I'm using steel v-rail and wheels. The rail isn't as straight as you think it would be and spacers were too much of a hassle to get a hold of. I plan on building a plasma table for someone and I'm on the edge about using this system again. I'm considering a nice profile slide. aluminum vwheels would be great for open rail.

 

Hello @Hytech2k
Looking at wheel pictures and trying to figure out what happened, as we have not experienced this on any of our test rigs with the PC wheels.
I can see that if too much weight is applied pushing on down onto the wheels over time they would want to push apart at the centers.
From the updates you posted it looks like the machine was working great until the new heavier spindle was introduced and this makes me wonder if this was the extra weight of the spindle that caused the wheels to push apart.
It may just be in the nature of the internal V Wheel as well after a certain amount of weight. With the solid V-Wheel the pressure will always be pushing into itself so this should never happen with these wheels.
Either way its good feedback and we will look into what can be done to make this better.
Thank you
Mark

 

Thank you Gerald,
I do remember that post but to be honest I am not sure where is. (The search function for OpenBuilds is being worked on, so that is more of a dynamic search)
If I find it I will send your way. Not sure it worked out though as being aluminum on aluminum I think they found it wore down pretty quickly. We had considered using aluminum as well but after seeing the results we decided against it. Maybe the best best to try the Solid Xtreme Wheels with V-Slot or go to all steel rack with steel wheels.
Thanks again for the feedback.
Mark

 

Gerald, the trail on the aluminum V-wheels goes cold here. You might be able to message the OP but the website he was creating has become unavailable.

 

Gerald, it might be a good idea to also change out the bearings while you have it all apart. I trashed a set on a small router jig setup in just over a week of heavy abuse. There was no apparent looseness in the wheels just mounted on the plate but when I got the assembly all put back together the slack was very clear. The only difference I noted while they were just mounted on the plate was that they seemed to spin more freely and more smoothly. In hindsight they may have just been spinning on the plastic shield plates rather than having proper contact with the ball bearings.

 

Hey guys,
Looking into this more I think its really a matter of material/design combination.
I believe that in the design of the V wheel with the amount of plastic already removed from the wheel (almost in half already) coupled with the weight of the gantries pushing down and the V of the rail pushing theses wheels apart they are a bad choice in PC, because PC does not want to give at all. So in time with wear it makes sense that this would happen as it has to give somewhere.
The harder PC wheel with no give in most cases is a great thing and is especially good with the Solid V Wheels and the way they can distribute the weight into themselves. But with the V wheel and your experiences we can see this is not the best combination.
We are working on a few ideas here with the V wheel that may solve some of these issues, in the meantime we have removed them from the store so that others do not run into this as well.
We thank you again for this invaluable feedback, as it helps us all grow as builders.
Mark Carew

 

Will do Gerald! Thank you

 

I found the way the rail and wheels were set up in the video, quite interesting.
Certainly different! Could have done with a better video showing better angles.
Still, I think it's worth bearing in mind.

Gray

 

PC is better with compressive loads than delrin which acts a bit spongy. Introducing synthetic oil and/or grease such as that from some bearings and some cleaning/lubricating agents can lead to stress corrosion cracking in the PC. Solvents attack it and UV will too unless a stabilizer and/or coating is added.
If using an aluminum on aluminum solution then I think a hard coat anodize is the first route to take. However, It's likely to still not be enough for the repeated line loading and type of frictional force seen within groove. The aluminum oxide layer is very hard stuff, but it's brittle, has poor shear strength, and is thin. Once the hard coat is compromised the rest of the structure gets devastated pretty fast. Then issues like fretting or galling present themselves. There are some methods of impregnating the pourous structure with oils and ptfe, but these are tough and expensive to achieve because of the challenge of obtaining uniform pore structure and impregnation.
I've considered the company Gerald mentioned for aluminum rails and wheels. They didn't have steel at the time. I sourced steel in longer lengths elsewhere. Im not greatly satisfied, but it gets it done and is reliable.
Most grades of aluminum are unsuitable for constant contact load applications.
The hard coat will break unless there is greater contact.
The correct aluminum for this application would be one of the 3 series. Unfortunately it would cost less to use the steel options on the market. It would be nice to have investment molded wheels on top of spray cast extrusion or cast and ground rod/bar, but I can't see that happening on the cheap.

Edit: On another note. Mark, check some of these wheels under polarised light for internal stresses. I've seen these types of failures because of internal stresses related to rapid machining and mold flow. I have access to a polariscope. If you want you could send me samples from different batches or from the same machine but with different feeds and speeds. It's possible that a simple solution to this is just a quick anneal in a kitchen oven or backing off on the production time.

Joe

 

Am I not seeing 2 pairs of rails being used Horizontally, with sets of two wheels in each slot, being pinched, and held in place by bolts determining the exact width?
I've not had much to do with Openrail, but I don't think I've seen that method used in a Vertical situation either. If what I'm seeing is right, it does of course put quite a stress onto the top side of each wheel. Couldn't see how many he had on each board though.

Gray