U30b chassis for Tillig Gear Tower

Re: U30b chassis for Tillig Gear Tower

Postby Bernd » Tue Mar 05, 2019 8:39 pm

TiTan downunder wrote:Well actually, it's not a drawing but, a tracing of the finished brass plate. Sorry, I usually manage to leave something off when I do these things but, I see MacG has provided the answer.
Don't get too thick. There are mounting 'clips' in the body shell to hold the chassis in. Even with the .032" i used I had to chamfer the edges. Clipping it in is not as big a problem as getting it back out without breaking the body and gluing nylon is a pain in the rear end.

>> I'll crank out some chassis's. << Put me down for 2 - I'll just HAVE too expand the roster.

Ian


Nothing to be sorry about Ian. Maybe if I had made several hundred and nothing worked. This was just a test to see if the program worked OK.

I was going to ask about the thickness. If the clips weren't there what would be the thickest material you could use? I was thinking I could cut a rabbit down both sides so it would fit under the clips. I could make it less than .032". Perhaps .020" would make it easier to get under the clips. Just some thoughts to toss around while I get the machining down to production.

Ok, you're down for two. With over sea shipping and all that will cost you your first born, a leg and an arm. :lol:

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Re: U30b chassis for Tillig Gear Tower

Postby Bernd » Tue Mar 05, 2019 9:55 pm

Just finished the drawing and ran it through the CAM program. Here's what it looks like. The red is the outline of the chassis and gear tower holes. The blue and green lines show the path of the cutter. The red square boxes are that tabs the keep the chassis attached to the main piece of brass.

Image

Waiting to see what Ian says about the thickness of the chassis before I order some brass plate.

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Re: U30b chassis for Tillig Gear Tower

Postby Rob M » Wed Mar 06, 2019 2:06 am

Assuming your X axis is left-right and Y axis is top-bottom in your pics, your Y axis has a lot of backlash.

Are you using Mach3 for your controller? If so, it has a backlash compensation setting somewhere. Other controllers should as well.

But, it is best to eliminate the backlash.
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Re: U30b chassis for Tillig Gear Tower

Postby TiTan downunder » Wed Mar 06, 2019 6:13 am

Bernd,

>> With over sea shipping and all that will cost you your first born, a leg and an arm. << NAH, you don't wanta go there, she's been quite a handful, at times, over the years but, now has her own hands full and we just get to visit and go home again!! :crazy: :lol:

There is 2mm / 0.080" to bottom of sill and 1mm / 0.040" between walkway and chassis clips BUT it's a tight fit with NO give.
I'll try and get a couple of close shots to explain easier.

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Re: U30b chassis for Tillig Gear Tower

Postby TiTan downunder » Wed Mar 06, 2019 6:53 am

IMG_0775.JPG

There are 4 x clips each side - marked in red texta for clarity.
IMG_0774.JPG

IMG_0777.JPG

camera won't focus on shiny sytrene

>> I was thinking I could cut a rabbit down both sides so it would fit under the clips. I could make it less than .032". Perhaps .020" would make it easier to get under the clips. <<

Probably a good idea to go with 0.040". I have noticed the 0.032" I used does flex a bit if I fiddle too much. Going too thick could create to big a gap between the body and the trucks.
The other option would be to remove the clips but then it would rely on the couplers passing through the pilots to hold it all together. If the pilots broke you would be in deep 'doggie-do'. I've had one small disaster but was salvageable.
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Re: U30b chassis for Tillig Gear Tower

Postby Bernd » Wed Mar 06, 2019 9:34 am

Rob M wrote:Assuming your X axis is left-right and Y axis is top-bottom in your pics, your Y axis has a lot of backlash.

Are you using Mach3 for your controller? If so, it has a backlash compensation setting somewhere. Other controllers should as well.

But, it is best to eliminate the backlash.


Hi Rob,

Thanks for stopping by and offering some ideas. To answer your first question, yes, left/right = X and top/bottom = Y.

We talked about your second question quite a while back. Sherline uses Lunix and the software running on the Sherline is EMC. I use CamBam for my CAM program. As far as I can determine from the manual there is no backlash compensation in the software. The machine has hardware backlash adjustment screws. See pic.

Image

Each of the three axis has one of these. I have adjusted them for zero backlash. I cannot shake any of the axis by hand. They are pretty stiff. I believe it's the software or perhaps to fast of a feed rate. The stepper motors may be losing count in circular interpolation. I need to check this out further. Thanks for offering some solutions.

@Ian,

I'll get back with some ideas on the chassis. Thanks for the pics, they help tremendously even if they are a bit out of focus.

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Re: U30b chassis for Tillig Gear Tower

Postby Bernd » Wed Mar 06, 2019 11:46 am

This went faster than I thought.

Here's two ideas. First, using a piece of .080" (2mm) thick piece of brass with cutouts for the clips. The cutouts are 1/32" (.8mm) thick so they fit under the clips. My reason for using that thick a piece of brass is for weight. Here are 2 3D pics. The cutouts are just placed arbitrarily since I have no idea of the dimensions.

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Image

My other idea is to glued or epoxy some blocks of styrene and drill and tap for 2-56 or what ever mm equivalent to screw the chassis to the shell. Maybe we can convince Alex to add those to the shell down the line.

Image

There's no worry of the coupler pocket having to hold the chassis to the shell. Your decision on which way to go.

Edited to add: Will .080" thick stock work on the truck towers?

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Re: U30b chassis for Tillig Gear Tower

Postby MacG » Wed Mar 06, 2019 1:03 pm

Yes, it works. A 0.080" plate does not cause any problems. I have almost 0.157" (4mm) at my ML-4000 (with 3-point bearing).
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Re: U30b chassis for Tillig Gear Tower

Postby Rob M » Wed Mar 06, 2019 1:27 pm

Bernd wrote:Sherline uses Lunix and the software running on the Sherline is EMC. I use CamBam for my CAM program. As far as I can determine from the manual there is no backlash compensation in the software. The machine has hardware backlash adjustment screws. See pic.

Bernd


You need to measure backlash with a dial indicator. Your hand is not sensitive enough to feel a few thousandths of an inch movement.

http://linuxcnc.org/docs/2.6/html/config/ini_config.html
"BACKLASH = 0.0000 - Backlash in machine units. Backlash compensation value can be used to make up for small deficiencies in the hardware used to drive an axis. If backlash is added to an axis and you are using steppers the STEPGEN_MAXACCEL must be increased to 1.5 to 2 times the MAX_ACCELERATION for the axis.
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Re: U30b chassis for Tillig Gear Tower

Postby Bernd » Wed Mar 06, 2019 2:51 pm

MacG wrote:Yes, it works. A 0.080" plate does not cause any problems. I have almost 0.157" (4mm) at my ML-4000 (with 3-point bearing).


Thanks MacG.

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