Karatech CNC Processing Co Ltd: The Rest of the Steps

• 1
  What matters after the first op
• 2
  Why Karatech CNC Processing Co Ltd the rest of the steps decide your yield
• 3
  Setup and datum control before the first chip
• 4
  Tool life, coolant, and chip control on the run
• 5
  In-process inspection and how to read a size trend
• 6
  Finishing, assembly, and the tolerance budget
• 7
  Shipping release and the documents buyers should require
• 8
  The 7 steps after the first cut
• 9
  Typical parameters for the main post-cut steps

Most quotes focus on the machining cycle. In practice, a ±0.005 mm callout is lost after the spindle stops: bad clamping, a worn insert, a thermal shift on the second op, or a tumbler that rounds a corner. Each of these sits in the steps that follow the first cut.

On a 4,000 mm travel machine, thermal growth alone can move the tool 0.03 mm over a 6-hour run. A shop that checks the first article and then walks away will ship a mixed lot. A shop that logs size every 30-50 parts will catch the drift before the tolerance band closes.

The same logic applies to surface finish. A Ra 0.8–1.6 μm spec on a sealing face is easy to hit on a fresh carbide tool and hard to hold at part 400. This guide walks through the sequence in the order it happens on the floor, so you can audit a supplier against it.

Read it as a checklist. If a supplier cannot answer the questions in each section with numbers, the ±0.005 mm on their website is a marketing line, not a process capability.

• 1
  First article is not enoughLog size at intervals, not just at part 1.
• 2
  Thermal drift is realWarm up the spindle and check again after 2 hours.
• 3
  Finishing moves metalAnodize, plate, and coat all add or remove microns.

The datum is the only thing that makes a multi-op part repeatable. On a 5-axis job, we pick the datum from a machined surface, not a raw casting skin. A cast skin can vary 0.5 mm; a machined face varies under 0.01 mm. That difference decides whether op 2 lines up with op 1.

Clamping pressure is the next variable. A hydraulic vise at 40 bar will distort a thin 6061 wall; the same part at 15 bar holds shape. For thin-wall parts, we switch to soft jaws machined to the part profile, or use a vacuum plate for flat covers.

Work offset should be set with a probe, not a edge finder, on anything tighter than ±0.02 mm. A Renishaw-style probe resolves to about 1 μm. An edge finder resolves to maybe 0.01 mm on a good day, and the operator's feel adds more.

Finally, warm up. Run the spindle at 8,000-10,000 rpm for 20-30 minutes before the first article. On a 750 × 1,150 × 550 mm machine, the headstock grows a few microns in that window. Cutting the first article cold and the last article hot is a common cause of a drifting lot.

• 1
  Datum from machined faceRaw casting skin can vary 0.5 mm.
• 2
  Probe, not edge finderProbe resolves about 1 μm; edge finder about 0.01 mm.
• 3
  Warm up 20-30 minSpindle growth settles before the first article.

Tool wear is predictable if you track it. On 6061-T6 with a coated carbide end mill, we log flank wear every 30-50 parts. Once flank wear passes 0.15 mm, size starts to drift and finish drops below Ra 0.8 μm. Changing the tool at 0.10 mm wear keeps the lot in band.

Coolant choice matters more on stainless and titanium. 316L and Ti-6Al-4V both work-harden, so a starving tool rubs instead of cuts. High-pressure through-spindle coolant at 50-70 bar breaks the chip and keeps the edge cool. Flood coolant on a deep pocket in 17-4PH is a recipe for a broken Ø6 mm tool.

Chip control is not cosmetic. A bird-nested chip in a pocket will recut and scratch a finished wall. On aluminum we run aggressive feed to break the chip; on Inconel we slow down and accept stringy chips, then clear them with a chip fan between passes.

Speed and feed should come from the tool maker's data, then be trimmed by 10-20% for the first article. Running the book number on a long-reach tool will chatter. Shorten the gauge length or reduce radial engagement to 5-8% of diameter on deep walls.

• 1
  Change at 0.10 mm flank wearSize drifts once wear passes 0.15 mm.
• 2
  Through-spindle coolant 50-70 barEssential on 316L and Ti-6Al-4V.
• 3
  Trim book feeds 10-20%First article is not the place to push.

In-process inspection is a trend, not a pass or a fail. We measure the first article, then every 30-50 parts, and compare against the nominal. If the size walks 0.01 mm over 200 parts, that is thermal drift; if it jumps 0.02 mm between two consecutive parts, that is a tool or a chip issue.

A CMM is the right tool for a first article on a complex 5-axis part. For a run, a bench micrometer or a bore gauge at the machine catches drift faster. We keep the CMM for the final report and use hand tools to steer the process.

GD&T callouts need a fixture, not a free-hand check. A true position of Ø0.05 mm MMC cannot be verified with calipers. If a supplier says they check position with calipers, their report is not worth much.

A 100% inspection before shipment is the last line, not the first. If parts only get checked at the end, a bad lot is already made. The value is in the in-process log: it tells you when the process moved and what was done about it.

• 1
  Measure every 30-50 partsTrend matters more than a single reading.
• 2
  CMM for first articleBench tools steer the run.
• 3
  GD&T needs a fixtureCalipers cannot verify Ø0.05 mm MMC.

Finishing is where a good machined lot goes out of spec. Clear anodize adds 5-15 μm per surface; hardcoat on aluminum adds 25-50 μm. If the print calls for a Ø20.00 mm shaft with hardcoat, the machined size should be Ø19.95-19.97 mm. Send the finisher the final dimension and the coating callout, not the pre-plate size.

Plating behaves differently. Electroless nickel adds 5-25 μm uniformly; zinc plating is thinner but can throw off a thread. A M6 × 1.0 thread plated without allowance will not gauge. Mask the threads or cut them undersize before plating.

Assembly is the last place to catch an error. Press fits, dowel locations, and shim stacks all depend on the previous steps being in band. If a fixture is used for assembly, verify it before the run, not after the first 50 units.

Bead blasting and tumbling change edges. A tumbler can round a 0.2 mm edge to 0.5 mm. If the print calls a sharp edge or a specific radius, specify that the finishing step must protect it with a mask or a fixture.

• 1
  Send final size to the finisherNot the pre-plate size.
• 2
  Mask threads before platingA plated M6 × 1.0 will not gauge.
• 3
  Protect sharp edges in tumblingA 0.2 mm edge can become 0.5 mm.

The release package is where the process becomes auditable. At minimum, ask for a dimensional report that matches the print revision, part number, and lot quantity. A report with the wrong revision number is worse than no report, because it hides the mismatch.

Material certs matter on 17-4PH, Ti-6Al-4V, and any alloy with a heat number. Ask for the mill cert with the heat number and confirm it matches the parts. On medical and aerospace work, the traceability requirement is not optional.

For finishing, ask for the coating thickness and, on anodize, a color or class callout. For plating, ask for the spec and the measured thickness. A supplier who cannot state the thickness is guessing.

Packaging is part of the release. A 4,000 mm shaft needs a support every 800-1,000 mm to avoid bending in transit. Small parts in a single bag will rub. Ask how the parts are separated and protected before you approve the shipment.

• 1
  Match report to print revisionWrong revision hides the mismatch.
• 2
  Ask for mill certs with heat numbersRequired on 17-4PH and Ti-6Al-4V.
• 3
  Support long parts in transitEvery 800-1,000 mm for a 4,000 mm shaft.