plasmacam " Z " screw

[lobsterlift]

hello, i have a plasmacam dhc machine and have worn out my z axis screw again. they do not offer it seperatly and want to sell the z motor assembly. i am going to look at having some made. any interest here? or anyone know of a source for them? thank's all!!

[Joe Jones]

It is possible to have one made, but it will cost you about $250.00, unless you buy them in large quantities (25 or more) at a lower price. Machine shops do not want to tool up to make just ONE lead screw. It isn't worth their time. Sadly, PlasmaCam didn't consider stocking spare parts like lead screws, so they will only sell you the complete motor.

I suspect that PlasmaCam doesn't want you to replace ONLY the lead screw, because the threaded nut that drives it is ALSO worn, and a new screw ALONE will result in sloppy Z control. By replacing the entire motor, you get a new motor, a new nut and a new screw.

Keep the old motor handy for when your replacement Z motor gives up the Ghost, and you just need a working motor to finish a project.



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[Bobcat320]

hello, i have a plasmacam dhc machine and have worn out my z axis screw again. they do not offer it seperatly and want to sell the z motor assembly. i am going to look at having some made. any interest here? or anyone know of a source for them? thank's all!!

Should you find a source I am interested!
Carl

[Joe Jones]

Frankly, I cannot imagine those lead screws wearing out. The nut that rotates to raise and lower the lead screw through is PLASTIC, a softer material than the shaft, so it would seem logical that the NUT is what needs to be replaced. I don't see how a plastic nut can wear out a steel shaft.

[lobsterlift]

it is visibly worn and i can feel it when i run my finger across it. same thing happened to my last one, motor drives screw sdown til it hits bad threads and thinks its hitting metal on the table, so it stops, raises to pierce height and fires, like 3/8" above the plate to be cut. a sloppy "z" im ok with, but a stuck "z" not so much. i'd be surprised if the nut is plastic i will investigate further....

[PlasmaMac]

Yes, that is hard to imagine. There are people that have run the old DHC's hard for years and I can't say that I have ever heard of the z axis screw ever wearing out. If your z-axis accuracy is some how being effected by this, something must be off. The techs at plasmacam may be able to offer you some insight in to this.

JAG

[Joe Jones]

it is visibly worn and i can feel it when i run my finger across it. same thing happened to my last one, motor drives screw sdown til it hits bad threads and thinks its hitting metal on the table, so it stops, raises to pierce height and fires, like 3/8" above the plate to be cut. a sloppy "z" im ok with, but a stuck "z" not so much. i'd be surprised if the nut is plastic i will investigate further....

I'm sorry. That just doesn't sound right. The nut is made out of PLASTIC! How can it possibly wear out a hardened steel rolled thread lead screw?!?

I am toying with the idea of having 30 or 40 of them made, and selling them to those who want to replace their lead screws, but I have to be convinced hat they actually wear out. Can you provide a good, close, in-focus photograph of these damaged threads on the lead screw?


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[lobsterlift]

yes i'll get some carb cleaner, get it clean, and shoot some pics. and yes your right, i disassembled my old z motor and sure enough its plastic (the nut). i agree completely with you but it is happening.

[Greolt]

You could possibly adapt one like this as a generic replacement. Could be a much cheaper alternative.

I use one like this for the Z axis on my plasma table.

http://www.omc-stepperonline.com/nema-2 ... p-151.html

If you search that site, they have a range of non-captive linear steppers. They have a brass nut.

[lobsterlift]

here you go. it may be hard to see but its worn out. this is my old one that i flipped over, welded a nut on the other end to get it on a different part of the threads.

[Joe Jones]

You could possibly adapt one like this as a generic replacement. Could be a much cheaper alternative.

I use one like this for the Z axis on my plasma table.

http://www.omc-stepperonline.com/nema-2 ... p-151.html

If you search that site, they have a range of non-captive linear steppers. They have a brass nut.

Have you actually TRIED one of these motors on a PlasmaCAM table? PlasmaCAM uses very high voltages and resistance. I don't think that they will work with the PlasmaCAM tables. PLEASE tell me if I am wrong!



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[PlasmaMac]

I think that you have a very valid point on that one, Joe.

[Bigrhamr]

Plasma dust will wear out lead screws and plastic or bronze nuts. I doubt Plasmacam is making their own screws, try this site http://www.roton.com/
You need to know pitch, number of thread starts, and thread size then you should be able to ID what screw you have.

[Joe Jones]

I have never taken the Z motor apart to see what nut it uses. So busy now. That will have to wait for another time.