tormach 1100 series 3 not making round 1in dia 1/2in deep holes

[cncbuilt]

hey team
been using the mill for a year or so and its been running great. well i had my 4th axis on the left side of the table not bolted down and it fell off into the enclosure and the left side of the mill bumped into it. now when i got to mill a hole (1in dia 1/2in deep) like before using the same everything the hole is not round. i can actually fell a line at the 12 oclock and 6 oclock position inside the piece and the outside is slightly out of round.
i tried sprutcam which was what i was using and also pathpilot conversational.

i went to each motor mount and tightened those screws and everything looks fine when its running visually. after playing with this for a week now i am scratching my head. i have another call into tormach but until then anybody have any suggestions?

question 2 - anybody know of a fellow tormach user in NH or MA?

craig

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[SCzEngrgGroup]

What you describe is classic symptoms of backlash, which is typically caused by one or more of the following, in no particular order:

1) Backlash in the ballscrew/ballnut
2) Inadequate pre-load on the ballscrew bearings
3) Worn ballscrew bearings
4) Ballnut not properly secured to its mounting block
5) Loose or broken shaft coupling between the ballscrew and the drive motor
6) Loose gibs

In your case, it would be the Y axis that is at fault. The only way to fix it is to check each of the above, and figure out exactly where the problem is.

Regards,
Ray L.

[Steve Seebold]

I never have been able to interpolate holes closer than .001 round. If I need a hole closer than that, I'll bore it. I'll do a bore in bore out program, then if I need it really close, I'll do a spring pass.

It is possible too that your code is creating your problem. Can you post the finish pass of your code?

[cncbuilt]

hi steve
i tried both sprutcam and pathpilot conversational but have determined i have to click 3 times for the y axis to engage the xaxis is immediate i am getting a couple spanner wrenchs tomorrow and will adjust the yaxis bearing preload as a 1step to address the issue i will post the results


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[Steve Seebold]

Are you climb cutting or conventional cutting? Are you taking any spring passes? If yes, how many?

Judging by what you are telling me, you are not cutting a circle, you are actually cutting a series of lines.

[cncbuilt]

Are you climb cutting or conventional cutting? Are you taking any spring passes? If yes, how many?

Judging by what you are telling me, you are not cutting a circle, you are actually cutting a series of lines.

A series of lines??? I select a pocket in sprutcam and it cuts the round hole.


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[cncbuilt]

I have been working with Tormach but not making much progress. I ended up replacing the dual bearings on the ball screw end of the y axis by the stepper. I now have .0005 measured on the end of the other side of the ballscrew which is in spec. I tighten down the gib on the yaxis and backed it off a little bit so everything looks good and tight.

But when I go an mill a 1” boss I still have a line on the side of the boss in the 2 and 7 o’clock position. Any chance it might be electrical? What’s strange is if i click the arrow keys for the x-axis either direction responds immediate. If I do the same for yaxis arrow keys it takes 5 keyboard clicks for the yaxis to respond. Sure maybe the kB but it never did this in the past and it tried another new kB. I think it’s related to the above issue.


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[cncbuilt]

You can see the line and feel it on the side of the milled boss


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[kstrauss]

Is it possible that the coupler between the y-axis stepper and the ball screw is slipping or the mounts for the y-axis stepper are loose?

[Steve Seebold]

A series of lines??? I select a pocket in sprutcam and it cuts the round hole.


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Are you doing a circle in circle out or are you plunging straight down, cut your circle and pull straight out? Are you doing ruff and finish cuts? Are you conventional cutting or climb cutting? What is your RPM and feed rate?

You've told us what it's doing but you're not telling us what you're not doing. You're not posting any code so we can't see if it's a programming error.

My 1100 is 6 years old and I have absolutely no complaints about it other than it's slow, but hey, I'm supposed to be retired so what do I have besides time.

And I am still using Mach III which has never let me down. And I can hold plus/minus .00075 ALL DAY LONG.

[popspipes]

I use sprutcam 7 and this was a problem for me cutting bosses or contours, it would leave lines/marks in the finish, I found this setting in the strategy page, it uses arcs instead of straight segments to cut circular contours.
My machine was hesitating at points as it was cutting an arc, by selecting use arcs it stopped the hesitation and the the finish is smoother. This feature is not selected by default in sprutcam, it has to be selected each time for each operation that is available.

[cncbuilt]

Interesting on that sprutcam setting I will check in 10. I don’t believe I saw a smooth by arcs setting I will check.


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[cncbuilt]

I measured loss of motion using an indicator in the spindle and on the table. Everything is pointing to a bad ball screw nut so I ordered one I will post my findings.


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[IMT]

How much lost motion are you measuring in Y? How out of round is the boss? The line where it changes direction is obvious but how bad is it?
When my machine was new (2011) it would leave a visible line at 12,3,6,9 o'clock on interpolated holes. Measured the hole runout (relative to the spindle runout) by mounting an indicator in the spindle and sweeping the hole and found it to be less than .001. The lines are more pronounced now but I haven't measured it in a while.

[cncbuilt]

hey guys

i wanted to post an update in that i am up and running. my mill is running the best it ever has after replacing the y-axis ball screw with nut it is stunning how well it now mills pockets, holes etc.

gosh it was a major effort which took weeks to diagnose, order the part and get it installed but i am back in business

it seems that the mill casting changed at some point in time in that if the back two holes in the casting were larger the ball screw could slip into position from behind the mill taking maybe 1hr to accomplish vs 4+ hours from the front. the major challenge is having to remove the ball screw nut housing from inside that small little space under the billow covers. my 1100 mill is dated 4/2013

below is the steps i followed to get the job done

Tormach Y-axis Ball Screw w/ Nut Installation


Install time 4 hours with 2 people


Prep - remove the complete enclosure including the chip tray so that you can access the front casting hole.

1. remove the yaxis stepper motor, motor housing, coupling, double nut and double bearing with washer.




2. remove both billow covers and the front billows brace and then insert your hands into the open space and remove the four bolts on the bottom of the ball screw nut housing allowing the old ball screw to drop onto the top of the stand. Remove the 6 bolts holding the old ball screw to the nut housing allowing you to slip the old ball screw out the front hole on the casting.





3. slip the new ball screw with nut through the front casting hole and install the slip ring and bumper. continue slipping the ball screw through the middle casting hole until it exits out the back casting hole.




Note – tape up the threads on the new ball screw to avoid damaging any threads.


4. install front bumper, washer and screw onto the ball screw.



5 – connect a electric drill to the end of the ball screw sticking out the back and turn the ball screw so the nut advances all the way towards the back giving you room to insert it into the nut housing inside the tight space

6 - insert the ball screw with the nut into the nut holder and secure it with the 6 bolts. Note – do not over tighten or a bolt will easily snap.

Warning - At no time can you remove the ball nut from the ball screw or it will destroy the unit and you will end up will a handful of ball bearings. Having to keep them both together is the main challenge of the install



7- with the ball screw attached to the nut holder you can lift it up into postion under the xaxis and tighten the 4 bolts and then secure the oil lines.

Note – a long screw driver through the front hole helps in keeping the nut holder in place while it is being secure in the narrow space.


8 – Reassemble the items in step 1.


Note - The double bearing with washer that goes onto the ball screw and sits flush in the motor housing might be a little tight slipping over the new ball screw. Using a deep socket you can tap them into position so they seat flush in the motor housing.
Note - A bearing has a thick and a thin ring. The thinner rings of each bearing set must face each other.


9 –lightly tighten a pair of vise grips on the aluminum bushing which connects the stepper to the ball screw so it doesn’t turn. Use a large flat head screw driver with a hammer tighten the inside nut until the bearing preload shows a measurement of less than .0005. Then insert the lock washer and the other nut so both nuts lock onto each other.

[IMT]

Good to hear you got it going. Thanks for the step by step details.
How much better is it now? How much lost motion did it have before and how much does it have now?

[cncbuilt]

.026 loss of motion before now less then .0005

it apparently has been going for sometime and giving it a good bump did it in. i use to always have to play with my cam and cad to get stuff good enough for stuff to fit in a hole. since doing the repair now when i want to mill 1.001 it mills 1.001 which i didnt think was possible.....it sure makes things much easier to work with.....now i am going back to all my cam and tweaking them so i am not over compensating which is a good thing..

[cncbuilt]

Step 6 above might not be clear but the ball screw nut is still attached to the ball screw. At no time can you remove the ball nut from the ball screw or it will destroy the unit and you will end up will a handful of ball bearings. Having to keep them both together is the challenge of the install


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[mountaindew]

Brilliant outcome ! Good work ! Cheers Cliff

Agreed! Im going to look at this carefully in a week or so when I do my 4 month clean and adjustment cycle. Think I have a cracked oil line that goes to the y axis ball screw. Might replace the whole assembly while I am in there. Do you have a parts list? Did you replace the bearings?

[cncbuilt]

what i ended up replacing was the double bearing set for the preload on the y-axis $40 for the set tormach # 30430 and the complete y-axis ball screw with nut $525 tormach # 30448. you can not just purchase the ball screw nut but you have to get the complete matched unit. the oil line can be attached from the top just under the back bellow.
blessings!
craig