Screw machines simultaneously cut materials using a number of tools mounted on a spindle, yielding small final pieces. At the heart of these machines is a drum that operates multiple spindles, each of which rotates horizontally to perform tasks on the workpiece.
These machines can perform a number of operations on the workpiece within one rotation. They consist of many intricate parts, which perform complex tasks through the use of automated systems.
As such, it’s important to regularly troubleshoot and maintain multi-spindle machines to ensure smooth operation within your facility. Keeping your machinery cool, lubricated, and in good repair means less costly downtimes and higher degrees of accuracy in your manufacturing processes.
Set Up a Troubleshooting Checklist
Multi-spindle machine operators must ask themselves a number of questions to ensure their machines are in proper working order:
Is the Form Tool Diameter Changing in Size, Varying, or Chattering?
Check that the tool’s setup and head positioning maintain maximum rigidity. Then, look for any sloppy work spindle bearings and make sure that the tool has the proper center height setting. Verify the proper grind of your tool and check to see whether it’s properly supported during cutting. Look for a loose slide or tool, and make sure you tightly fasten all the bolts. Lastly, check for dull tools and make sure you’re working with the correct stop screw pressure.
Is the Hole too Big?
Verify that the machine is locking the head in the proper position, and check for sloppy spindles as these could signify off-center or chipped center drills. Next, check whether the drill is dulled or loaded up, and make sure the drill and spindle are properly aligned.
Is the Machine Stripping Threads?
Make sure the head’s locked properly, and verify that you’re working with the correct hole and body size. Look at the alignment of the spindle, and check for dull/loaded taps or dies. Finally, check the summary settings to make sure you’ve found the problem.
Does the Length Vary?
Many issues could cause variations in length. Most commonly, worn or sloppy bearings in the spindle or dull-end working tools can push work back into collets. Generally, loose, worn, or dirty collets can cause problems, and you may need to check for the proper feed finger tension on the five spindles.
At the bar end, check for a clean cutoff, and make sure the stock stop is tight, polished extensively, and at the right length of the stop plate. Feed the stock to the stock stop if this isn’t already the case. You should also check head thrust bearings as well as the rolls and pins on the end working cam lever for wear and tear.
Do the Parts Have Burrs on the Cutoff?
Evaluate the stop collar to make sure it has the proper pressure, and make sure the pickoff collet is adjusted properly. See if the cutoff is on center, and check the timing of the closing dog.
Is the Box Tool Dimension Rough or Varying in Size?
The box tool should have a proper grind and feed, so check for these first. Then, make sure the rollers have the proper tension.
Is the Hollow Mill Dimension Rough or Varying in Size?
Verify that the machine achieves the proper grind, and check for worn or loaded cutting edges. Then, look for the proper alignment and feed.
Has an Improper Step or Shoulder Appeared?
First, look at the form tool alignment and the box tool alignment, and then make sure the box tool has an appropriate travel distance. Evaluate the sharpness of the drills and verify that they reach the proper depth. Finally, check for any loose tools or holders.
Are the Rolled Threads Out of Form or Flaky Like the Scissor Type?
Look at the work’s feed or penetration, and check for the proper blank size. See if the blank has a taper, check whether the rolls are on the center of the work, and look for proper roll synchronization. Finally, check rolls for any nicks.
Is the Reamer Chattering?
It’s possible that there might be too much clearance on the spiral relief. You should also check to see whether it’s out of alignment. Make sure the feed is the right size for the particular reamer you’re using, and find and fix any low cutting edges.
Is There Tap Trouble?
If the tap’s cutting below the correct size, you might need a different tap for the job. The tap also must align with the workpiece. Look for proper float in the holder, and check to make sure that the hole’s of the proper size. Finally, check the summary settings.
Is the Knurl Out of Form or Flaky?
Make sure your blank’s the right size, and check both works’ feed and penetration. Look for taper on the blank, and check the knurl pins and the knurls themselves for signs of wear or nicks.
Preventative Maintenance For Multi-Spindle Screw Machine Services
Multi-spindle machines require comprehensive maintenance schedules. While you should perform some tasks daily, other processes require quarterly or yearly checkups.
Make sure you have sufficient lubricating oil levels in the lube pump reservoir. Then, check the machine pan reservoir’s coolant level. It may be necessary to clean the coolant intake pipe screen or pump screen, so check this as well. Make sure the stock reel and its support are in good condition and aligned, since they should be lagged to the floor. Finally, verify that the machine is properly delivering lubricating oil to the work spindle bearings.
Once a month, take each of these items off the revolving head, clean and inspect them, and replace them if needed:
- Feed tubes
- Feed fingers (also make sure they’re appropriately tensioned)
- Inner spindles
Then, check on the wear and tear and general condition of the following parts:
- Stop screws
- Cross slides
- Gib adjustments
- Stock reels and stands
Clean the outer spindles with a boiler brush, and make sure the locating lever is locking correctly and that the roll turns. Check the condition of the following components:
- Chuck slides, rolls, and pins
- Cam levers, rolls, and pins
- Tooth wear
- Gear mountings
The shafts are particularly important: check for a potentially twisted front cam shaft, since the locating lever must clear the locating blocks on index, and you want it to make contact, angle side first, with 0.012” pushback when locking.
Check to see whether the revolving head has end play, and adjust the thrust ring if needed. Lastly, make sure that the locking nuts and set screws on the spindle change gear shafts are in good repair.
Once every quarter, clean the coolant pan: remove all coolant and get rid of any sediments and fine chips before adding new coolant. If you have long runs that make changing the cams difficult, take the cross slides off and clean them before checking for proper gib adjustments. Remove the plugs at the bottom of the worm gear housing, and flush the housing with an OSHA-approved solvent. Finally, replace the plugs, and fill with fresh oil.
Twice a year, drain, clean, flush, and refill the main lube pump reservoir. Check the filter, and make sure there isn’t excessive end play in the revolving head or thrust bearings. You should also verify that there’s no excessive looseness in the work spindles or tool spindles.
This is also a good time to check the condition of the electrical controls, including the switches, solenoid valves, wiring, panel box, cables, motors, and other elements, but make sure that only authorized personnel handle electrical control maintenance. Check pneumatics as well, including the air lines, valves, cylinders, and fitting.
Once a year, perform a thorough inspection and cleaning of the entire machine as a unit. Check the tool spindles to ensure proper alignment with the work spindles, and align special attachments to the work spindles as needed.
Check for any cracks or breaks in the cross slides, and make sure all levers, rolls, and pins are in good condition. Check the chip conveyor’s condition as well as the condition of all the lubricating and coolant systems, including the:
- Lube pump
- Coolant pump
- Lube lines
- Meter units
- Coolant screens
- Coolant hoses/valves
Multi-Spindle Success at Davenport Machine
Davenport Machine always seeks to provide the best machines, parts, and attachments in the screw machining industry. We’ve produced cutting-edge machining technology for over 100 years, and we continue to offer revolutionary and valuable machine options for multi-spindle screw machine operators.
To learn more about our machines and how Davenport can help you achieve your machining needs, request a quote today.