More design issues/frustrations: 1/ The two lower adjusting screws for the y-axis steppers are

General CNC CNC Routers
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More design issues/frustrations:

1/ The two lower adjusting screws for the y-axis steppers are inaccessible when the gantry is mounted on the rails. How exactly are we meant to take up the slack in the belt when you can’t get at the screws while the belt is in place. The only way to adjust the stepper is while the gantry is off the rails, at which time you don’t have the belt fitted to the sprocket, so you have no idea how much to adjust. It looks like the only opportunity for adjustment is by tensioning the belt at the anchor point - completely the wrong way to do it.

2/ Unless you buy stepper motors threaded for M5 bolts, you need to fit a nut to your mounting bolt. The best way to do this is to mount the screw and the stand-off to the stepper, push it through the holes in the gantry plate and then affix a nut on the wheel-side of the gantry plate - except you can’t. There is no clearance. SO, you have to push the low-profile screw through the plate from the wheel-side, then try and fit a spanner or socket in the tiny space between the stepper and the nut - I tried 4 different types of stepper - the clearance is all similar - negligible. That’s because they weren’t designed to be used that way - the screw is meant to come from the back side of the stepper, through to the face. That’s how they have ALL been designed, except for the ones that have been tapped for an M5 screw - which are few. I can’t understand why the designer didn’t encounter this problem in assembly himself? I’ve had my gantry apart a few times now - all because of things like this - inaccessible adjustment points.

3/ Even if you did buy threaded steppers, you can’t access the lower stepper mount screws to loosen or tighten them with the gantry in place. So why are they even adjustable? You can’t adjust them - unless you kept the bottom two finger-tight and only tighten the top two? You will have to thread-lock them and hope they don’t work loose over time.

Again, how did that pass any sort of assembly test?

If you are making one of these - make sure you buy steppers that have threaded mounts, but don’t tighten the bottom two, or you will never be able to effectively tension the belts. Make sure you use thread lock, and cross your fingers it doesn’t fall apart on you.

No doubt if you buy all your components from the Openbuilds store, you won’t have a problem - but it’s meant to be open source, not ‘buy it all from me or it won’t work’

Becoming increasingly frustrated at the amount of bad engineering decisions that went into this design.

I would be interested to hear @Mark_Carew_OpenBuild 's take on how exactly we are meant to make this work, in practise.

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FYI, the Nema 23s that I just bought from OB have mounting holes too big to tap for M5.

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So they are selling stuff that doesn’t work with their own design… I wonder where the quality control is?

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@Jim_Fancher I would be interested to know if you had the same difficulty I did in fitting a spanner to the tiny M5 nuts within the confines of the stepper housing. I have some pretty good tools, including slim spanners, sockets and such, and found it it very difficult to do.

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I haven’t started assembling it yet. I did a quick test fit and saw it was going to be a pain. I even thought about using JB Weld and re drilling the holes so they could be tapped.

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That’s not a bad idea - still doesn’t solve the adjustment problem, though.

I am about to fit my new motors - I am going to try one of these instead of a nut for the lower two screws: https://dzevsq2emy08i.cloudfront.net/paperclip/technology_image_uploaded_images/23630/default/m3_pre_assy.jpg?1365045274

I can use a screwdriver blade to stop them rotating when I do them up. Maybe even cut a notch and bend them to fit inside the screw slot, so they can be tightened and loosened from the other side… time to get back in there.

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@Mike_Thornbury That’s a neat idea. I had thought of a low profile nut, but only looked at conventional hex nuts.

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Hi @Mike_Thornbury Sorry to hear of your building frustrations. As you know there are a lot of ways to go about this, I just used what I had at the time for my initial build. As with any build and especially open source having more people being part of a project opens up more ideas and helpful feedback for everyone. Thank you for the feedback Mike, looking forward to your solution.

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@Mike_Thornbury install the Nema 23s in the highest slot setting. The nuts are slightly difficult to put on but a 5/16" combination wrench can be used to successfully grab two sides of the nut.

To adjust the belt, if your plates were cut correctly there is an access hole in the plate where the belt can be pulled through the Y gantry plate. Simply loosen the bolt in the T-nut, pull the belt through the access window and re tighten. The belt should not need to be tightened via moving the stepper.

Hope this is helpful.

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If that’s the case, why is the stepper mounted in slots?

And sorry, but that’s a half-baked way of tightening a belt. It’s clear it was meant for the stepper to move, but the design is an abortion.

The build notes/documentation even states this.

When you have to remove the gantry to replace a stepper, you know the design is bad.

And @Mark_Carew_OpenBuild , that’s the kind of shrugging, hands-in-the-air response from you I’ve come to expect.

You can’t just lay it all at the feet of ‘open source’ to absolve you of any liability -you, and @Brandon_Satterfield are running businesses selling products with big technical design issues and don’t seem the least bit interested in letting the customers know.

Unless I am the first person to find that this is a problem?

Just like I was the first one to find your limit switches couldn’t be used, as delivered and that the z-axis couldn’t be aligned in place.

So many firsts!

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Sorry to hear you feel this way @Mike_Thornbury The OX is not a kit, it is designed around an modular building platform. There is a full video ‘build along’ to show the way that we built ours as a guide to offer help. The whole idea behind the OX was to bring a simple easy to use CNC machine to our shop and to share with everyone else who may be interested as well. and we have to say the OX design has done just that. Absolutely there will be mistakes along the way like design issues, video mistakes, etc. everything can be improved on, for example the limit switches error, we have fixed them and moved forward. To be perfectly honest we were able to work with the ones we were using as well. All that being said the reality is there are lots of happy folks out there building and modifying the OX design to suit their needs as well having a blast making awesome projects with their machines. Again we apologize that your experiencing these frustrations with your build, but I think if you can just push though the build you will find how much fun owning a CNC router can be. Plus all you gain from the experience can help you better design and build your next machine and share your improvements with others. This is the true beauty of open source and what helps to keep the innovative juices flowing. Hope its smooth sailing for you from here on Mike. All the best with your build, my friend.

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Well it’s being sold as a kit… perhaps you need to talk to the people that are marketing it as such, @Mark_Carew_OpenBuild @Brandon_Satterfield ???

You seem to be missing the point, Mark. I can’t have been the first person to find these shortcomings. You must have when you put together the machine in the first place. You must have when you went and made the construction videos and the build notes - yet there isn’t a single mention of these issues.

Why is that?

Why are you still promoting it without informing people of the possible gotcha’s?

Why is there nothing saying in big letters 'THIS IS NOT A KIT - IT MIGHT NOT WORK!" - when you are promoting the Ox?

I understand that it isn’t and am happy - although frustrated that such basic engineering fuckups made it through testing - to continue to work with it, but others might find it is a show-stopper.

I think you should look at how much of a cheerleader you two are being without actually being responsible and saying ‘there are some real issues with this design’ - because there are.

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My motors have 5mm holes, making it hard to get a spanner on the nuts. I just reversed the screws, putting the nuts on the inside…adjustment problem solved.