RampEntry Dressup

Here's the place for discussion related to CAM/CNC and the development of the Path module.
herbk
Posts: 1545
Joined: Mon Nov 03, 2014 3:45 pm
Location: Windsbach, Bavarya (Germany)

Re: RampEntry Dressup

Postby herbk » Mon May 08, 2017 7:09 pm

Hi Markus,
i see a entry ramp as something different as a helix milling... Not each milling operation i have to do is a "complete round", sometimes it is only one side on a workpeace and it would be nice to have a entry ramp for that to.

Hi roivai,
for a milling operation it doesn't metter where the path ends... In this case it would be a round and one additional peace of a path, - the machine makes wath the gcode "says". ;)
Take a look at the the gcode at the file in my first post, it works on the machine without any problem.
Gruß Herbert
mlampert
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Joined: Fri Sep 16, 2016 9:28 pm

Re: RampEntry Dressup

Postby mlampert » Mon May 08, 2017 7:15 pm

So far we've talking about profile/contour milling, that's the context I used for the bottom loop comment.
herbk wrote:i see a entry ramp as something different as a helix milling... Not each milling operation i have to do is a "complete round", sometimes it is only one side on a workpeace and it would be nice to have a entry ramp for that to.
Agreed - yet whichever side you're milling, it better mills the entire side and doesn't leave you with a wedge attached to stock.
roivai
Posts: 117
Joined: Thu Feb 02, 2017 5:29 pm
Location: Oulu, Finland

Re: RampEntry Dressup

Postby roivai » Wed May 10, 2017 7:24 pm

I came up with third method to implement the ramp. I think this minimizes the movement needed for the ramp. On the other hand there is a sudden direction change in the middle of the ramp, which may or may not affect surface finish on that spot.
method3.png
method3.png (51.44 KiB) Viewed 683 times
Example:
2017-05-10-184035_3840x1200_scrot.png
2017-05-10-184035_3840x1200_scrot.png (41.19 KiB) Viewed 683 times
mlampert
Posts: 1349
Joined: Fri Sep 16, 2016 9:28 pm

Re: RampEntry Dressup

Postby mlampert » Wed May 10, 2017 8:04 pm

sweet - I like it.

If one cares about surface finishing so much they'll probably add a helix to finish off at the end, so I wouldn't worry too much about it for this dressup.
chrisb
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Joined: Tue Mar 17, 2015 9:14 am

Re: RampEntry Dressup

Postby chrisb » Wed May 10, 2017 9:47 pm

I like it. What a pity that my current project uses only a milling depth of 0.1 mm . Thats not enough to see the advantages of ramping.
herbk
Posts: 1545
Joined: Mon Nov 03, 2014 3:45 pm
Location: Windsbach, Bavarya (Germany)

Re: RampEntry Dressup

Postby herbk » Thu May 11, 2017 5:38 am

Hi roivai,
yep, it looks good. :D

About the surface finish i have no scruples... If i need a good surface, i make it like on the surface on the top: leave a bit of material and take it away with a individual operation.
And: most contour operations don't realy need that quality of the surface. ;) ;)
Gruß Herbert
GeneFC
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Location: Punta Gorda, FL

Re: RampEntry Dressup

Postby GeneFC » Thu May 11, 2017 2:18 pm

herbk wrote: And: most contour operations don't realy need that quality of the surface. ;) ;)
I won't agree that "most" contour operations don't need "quality", but I think this ramp approach is worth trying. If I need good surfaces and good dimension control I manually add a clean-up pass to the end of the G-code. It is pretty easy to just duplicate the last circuit provided by the Path operation.

Gene
mmxe
Posts: 2
Joined: Wed May 24, 2017 12:13 pm

Re: RampEntry Dressup

Postby mmxe » Wed May 24, 2017 2:22 pm

roivai wrote:I came up with third method to implement the ramp. I think this minimizes the movement needed for the ramp. On the other hand there is a sudden direction change in the middle of the ramp, which may or may not affect surface finish on that spot.
method3.png
Hi,
I'm a mechanical engineer and I work sometimes in a very busy machine shop. I think you're over-thinking this ramp operation. Ramp entries are great, but the first consideration is what ramp angle can your cutter handle. This is specified by the cutter manufacturer, and you respect it or you damage your cutter.
So, from this standpoint, by trying to compute this angle in software based on the requested Z level plunge depth, you take away all the certainty required by the machinist to respect the tool capabilities and specs, and you force him/her to pull out a calculator to make sure your software isn't going to ruin the cutting tool.
Please let the machinist specify the max allowable ramp angle, and the depth they want to ramp down to. This should be specified as the entry method for a pocket operation. Or allow the tool definition to include the max allowable ramp angle. 0 angle should mean the tool isn't designed for center cutting (plunging cuts).

Modern machining practices are typically shifting toward getting down to a deeper Z level as quickly as possible using a helix or linear ramp operation, then using more of the flute length of the cutter to make shallower passes at the pocket. Depths can be as high as 3/4 - 1" for a 3/4" diameter cutter, depending on the material.

For outer contours/profiles the a similar method is becoming more and more main stream. The cutter starts at a Z level that allows the flutes full engagement in the material, then makes as many passes as possible at this depth. Then the cutter moves UP to the next highest Z level and make as many passes as possible. It's the best for rapid material removal, the best for tool life, and the best for machine life (fewer passes to take away a given amount of material means less machine wear, and the spindle load you can choose based on the cutter engagement (step over as a percentage of cutter diameter.)
chrisb
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Joined: Tue Mar 17, 2015 9:14 am

Re: RampEntry Dressup

Postby chrisb » Wed May 24, 2017 4:32 pm

We already have a "Cutting edge angle" in the tool description. Is this what you mean or do we need another attribute in the tool table?
herbk
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Location: Windsbach, Bavarya (Germany)

Re: RampEntry Dressup

Postby herbk » Thu May 25, 2017 8:37 am

chrisb wrote:We already have a "Cutting edge angle" in the tool description. Is this what you mean or do we need another attribute in the tool table?
Hi Chris,
in my mind "Cutting edge angle" describes the shape of the tool. E.g. tools for milling a prism or a V-groove
"Cutting edge length" is the dimension for that what mmxe is talking about with " that allows the flutes full engagement".
If you want to add a attribute to the tooltable, then a checkbox for "tool allows vertikal touch in" and a field for setting the entry ramp angle for that tool. If you do so, then "not checking the box" shoud automaticly select the entry ramp dressup if the tool is selected.
mmxe wrote:Then the cutter moves UP to the next highest Z level
This i don't undersdtand... most of my endmills have a cutting diameter less or simular to shaft diameter, so it's not possible to work from "low to top".

For using the full tool size for cutting, you need also a machine which is powerfull and strong enough to handle it. I think most of us don't own a machine like that, - and for that reason we work with little "step down steps"...
Gruß Herbert