better to use off the shelf linear guideways?

[learningallthetime]

I've been happily working on a platform design as above (500mm long, 350mm wide, vertical angle-irons 450mm long; cylinder represents linear actuator). The purpose is to provide 300mm of vertical motion and carry a load up to 20kg (that could even be placed at the far end).

The rollers are mounted on a bolt with a flange, then washer, then cam nut, such that the platform can be aligned, compensating for any distortions in the welded frames of the support (not shown) and the platform itself. Have built one prototype and it all seems to work quite well. Still need to add some blocks to provide lateral stability.

A friend took one look at all this and said I should use linear guideways (such as Hiwin HG series). They are not cheap but he insists it will be cheaper than machining all the relevant components to make my setup work.

I had the impression that I was designing something pleasingly simple that would deal with the load whilst providing adequate stability; that ultimately it should be a cost effective approach.

So my natural reaction is to start thinking how to cut lots of plates with 20mm holes (for the cam nuts) efficiently, how to mill the nuts without finishing passes to do so fast, how to turn the bolts quickly etc. and so forth. Is it just obvious that my friend is right and should go with prebuilt linear guideways?

Would anyone like to chime in on this matter?

 

[TheTick]

It seems simple until you try to make it work. Sliding parts require precision which is difficult to attain or tube.

When you use OTS components, someone else already figured all this stuff out. That is what you are paying for.

Then there's the controls. Are you going to design and build controls? Is that going to cost less in terms of time and money? If it is then you are a savant and working in the wrong field.

 

[learningallthetime]

I'm satisfied with the precision of the above arrangement but it was just a naive assumption that it would become a cost effective approach.

Items like Hiwin HG guides have a lot of extra precision that didn't seem warranted here (purpose is to lift a container of food up and down) and so the naive hunch was that in the end (after making a couple of hundred?) with OTS guides might be paying for something that we didn't need?

 

[TheTick]

There are many manufacturers and many degrees of precision available.

 

[JNieman]

It's not a waste to buy something that is /better/ than you need, if it's cheaper than something which is /barely/ what you need.

As @TheTick mentions: they've also the benefit of dedicated design minds inventing the best way to solve that niche issue. When possible, use OTS components. You're not a lesser designer for it. You're not a better designer for reinventing a wheel. You're a smart designer, using your boss's money more frugally, to get good performance from less investment. The novelty of a design task like this is not in how 'customized' it is but rather in its performance and arrangement.

Something that is only 10% beyond design requirements can easily be 5x the expense of something that's 100% beyond design requirements.

There may be more affordable linear rail systems. There are a good number of styles out there. Don't stick to the one brand or product style. You might find something that doesn't look like lipstick on a pig, if that's what you fear an expensive rail will seem.

 

[learningallthetime]

This sounds right. Thanks guys.

I need to find a lower precision / robust OTS solution.

My suppliers have more precision type CNC linear guides which are overkill.

Will now start looking further afield. Trying to find the right search terms so that don't end up wading through lots of higher precision stuff....

 

[MintJulep]

There are a few liner guide makers that advertise right here on Eng-Tips.

 

[hendersdc]

These guys offer some lower precision, lower cost solutions. [URL unfurl="true"]http://www.igus.com/drylin[/url]

No affiliation, just like their products.

 

[Tmoose]

https://www.amazon.com/Zeny-Motorcy...8884526&sr=8-5&keywords=motorcycle+lift+table

 

[Jboggs]

The two main factors you must understand are loading and precision. You must understand how your geometry translates payload into actual force on the rollers. You must also understand exactly how much precision is required in your motion. High precision = high $. For applications where precision and loading are not excessive these two companies provide excellent products. I have used both extensively.

http://www.bwc.com/

http://www.pbclinear.com/

 

[Compositepro]

Look at sliding door hardware from your local hardware store. Inexperience in design is always going to be a problem for the inexperienced. That is not a reason not to try.

 

[KENAT]

Places like McMaster even have a limited selection- not sure they are big enough or not but worth considering.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[MintJulep]

http://www.bwc.com

 

[GregLocock]

You might have a look at slide out drawers used for 12/110 V camping fridges. They are relatively cheap, and quite robust.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[BUGGAR]

I built a prototype CNC slide from McMaster parts for less than US$50 Fully adjustable, preloaded bearings, worked great.