Offtopic-Portable Miling Machine in 15 Days

[khalid]

Hi All,
Plunged into new adventure for fabrication of CNC Portable Milling/Boring machine from readily available material. I am working in a reputable petrochemical industry. Presently, we have to make a 150 x 80x 90mm deep tappered slots (15 degree draft angle) for repair of a crack on a thick pressure vessel. The existing portable machine did good job on a mockup but due to increase in depth and lot of vibration issues the mock-up job completed in 90Hrs. Thats a big downtime for a plant.
This is the time to make a more rigid and efficient CNC machine that may be portable and mounted on a circular shell at any orientation .. The CNC will be added benefit.
Here are some pictures of the build. The Cross slides working area is 200mm and the Z-axes can travel 150mm. I used salvaged Linear rails and ball screws for this. The machine base is not casted but we have used 30mm Carbon Steel plate
We hope that by implementation of this machine we will drastically reduce the time from 90Hrs to 12Hrs or less.

The target completion date is 15days. Designing by FEA till actual mockup test---15 Days.....

[t_vandemark]

Hey Khalid, I am a maintenance coordanator for Canadian Natural Resources Ltd. a large oil company in Canada. I work at their Horizon Oilsands facility in northern Alberta. I'm just curious why you guys are machining these cracks instead of grinding them? Over here we chase cracks with a grinder then do a mag particle test to confirm that we got it all and then fill it back up the weld. We do a ton of portable machining on site but never on vessels to chase cracks, is this a standard procedure over there?

[khalid]

Hey Khalid, I am a maintenance coordanator for Canadian Natural Resources Ltd. a large oil company in Canada. I work at their Horizon Oilsands facility in northern Alberta. I'm just curious why you guys are machining these cracks instead of grinding them? Over here we chase cracks with a grinder then do a mag particle test to confirm that we got it all and then fill it back up the weld. We do a ton of portable machining on site but never on vessels to chase cracks, is this a standard procedure over there?

Thru Cracks needs to be arrested by drilling holes at the ends then removal of the crack itself by machining/gouging etc. Then joint preparation and rewelding considering all NDT/PWHT requirements... In our case, The crack start from the inner diameter and follow the path toward Outside diameter. Now, if it was superficial crack started from outside then we can use NDT (UT/MT/PT techniques) and grind the crack till it vanishes. However, tell me if you have 110mm thick wall pressure vesse have thru crack what will you do? how long it would take to remove the Thru crack by grinding?

[khalid]

The controler and the machine... Using 400watt delta servo drives...

[johnh]

Very nice work, but over my monkee-like head.

Does this mini-cnc machine bolt to the side of a boiler tank and machine away metal from a cracked area so it can be filled with weld?

Will it utilize a router of sort? spindle of sort? and a metal milling bit?

[khalid]

Very nice work, but over my monkee-like head.

Does this mini-cnc machine bolt to the side of a boiler tank and machine away metal from a cracked area so it can be filled with weld?



Will it utilize a router of sort? spindle of sort? and a metal milling bit?

Actually A plate shall be tack welded on the vessel over which this machine will be mounted. The machine will remove the crack by machining and prepare a special Groove for weld fill up. I will show you some mock-up testing what we have did on steel plate 110mm thick.
Tack welding on stress relieved vessel is also tricky so we shall do all NDT and will perform PWHT of complete circumferential band. Later on detailed NDT (UT/TOFD/MT etc) shall be carried out to check any other cracks developed due to this repair.


We have Hydraulic driven spindle. The maximum speed is 300RPM and can handle upto 19mm diameter end mill at sufficient torque.

[khalid]

Khalid, that machine looks great. I can't wait to hear how it performs. And yes, for a through crack of that depth we would just end up using a gouger. I have never seen them machined before. I would be interested to see some pics of the machine in action, that is if you are allowed to take pics in the plant. You are one creative individual, can't wait to see what you come up with next.

Gouging is one of the low-cost readily available , less time consuming option,but, we are avoiding gouging in this special case due to metallurgy and nature of cracks . This is due to unnecessary high heat input during gouging operation that may cause propagation or generation of new cracks in adjascent material or HAZ portions of the circumferential weld..

I shall show you pictures in another suitable forum/media i.e. email as this is not the part of this thread.

[khalid]

The machine is complete and the controller is also complete. We will use UC100 from cncdrive to control this unit using USB port of laptop
Tomorrow we will calibrate and test the machine. On Saturday we shall do a mockup testing an 110mm thick plate.
This machine cost us with all electronics and hardware : US $4000/-
If we have to purchase this machine from reputable manufacturer we would have to pay around US $30,000/-

[chiloquinruss]

You know, just looking at your pictures, it appears to me you've done this type of stuff before! Very well done. Russ

[khalid]

You know, just looking at your pictures, it appears to me you've done this type of stuff before! Very well done. Russ

A man who do know programming, electronics, mechanical having ability to synchronize all three can do anything in this world. Here is the picture of mock up testing of one of expensive commercial manual portable milling machine, that took 90 Hr for one slot ... This make me design customized machine that having working envelop of 200mm x 200mm x 140mm. Lets see how much time it will take to machine 140mm x 70mm x 90mm(deep) slot with tappered angle 15 degree in 110mm thick Low Alloy steel. I guess not more than 10 Hrs...

Thanks