Hi, during the last step of the M4 assembly, the step states: “Join the linear rod supports to the sled using six bolts each. There will be a small gap between the base of the upright and the sled initially, go around in a circle tightening each bolt gently to remove it”
However, when I do, I get a very noticable bend in the linear rod support. Is that an issue that can negatively effect the M4? or reduce it’s lifetime?
Thanks
Yeah, the instructions really need to be updated. Looks like your uprights were probably too long, should be 210 mm. I did the same with mine, cracked just like in your picture. I don’t think there is much long term damage, but it really should have you measure the rods and either shim beneath the support or trim the rod to the correct length. The instructions to tighten it down are just misleading since we know the rods have typically been too long in quite a few cases.
What shim material would be best? I didn’t notice a problem when assembling … but I’m not really that observant … I’ll go out and check.
If the rod is ‘too long’ does that mean it did not get set into the base far enough or is the rod just too long?
Thanks for the heads up!
The rods are too long. I just grabbed a dremel and cut mine (took off almost 1/4"!) to get them to where there was still some standoff between the supports and the sled before tightening, but not so much that I cracked the clamps. I ended up buying rod supports also to replace the cracked ones, just to make sure everything is stable long-term.
This is 100% our issue, the factory that made the linear rods cut them on the long side and shortening the rod is the best solution.
I will DM you a code to get a free replacement for the cracked part right now
I also had rods that were too long. I went to Lowe’s and bought a 10" cut off blade (<$10) and used my miter saw to cut them to 210mm… I taped them together before cutting, measured them from one end to the blade. This way they would both be the same length. Worked like a charm.
Mechanical setup of the machine is complete - On to firmware and garage floor setup
Benchgrinder made short work of shortening mine, also gave opportunity to put a nice chamfer on the sharp cuts. I have to admit that I tapped on mine with a hammer thinking it needed to be pressed in a bit harder, before I took them out and compared them.
I ended up with this exact issue. I backed off the screws after cracking the top supports and set the project aside while deciding to cut the rods or create a shim. Anyway to get a new set of supports?
yeah, for sure! Ill DM you a code. one sec
My rods are a bit too long, but not so long as to crack the top supports. I was able to get the supports screwed into the base. There’s a slight upward bend in the top supports. I considered grinding the rods down a little, but decided just to keep as-is since they are firmly in place and working now. With my luck, I’d take too much off of them and need to get new rods altogether.
@anna Do you think its best to shorten the rods in my situation for an optimal fit or agree that things sound find as they are now with a slight bend in the top support?
The machine I am running at Altspace has that bend too, so you should be ok. Let us know if you see the crack in the web section over time. But over all, I think its somewhat easier to shim under the support riser, rather than cut the linear rod.
My rods were a little long as well, though I didn’t notice initially and kinda forced the install. Eventually, I noticed that the entire sled had a small bow to it and would rock side-to-side but not front to back. After realizing the issue, I added shims to compensate and the sled is flat again now.
I have another issue with the rods: one of my rods is a precise shaft rod whereas the other has different tolerance, variation in the diameter, so much so that the linear bearings do not spin and freely rotate on one of my rods.
And the replacement rod that was so kindly sent to me sadly has the same issue.
Hmm can you post a picture? All of the rods came from the same batch so they should all be identical
@bar A photo wont work need to see this video
The replacement rod is shown on the sled and it acts like the rod on the left – very catchy/sticky to the bearing and lots of friction under rotation. And yes I tried the other bearings same issue points to bad rods
Yeah, that shouldn’t be like that.
I’ll go through the ones that we have here tomorrow and see if I can figure out what is going on. Thanks for the heads up!
I went down to the warehouse and checked all the rods there and I coudn’t find any which would bind up, the bearings run smooth on all the ones that we have in stock. I did find a couple where the bearings didn’t love to rotate but that seems to be in spec since they aren’t designed to rotate in that direction.
I can send you a code for free replacement bearings and a new rod, but I’m a little worried that something funky is going on since you’ve had two bad ones in a row and I can’t find any bad ones in the 200 or so we have here.
Its great that you don’t see any issue with your inventory and thanks again for the replacement.
