Mohou.com 3D Printing Service User Guide

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  Five things to settle before you upload
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  Process fit for common part types
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  What a 3D printing service user guide should tell you first
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  Tolerance, material, and build size limits
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  Lead time, MOQ, and how the quote is built
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  Certifications, inspection, and confidentiality
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  Common mistakes buyers make with printed parts
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  Step by step: from file to delivered part

Most quote requests fail for a boring reason: the file does not say what matters. A STEP or STL shows geometry, but it does not state which faces are functional, which hole takes a bearing, or which surface will be seen by a customer. The shop then guesses, and the guess shows up in the price. Before uploading, write one page with the critical dimensions, the material, the finish, and the quantity. That page is worth more than a perfect model.

The second thing to settle is the process. Printing covers several methods with different strengths. Resin printing holds fine detail and smooth surfaces, which suits small housings and dental or medical models. Filament printing is cheaper per part and better for jigs, brackets and large covers. Powder-based printing handles complex internal channels and needs no support removal. Naming the method you want, or asking the shop to recommend one, removes a whole round of email.

Third, decide what you will measure when the box arrives. Printed parts cannot hold machined tolerances across every feature. A printer that quotes ±0.1 mm on a small feature may drift more on a 300 mm span. If three dimensions decide whether the assembly works, say so. The shop can then orient the part, add witness marks or inspect those features first.

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  Send a drawing, not just a modelA 2D PDF with critical dimensions avoids assumptions.
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  Name the processResin, filament, or powder. Each has a different cost curve.
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  List the inspection pointsThree to five dimensions is usually enough.

Tolerance on a printed part comes from the machine and the material, not from the operator's skill. Resin printers hold tighter detail than filament printers, and both change with part size. As a rule, keep printed tolerances at ±0.1 mm for small features and loosen them as the part grows. If a bore must take a bearing or a shaft, print it undersized and ream or bore it on a CNC machine afterward. That two-step route is common and usually cheaper than chasing an impossible print tolerance.

Material choice follows the load and the environment. ABS and PC take impact and heat better than generic resin. POM and PA slide well and hold threads. PEEK survives high temperature and chemical exposure but costs far more and needs a hot print chamber. Carbon-fiber-filled filament is stiff and light, which suits brackets, but it wears nozzles and leaves a rough surface. For parts that must match a machined aluminum housing, print the prototype first and then run the final part in 6061 or 7075.

Build size sets a hard ceiling. Small desktop printers top out near 200-300 mm, while industrial machines handle much larger single pieces. A 4,000 mm maximum processing size is available on the CNC side, so a printed prototype that is too large can still be split, printed in sections, and bonded, or cut from sheet and machined. Ask the shop which route it recommends before you redesign the part.

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  Small features±0.1 mm is a realistic print target.
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  Large spansExpect more drift; add a machining step for critical bores.
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  High-load partsPrint for form, machine for function.
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  Oversized partsSplit and bond, or switch to sheet metal and CNC.

Lead time on a quote is not the same as lead time on a purchase order. The useful question is when production starts and what can delay it. A shop that reviews files, returns a DFM report, and answers within 12 hours gives you room to fix problems before the machine is booked. Production can start within 24 hours once the file and the material are confirmed. Parts typically ship in 3-5 days for standard jobs. Custom finishing, such as anodizing or laser marking, adds days and should be quoted separately.

Minimum order quantity is the check that surprises buyers most. Some service bureaus push small orders to a broker and add margin. A shop with no minimum order quantity will run one prototype and a 10,000+ part run on the same floor, so the unit price falls as quantity rises without a jump in setup fees. Ask directly: is there a minimum, and does the price break at 10, 100, or 1,000 pieces?

Read the quote line by line. Material, machine time, support removal, surface finish, inspection, and shipping are separate costs. A low unit price with finishing excluded is not a low price. Ask what the quote includes and what triggers an extra charge: thin walls, tight tolerances, hand polishing, or a certificate pack. A shop that itemizes is easier to compare than one that sends a single number.

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  Quote in 12 hoursIncludes a free DFM analysis.
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  Start in 24 hoursOnce files and material are locked.
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  Ship in 3-5 daysStandard jobs, finishing quoted separately.
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  No MOQOne piece or 10,000+, same floor.

Certificates describe the management system around your part, not the part itself. ISO 9001:2015 covers general quality management and says the shop documents and audits its processes. IATF 16949:2016 adds automotive requirements, including traceability and change control, which matters for engine and vehicle hardware. ISO 13485:2016 is written for medical devices and covers design, production, and servicing records. ISO 27001:2022 covers information security, which is what protects your CAD files and drawings.

Inspection is the part of the guide buyers skip. Printed parts are usually checked against the drawing on critical features, not every surface. A shop running 100% inspection before shipment will check raw material, monitor during production, and do a final inspection, with reports available on request. Ask which dimensions are measured and whether the report lists actual values or just a pass mark. For a first article, actual values are worth the extra day.

Confidentiality is a practical concern for anyone sending unreleased designs. Uploads should be secure and confidential, and an NDA should be available on request. If your project is under a development agreement, sign the NDA before the first file transfer, not after. Ask who inside the shop can open the files and how long they are retained.

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  ISO 9001:2015General quality management.
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  IATF 16949:2016Automotive and engine hardware.
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  ISO 13485:2016Medical device quality system.
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  ISO 27001:2022Information security for your files.

Mistake one is designing for machining and printing the same file. Printed walls need a minimum thickness, usually 0.8-1.2 mm, and unsupported overhangs need either a support structure or a redesign. A sharp internal corner printed in resin will crack under load, while the same corner machined in aluminum will not. Add a fillet and the print survives.

Mistake two is ignoring anisotropy. Filament parts are weaker along the layer direction. A bracket printed flat may snap where a bracket printed on its side holds. Tell the shop how the part is loaded so the print orientation can be chosen for strength, not just speed.

Mistake three is comparing printed and machined parts on unit price alone. A printed prototype may cost less per piece, but if the design later needs a bearing bore, a thread, or a flat sealing face, those features move to a CNC operation. Budget for the second step when you plan the first.

Mistake four is skipping the DFM report. A shop that returns the file with comments on wall thickness, draft, and support removal is telling you where the cost sits. Ignoring that report and ordering anyway is how a cheap quote becomes an expensive rework.

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  Wall thicknessKeep 0.8-1.2 mm minimum, more for load.
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  OverhangsRedesign or accept support marks.
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  Load directionOrientation changes part strength.
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  DFM feedbackRead it before you pay.