Need Help!- Making a Steel Cutting Router

[Khalid]

I have not seen in this Forum a Router that cut Steel components.. I am watching Milling Machines with Movable bed .. I think the Milling Machine are more rigid and sturdier than a router...

But My current job requirement is a Carbon Steel Cutting Router.. For Hole drilling and Machining of HeatExchangers Tubesheets and its Baffles... Following will be the specifications of the Route:

1- Cutting Area 5feet x 5feet x 1feet (X,Y, Z)
2- Accuracy and repeatability 0.01mm
3- Hiwin Rails will be used as linear slides
4- Using of Precision Ball screws
5- Will search for a good 3Hp spindle
6- The bed will be 1" thick Cast Iron with T-slots
7-The remaining structure including the Gantry, Z-axis and Y-axis bed will be Heavy Structural steel
8- I will use 1200 Oz-in Stepper Motors (02 on X-axis , One each on Y-axis and Z-axis)

Is it possible to machine Carbon steel with a Router?.. I will use DOP 2mm Per Pass and Looking a Feed of 20 IPM...


Please share your ideas with me... You can give me Links of Router cutting Carbon steel...
Regards

[RICHARD ZASTROW]

Khalid, what you are proposing sounds like a light duty bridge mill to me.

Dick Z

[wildwestpat]

Hi Khalid

This will be a monster of a router and is heading to be a verical mill or bridge mill as suggested by Dick Z.

1. The weight of the cast iron table will exceed 400kg (900 lbs) and possibly treble this ias you intend to have 'T' slots let into the top surface of the bed. The bed will require a careful design of strengthening webs on its under side to give adequate stability - look to the design of a cast iron surface plate of that size to give you the sort of cross bracing and webs that are required. Initial machining would be a difficult to do on the actual machine due to the tough nature of the outer skin on a sand cast iron item.

2. This is going to be a tough order to maintain over 60 inches. Look at the ballscrew specs and be prepared for the price as these will have to be large diameter. The use of servo motors and linear glass scales would be a better approach and you could then use a less highly specified ball screw as the absolute accuracy is provided by the glass scale.

3. Yes but to get the necessary ridgidity over the 60 inch span of the bridge will entail a very robust and hence heavy assembly. You should be thinking box ways not simple slide rails although the total weight of the bridge will help to dampen any tendency for the bridge to tilt under the infulence of cutting forces.

4. Same observations as under 2 for accuracy use glass scales as the feed back element in a servo system as this will be cheaper and much better than using precision ball screws.

5. I sense that this is not the right approach. Identify the cutter you will be using and from there obtain the speed and power required. Mild steel in thin section is nasty stuff to machine if you are going to rely on 'T' slots and clamps to hold the work down. Much better to thing along the lines of double sided tape and a sacrificial ply or mdf backing plate that is screwed at frequent intervals to the bed. A magnetic chuck would be the ideal but one hell of a device if you must take a 60 inch square sheet at one go. Why not chop the sheet up first and make the mill that bit smaller.

6. I have responded in 1 as this is linked to the size weight issue. The use of 'T' slots I have questioned in my response to 5 as mild steel in thin section and under high feed rates can pickup on the work. You will need to think of both swarf removal and adequate cooling and lubrication of the cutting tool. As mentioned under 5 above.

7. Do the sums on a gantry that is to deflect less than the 0.01mm you have set which has also to accomodate the other inaccuracies in your machine that in the z direction. It may be that you don't require to control 'Z' to the same accuracy as 'X'&'Y'

8. Do some preliminary design work. The motors need to drive your gantry and the mass to be moved and the speed required will indicate the sizing of the motor. You have two additional considerations - How do you drive the gantry (one sided drive has issues with judder due to the axis twisting and most special builds use separate but linked ballscrew drives on each side of the gantry)? - Is the stepper resolution and linearity suitable for the application? Steppers have their own rotation inaccuraqcies in athe way a single revolution is divided as all the steps have a possitional tolerance. The use of linear glass scales with the scale used as the feed back element with servo motors not steppers is the way most designers go.

Kind regards and hope the budget is big enough

Pat

.

[dertsap]

Originally Posted by Khalid Is it possible to machine Carbon steel with a Router?.. I will use DOP 2mm Per Pass and Looking a Feed of 20 IPM...

using a router isn't a great choice and it won't have the accuracies that your looking for but can be done within a thou or two , your planned feed rate will burn up your tool quickly , use AlTin variable flutes and if your router is 25000 rpm then run it at about 100-120ipm (assumiming your using a 1/2" end mill ) with light depth and engagement with high speed toolpathing .

best thing to do would be to find yourself a proper spindle to match the machine that you plan to build .
for the gantry and base are you planning on welding and or bolting together the structural steel ? if so then you will probably need to pour a thick concrete slab so that the machine will not shift along with the floor and affect the tolerances that you want to control , if its a solid cast iron base then it shouldn't be as much of an issue

[Khalid]

Hi Pat, Thank You for your valuable feedback and time... Following is my Point to Point Reply...

Originally Posted by wildwestpat Hi Khalid This will be a monster of a router and is heading to be a verical mill or bridge mill as suggested by Dick Z. 1. The weight of the cast iron table will exceed 400kg (900 lbs) and possibly treble this ias you intend to have 'T' slots let into the top surface of the bed. The bed will require a careful design of strengthening webs on its under side to give adequate stability - look to the design of a cast iron surface plate of that size to give you the sort of cross bracing and webs that are required. Initial machining would be a difficult to do on the actual machine due to the tough nature of the outer skin on a sand cast iron item. Ans: I totally agreed with you and no doubt I have in mind to make a Truss-support structure for holding the heavy top bed plate..I was thinking that i will level the Top plate with the Router itself, but Now I will see some more ways to reduce the misalignments and inacuracies in the bedplate so that minimal DOC require for the router to surface the Bed... I think of using Cast Iron bed for vibration dampning..can i use ordinary thick Steel plate as bed... As far as T-slots are concerned, We can have some alternate ways to hold the Work Piece... 2. This is going to be a tough order to maintain over 60 inches. Look at the ballscrew specs and be prepared for the price as these will have to be large diameter. The use of servo motors and linear glass scales would be a better approach and you could then use a less highly specified ball screw as the absolute accuracy is provided by the glass scale. Ans: Tomorrow i will raise PRICE ENQUIRY for 6ft 1" dia ball screw, and will see the actual price... However as per your advice I will also study on the servo and linear glass scales as i am newer to servo things... I will make the drawings of the machine and will share with all of you... I am Incharge of big Machine shop( Later i will disclose the capabilities of the machines i have)... 3. Yes but to get the necessary ridgidity over the 60 inch span of the bridge will entail a very robust and hence heavy assembly. You should be thinking box ways not simple slide rails although the total weight of the bridge will help to dampen any tendency for the bridge to tilt under the infulence of cutting forces. Ans: Agreed with You on this... The first day i have in mind to get the accuracy the machine should be heavy weight, rigid and carfully designed... The most important for me is the design of Z-axis... It should be very rigid and accurate... Again In the Drawings I will show you the sizes and thickness of H-beams, C-channels, Angle Irons that will make the Gantry...I have doubt on the vibration dampening capabilities of structure steel.. So i have to make some concrete pouring arrangments or other ways as per yours suggestions... 4. Same observations as under 2 for accuracy use glass scales as the feed back element in a servo system as this will be cheaper and much better than using precision ball screws. Ans: I will Look into it... Thanks for guiding me...Currently I have 1200 Oz-in 4amp/phase 80V Stepper Motors....The servos will be in my secondery List, If i failed in stepper i will definitly look for servo system... 5. I sense that this is not the right approach. Identify the cutter you will be using and from there obtain the speed and power required. Mild steel in thin section is nasty stuff to machine if you are going to rely on 'T' slots and clamps to hold the work down. Much better to thing along the lines of double sided tape and a sacrificial ply or mdf backing plate that is screwed at frequent intervals to the bed. A magnetic chuck would be the ideal but one hell of a device if you must take a 60 inch square sheet at one go. Why not chop the sheet up first and make the mill that bit smaller. Ans: Yes You are right, I gave the 20IPM and DOC values as the Minimum the machine should able to do... I know the Feed, DOC depends on many parameters i.e. Spindle Speed, No of Flutes, Material of cutter, Size/Dia of cutter, Cutting Fluid etc... I use Double sided tape on my wood router... I never saw double sided tape and MDF backing plate on any metal cutting machines.. Do they have power to hold the workpiece combating heavy cutting forces and cutting fluids?... Hmmm.. some time we have Tube sheets upto 5feet in diameter.. On which we have to machining and later drilling operations.. Currently the drilling operation is manually and very hectec... We have three radial drill machines and currently we are doing drilling of baffles plates each 20mm thick (Material is Low Alloy Steel A182 F22 or equivalent) Almost Eight plates are tack-weld and then they go through drilling operations ( 19.05mm final hole dia)... So we change the drills sizes more than 5-times to get the final size... This is the reason I want to make the working area 5ft x 5ft.. I know the smaller the working area the rigid the machine and less complex design... 6. I have responded in 1 as this is linked to the size weight issue. The use of 'T' slots I have questioned in my response to 5 as mild steel in thin section and under high feed rates can pickup on the work. You will need to think of both swarf removal and adequate cooling and lubrication of the cutting tool. As mentioned under 5 above. Ans: You are 100% right... But Once the workpiece hold with the clamp in T-slots...The machining operation started , then all the T-slots will strted filling with chips and may be the chip removal will be difficult.. I need your advice and suggestion for improving the clamping system... 7. Do the sums on a gantry that is to deflect less than the 0.01mm you have set which has also to accomodate the other inaccuracies in your machine that in the z direction. It may be that you don't require to control 'Z' to the same accuracy as 'X'&'Y' Ans: The precision in all axes i wanted from the machine should be not greater than 0.01mm .. I am thinking of no-flex, 0-alignment Gantry and Z-axis... 8. Do some preliminary design work. The motors need to drive your gantry and the mass to be moved and the speed required will indicate the sizing of the motor. You have two additional considerations - How do you drive the gantry (one sided drive has issues with judder due to the axis twisting and most special builds use separate but linked ballscrew drives on each side of the gantry)? - Is the stepper resolution and linearity suitable for the application? Steppers have their own rotation inaccuraqcies in athe way a single revolution is divided as all the steps have a possitional tolerance. The use of linear glass scales with the scale used as the feed back element with servo motors not steppers is the way most designers go. Ans: I am currently brain-storming and need suggestions from you before putting the design in computer... I am keeping in mind the heavy cutting forces, acceleration deceleration, inertia of the system, precision, rigidity, heavy weight etc... I will drive the X-axis with two motors along the two sides not with one motor in the center... This will reduce the racking issues.... I will again look into the servo system and glass scales ... Kind regards and hope the budget is big enough ( No..I have limited budget.. But the Plus point is that I have all the material (Structure steel, machines, manpower) except servos, linear slides and ball screws available with me)Pat .

[asuratman]

You may think of gantry mill but less steel such as in thickness, in width of structure, etc.

[Khalid]

Originally Posted by dertsap using a router isn't a great choice and it won't have the accuracies that your looking for but can be done within a thou or two , your planned feed rate will burn up your tool quickly , use AlTin variable flutes and if your router is 25000 rpm then run it at about 100-120ipm (assumiming your using a 1/2" end mill ) with light depth and engagement with high speed toolpathing . best thing to do would be to find yourself a proper spindle to match the machine that you plan to build . for the gantry and base are you planning on welding and or bolting together the structural steel ? if so then you will probably need to pour a thick concrete slab so that the machine will not shift along with the floor and affect the tolerances that you want to control , if its a solid cast iron base then it shouldn't be as much of an issue

Hi Curt,
The Spindle RPM will be within 0~ 10000 RPM with VFD control...For rigidity I am thinking of Welding+Bolting.. Yes , The Foundation will be RCC concrete to hold the Machine weight and solid anchor... I don't have Foundary and if i go to the Cast Iron Option, this will add up a lot in the budgeted amount..

[Mike Ray]

Check out

http://www.mechmate.com

It is a full size steel construction table that can do drilling operations.

Some are even using the machine to route aluminium. Just making small passes.

But for drilling you can set the Z axis feed and the system is desinged to give if you try to feed in to fast.

[Khalid]

Originally Posted by Mike Ray Check out http://www.mechmate.com It is a full size steel construction table that can do drilling operations. Some are even using the machine to route aluminium. Just making small passes. But for drilling you can set the Z axis feed and the system is desinged to give if you try to feed in to fast.

Hi Mike,
No way...Mechmate can't handle the high cutting forces when working with Steel... Do you have any reference of Mechmate cutting/Drilling in carbon steel plates???
Regards

[RICHARD ZASTROW]

Khalid, You may want to investigate the Newall "Spherosyn" for a feedback system. I used this to replace glass scales where we had a vibration problem on large machinery.

Those were 12 ft. long scales on a 24 ft. dia. vertical boring mill. 1 on the right hand and 1 on the left hand ram.

Also, a 1" ballscrew might be a bit light for the length.

Dick Z

[LeeWay]

Yeah. My little steel frame router will route aluminum okay. No way it would do steel though. It is simply material with much different properties and requires much more rigidity to work. You can actually mill aluminum to some extent with standard woodworking tools. You won't get anywhere trying that on any steel.

That said, if it is only drilling ops, then there is a possibility for a router. Any other type machining though and you have to have something built at least as sturdy as a mill. Could be a spindle type that some call a router, but needs beefy bearings. Plunging even mildly into steel puts all the load on your bearings. That is as long as the gantry doesn't give any.

I am interested to see what comes out of this and if it will still be called a router when completed.

[wildwestpat]

Hi Khalid

The ball screws need to be longer than the travel to alow for the gantry overhang. There are tables and graphs that show the diameter of the ball screw required for a given speed of rotation and the bearing supports. Work out how big a diameter you need as well as looking at the possitional accuracy over the travel you intend. Take into account the point at which you nominate as zero for measurement as this will give the best results rather than take the axis end stop as datum zero. The accuracy is tru possition over the travel not the accuracy over a much shorter distance.

What are you machining? Is this machine to drill holes with a tqwist drill or are you going to pocket mill with an end mill? The forces needed for drilling by plunge cutting with a twist drill give large upwards forces which will have to be factored into the design.

Not sure I understand the tack welds. Are these weld holding several sheets of thin material together? If so the metal is sure to pick up on the drill and probably on a mill bit with anything other than a reverse helix (down cutting) - climb milling is almost certain to pick up on the edge of multiple sheets unless very near to the clamp point.

Yes double sided Scotch tape is ok just clean all surfaces and use safety clamps as well. In some cases glue is useful but do ensure safety clamps as well.

Can you arrange for the part or the waste to permit clamping bolts to be inserted into a sub support / jig. Drill the holes with the jig and then use as an under sheet - just an idea but one I have used on a much smaller scale to machine very thin material.

You might like to experiment with an expoxy cement filling for box beams as a help in damping. However you need to make a cross braced structure like a minature rail / raoad bridge - this is where the bridge mill name comes from I guess! Don't forget it can resonate in all planes.

You might like to think about using a separate mobile clamping arm that follows the cutting head. Clamp - mill a portion of the job - stop the cutting - raise the clamp - reposition clamp and re clamp - start cutting again.

The swarf removal is a problem and as you will probably have to use flood cooling (mist cooling might be a long term health hazard) you would have to use some form of vaccum extraction with a fluid recovery system. Cleaning out the 'T' slots would be labour intensive but not impossible - however I would avoid 'T' slots if possible and use a tapped hole metal plate as a sub base. I have suggested using the sub base as a jig to drill clamping holers OR devise a mobile clamp and do the machining in stages.

Good luck with the design. Regrads Pat.