grade of screw??

Cheers,
Jeremy

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[louieatienza]

There should be flats milled on the ballscrew... somewhere. Also did you use the provided spacers?

The springiness could be flex in your machine. The stepper is also like a spring, since it's basically a big magnet; you could be back driving the screw. Finally the coupler vould br a source of flex if it's a spring type or Lovejoy with an improper spider. Some couplers are designed for a little lash to absorb shock from the liad or reversing. Using Oldham style couplers can mitigate that movement.

[NIC 77]

I bought the C5 end supports, "Bun" brand because of the many complaints of this problem, then I sourced my ballscrews and had them custom machined to use double nuts at the ends. It probably isn't necessary to use double nuts at the ends, but I'm still happy I did it.

I ended up buying my ballscrews from BST Automation, and the end machining was done as I requested, very happy with the excellent customer service and products from BST.

I have since tried to find the company I bought the end supports from on Alibaba, but they have changed their name or gone out of business? I don't actually need to contact them, I was just going to give the link to someone else. I'm quite happy with my "Bun" brand end supports, I can't feel any of this slop / backlash in the ones I have.

A good quality end support should not require shims to be backlash free, but some of the cheaper ones from China do. That's the thing, some things from China can be excellent, and some can be sub par, even though they are the "same" part, they are made by different companies in different factories by different people. It's hard to figure this out especially when the brand names aren't always mentioned in the advertisements.

By shims, I mean that you have to take it apart and shim in between the bearings.

You may also want to consider a Taiwan brand like SYK for end support units.

Louie, I didn't even realize that they gave you shims with them?

You may also be able to use larger balls or a double nut, which I believe is available in 1605, if you have backlash in the actual ballscrew also.

Machine flex may be an issue, and as Louie mentioned, there are some additional potential causes. Mostly it is the need for shims in the end supports that people complain about from what I've seen.

[louieatienza]

I bought the C5 end supports, "Bun" brand because of the many complaints of this problem, then I sourced my ballscrews and had them custom machined to use double nuts at the ends. It probably isn't necessary to use double nuts at the ends, but I'm still happy I did it.

I ended up buying my ballscrews from BST Automation, and the end machining was done as I requested, very happy with the excellent customer service and products from BST.

I have since tried to find the company I bought the end supports from on Alibaba, but they have changed their name or gone out of business? I don't actually need to contact them, I was just going to give the link to someone else. I'm quite happy with my "Bun" brand end supports, I can't feel any of this slop / backlash in the ones I have.

A good quality end support should not require shims to be backlash free, but some of the cheaper ones from China do. That's the thing, some things from China can be excellent, and some can be sub par, even though they are the "same" part, they are made by different companies in different factories by different people. It's hard to figure this out especially when the brand names aren't always mentioned in the advertisements.

By shims, I mean that you have to take it apart and shim in between the bearings.

You may also want to consider a Taiwan brand like SYK for end support units.

Louie, I didn't even realize that they gave you shims with them?

You may also be able to use larger balls or a double nut, which I believe is available in 1605, if you have backlash in the actual ballscrew also.

Machine flex may be an issue, and as Louie mentioned, there are some additional potential causes. Mostly it is the need for shims in the end supports that people complain about from what I've seen.

Sorry I should clarify... The spacers I refer to are the ones that slip over the threaded journal for clearance of the locking nut to the bearing seals. Depending on the bearing block a spacer may be needed at both ends, and I'm thinking the wrench flats may be somewhere under the bearing seal.

The end supports I got from SYK are C3, and they exhibit zero play at least with the cheapo test indicator I have. I still have the end supports I bought from the famous Chai, and between the rough bearings, poorly machined housing, decided not to use them, though with some TLC they're probably OK. The helical couplers often used can suffer from wind-up which shows up as lash (and can be the "springy" feel.) Same with the Lovejoy spiders. They make them in different durometers. They also recommend curved jaw couplers, not the "L" type most commonly sold, for positioning.

[wizard]

Those shims are likely there so that regular ball bearings can be used instead of angular contact bearings. As you note they shouldn't be needed for angular contact bearing. Using standard ball bearings this way will work for a short time on a lightly loaded screw.

I bought the C5 end supports, "Bun" brand because of the many complaints of this problem, then I sourced my ballscrews and had them custom machined to use double nuts at the ends. It probably isn't necessary to use double nuts at the ends, but I'm still happy I did it.

I ended up buying my ballscrews from BST Automation, and the end machining was done as I requested, very happy with the excellent customer service and products from BST.

I have since tried to find the company I bought the end supports from on Alibaba, but they have changed their name or gone out of business? I don't actually need to contact them, I was just going to give the link to someone else. I'm quite happy with my "Bun" brand end supports, I can't feel any of this slop / backlash in the ones I have.

A good quality end support should not require shims to be backlash free, but some of the cheaper ones from China do. That's the thing, some things from China can be excellent, and some can be sub par, even though they are the "same" part, they are made by different companies in different factories by different people. It's hard to figure this out especially when the brand names aren't always mentioned in the advertisements.

By shims, I mean that you have to take it apart and shim in between the bearings.

You may also want to consider a Taiwan brand like SYK for end support units.

Louie, I didn't even realize that they gave you shims with them?

You may also be able to use larger balls or a double nut, which I believe is available in 1605, if you have backlash in the actual ballscrew also.

Machine flex may be an issue, and as Louie mentioned, there are some additional potential causes. Mostly it is the need for shims in the end supports that people complain about from what I've seen.

[Eldon_Joh]

Those shims are likely there so that regular ball bearings can be used instead of angular contact bearings. As you note they shouldn't be needed for angular contact bearing. Using standard ball bearings this way will work for a short time on a lightly loaded screw.

if regular ball bearings are correctly applied, they will last as long as angular contact bearings. but they will be larger and they will be more "springy" unless they are much larger. like twice or three times the size. but regular ball bearings can handle it, for example there is a 6308 bearing on the input shaft of certain toyota truck transmissions, and the helix is at least 30 degrees on the input gear.

even with angular contact bearings you still need a shim of the correct thickness unless they are matched pairs ground for a specific preload and those are expensive.


unfortunately the cost of buying oversize bearing balls probably exceeds the cost of buying a second ballnut for a common 1605 ballscrew, and it isn't a trivial matter to figure out how much oversize you need. you might be able to guess based on the backlash to within half a thousanth.. but i'm not sure if you can just throw .126" balls in a ballnut designed for .125" balls and hope it works. it might but the balls might not last very long.

[wizard]

When solving these sorts of problems you need locate and attack specific areas that testing indicates are an issue. This can be time consuming, also you need to realize when you are seeing flex and when you are seeing the impact of backlash.

The first thing here is to verify that some of your problem is in the end plate bearings or mounts. Actually you should verify what bearings are in those mounts before doing anything. If they are standard ball bearings there will be shims or spacers to deal with. In a nut shell you need to determine where the axial movement is coming from. You could have the Leadscrew sliding in the inner race, clearance in the bearings or the outer races slipping in the housing. One or all of these could result in seeing axial movement.

While less than desirable the axial movement in the leadscrew is pretty minor considering your overall displacement. That apparent spring back could be lots of things including overcoming holding torque but not losing steps. The same thing can happen with servos especially if tuned soft. Also backlash in you linear bearings can masquerade as springy behavior. In this case imagine the axis saddle rocking on the linear bearings as you apply pressure. Relieve the pressure and the saddle returns. In basic terms looseness can show itself as springy behavior. Beyond this anything mechanical that can twist or bend is a possible cause.

If everything us right mechanically, that is no backlash and nothing twisting then you have to consider the possibility of a mechanical stiffness issue. Often this comes down to a poor design or materials problem. Let me first say that you are going to see deflection under load for the vast majority of DIY routers seen on these forums. This simply because most of us don't have access to the material handling and machine shop equipment to produce a really stiff machine. So the key here is to understand how much force is being applied and is that force reasonable for the machine. In other words 50 pounds of force will have a smaller impact than 250 or 500 pounds of force. One weak area on DIY machines is the plates that support the gantry which can easily spring back and forth under load. It wouldn't hurt to set up your indicators to make sure the spring you are seeing isnt in those side plates.

I could go on but maybe this will help. Post picture of your machine as that might help people see an obvious issue.

[JermNZ]

Hi Everyone,

Firstly, thanks for your responses.

I do not believe there are flats anywhere on the screws, this is my first serious problem. Granted it has been several years since I assembled the machine, but i'm pretty sure this is the obvious solution which I would have checked for.

I should have mentioned that I ruled out any significant machine flex by also taking indicator readings from the outside of the bearing housing and also the outside of the gantry plate, these showed very little movement. Isolating the movement to the screw.

Rotation of the screw being driven by the force on the ballnut is a possibility, but I don't think this is the primary cause, as I am seeing axial movement of the screw also.

I am using the love-joy style couplings with the red insert.

The bearing blocks did not come with any shims I don't think and I did not disassemble them prior to fitting.

As suspected it sounds like I also have excessive play in the ball nut.

I think the best option will be to remove the screw from the machine and confirm there are no flats on the screw. Then I will disassemble the fixed side mount and figure out what's going on in there. Depending on the findings here I may have to source some decent mounts. Hopefully they will fit, it seems like a standard design which manufacturers have adopted.

The outcome is that I will most likely need to purchase new nuts and probably machine flats somewhere onto my screws. Failing that, a brand new high quality screw and nut.

Does anyone have any other recomendations for good reliable sellers of ballscrews and supports?

Is this similar to what you bought from BST Nic 77?
https://www.aliexpress.com/store/pro...78b753cbPxP35G


J

[JermNZ]

When solving these sorts of problems you need locate and attack specific areas that testing indicates are an issue. This can be time consuming, also you need to realize when you are seeing flex and when you are seeing the impact of backlash.

The first thing here is to verify that some of your problem is in the end plate bearings or mounts. Actually you should verify what bearings are in those mounts before doing anything. If they are standard ball bearings there will be shims or spacers to deal with. In a nut shell you need to determine where the axial movement is coming from. You could have the Leadscrew sliding in the inner race, clearance in the bearings or the outer races slipping in the housing. One or all of these could result in seeing axial movement.

While less than desirable the axial movement in the leadscrew is pretty minor considering your overall displacement. That apparent spring back could be lots of things including overcoming holding torque but not losing steps. The same thing can happen with servos especially if tuned soft. Also backlash in you linear bearings can masquerade as springy behavior. In this case imagine the axis saddle rocking on the linear bearings as you apply pressure. Relieve the pressure and the saddle returns. In basic terms looseness can show itself as springy behavior. Beyond this anything mechanical that can twist or bend is a possible cause.

If everything us right mechanically, that is no backlash and nothing twisting then you have to consider the possibility of a mechanical stiffness issue. Often this comes down to a poor design or materials problem. Let me first say that you are going to see deflection under load for the vast majority of DIY routers seen on these forums. This simply because most of us don't have access to the material handling and machine shop equipment to produce a really stiff machine. So the key here is to understand how much force is being applied and is that force reasonable for the machine. In other words 50 pounds of force will have a smaller impact than 250 or 500 pounds of force. One weak area on DIY machines is the plates that support the gantry which can easily spring back and forth under load. It wouldn't hurt to set up your indicators to make sure the spring you are seeing isnt in those side plates.

I could go on but maybe this will help. Post picture of your machine as that might help people see an obvious issue.

Hi Wizard,

Yes all valid points. Pinpointing the exact cause of this deflection is exactly what I am trying to do by using multiple indicators. Please see my reply above, I have taken readings from several points on my structure and ruled out gantry flex etc..

I am also aware that the force which I was exerting by hand is probably much higher than what cutting force can be transferred through most cutters, I am keeping this in mind when considering what is realistically achievable.

Yes I tend to agree that the axial movement of the ballscrew is in fact fairly small compared to the overall deflection, which I suspect to be the ballnut.

Cheers
J

[NIC 77]

I do not believe there are flats anywhere on the screws, this is my first serious problem.

I don't have flats on my my screws either, and I'm not the least bit worried about it.

I should have mentioned that I ruled out any significant machine flex by also taking indicator readings from the outside of the bearing housing and also the outside of the gantry plate, these showed very little movement. Isolating the movement to the screw.

I believe you're probably correct that most of what you're seeing isn't machine flex, however I can see a few areas where you could make this machine stiffer that would not be a whole lot of work. Like a full back plate (not cut out), ribs in between your extrusions, and a more reinforced structure with your end plates. However this is not the subject of the thread, I'm just making conversation. Overall, I like many things about what you've done . We could come back to it after you get this problem fixed if you want to.

The bearing blocks did not come with any shims I don't think and I did not disassemble them prior to fitting.

No, they wouldn't. People have to make their own. No idea if there's a perfect sized commercially available shim repurposed from something else.

As suspected it sounds like I also have excessive play in the ball nut.

From what's been said so far I'm not convinced that's your main problem, but it might be.

I think the best option will be to remove the screw from the machine and confirm there are no flats on the screw. Then I will disassemble the fixed side mount and figure out what's going on in there. Depending on the findings here I may have to source some decent mounts. Hopefully they will fit, it seems like a standard design which manufacturers have adopted.

Don't worry about the flats. Yes, take the ballscrew and mounts off and have a look if there is play in the fixed end mounts.

The outcome is that I will most likely need to purchase new nuts and probably machine flats somewhere onto my screws. Failing that, a brand new high quality screw and nut.

Again with the flats. Don't get hung up on it. If the ballnut is to blame, you can buy a double ball nut, pretty sure in that size it's common. Also, Arizona Video (a member here) makes conversion kits for mills and I believe he uses oversized balls on his kits to prevent backlash. You could ask him nicely, perhaps he'll sell you some or at least give you some better info than I can.

Are you happy with the speed of your machine? If you do switch ballscrews, you can consider going to 10mm lead.

Does anyone have any other recomendations for good reliable sellers of ballscrews and supports?

Is this similar to what you bought from BST Nic 77?
https://www.aliexpress.com/store/pro...78b753cbPxP35G
J

I think it is very premature for you to think about getting rid of your ballscrews. I bought ballscrews from BST and I am happy with the service from them. My thread about it is here:

http://www.cnczone.com/forums/linear...ce-needed.html

I can't honestly say what their end supports are like, as I have the "Bun" brand ones. I am happy with them, but I don't know what has become of the company making them. If it turns out that you have slop in your end supports and you can't shim it out, I think the easiest thing is to buy made in Taiwan SYK fixed end supports so you know there's no problems. These are 12mm bearings, so they shouldn't be expensive. Lots of sellers on Aliexpress, Alibaba, and EBay stock SYK brand stuff. You can reuse the free end ones. Of course, a couple well placed shims could potentially fix up what you have if they are at fault.

[louieatienza]

The only reliable way to remove play in the ballnut is to order another nut and space them with Belleville washers, unless they sell a double nut. There'll always be clearance, even though they're advertised as anti-backlash, because the forming process of the screw limit's it's pitch accuracy, so if the ballnut had no clearance, it would bind or the torque required to turn the screw would vary. The other way would be to buy a surplus ground ballscrew C5 or better, which by the nature of its manufacture, has anti-backlash properties even with a single nut.

[louieatienza]

I would not go with oversize balls. You'd have to figure out exactly how large a BB you can go, otherwise you stand the risk of damaging or prematurely wearing your ballscrew of ballnut. Again, there's clearance for a reason.

The spacers I'm talking about look like small lengths of tube that slip over the threaded part of the journal. With a rolled ballscrew you're supposed to use two, one at the side of the drive journal (of which the lock nut is against), and the other on the shoulder of the bearing journal (by the threads). This is so that the proper seal can be made at the screw side. as well as seat firmly against the inside race of the AC bearing. It would be pretty difficult to tighten the who assembly fully if there no flat on the screw. Maybe, unless, you bridged something through the coupler that you can hold the screw steady while you apply torque to the locking nut. Heck, I even have ACME screws with drive and bearing journals and flats machined.

[NIC 77]

The only reliable way to remove play in the ballnut is to order another nut and space them with Belleville washers, unless they sell a double nut. There'll always be clearance, even though they're advertised as anti-backlash, because the forming process of the screw limit's it's pitch accuracy, so if the ballnut had no clearance, it would bind or the torque required to turn the screw would vary. The other way would be to buy a surplus ground ballscrew C5 or better, which by the nature of its manufacture, has anti-backlash properties even with a single nut.

They do sell a double nut.

Interestingly enough there is a guy on the UK forum who uses belleville washers, but he modifies the double nut ballnut to do it as it is easier than trying to do it with two single nuts. I recall reading through his post about it.

I would not go with oversize balls. You'd have to figure out exactly how large a BB you can go, otherwise you stand the risk of damaging or prematurely wearing your ballscrew of ballnut. Again, there's clearance for a reason.

Arizona video does it, I believe, and it works for him. I never have. If he is thinking about getting entirely new screws and tossing these ones, then he won't have lost much other than the cost of some ball bearings. I admit that I am not an expert on it, but I would rather try that out than to simply buy new ones without trying it.

The spacers I'm talking about look like small lengths of tube that slip over the threaded part of the journal. With a rolled ballscrew you're supposed to use two, one at the side of the drive journal (of which the lock nut is against), and the other on the shoulder of the bearing journal (by the threads). This is so that the proper seal can be made at the screw side. as well as seat firmly against the inside race of the AC bearing. It would be pretty difficult to tighten the who assembly fully if there no flat on the screw. Maybe, unless, you bridged something through the coupler that you can hold the screw steady while you apply torque to the locking nut. Heck, I even have ACME screws with drive and bearing journals and flats machined.

Good point about the spacers. I don't think they are always included (2 in each) in the less expensive Chinese ones? If I did not use the two spacers with my bearings, on the fixed side, well, with the rubber seals it wouldn't work. So good to check the spacers being used before thinking of buying replacements where the current end machining won't work if two spacers are used.

I believe that many people have shimmed these successfully, so I am guessing the OP can to.

[louieatienza]

They do sell a double nut.

Interestingly enough there is a guy on the UK forum who uses belleville washers, but he modifies the double nut ballnut to do it as it is easier than trying to do it with two single nuts. I recall reading through his post about it.

Pretty simple to do a double nut with two single nuts... though they're cheap enough.

Arizona video does it, I believe, and it works for him. I never have. If he is thinking about getting entirely new screws and tossing these ones, then he won't have lost much other than the cost of some ball bearings. I admit that I am not an expert on it, but I would rather try that out than to simply buy new ones without trying it.

Yes, but he measures the BBs inside the nut, then figures out what size BBs he needs to take up the slack. The guys that do it know what they're doing. The OP can do whatever he wants; just pointing out that it's faster (and better) to use a double nut than to try to preload a ballnut with oversize balls, on a screw form that's not designed to take the added pressure.

Good point about the spacers. I don't think they are always included (2 in each) in the less expensive Chinese ones? If I did not use the two spacers with my bearings, on the fixed side, well, with the rubber seals it wouldn't work. So good to check the spacers being used before thinking of buying replacements where the current end machining won't work if two spacers are used.

I believe that many people have shimmed these successfully, so I am guessing the OP can to.

Even the Chai ones I received came with 2, specifically for the purpose of using them on rolled screws. This problem doesn't usually arise with ground screws because the way they're made, unless the screw was cut and remachined - and that would almost certainly be done on the floated end. It's possible the shoulder of the bearing journal is not seated well again the inside race of the AC bearing., a problem exacerbated if the retaining nut is not properly torqued, and maybe alleviated with the correct spacer.

A picture of the driven end of the screw would help...

[JermNZ]

Thanks for your replies Louieatienza and Nic 77,

You're right, it is pre-mature for me to order new screws, but I was interested in your opinions on who were reliable sellers these days.

Regarding the flats on the screw, out of the many pictures and videos i've seen online, only a small proportion I have noticed with machined flats. Although now that I think about it, the lock nut probably doesn't need much torque, provided there is a solid stack up with good contact between the shoulder of the screw, the inner races of the bearings and the nut. And I think I understand correctly that the spacers and shims are used to achieve that.

Yes I have thought of the possibility of using a dual nut setup, this will require quite a bit of work/fabrication.

Re-packing with oversize balls is also another option. As you mentioned Louieatienza, I would need to take careful measurements etc..

I will take a look at my machine today or tomorrow and let you guys know how I go.

More details on my machine/build are on my site.
https://www.jeremyyoungdesign.com/

Cheers
J

[JermNZ]

Ok, I disassembled one of my Y axis screws as they are more accessible than the X axis.

It turns out that my bearing blocks look ok, except the bearings seem to be a pair of standard deep groove ball bearings (6001Z), rather than angular contact bearings. There were in fact spacers installed correctly on either side of the bearing block, perhaps they came pre-installed in the block, which is why I missed them previously.

I disassembled the whole block and i'm not sure if it needs shimming. The inner races of the bearings seem to contact each other, but only just, no pre-load.

It is my understanding that deep groove BB are not designed for axial loading. It seems to me that I should replace them if I can find a pair of angular contact bearings which would fit straight into these blocks??

What is the best way to remove these bearings? There is no access to the outer races on the side required to press them out. I guess the only way is to press on the exposed inner races and shields? But obviously this isn't ideal..

The lock nut set screw also tightens directly onto the thread, which causes slight damage to the thread, shouldn't be too much of an issue as long as I don't clamp it too many times.

[JermNZ]

I also further inspected my X axis ballnut, there is definitely backlash between the nut and the screw. Even with fairly light force applied to the Z carriage I can see/feel the movement.

Out of curiosity, on a machine like this, would the increase in performance warrant the extra cost of using C5 ground screws in place of C7 rolled?

I believe my machine structure is fairly robust, and the poor quality screws/nuts may be the let down. Perhaps in the future it would be worth upgrading?

[NIC 77]

I personally don't give a hoot about what kind of bearings are in them.

The biggest point was missed. When assembled, is there any play in the system? You will be able to feel it! With your hands. If you are a hamfisted simpleton then ask someone to help you.

All kinds of people have all kinds of opinions and I realize that this post will set them all off into a blaze of stupidity. But really, at the end of the day........shhhhh.....listen.....

Is there any play in the system that requires a shim?

That's all I need to know.

It's a cheapo Chinese bearing block, what kind of bearings did you expect? We are troubleshooting, not reinventing the wheel here.

[NIC 77]

I really hate it when someone sneaks in another post in between the time I have read their first post and responded to it.

Out of curiosity, on a machine like this, would the increase in performance warrant the extra cost of using C5 ground screws in place of C7 rolled?

Not really.

I believe my machine structure is fairly robust.

Nope. It's not. Not even close.

[JermNZ]

The biggest point was missed. When assembled, is there any play in the system? You will be able to feel it! With your hands. If you are a hamfisted simpleton then ask someone to help you.

I determined this right at the beginning, yes there is, and I measured it.

It's a cheapo Chinese bearing block, what kind of bearings did you expect? We are troubleshooting, not reinventing the wheel here.

Well I was interested, because I have seen similar blocks which do indeed have angular contact bearings.