# Update! New spindle location to reduce flex



## difalkner (Jan 3, 2012)

I have been thinking about the flex in my Z axis and wondering, designing, and pondering solutions. Today I believe I have figured the easiest and best way to handle this problem. Mind you, the flex is very, very slight but I can see the effects when I plunge full depth into 1/2" Baltic Birch at 175 ipm.

The issue, I believe, lies in the extended distance of the single plate of 5/8" aluminum that came with the tramming kit. Prior to the tramming plate the spindle was mounted about 3" higher than it is now and 5/8" closer to the trucks. To me, and I voiced this to Nate when he sent the tramming plate, the cantilevered effect of a nearly 20 lb. spindle hanging that far below and in front of the trucks is just asking for flex.

So my remedy is to move the spindle mount up as far as I can on the tramming plate. This will actually place it about 3/4" higher than it was originally as shipped. I will have to remove the tramming plate, drill and tap new holes, then mount everything back into place and redo the tramming but in the end I think the effort will pay off.

Here are some supporting photos so y'all can see if you concur with my thinking - 

Flex shows in the plunge to begin these slots. I can't ramp because the compression bit with its upcut start causes the face veneer to splinter and I can't have that.








You can see the flex potential here by how far in front of and below the trucks the spindle hangs - 








Proposed location (approx.) - 








Proposed location will still allow access to the tramming bolts - 








Proposed vs. original vs. current locations - 








Thoughts?

David


----------



## Pro4824 (Oct 17, 2015)

I passed on the Avid tramming mount for that reason. The closer to the gantry, the better.
.001 stainless steel feeler gauge for shim.


----------



## UglySign (Nov 17, 2015)

What about adding a 2nd holder?
Put another one in that proposed spot.
Just a thot.


----------



## ger21 (Feb 10, 2019)

Stop plunging. Ramp in one way, and full depth on the way back.

Or, if you have enough Z travel, flip the entire tramming plate upside down.


----------



## Pro4824 (Oct 17, 2015)

ger21 said:


> Or, if you have enough Z travel, flip the entire tramming plate upside down.


Hmmm..... Nice!


----------



## RainMan 2.0 (May 6, 2014)

Pro4824 said:


> I passed on the Avid tramming mount for that reason. The closer to the gantry, the better.
> .001 stainless steel feeler gauge for shim.


Dang I never even thought of that . Paid for it already to


----------



## difalkner (Jan 3, 2012)

ger21 said:


> Stop plunging. Ramp in one way, and full depth on the way back.
> 
> Or, if you have enough Z travel, flip the entire tramming plate upside down.


Can't ramp, Gerry. Unless you can tell me how to get around the problem I stated above. 

Fwiw, I have read and seen where tool manufacturers say to plunge as fast as you can, which contradicts what I learned before I built the CNC. 

But I like the idea of flipping the tramming plate upside down! I'll see if that will work. I have more Z travel than I will use. Right now it goes about 2" below the spoilboard and about 10" above the spoilboard.

But the real issue beyond this is that I know there's more flex than there should be given the cantilevered and offset mounting and I want to do what I can to correct that as much as possible.

David


----------



## ger21 (Feb 10, 2019)

> Fwiw, I have read and seen where tool manufacturers say to plunge as fast as you can, which contradicts what I learned before I built the CNC.


Probably because plunging is bad, so get it over with as quickly as possible.  Ramping is always better.

Perhaps plunge just below the tip of the compression bit, and ramp from there? Better than nothing.


----------



## difalkner (Jan 3, 2012)

Oh, believe me, I don't like plunging at all. It looks hard on everything. But I can't put out work that has chips in the face veneer. I'll have to see if I can figure out how to plunge part of the way and then ramp. But I don't know how much it will help because the BB material is 0.480" and I need to go at least 0.300" to get safely past the upcut portion. If I'm going to plunge that far I might as well plunge the rest of the way.

In every other instance I ramp. I thought about using a downcut bit to cut 0.125" deep and then switch bits but then I get days like Monday; I had 6 Longworth chuck orders - four 12", one 16", and one 24" - so that's 12 plates and would have been 24 bit changes with stopping to set Z zero on every change. So something that I comfortably did in one morning would take most of the day.

David


----------



## Pro4824 (Oct 17, 2015)

RainMan 2.0 said:


> Pro4824 said:
> 
> 
> > I passed on the Avid tramming mount for that reason. The closer to the gantry, the better.
> ...


Oh, you'll be fine, we don't work our machines anywhere near as hard as David does his. 🙂


----------



## difalkner (Jan 3, 2012)

ger21 said:


> ...flip the entire tramming plate upside down.


So the question at hand is whether or not I can flip this plate on the truck mounting plate, correct? I can't flip the entire thing because it would go too much in the other direction and would hit the Z motor mount at the top of the rack. 

There are four threaded holes for the tramming portion with three different types of bolts and I don't know if the pattern is symmetrical or even if they're the same size fastener. Seems like I had to use both Metric and SAE wrenches for adjusting the tramming portion.

Flip this plate?








David


----------



## ger21 (Feb 10, 2019)

Yes, and maybe add two bolts behind the spindle bracket to stiffen it up.
Even better would be to get rid of that plate, and mount the spindle clamp to the back plate right over the bearings. Looks like that would require drilling and tapping, though.


----------



## difalkner (Jan 3, 2012)

If I were to do that then I would be better off putting the original plate back on and that leaves me no opportunity to tram the spindle, unless I am missing a way to do that and it was off before so that's why I got the tramming plate.

Flipping the tramming plate on the back plate isn't an option - threads are different. The pivot point is 5/16" and the others are M8. 

If I drill and tap on the tramming plate where I indicated then the spindle will be mounted about 3/4" higher than on the original plate and I will still have the ability to tram the spindle. It will be 5/8" further away from the trucks but compensated by moving up another 3/4" and this should significantly reduce the moment of inertia relative to the spindle's current location.









David


----------



## difalkner (Jan 3, 2012)

Update - since my last post we got an order for a 14" Longworth chuck so I tried something; I put blue tape where the entry points are for the slots so I could go back to a ramp instead of plunging. So I modified the toolpath to include a steep ramp, 45° to get the bit into the wood quickly but not plunge, and made sure in the simulation that all looked correct.

I lightly sanded the area and then used my hard veneer roller to press the tape down firmly and cut the first disc. When I pulled the tape up I pulled up a few fibers of the face veneer but not too much. I also saw that the cuts were perfect! Plunging causes the bit to pull everything to the side by a very tiny amount, probably less than 1/64" and it's only happening at certain slots, the ones where the entry is parallel to the X axis. When the slots begin parallel to the Y axis there is no movement and the cut is very clean.

Also, when the cut starts out across the grain there is a greater likelihood that grain will pull up from the face veneer, as can be expected. Those that begin with the grain never chip or splinter.

I have seen several times where y'all have used some sort of mask, like contact paper, to put over the workpiece before engraving and I guess that's sort of what I did with the blue tape. What is the mask I have seen and where can I get it?

Anyway, I can continue doing this because it works but it doesn't address the flex that I know is there. But maybe I have prolonged the issue and will address it later because I don't really have time right now to pull all of this apart and drill/tap holes to then go through the tramming process again.

But getting rid of the plunge will keep me in good graces with Gerry and that's also important! :wink:

Tape at entry points -
















Perfect cuts - 








Not yet sanded - 








I appreciate the suggestions and if you have any new ideas on the removing the flex then please post them here. Again, the flex is extremely minimal and unless I plunge parallel to the X axis I never see any flex so it's not like I am dead in the water or producing sloppy work.

David


----------



## ger21 (Feb 10, 2019)

Do you put any finish on these?
A coat of sealer before cutting will reduce or stop the chipping.


----------



## difalkner (Jan 3, 2012)

No sir, I ship them lightly sanded and the end user can finish, wax, buff to their heart's content.

David


----------



## UglySign (Nov 17, 2015)

difalkner said:


> In every other instance I ramp. I thought about using a downcut bit to cut 0.125" deep and then switch bits but then I get days like Monday; I had 6 Longworth chuck orders - four 12", one 16", and one 24" - so that's 12 plates and would have been 24 bit changes with stopping to set Z zero on every change. So something that I comfortably did in one morning would take most of the day.
> David



I was going to mention the downcut bit. Do it in 2 bit changes.
Run all your down cut files then switch bits to run the rest, no?



Sounds like David needs a ATC machine


----------



## difalkner (Jan 3, 2012)

UglySign said:


> I was going to mention the downcut bit. Do it in 2 bit changes. Run all your down cut files then switch bits to run the rest, no?
> 
> Sounds like David needs a ATC machine


I have done that, Ronnie, and it takes too long. Especially when I have multiples to cut and I'm trying to get everything cut, sanded, boxed, labeled and out the door before the mailman gets here around 11 a.m. If it's Friday he's off and we have a sweet lady running the mail but she's a bit slower and doesn't get here until about 2 p.m. so I have more time.

And yes, David _*definitely *_needs an ATC but they simply cost too much. One day that's gonna happen, though, I can _feel _it! LOL!

David


----------



## BalloonEngineer (Mar 27, 2009)

To reduce the cantilever effect, I designed my Z-axis differently than almost every one I’ve ever seen. I spread the guide out and tucked the spindle in between, closer to gantry, spacing the bearing blocks out. Spindle centerline only 3” from gantry. So far not seeing any deviation on plunge (but I still always ramp in). Even when ballscrew is in center, it is off axis relative to spindle, so I see no problem having it off axis.


----------



## difalkner (Jan 3, 2012)

UglySign said:


> What about *adding a 2nd holder*? Put another one in that proposed spot. Just a thot.


I've decided to do just that, Ronnie - great suggestion! 

I have a new spindle mount coming from Nate at FLA and should be here in a few days. It may be next week or the week after before I can do the modification, though.

That should also allow the spindle to act as a stiffener for the tramming plate and setup so this will help considerably, even though I don't see evidence of flex unless I plunge.

David


----------



## UglySign (Nov 17, 2015)

D,
It was the moment you posted the pic.
So it sorta made sense to add another one for rigidity.
As for addt'l weight from the bracket maybe hog out some material.
Another possibility is to add side gussets to the 2 holders. Probably not needed tho.
This is what SS did on mine as well as all of their machines. 

Well, hope it works out for you. Is there a possibility that Nate could exchange
that plate w/ holes tapped to accomodate the 2nd holder? I mean the plate you
have now is essentially good.



difalkner said:


> I've decided to do just that, Ronnie - great suggestion!
> 
> I have a new spindle mount coming from Nate at FLA and should be here in a few days. It may be next week or the week after before I can do the modification, though.
> 
> ...


----------



## difalkner (Jan 3, 2012)

UglySign said:


> Is there a possibility that Nate could exchange that plate w/ holes tapped to accomodate the 2nd holder? I mean the plate you have now is essentially good.


He probably could, and would, but I can do it. Matter of fact, I have a plan to do it on the machine and I believe I have worked out all the logistics and steps to ensure alignment of the two brackets. This bracket and tramming plate is about as close as I can get to being perfectly perpendicular and if I can get away without taking the plate off then I'm one step ahead of the game.

It's probably going to take me just as long doing it on the machine as it would to mark the holes and use the drill press but I want to give this a shot. However, I reserve the right to change my mind once I dive into the project. :grin:

David


----------



## chessnut2 (Sep 15, 2011)

difalkner said:


> I have seen several times where y'all have used some sort of mask, like contact paper, to put over the workpiece before engraving and I guess that's sort of what I did with the blue tape. What is the mask I have seen and where can I get it?
> 
> 
> David


https://www.amazon.com/s?k=Oracal+O...+Roll,+12"+x20'+,+Light+Blue&ref=nb_sb_noss_2


----------



## UglySign (Nov 17, 2015)

chessnut2 said:


> https://www.amazon.com/s?k=Oracal+O...+Roll,+12"+x20'+,+Light+Blue&ref=nb_sb_noss_2



Make sure its Oracal 813

Best bet is the 24" x 50yd. It'll last a good while and cost less.
Also look into Avery, its white, dont know the # offhand.


----------



## ger21 (Feb 10, 2019)

You might consider going with a better mount like this, but the two is probably even better.
https://www.rovercnc.com/products/80mm-spindle-mount


----------



## difalkner (Jan 3, 2012)

I considered one of those, Gerry, but the 100mm is out of stock. Going with two should be better anyway, I agree.

David


----------



## difalkner (Jan 3, 2012)

chessnut2 said:


> https://www.amazon.com/s?k=Oracal+O...+Roll,+12"+x20'+,+Light+Blue&ref=nb_sb_noss_2





UglySign said:


> Make sure its Oracal 813
> 
> Best bet is the 24" x 50yd. It'll last a good while and cost less.
> Also look into Avery, its white, dont know the # offhand.


Do both of you use this for V-bit carving of letters and such? How about the way I use it with a compression 1/4" bit into BB? I hate to buy this if it won't keep the face veneer from chipping during the steep ramp I am using with the compression bit.

Blue tape is about 5.4 mil thickness, Avery is 3.2 mill thickness, shelf liner about 1.2 to 1.5 mil thickness, and Oracal 813 is 0.8 mil so I am wondering if Oracal is strong enough to do what I need it to do or should I go with the Avery?

David


----------



## difalkner (Jan 3, 2012)

Here's a new development, guys - 

In keeping the tramming plate I get the ease of tramming, but assuming no catastrophic event, once it's set I shouldn't have to do it again. However, and I didn't notice this when I changed out the plates, today I realized the original plate is 0.200" thicker than the tramming plates. They are 0.600" where the original is 0.800" and that's a significant difference. 

The extra mount should be here in a couple of days and I can see how large the mounting holes are, to see if there's any wiggle room for tramming without the tramming plate. I guess another advantage to using the original plate is that it's already off and will be easy to drill and tap.

Original plate with proposed new mount location (approx.) - 








Original plate thickness relative to the new plates - 








Close up of the original plate thickness relative to the new plates - 








Thoughts now, given what I just learned?

David


----------



## difalkner (Jan 3, 2012)

New mounts should be here Friday so take a look at what I posted above and see what y'all think about going back to the original plate. The biggest issue I see is tramming because there's no provision for that on the original plate.

David


----------



## difalkner (Jan 3, 2012)

Adding two bearing blocks per rail would be a better solution and would likely stiffen things up considerably. That's what's on the Y axis. However, to add two more bearing blocks would require some serious modification to the original plate. I just looked at it and there is possibly enough room for that but the symptoms aren't significant enough to warrant that modification. If I did that, though, I would lose about 5" of Z travel and I don't think the trade-off would be worth it, especially no more flex than I am seeing now (again, _very slight _and not noticeable except when plunging but I try to avoid doing that). 

Going back to the original plate, adding a second spindle mount, and reducing the cantilever effect by almost 3" should help considerably. I just measured from the center of the bearing blocks to the bottom of the collet for reference. I could pick about any point from which to measure but the spindle is going up almost 3" and toward the gantry about 1/2".

New mounts, screws, original plate - 








New mounts, screws, original plate, new 3.2kW spindle -








Current spindle location vs. new spindle location - 








David


----------

