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p1lts
22-11-2011, 04:42 PM
I have a small machine with a 1.5kW water cooled spindle with an ER11 collet. I have been doing bit of engraving and have been struggling with ensuring that the material is absolutely flat on the sacrficial MDF substrate.

A bit of googling has revealed that there are devices called "nose cones" to overcome this problem. I cant find much more information than this though. I resume that they are some form of spring loaded device similair to drag engravers.

Can anybody cast any light on this subject.

Thanks

Rogue
22-11-2011, 05:11 PM
If it's a sacrificial surface, can't you make a few very light passes to ensure it is entirely flat in relation to the router? Or do you mean the workpiece itself won't lay flat?

p1lts
22-11-2011, 05:18 PM
The materials that I am using are very thin and no matter how careful I am, they don't lie entirely flat. It's not a major problem but I am just curious to learn more about the use of "nose cones" to overcome this issue.

blackburn mark
22-11-2011, 06:58 PM
The materials that I am using are very thin and no matter how careful I am, they don't lie entirely flat. It's not a major problem but I am just curious to learn more about the use of "nose cones" to overcome this issue.

i cant find any refrence to any such device but im pretty sure i know what your driving at, a bit like the "foot" on a sewing machine

i cant see it being to difficult to make a devise like this with a "foot" of somthing slippy like nylon or acetal

how thick is the material you are cutting and what deapth are you cutting into the thin material ?

p1lts
22-11-2011, 08:03 PM
Im engraving traffolyte. Nothing fancy, but obviously if you get the depth wrong, you can end up cutting through to the wrong layer (colour).

Theres plenty of references to nose cones and constant depth engraving if you google it, but none that fully explain how it works.

Thanks for any help.

blackburn mark
22-11-2011, 08:25 PM
if i had this issue i would be pretty confident that a simple acetal leg running 45 degrees (ish) from my spindle clamp to the tip of my tool with a nice C shape cutout in the foot for chips to exit the tool aria, take any sharp edges off the foot (acetal polishes quite well)

no fancy springs, just skim a bit off the leg untill it gave the right amount of flex V pressure

might just work :)

p1lts
22-11-2011, 08:36 PM
Thanks Mark

I think I can probably manage something along those lines.

Jonathan
23-11-2011, 12:30 PM
Another method, though more more complicated than what Mark suggested, so definitely try that first, is to use a probe to measure the height of the material. Set it to measure the heigh over a grid of points and record the values. You then take that matrix and use it to offset the Z co-ordinates in your engraving G-code to compensate for variations in height. Clearly it's effectiveness depends on the flatness to number of points ratio. It is apparent if you search on google that this method is effective when engraving PCBs which is a similar process, I believe your material is a similar thickness?